Advances and Applications of 2D Materials

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.3	2011	18.4 Days	CHF 2400
Applied Nano applnano	-	-	2020	25.4 Days	CHF 1000
Nanomaterials nanomaterials	4.4	8.5	2010	14.1 Days	CHF 2400
Electrochem electrochem	-	6.3	2020	20.5 Days	CHF 1000
Materials materials	3.1	5.8	2008	13.9 Days	CHF 2600

12 pages, 3612 KiB

Open AccessArticle

Development and Characterization of PBSA-Based Green Composites in 3D-Printing by Fused Deposition Modelling

by Babacar Niang, Nicola Schiavone, Haroutioun Askanian, Vincent Verney, Diène Ndiaye and Abdoulaye Bouya Diop

Materials 2022, 15(21), 7570; https://doi.org/10.3390/ma15217570 - 28 Oct 2022

Cited by 9 | Viewed by 2293

Abstract

Fused deposition modelling is a rapidly growing additive manufacturing technology due to its ability to build functional parts with complex geometries. The mechanical properties of a built part depend on several process parameters. The effect of wood content on the properties of 3D [...] Read more.

Fused deposition modelling is a rapidly growing additive manufacturing technology due to its ability to build functional parts with complex geometries. The mechanical properties of a built part depend on several process parameters. The effect of wood content on the properties of 3D printed parts has been studied. Four types of filaments using poly(butylene succinate-co-adipate) (PBSA) with different reinforcement levels of Typha stem powder 0%, 5%, 10%, and 15% by weight were used for 3D printing. The density of the filaments and parts printed in this study increased with the Typha stem powder content. The thermal stability, mechanical performance, and viscoelastic properties of the different biocomposite filaments and 3D printed objects were analysed. The results show an increase in the crystallisation kinetics and a slight decrease in the thermal stability of the biomaterials. Compared to virgin PBSA FDM filaments, the PBSA biocomposite filament filled with Typha stem powder showed an increase in the tensile strength of the parts and specimens from 2.5 MPa to 8 MPa and in the modulus of elasticity from 160 MPa to 375 MPa, respectively, with additions of 5%, 10%, and 15% by mass. The addition of Typha stem fibres generated an increase in the elastic behaviour and relaxation time of the biomaterial structure, visualised by increases in the values of the viscosity components. The surface morphology reveals a decrease in the porosity of the printed samples. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 8019 KiB

Open AccessArticle

Synthesis of Eco-Friendly Silver Nanoparticles Using Glycyrrhizin and Evaluation of Their Antibacterial Ability

by Danni Feng, Renyin Zhang, Mengting Zhang, Ashe Fang and Feng Shi

Nanomaterials 2022, 12(15), 2636; https://doi.org/10.3390/nano12152636 - 30 Jul 2022

Cited by 28 | Viewed by 2962

Abstract

In the present study, the biosynthesis of silver nanoparticles (AgNPs) and their antibacterial activity against gram-positive and gram-negative bacteria were investigated. Glycyrrhizin (GL) was used as a reducing agent and stabilizer to rapidly prepare the AgNPs. The distinctive absorption peak at 419 nm [...] Read more.

In the present study, the biosynthesis of silver nanoparticles (AgNPs) and their antibacterial activity against gram-positive and gram-negative bacteria were investigated. Glycyrrhizin (GL) was used as a reducing agent and stabilizer to rapidly prepare the AgNPs. The distinctive absorption peak at 419 nm confirmed the formation of GL-reduced AgNPs. The TEM and particle size analysis shows that the prepared GL-reduced AgNPs were mostly circular with good dispersion and a relatively uniform particle size of 35 nm on average. Fourier transform infrared spectroscopy analysis was performed to identify the possible biomolecules in the capping and active stabilization of the GL-reduced AgNPs. The antibacterial activity of the GL-reduced AgNPs was analyzed with the Oxford cup diffusion method and filter paper diffusion method. The experimental results show that these properties endowed the GL-reduced AgNPs with high antibacterial activity against Escherichia coli and Staphylococcus aureus and lay a foundation for the use of colloidal silver in antibacterial applications. The GL-reduced AgNPs also had stronger antibacterial activity than sodium citrate-reduced AgNPs, which indicates the advantages of GL-reduced AgNPs compared with sodium citrate-reduced AgNPs in inducing bacteriostasis. The cytotoxicity of GL-reduced AgNPs on human kidney epithelial 293A (HEK293) cells was evaluated via the MTT assay. The results show that GL-reduced AgNPs had lower toxicity to HEK293 cells than sodium citrate-AgNPs, which indicates that the as-prepared GL-reduced AgNPs are environmentally friendly. Full article

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15 pages, 5601 KiB

Open AccessArticle

Large Vertical Piezoelectricity in a Janus Cr₂I₃F₃ Monolayer

by Haibo Niu, Yachao Liu, Jing Shi and Vei Wang

Materials 2022, 15(13), 4418; https://doi.org/10.3390/ma15134418 - 22 Jun 2022

Cited by 7 | Viewed by 2587

Abstract

Two-dimensional (2D) materials have potential applications in nanoscale sensors and spintronic devices. Herein, motivated by experimental synthesis of a CrI

_{3}

monolayer possessing intrinsic magnetism and a Janus MoSSe monolayer with piezoelectricity, we propose a 2D Janus Cr

_{2}

I

_{3}

F

_{3}

[...] Read more.

Two-dimensional (2D) materials have potential applications in nanoscale sensors and spintronic devices. Herein, motivated by experimental synthesis of a CrI

_{3}

monolayer possessing intrinsic magnetism and a Janus MoSSe monolayer with piezoelectricity, we propose a 2D Janus Cr

_{2}

I

_{3}

F

_{3}

monolayer as a multifunctional material exhibiting both piezoelectricity and ferromagnetism. Using density functional theory calculations, we systematically investigated the structural stability and the electronic, magnetic, and piezoelectric properties of the Janus Cr

_{2}

I

_{3}

F

_{3}

monolayer. We predicted that a vertical polarization of up to −0.155 × 10

^{- 10}

C/m is induced in the Cr

_{2}

I

_{3}

F

_{3}

monolayer due to the breaking of symmetry. The origination mechanism of polarization was demonstrated in terms of a local dipole moment calculated by maximally localized Wannier functions. Meanwhile, it was found that a remarkable piezoelectric response can be produced under a uniaxial strain in the basal plane. The calculated piezoelectric coefficients of the Cr

_{2}

I

_{3}

F

_{3}

monolayer compare favorably with those of the frequently used bulk piezoelectric materials such as

α

–quartz and wurtzite AlN. Particularly, the e

_{31}

and d

_{31}

values of the Cr

_{2}

I

_{3}

F

_{3}

monolayer are nearly 10 times as large as that of Mo-based transition metal dichalcogenides. We also found that the magnitude of e

_{31}

mainly arises from the ionic contribution, while the electronic contribution can be nearly neglected. The considerable piezoelectric response combined with the intrinsic magnetism make the Janus Cr

_{2}

I

_{3}

F

_{3}

monolayer a potential candidate for novel multifunctional devices integrating both piezoelectric and spintronic applications. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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47 pages, 6738 KiB

Open AccessReview

Advances in the Robustness of Wearable Electronic Textiles: Strategies, Stability, Washability and Perspective

by Mohammad Shak Sadi and Eglė Kumpikaitė

Nanomaterials 2022, 12(12), 2039; https://doi.org/10.3390/nano12122039 - 14 Jun 2022

Cited by 32 | Viewed by 6542

Abstract

Flexible electronic textiles are the future of wearable technology with a diverse application potential inspired by the Internet of Things (IoT) to improve all aspects of wearer life by replacing traditional bulky, rigid, and uncomfortable wearable electronics. The inherently prominent characteristics exhibited by [...] Read more.

Flexible electronic textiles are the future of wearable technology with a diverse application potential inspired by the Internet of Things (IoT) to improve all aspects of wearer life by replacing traditional bulky, rigid, and uncomfortable wearable electronics. The inherently prominent characteristics exhibited by textile substrates make them ideal candidates for designing user-friendly wearable electronic textiles for high-end variant applications. Textile substrates (fiber, yarn, fabric, and garment) combined with nanostructured electroactive materials provide a universal pathway for the researcher to construct advanced wearable electronics compatible with the human body and other circumstances. However, e-textiles are found to be vulnerable to physical deformation induced during repeated wash and wear. Thus, e-textiles need to be robust enough to withstand such challenges involved in designing a reliable product and require more attention for substantial advancement in stability and washability. As a step toward reliable devices, we present this comprehensive review of the state-of-the-art advances in substrate geometries, modification, fabrication, and standardized washing strategies to predict a roadmap toward sustainability. Furthermore, current challenges, opportunities, and future aspects of durable e-textiles development are envisioned to provide a conclusive pathway for researchers to conduct advanced studies. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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14 pages, 4177 KiB

Open AccessArticle

Two-Dimensional ZnS/SnS₂ Heterojunction as a Direct Z-Scheme Photocatalyst for Overall Water Splitting: A DFT Study

by Xing Chen, Cuihua Zhao, Hao Wu, Yong Shi, Cuiting Chen and Xi Zhou

Materials 2022, 15(11), 3786; https://doi.org/10.3390/ma15113786 - 26 May 2022

Cited by 27 | Viewed by 4913

Abstract

Direct Z-scheme photocatalysts have attracted extensive attention due to their strong redox ability and efficient separation of photogenerated electron-hole pairs. In this study, we constructed two types of ZnS/SnS₂ heterojunctions with different stacking models of ZnS and SnS₂ layers, and investigated [...] Read more.

Direct Z-scheme photocatalysts have attracted extensive attention due to their strong redox ability and efficient separation of photogenerated electron-hole pairs. In this study, we constructed two types of ZnS/SnS₂ heterojunctions with different stacking models of ZnS and SnS₂ layers, and investigated their structures, stabilities, and electronic and optical properties. Both types of heterojunctions are stable and are direct Z-scheme photocatalysts with band gaps of 1.87 eV and 1.79 eV, respectively. Furthermore, their oxidation and reduction potentials straddle the redox potentials of water, which makes them suitable as photocatalysts for water splitting. The built-in electric field at the heterojunction interface improves the separation of photogenerated electron-hole pairs, thus enhancing their photocatalytic efficiency. In addition, ZnS/SnS₂ heterojunctions have higher carrier mobilities and light absorption intensities than ZnS and SnS₂ monolayers. Therefore, the ZnS/SnS₂ heterojunction has a broad application prospect as a direct Z-scheme visible-light-driven photocatalyst for overall water splitting. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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14 pages, 3618 KiB

Open AccessArticle

Performance Analysis and Optimization of a PBDB-T:ITIC Based Organic Solar Cell Using Graphene Oxide as the Hole Transport Layer

by Ghazi Aman Nowsherwan, Abdul Samad, Muhammad Aamir Iqbal, Tauqeer Mushtaq, Ameer Hussain, Maria Malik, Sabah Haider, Phuong V. Pham and Jeong Ryeol Choi

Nanomaterials 2022, 12(10), 1767; https://doi.org/10.3390/nano12101767 - 22 May 2022

Cited by 44 | Viewed by 5655

Abstract

The hole transport layer (HTL) in organic solar cells (OSCs) plays an imperative role in boosting the cell’s performance. PEDOT:PSS is a conventional HTL used in OSCs owing to its high design cost and instability issues. It can be replaced with graphene oxide [...] Read more.

The hole transport layer (HTL) in organic solar cells (OSCs) plays an imperative role in boosting the cell’s performance. PEDOT:PSS is a conventional HTL used in OSCs owing to its high design cost and instability issues. It can be replaced with graphene oxide to increase the cell performance by overcoming instability issues. Graphene oxide (GO) has gained popularity in recent years for its practical use in solar energy due to its remarkable mechanical, electrical, thermal, and optical properties. This work uses SCAPS-1D to examine the results of graphene oxide (GO)-based organic solar cells by giving a comparison between the performance of absorber layers and a GO-based HTL to see which absorber material interacts more strongly with GO. The absorber layer PBDB-T:ITIC paired with GO as HTL outperforms the other absorber layers due to its better optical and electrical characteristics. Numerical simulations are performed within the SCAPS software at various absorber layer thicknesses, defect densities, and doping values to assess the influence on device performance and efficiency. After cell optimization, the best efficiency of an improved OSC is found to be 17.36%, and the outcomes of the simulated OSC are referenced to the results of the experimentally implemented OSC. These results provide a possible future direction for developing GO-based OSCs with higher efficiency. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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19 pages, 3900 KiB

Open AccessArticle

The Graphene Structure’s Effects on the Current-Voltage and Photovoltaic Characteristics of Directly Synthesized Graphene/n-Si(100) Diodes

by Šarūnas Jankauskas, Rimantas Gudaitis, Andrius Vasiliauskas, Asta Guobienė and Šarūnas Meškinis

Nanomaterials 2022, 12(10), 1640; https://doi.org/10.3390/nano12101640 - 11 May 2022

Cited by 8 | Viewed by 2905

Abstract

Graphene was synthesized directly on Si(100) substrates by microwave plasma-enhanced chemical vapor deposition (MW-PECVD). The effects of the graphene structure on the electrical and photovoltaic properties of graphene/n-Si(100) were studied. The samples were investigated using Raman spectroscopy, atomic force microscopy, and by measuring [...] Read more.

Graphene was synthesized directly on Si(100) substrates by microwave plasma-enhanced chemical vapor deposition (MW-PECVD). The effects of the graphene structure on the electrical and photovoltaic properties of graphene/n-Si(100) were studied. The samples were investigated using Raman spectroscopy, atomic force microscopy, and by measuring current–voltage (I-V) graphs. The temperature of the hydrogen plasma annealing prior to graphene synthesis was an essential parameter regarding the graphene/Si contact I-V characteristics and photovoltaic parameters. Graphene n-type self-doping was found to occur due to the native SiO₂ interlayer at the graphene/Si junction. It was the prevalent cause of the significant decrease in the reverse current and short-circuit current. No photovoltaic effect dependence on the graphene roughness and work function could be observed. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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19 pages, 8623 KiB

Open AccessArticle

Photocurable Hydrogel Substrate—Better Potential Substitute on Bone-Marrow-Derived Dendritic Cells Culturing

by Jiewen Deng, Yao Xie, Jian Shen, Qing Gao, Jing He, Hong Ma, Yongli Ji, Yong He and Meixiang Xiang

Materials 2022, 15(9), 3322; https://doi.org/10.3390/ma15093322 - 5 May 2022

Cited by 6 | Viewed by 3087

Abstract

Dendritic cells (DCs) are recognized as the most effective antigen-presenting cells at present. DCs have corresponding therapeutic effects in tumor immunity, transplantation immunity, infection inflammation and cardiovascular diseases, and the activation of T cells is dependent on DCs. However, normal bone-marrow-derived Dendritic cells [...] Read more.

Dendritic cells (DCs) are recognized as the most effective antigen-presenting cells at present. DCs have corresponding therapeutic effects in tumor immunity, transplantation immunity, infection inflammation and cardiovascular diseases, and the activation of T cells is dependent on DCs. However, normal bone-marrow-derived Dendritic cells (BMDCs) cultured on conventional culture plates are easy to be activated during culturing, and it is difficult to imitate the internal immune function. Here, we reported a novel BMDCs culturing with hydrogel substrate (CCHS), where we synthesized low substituted Gelatin Methacrylate-30 (GelMA-30) hydrogels and used them as a substitute for conventional culture plates in the culture and induction of BMDCs in vitro. The results showed that 5% GelMA-30 substrate was the best culture condition for BMDCs culturing. The low level of costimulatory molecules and the level of development-related transcription factors of BMDCs by CCHS were closer to that of spleen DCs and were capable of better promoting T cell activation and exerting an immune effect. CCHS was helpful to study the transformation of DCs from initial state to activated state, which contributes to the development of DC-T cell immunotherapy. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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14 pages, 3520 KiB

Open AccessArticle

Electrohydrodynamics Analysis of Dielectric 2D Nanofluids

by Mrutyunjay Maharana, Niharika Baruah, Sisir Kumar Nayak, Niranjan Sahoo, Kai Wu and Lalit Goswami

Nanomaterials 2022, 12(9), 1489; https://doi.org/10.3390/nano12091489 - 27 Apr 2022

Cited by 5 | Viewed by 2269

Abstract

The purpose of this present study is to prepare a stable mineral-oil (MO)-based nanofluid (NF) for usage as a coolant in a transformer. Nanoparticles (NPs) such as hexagonal boron nitride (h-BN) and titanium oxide (TiO₂) have superior thermal and electrical characteristics. [...] Read more.

The purpose of this present study is to prepare a stable mineral-oil (MO)-based nanofluid (NF) for usage as a coolant in a transformer. Nanoparticles (NPs) such as hexagonal boron nitride (h-BN) and titanium oxide (TiO₂) have superior thermal and electrical characteristics. Their dispersion into MO is likely to elevate the electrothermal properties of NFs. Therefore, different batches of NFs are prepared by uniformly dispersing the insulating h-BN and semiconducting TiO₂ NP of different concentrations in MO. Bulk h-BN NP of size 1μm is exfoliated into 2D nanosheets of size 150–200 nm, subsequently enhancing the surface area of exfoliated h-BN (Eh-BN). However, from the zeta-potential analysis, NP concentration of 0.01 and 0.1 wt.% are chosen for further study. The thermal conductivity and ACBDV studies of the prepared NF are performed to investigate the cooling and insulation characteristics. The charging-dynamics study verifies the enhancement in ACBDV of the Eh-BN NF. Weibull statistical analysis is carried out to obtain the maximum probability of ACBDV failure, and it is observed that 0.01 wt.% based NF has superior cooling and insulation properties than MO and remaining batches of NFs. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 1901 KiB

Open AccessArticle

Controlling Tunneling Characteristics via Bias Voltage in Bilayer Graphene/WS₂/Metal Heterojunctions

by Zongqi Bai, Sen Zhang, Yang Xiao, Miaomiao Li, Fang Luo, Jie Li, Shiqiao Qin and Gang Peng

Nanomaterials 2022, 12(9), 1419; https://doi.org/10.3390/nano12091419 - 21 Apr 2022

Cited by 4 | Viewed by 3427

Abstract

Van der Waals heterojunctions, formed by stacking two-dimensional materials with various structural and electronic properties, opens a new way to design new functional devices for future applications and provides an ideal research platform for exploring novel physical phenomena. In this work, bilayer graphene/WS [...] Read more.

Van der Waals heterojunctions, formed by stacking two-dimensional materials with various structural and electronic properties, opens a new way to design new functional devices for future applications and provides an ideal research platform for exploring novel physical phenomena. In this work, bilayer graphene/WS₂/metal heterojunctions (GWMHs) with vertical architecture were designed and fabricated. The tunneling current–bias voltage (I_t − V_b) properties of GWMHs can be tuned by 5 × 10⁶ times in magnitude for current increasing from 0.2 nA to 1 mA with applied bias voltage increasing from 10 mV to 2 V. Moreover, the transfer properties of GWMHs exhibit n-type conduction at V_b = 0.1 V and bipolar conduction at V_b = 2 V; these findings are explained well by direct tunneling (DT) and Fowler–Nordheim tunneling (FNT), respectively. The results show the great potential of GWMHs for high-power field-effect transistors (FETs) and next-generation logic electronic devices. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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7 pages, 3033 KiB

Open AccessBrief Report

Octagonal Quasicrystal Defect Mode Laser-Based PVK: Ir(ppy)₃ Polymer Driven by Optical Pumping

by Yuanyuan Cai, Shuai Zhang, Chenyu Wu, Zhiwei Wang, Weiran Xu, Xiao Chen and Yiquan Wang

Nanomaterials 2022, 12(9), 1386; https://doi.org/10.3390/nano12091386 - 19 Apr 2022

Cited by 2 | Viewed by 2198

Abstract

Based on the conjugated complex PVK: Ir(ppy)₃, a green-emitting organic quasicrystal microcavity laser is demonstrated driven by optical pumping. The organic laser adopts a sandwich structure of DBR/organic gain membrane/output Ag-layer for the vertical oscillation and an octagonal quasi-crystal for in-plane [...] Read more.

Based on the conjugated complex PVK: Ir(ppy)₃, a green-emitting organic quasicrystal microcavity laser is demonstrated driven by optical pumping. The organic laser adopts a sandwich structure of DBR/organic gain membrane/output Ag-layer for the vertical oscillation and an octagonal quasi-crystal for in-plane light localization. The experimental results show that the single-mode lasing action is observed at 521 nm with an FWHM of 0.8 nm. The threshold of lasing is lowered to 0.181 μJ/cm². Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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15 pages, 4694 KiB

Open AccessArticle

Electron-Level Mechanistic Insights into Ce Doping for Enhanced Efficiency Degradation of Bisphenol A under Visible Light Irradiation

by Qi Zeng, Chu-Ya Wang, Bo-Xing Xu, Jianyu Han, Xin Fang and Guangcan Zhu

Nanomaterials 2022, 12(8), 1382; https://doi.org/10.3390/nano12081382 - 18 Apr 2022

Cited by 12 | Viewed by 2815

Abstract

Bismuth oxybromide (BiOBr), with its special layered structure, is known to have potential as a visible-light-driven photocatalyst. However, the rapid recombination and short lifetime of the photogenerated carriers of BiOBr restrict its photocatalytic efficiency for the degradation of organic pollutants. Given the similar [...] Read more.

Bismuth oxybromide (BiOBr), with its special layered structure, is known to have potential as a visible-light-driven photocatalyst. However, the rapid recombination and short lifetime of the photogenerated carriers of BiOBr restrict its photocatalytic efficiency for the degradation of organic pollutants. Given the similar ionic size of Ce and Bi, Ce atoms might be easily introduced into the crystal of BiOBr to tailor its band structure. In this study, Ce doped BiOBr (Ce-BiOBr) samples with different percentages of Ce contents were prepared via a hydrothermal method. The intrinsic photocatalytic efficiency of Ce_0.2-BiOBr for the degradation of bisphenol A (BPA) was 3.66 times higher than that of pristine BiOBr under visible light irradiation. The mechanism of Ce-doping modification for the enhanced photocatalytic performance was demonstrated based on a series of experiments and DFT calculation. The narrowed bandgap, the enhanced charge separation efficiency and Ce-doping energy level contributed to the remarkable photocatalytic performance of Ce-BiOBr. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 2842 KiB

Open AccessArticle

Ultra-Narrowband Anisotropic Perfect Absorber Based on α-MoO₃ Metamaterials in the Visible Light Region

by Gui Jin, Tianle Zhou and Bin Tang

Nanomaterials 2022, 12(8), 1375; https://doi.org/10.3390/nano12081375 - 17 Apr 2022

Cited by 22 | Viewed by 3240

Abstract

Optically anisotropic materials show important advantages in constructing polarization-dependent optical devices. Very recently, a new type of two-dimensional van der Waals (vdW) material, known as α-phase molybdenum trioxide (α-MoO₃), has sparked considerable interest owing to its highly anisotropic characteristics. In this [...] Read more.

Optically anisotropic materials show important advantages in constructing polarization-dependent optical devices. Very recently, a new type of two-dimensional van der Waals (vdW) material, known as α-phase molybdenum trioxide (α-MoO₃), has sparked considerable interest owing to its highly anisotropic characteristics. In this work, we theoretically present an anisotropic metamaterial absorber composed of α-MoO₃ rings and dielectric layer stacking on a metallic mirror. The designed absorber can exhibit ultra-narrowband perfect absorption for polarizations along [100] and [001] crystalline directions in the visible light region. Plus, the influences of some geometric parameters on the optical absorption spectra are discussed. Meanwhile, the proposed ultra-narrowband anisotropic perfect absorber has an excellent angular tolerance for the case of oblique incidence. Interestingly, the single-band perfect absorption in our proposed metamaterials can be arbitrarily extended to multi-band perfect absorption by adjusting the thickness of dielectric layer. The physical mechanism can be explained by the interference theory in Fabry–Pérot cavity, which is consistent with the numerical simulation. Our research results have some potential applications in designs of anisotropic optical devices with tunable spectrum and selective polarization in the visible light region. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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20 pages, 4229 KiB

Open AccessReview

A Review of the Effects of Raw Material Compositions and Steam Curing Regimes on the Performance and Microstructure of Precast Concrete

by Yucheng Zhou, Yijian Zhan, Mintao Zhu, Shengyi Wang, Juanhong Liu and Ning Ning

Materials 2022, 15(8), 2859; https://doi.org/10.3390/ma15082859 - 13 Apr 2022

Cited by 15 | Viewed by 3559

Abstract

In this paper, the effects of steam curing conditions on concrete properties and microstructural characteristics are reviewed, and technical approaches such as appropriate raw material compositions and curing regimes are explored. Moreover, the environmental effects of precast concrete are evaluated. The main conclusion [...] Read more.

In this paper, the effects of steam curing conditions on concrete properties and microstructural characteristics are reviewed, and technical approaches such as appropriate raw material compositions and curing regimes are explored. Moreover, the environmental effects of precast concrete are evaluated. The main conclusion is that steam curing can improve the early strength of concrete, but thermal damage, shrinkage cracking, delayed ettringite formation (DEF), and other factors cause the later strength to increase more slowly or even deteriorate. Accordingly, it is necessary to undertake methods for improvement: (1) Adopt a lot of high-activity mineral admixture + a few low-activity mineral admixture combinations to ensure that the early strength of concrete meets the standard while allowing the subsequent development of concrete hydration to ensure durability. (2) Control the precuring time and temperature gradient of the concrete to allow the initial structure of the concrete to form. (3) Use effective secondary curing, such as soaking in an aqueous solution of limestone, in addition to standard curing to further improve the compactness of concrete. Moreover, the replacement of cement with less than 30% mineral admixtures in steam-cured concrete should be promoted to alleviate the environmental hazards caused by excessive CO₂ emissions. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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8 pages, 2055 KiB

Open AccessArticle

Air Annealing Process for Threshold Voltage Tuning of MoTe₂ FET

by Soojin Kim, Yeeun Roh, Younguk Choi, Ah Hyun Jun, Hojun Seo and Byeong-Kwon Ju

Appl. Sci. 2022, 12(8), 3840; https://doi.org/10.3390/app12083840 - 11 Apr 2022

Cited by 5 | Viewed by 3095

Abstract

A stable doping technique for modifying the conduction behaviour of two-dimensional (2D) nanomaterial-based transistors is imperative for applications based on low-power complementary oxide thin-film transistors. Achieving an ambipolar feature with a controlled threshold voltage in both the p- and n-regimes is crucial for [...] Read more.

A stable doping technique for modifying the conduction behaviour of two-dimensional (2D) nanomaterial-based transistors is imperative for applications based on low-power complementary oxide thin-film transistors. Achieving an ambipolar feature with a controlled threshold voltage in both the p- and n-regimes is crucial for applying MoTe₂-based devices as electronic devices because their native doping states are unipolar. In this study, a simple method to tune the threshold voltage of MoTe₂ field-effect transistors (FETs) was investigated in order to realise an enhancement-mode MoTe₂ thin-film transistor by implementing a facile method to modulate the carrier polarity based on the oxidative properties of MoTe₂ FETs. Annealing in air induced a continuous p-doping effect in the devices without significant electrical degradation. Through a precise control of the duration and temperature of the post-annealing process, the tailoring technique induces hole doping, which results in a remarkable shift in transfer characteristics, thus leading to a charge neutrality point of the devices at zero gate bias. This study demonstrates the considerable potential of air heating as a reliable and economical post-processing method for precisely modifying the threshold voltage and further controlling the doping states of MoTe₂-based FETs for use in logic inverters with 2D semiconductors. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 4320 KiB

Open AccessArticle

CTAB Enhanced Room-Temperature Detection of NO₂ Based on MoS₂-Reduced Graphene Oxide Nanohybrid

by Wenbo Li, Hao Li, Rong Qian, Shangjun Zhuo, Pengfei Ju and Qiao Chen

Nanomaterials 2022, 12(8), 1300; https://doi.org/10.3390/nano12081300 - 11 Apr 2022

Cited by 13 | Viewed by 3203

Abstract

A new NO₂ nanohybrid of a gas sensor (CTAB-MoS₂/rGO) was constructed for sensitive room-temperature detection of NO₂ by 3D molybdenum disulfide (MoS₂) and reduced graphene oxide (rGO), assisted with hexadecyl trimethyl ammonium bromide (CTAB). In comparison with [...] Read more.

A new NO₂ nanohybrid of a gas sensor (CTAB-MoS₂/rGO) was constructed for sensitive room-temperature detection of NO₂ by 3D molybdenum disulfide (MoS₂) and reduced graphene oxide (rGO), assisted with hexadecyl trimethyl ammonium bromide (CTAB). In comparison with MoS₂ and MoS₂/rGO, the BET and SEM characterization results depicted the three-dimensional structure of the CTAB-MoS₂/rGO nanohybrid, which possessed a larger specific surface area to provide more active reaction sites to boost its gas-sensing performance. Observations of the gas-sensing properties indicated that the CTAB-MoS₂/rGO sensor performed a high response of 45.5% for 17.5 ppm NO₂, a remarkable selectivity of NO₂, an ultra-low detection limit of 26.55 ppb and long-term stability for a 30-day measurement. In addition, the response obtained for the CTAB-MoS₂/rGO sensor was about two to four times that obtained for the MoS₂/rGO sensor and the MoS₂ sensor toward 8 ppm NO₂, which correlated with the heterojunction between MoS₂ and rGO, and the improvement in surface area and conductivity correlated with the introduction of CTAB and rGO. The excellent performance of the CTAB-MoS₂/rGO sensor further suggested the advantage of CTAB in assisting a reliable detection of trace NO₂ and an alternative method for highly efficiently detecting NO₂ in the environment. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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13 pages, 6857 KiB

Open AccessArticle

Improving the Photocatalytic Activity of Mesoporous Titania Films through the Formation of WS₂/TiO₂ Nano-Heterostructures

by Junkai Ren, Luigi Stagi, Luca Malfatti, Valentina Paolucci, Carlo Cantalini, Sebastiano Garroni, Marzia Mureddu and Plinio Innocenzi

Nanomaterials 2022, 12(7), 1074; https://doi.org/10.3390/nano12071074 - 25 Mar 2022

Cited by 7 | Viewed by 3157

Abstract

Heterostructures formed by anatase nanotitania and bidimensional semiconducting materials are expected to become the next-generation photocatalytic materials with an extended operating range and higher performances. The capability of fabricating optically transparent photocatalytic thin films is also a highly demanded technological issue, and increasing [...] Read more.

Heterostructures formed by anatase nanotitania and bidimensional semiconducting materials are expected to become the next-generation photocatalytic materials with an extended operating range and higher performances. The capability of fabricating optically transparent photocatalytic thin films is also a highly demanded technological issue, and increasing the performances of such devices would significantly impact several applications, from self-cleaning surfaces to photovoltaic systems. To improve the performances of such devices, WS₂/TiO₂ heterostructures obtained by incorporating two-dimensional transition metal dichalcogenides layers into titania mesoporous ordered thin films have been fabricated. The self-assembly process has been carefully controlled to avoid disruption of the order during film fabrication. WS₂ nanosheets of different sizes have been exfoliated by sonication and incorporated in the mesoporous films via one-pot processing. The WS₂ nanosheets result as well-dispersed within the titania anatase mesoporous film that retains a mesoporous ordered structure. An enhanced photocatalytic response due to an interparticle electron transfer effect has been observed. The structural characterization of the heterostructure has revealed a tight interplay between the matrix and nanosheets rather than a simple additive co-catalyst effect. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 3781 KiB

Open AccessArticle

Near-Interface Defects in Graphene/H-BN In-Plane Heterostructures: Insights into the Interfacial Thermal Transport

by Nana Zhang, Baoming Zhou, Dongbo Li, Dongfeng Qi, Yongling Wu, Hongyu Zheng and Bing Yang

Nanomaterials 2022, 12(7), 1044; https://doi.org/10.3390/nano12071044 - 22 Mar 2022

Cited by 7 | Viewed by 2977

Abstract

Based on nonequilibrium molecular dynamics (NEMD) and nonequilibrium Green’s function simulations, the interfacial thermal conductance (ITC) of graphene/h-BN in-plane heterostructures with near-interface defects (monovacancy defects, 585 and f5f7 double-vacancy defects) is studied. Compared to pristine graphene/h-BN, all near-interface defects reduce the ITC of [...] Read more.

Based on nonequilibrium molecular dynamics (NEMD) and nonequilibrium Green’s function simulations, the interfacial thermal conductance (ITC) of graphene/h-BN in-plane heterostructures with near-interface defects (monovacancy defects, 585 and f5f7 double-vacancy defects) is studied. Compared to pristine graphene/h-BN, all near-interface defects reduce the ITC of graphene/h-BN. However, differences in defective structures and the wrinkles induced by the defects cause significant discrepancies in heat transfer for defective graphene/h-BN. The stronger phonon scattering and phonon localization caused by the wider cross-section in defects and the larger wrinkles result in the double-vacancy defects having stronger energy hindrance effects than the monovacancy defects. In addition, the approximate cross-sections and wrinkles induced by the 585 and f5f7 double-vacancy defects provide approximate heat hindrance capability. The phonon transmission and vibrational density of states (VDOS) further confirm the above results. The double-vacancy defects in the near-interface region have lower low-frequency phonon transmission and VDOS values than the monovacancy defects, while the 585 and f5f7 double-vacancy defects have similar low-frequency phonon transmission and VDOS values at the near-interface region. This study provides physical insight into the thermal transport mechanisms in graphene/h-BN in-plane heterostructures with near-interface defects and provides design guidelines for related devices. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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15 pages, 2502 KiB

Open AccessArticle

Foam Synthesis of Nickel/Nickel (II) Hydroxide Nanoflakes Using Double Templates of Surfactant Liquid Crystal and Hydrogen Bubbles: A High-Performance Catalyst for Methanol Electrooxidation in Alkaline Solution

by Amani M. Bamuqaddam, Saba A. Aladeemy, Mohamed A. Ghanem, Abdullah M. Al-Mayouf, Nouf H. Alotaibi and Frank Marken

Nanomaterials 2022, 12(5), 879; https://doi.org/10.3390/nano12050879 - 7 Mar 2022

Cited by 8 | Viewed by 2932

Abstract

This work demonstrates the chemical synthesis of two-dimensional nanoflakes of mesoporous nickel/nickel (II) hydroxide (Ni/Ni(OH)₂-NFs) using double templates of surfactant self-assembled thin-film and foam of hydrogen bubbles produced by sodium borohydride reducing agent. Physicochemical characterizations show the formation of amorphous mesoporous [...] Read more.

This work demonstrates the chemical synthesis of two-dimensional nanoflakes of mesoporous nickel/nickel (II) hydroxide (Ni/Ni(OH)₂-NFs) using double templates of surfactant self-assembled thin-film and foam of hydrogen bubbles produced by sodium borohydride reducing agent. Physicochemical characterizations show the formation of amorphous mesoporous 2D nanoflakes with a Ni/Ni(OH)₂ structure and a high specific surface area (165 m²/g). Electrochemical studies show that the electrocatalytic activity of Ni/Ni(OH)₂ nanoflakes towards methanol oxidation in alkaline solution is significantly enhanced in comparison with that of parent bare-Ni(OH)₂ deposited from surfactant-free solution. Cyclic voltammetry shows that the methanol oxidation mass activity of Ni/Ni(OH)₂-NFs reaches 545 A/cm² g_cat at 0.6 V vs. Ag/AgCl, which is more than five times higher than that of bare-Ni(OH)₂. Moreover, Ni/Ni(OH)₂-NFs reveal less charge transfer resistance (10.4 Ω), stable oxidation current density (625 A/cm² g_cat at 0.7 V vs. Ag/AgCl), and resistance to the adsorption of reaction intermediates and products during three hours of constant-potential methanol oxidation electrolysis in alkaline solution. The high-performance electrocatalytic activity of Ni/Ni(OH)₂ nanoflakes is mainly derived from efficient charge transfer due to the high specific surface area of the 2D mesoporous architecture of the nanoflakes, as well as the mass transport of methanol to Ni²⁺/Ni³⁺ active sites throughout the catalyst layer. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 3688 KiB

Open AccessArticle

PDMS-Encapsulated MXene@Polyester Fabric Strain Sensor for Multifunctional Sensing Applications

by Wengang Lu, Beenish Mustafa, Zhiyuan Wang, Fuzhuo Lian and Geliang Yu

Nanomaterials 2022, 12(5), 871; https://doi.org/10.3390/nano12050871 - 5 Mar 2022

Cited by 20 | Viewed by 4242

Abstract

Flexible strain sensors based on 2D materials have been proven effective for wearable health monitoring devices, human motion detection, and fitness applications. These sensors are flexible, light, and user-friendly, but their sensitivity and detection range need to be enhanced. Among many 2D materials, [...] Read more.

Flexible strain sensors based on 2D materials have been proven effective for wearable health monitoring devices, human motion detection, and fitness applications. These sensors are flexible, light, and user-friendly, but their sensitivity and detection range need to be enhanced. Among many 2D materials, MXene attracts much interest due to its remarkable properties, such as high electrical conductivity, excellent mechanical properties, flexibility, and good hydrophilicity. However, it is a challenge to fabricate strain sensors with extreme sensitivity and a wide sensing range. In this work, a multifunctional, cost-effective, and highly sensitive PDMS-encapsulated MXene@polyester fabric strain sensor was fabricated. Firstly, complete adsorption of MXene within the fabric formed conductive networks, and then PDMS was used to endow superhydrophobicity and corrosion resistance. The strain sensor demonstrated multifunctional applications and outstanding performance, such as long-term stability (over 500 cycles) and a wide sensing range (8%). The proposed sensor has promising potential for wearable electronic devices such as health monitoring systems and physiological sensing applications. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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27 pages, 25480 KiB

Open AccessReview

The Photovoltaic Cell Based on CIGS: Principles and Technologies

by Billel Salhi

Materials 2022, 15(5), 1908; https://doi.org/10.3390/ma15051908 - 4 Mar 2022

Cited by 53 | Viewed by 8541

Abstract

Semiconductors used in the manufacture of solar cells are the subject of extensive research. Currently, silicon is the most commonly used material for photovoltaic cells, representing more than 80% of the global production. However, due to its very energy-intensive and costly production method, [...] Read more.

Semiconductors used in the manufacture of solar cells are the subject of extensive research. Currently, silicon is the most commonly used material for photovoltaic cells, representing more than 80% of the global production. However, due to its very energy-intensive and costly production method, other materials appear to be preferable over silicon, including the chalcopyrite-structured semiconductors of the CIS-based family (Cu(In, Ga, Al) (Se, S)₂). Indeed, these compounds have bandwidths between 1 eV (CuInSe₂) and 3 eV (CuAlS₂), allowing them to absorb most solar radiation. Moreover, these materials are currently the ones that make it possible to achieve the highest photovoltaic conversion efficiencies from thin-film devices, particularly Cu(In, Ga)Se₂, which is considered the most efficient among all drifts based on CIS. In this review, we focus on the CIGS-based solar cells by exploring the different layers and showing the recent progress and challenges. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 2767 KiB

Open AccessArticle

Atomic-Layer-Deposition-Made Very Thin Layer of Al₂O₃, Improves the Young’s Modulus of Graphene

by Aile Tamm, Tauno Kahro, Helle-Mai Piirsoo and Taivo Jõgiaas

Appl. Sci. 2022, 12(5), 2491; https://doi.org/10.3390/app12052491 - 27 Feb 2022

Cited by 2 | Viewed by 2786

Abstract

Nanostructures with graphene make them highly promising for nanoelectronics, memristor devices, nanosensors and electrodes for energy storage. In some devices the mechanical properties of graphene are important. Therefore, nanoindentation has been used to measure the mechanical properties of polycrystalline graphene in a nanostructure [...] Read more.

Nanostructures with graphene make them highly promising for nanoelectronics, memristor devices, nanosensors and electrodes for energy storage. In some devices the mechanical properties of graphene are important. Therefore, nanoindentation has been used to measure the mechanical properties of polycrystalline graphene in a nanostructure containing metal oxide and graphene. In this study the graphene was transferred, prior to the deposition of the metal oxide overlayers, to the Si/SiO₂ substrate were SiO₂ thickness was 300 nm. The atomic layer deposition (ALD) process for making a very thin film of Al₂O₃ (thickness comparable with graphene) was applied to improve the elasticity of graphene. For the alumina film the Al(CH₃)₃ and H₂O were used as the precursors. According to the micro-Raman analysis, after the Al₂O₃ deposition process, the G-and 2D-bands of graphene slightly broadened but the overall quality did not change (D-band was mostly absent). The chosen process did not decrease the graphene quality and the improvement in elastic modulus is significant. In case the load was 10 mN, the Young’s modulus of Si/SiO₂/Graphene nanostructure was 96 GPa and after 5 ALD cycles of Al₂O₃ on graphene (Si/SiO₂/Graphene/Al₂O₃) it increased up to 125 GPa. Our work highlights the correlation between nanoindentation and defects appearance in graphene. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 1672 KiB

Open AccessArticle

Computational Design of Gas Sensors Based on V₃S₄ Monolayer

by Ilya V. Chepkasov, Ekaterina V. Sukhanova, Alexander G. Kvashnin, Hayk A. Zakaryan, Misha A. Aghamalyan, Yevgeni Sh. Mamasakhlisov, Anton M. Manakhov, Zakhar I. Popov and Dmitry G. Kvashnin

Nanomaterials 2022, 12(5), 774; https://doi.org/10.3390/nano12050774 - 25 Feb 2022

Cited by 8 | Viewed by 3946

Abstract

Novel magnetic gas sensors are characterized by extremely high efficiency and low energy consumption, therefore, a search for a two-dimensional material suitable for room temperature magnetic gas sensors is a critical task for modern materials scientists. Here, we computationally discovered a novel ultrathin [...] Read more.

Novel magnetic gas sensors are characterized by extremely high efficiency and low energy consumption, therefore, a search for a two-dimensional material suitable for room temperature magnetic gas sensors is a critical task for modern materials scientists. Here, we computationally discovered a novel ultrathin two-dimensional antiferromagnet V₃S₄, which, in addition to stability and remarkable electronic properties, demonstrates a great potential to be applied in magnetic gas sensing devices. Quantum-mechanical calculations within the DFT + U approach show the antiferromagnetic ground state of V₃S₄, which exhibits semiconducting electronic properties with a band gap of 0.36 eV. A study of electronic and magnetic response to the adsorption of various gas agents showed pronounced changes in properties with respect to the adsorption of NH₃, NO₂, O₂, and NO molecules on the surface. The calculated energies of adsorption of these molecules were −1.25, −0.91, −0.59, and −0.93 eV, respectively. Obtained results showed the prospective for V₃S₄ to be used as effective sensing materials to detect NO₂ and NO, for their capture, and for catalytic applications in which it is required to lower the dissociation energy of O₂, for example, in oxygen reduction reactions. The sensing and reducing of NO₂ and NO have great importance for improving environmental protection and sustainable development. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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11 pages, 3071 KiB

Open AccessArticle

High Power and Large-Energy Pulse Generation in an Erbium-Doped Fiber Laser by a Ferromagnetic Insulator-Cr₂Si₂Te₆ Saturable Absorber

by Zhifeng Hong, Xiwen Jiang, Meixia Zhang, Huanian Zhang and Xiaojuan Liu

Nanomaterials 2022, 12(3), 564; https://doi.org/10.3390/nano12030564 - 7 Feb 2022

Cited by 8 | Viewed by 2843

Abstract

Large-energy mode-locked fiber lasers are extensively studied due to their indispensable use in various fields and applications. Recently, ferromagnetic insulators have attracted tremendous research interest in ultra-fast photonics because of their unique ferromagnetic properties and typical layered structure. In our work, Cr₂ [...] Read more.

Large-energy mode-locked fiber lasers are extensively studied due to their indispensable use in various fields and applications. Recently, ferromagnetic insulators have attracted tremendous research interest in ultra-fast photonics because of their unique ferromagnetic properties and typical layered structure. In our work, Cr₂Si₂Te₆ nanosheets are prepared and utilized as a saturable absorber (SA) in a large-energy mode-locked erbium-doped fiber (EDF) laser. With a total cavity length of 240 m, a stable mode-locked operation characterized by maximum pulse energy as high as 244.76 nJ with a repetition rate of 847.64 kHz is achieved. When the cavity length is extended to 390 m, the output maximum pulse energy is successfully scaled up to 325.50 nJ. To our knowledge, this is the largest pulse energy and highest output power level to be achieved in mode-locked fiber lasers by two-dimensional (2D) material saturable absorbers (SAs) so far. This work not only makes a forward step to the investigation of the generation of large-energy pulses in mode-locked fiber lasers but also fully proves that the ferromagnetic insulator-Cr₂Si₂Te₆ possesses an excellent nonlinear absorption property, antioxidant capacity in ambient conditions, as well as outstanding thermal stability, which enriches our insight into 2D materials. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 2684 KiB

Open AccessArticle

Investigation of the Crystallization Characteristics of Intermediate States in Ge₂Sb₂Te₅ Thin Films Induced by Nanosecond Multi-Pulsed Laser Irradiation

by Jia Du, Jun Zhou, Lianzhen Zhang, Na Yang, Xin Ding and Jin Zhang

Nanomaterials 2022, 12(3), 536; https://doi.org/10.3390/nano12030536 - 4 Feb 2022

Cited by 3 | Viewed by 2458

Abstract

Laser pulses can be utilized to induce intermediate states of phase change materials between amorphous and crystalline phases, making phase change materials attractive and applicable for multi-level storage applications. In this paper, intermediate states of Ge₂Sb₂Te₅ thin films [...] Read more.

Laser pulses can be utilized to induce intermediate states of phase change materials between amorphous and crystalline phases, making phase change materials attractive and applicable for multi-level storage applications. In this paper, intermediate states of Ge₂Sb₂Te₅ thin films induced via employing a nanosecond multi-pulse laser with different energy and pulse duration were performed by Raman spectroscopy, reflection measurement and thermal simulations. Upon laser-crystallized Ge₂Sb₂Te₅ films, optical functions change drastically, leading to distinguishable reflectivity contrasts of intermediate states between amorphous and crystalline phases due to different crystallinity. The changes in optical intensity for laser-crystallized Ge₂Sb₂Te₅ are also accompanied by micro-structure evolution, since high-energy and longer pulses result in higher-level intermediate states (corresponding to high reflection intensity) and largely contribute to the formation of stronger Raman peaks. By employing thermal analysis, we further demonstrated that the variations of both laser fluence and pulse duration play decisive roles in the degree of crystallinity of Ge₂Sb₂Te₅ films. Laser fluence is mainly responsible for the variations in crystallization temperature, while the varying pulse duration has a great impact on the crystallization time. The present study offers a deeper understanding of the crystallization characteristic of phase change material Ge₂Sb₂Te₅. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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13 pages, 3738 KiB

Open AccessArticle

Electromagnetic Shielding and Flame Retardancy of Composite Films Constructed with Cellulose and Graphene Nanoplates

by Zuwei Fan, Yuanyuan Yu, Xiaojie Cheng and Rangtong Liu

Materials 2022, 15(3), 1088; https://doi.org/10.3390/ma15031088 - 30 Jan 2022

Cited by 4 | Viewed by 3516

Abstract

Aimed at improving the electromagnetic (EM) shielding and flame retardancy of cellulose materials, graphene (GE) nanoplates were introduced into cellulose matrix films by blending in1-allyl-3-methylimidazolium chloride. The structure and performance of the obtained composite films were investigated using scanning electron microscopy, X-ray diffraction, [...] Read more.

Aimed at improving the electromagnetic (EM) shielding and flame retardancy of cellulose materials, graphene (GE) nanoplates were introduced into cellulose matrix films by blending in1-allyl-3-methylimidazolium chloride. The structure and performance of the obtained composite films were investigated using scanning electron microscopy, X-ray diffraction, thermogravimetric (TG) analysis, EM shielding effectiveness (SE), and combustion tests. GE introduction formed and stacked laminated structures in the films after drying due to controlled shrinkage of the cellulose matrix. The lamination of GE nanoplates into the films was beneficial for providing EM shielding due to multiple internal reflection of EM radiation; furthermore, they also increased flame resistance based on the “labyrinth effect.” The SE of these composite films increased gradually with increased GE content and reached 22.3 dB under an incident frequency of 1500 MHz. TG analysis indicated that these composite films possessed improved thermal stability due to GE addition. Reduced flammability was confirmed by their extended times to ignition or inability to be ignited, reduced heat release rates observed in cone calorimetry tests, and increased limiting oxygen index values. These films with improved EM shielding and flame retardancy could be considered potential candidates for multipurpose materials in various applications, such as electronics and radar evasion. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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7 pages, 1395 KiB

Open AccessArticle

Electron-Beam-Induced Fluorination Cycle for Long-Term Preservation of Graphene under Ambient Conditions

by Tianbo Duan, Hu Li and Klaus Leifer

Nanomaterials 2022, 12(3), 383; https://doi.org/10.3390/nano12030383 - 24 Jan 2022

Cited by 3 | Viewed by 2700

Abstract

The aging in air inevitably results in the accumulation of airborne hydrocarbon contaminations on a graphene surface, which causes considerable difficulties in the subsequent application of graphene. Herein, we report an electron-beam-activated fluorination/defluorination cycle for achieving a long-term preservation of CVD graphene. After [...] Read more.

The aging in air inevitably results in the accumulation of airborne hydrocarbon contaminations on a graphene surface, which causes considerable difficulties in the subsequent application of graphene. Herein, we report an electron-beam-activated fluorination/defluorination cycle for achieving a long-term preservation of CVD graphene. After experiencing such cycle, the accumulation of airborne hydrocarbon on the graphene surfaces is strongly reduced, and the initial chemical status of graphene can be restored, which is confirmed by employing atomic force microscopy and X-ray photoelectron microscopy. Our reported approach provides an efficient method for the cleaning and long-term preservation of graphene, and it is particularly useful for graphene microscopy characterizations. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 1851 KiB

Open AccessArticle

High Mobility Graphene on EVA/PET

by Munis Khan, Kornelia Indykiewicz, Pui Lam Tam and August Yurgens

Nanomaterials 2022, 12(3), 331; https://doi.org/10.3390/nano12030331 - 21 Jan 2022

Cited by 14 | Viewed by 5765 | Correction

Abstract

Transparent conductive film on a plastic substrate is a critical component in low cost, flexible and lightweight optoelectronics. CVD graphene transferred from copper- to ethylene vinyl acetate (EVA)/polyethylene terephthalate (PET) foil by hot press lamination has been reported as a robust and affordable [...] Read more.

Transparent conductive film on a plastic substrate is a critical component in low cost, flexible and lightweight optoelectronics. CVD graphene transferred from copper- to ethylene vinyl acetate (EVA)/polyethylene terephthalate (PET) foil by hot press lamination has been reported as a robust and affordable alternative to manufacture highly flexible and conductive films. Here, we demonstrate that annealing the samples at 60

^{\circ}

C under a flow of nitrogen, after wet etching of copper foil by nitric acid, significantly enhances the Hall mobility of such graphene films. Raman, Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the morphology and chemical composition of the graphene. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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13 pages, 4395 KiB

Open AccessArticle

Monolayer Graphene Radiation Sensor with Backend RF Ring Oscillator Transducer

by Mohamed W. Tawfik, Abdelhameed Sharaf and Mohamed Serry

Nanomaterials 2022, 12(3), 305; https://doi.org/10.3390/nano12030305 - 18 Jan 2022

Cited by 5 | Viewed by 3058

Abstract

This paper proposes a new graphene gamma- and beta-radiation sensor with a backend RF ring oscillator transducer employed to convert the change in the graphene resistivity due to ionizing irradiation into a frequency output. The sensor consists of a CVD monolayer of graphene [...] Read more.

This paper proposes a new graphene gamma- and beta-radiation sensor with a backend RF ring oscillator transducer employed to convert the change in the graphene resistivity due to ionizing irradiation into a frequency output. The sensor consists of a CVD monolayer of graphene grown on a copper substrate, with an RF ring oscillator readout circuit in which the percentage change in frequency is captured versus the change in radiation dose. The novel integration of the RF oscillator transducer with the graphene monolayer results in high average sensitivity to gamma irradiation up to 3.82 kΩ/kGy, which corresponds to a percentage change in frequency of 7.86% kGy⁻¹ in response to cumulative gamma irradiation ranging from 0 to 1 kGy. The new approach helps to minimize background environmental effects (e.g., due to light and temperature), leading to an insignificant error in the output change in frequency of the order of 0.46% when operated in light versus dark conditions. The uncertainty in readings due to background light was analyzed, and the error in the resistance was found to be of the order of 1.34 Ω, which confirms the high stability and selectivity of the proposed sensor under different background effects. Furthermore, the evolution of the graphene’s lattice defect density due to radiation was observed using Raman spectroscopy and SEM, indicating a lattice defect density of up to 1.780 × 10¹¹/cm² at 1 kGy gamma radiation, confirming the increase in the graphene resistance and proving the graphene’s sensitivity. In contrast, the graphene’s defect density in response to beta radiation was 0.683 × 10¹¹/cm² at 3 kGy beta radiation, which is significantly lower than the gamma effects. This can be attributed to the lower p-doping effect caused by beta irradiation in ambient conditions, compared with that caused by gamma irradiation. Morphological analysis was used to verify the evolution of the microstructural defects caused by ionizing irradiation. The proposed sensor monitors the low-to-medium cumulative range of ionizing radiations ranging from 0 to 1 kGy for gamma radiation and 0 to 9 kGy for beta radiation, with high resolution and selectivity, filling the research gap in the study of graphene-based radiation sensors at low-to-medium ionizing radiation doses. This range is essential for the pharmaceutical and food industries, as it spans the minimum range for affecting human health, causing cancer and DNA damage. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 3568 KiB

Open AccessArticle

Characterizing the Chemical Structure of Ti₃C₂T_x MXene by Angle-Resolved XPS Combined with Argon Ion Etching

by Yangfan Lu, Dongsheng Li and Fu Liu

Materials 2022, 15(1), 307; https://doi.org/10.3390/ma15010307 - 2 Jan 2022

Cited by 61 | Viewed by 7841

Abstract

Angle-resolved XPS combined with argon ion etching was used to characterize the surface functional groups and the chemical structure of Ti₃C₂T_x MXene. Survey scanning obtained on the sample surface showed that the sample mainly contains C, O, Ti [...] Read more.

Angle-resolved XPS combined with argon ion etching was used to characterize the surface functional groups and the chemical structure of Ti₃C₂T_x MXene. Survey scanning obtained on the sample surface showed that the sample mainly contains C, O, Ti and F elements, and a little Al element. Analyzing the angle-resolved narrow scanning of these elements indicated that a layer of C and O atoms was adsorbed on the top surface of the sample, and there were many O or F related Ti bonds except Ti–C bond. XPS results obtained after argon ion etching indicated staggered distribution between C–Ti–C bond and O–Ti–C, F–Ti bond. It is confirmed that Ti atoms and C atoms were at the center layer of Ti₃C₂T_x MXene, while O atoms and F atoms were located at both the upper and lower surface of Ti₃C₂ layer acting as surface functional groups. The surface functional groups on the Ti₃C₂ layer were determined to include O²⁻, OH⁻, F⁻ and O⁻–F⁻, among which F atoms could also desorb from Ti₃C₂T_x MXene easily. The schematic atomic structure of Ti₃C₂T_x MXene was derived from the analysis of XPS results, being consistent with theoretical chemical structure and other experimental reports. The results showed that angle-resolved XPS combing with argon ion etching is a good way to analysis 2D thin layer materials. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 2960 KiB

Open AccessArticle

Effect of Oxalic Acid Treatment on Conductive Coatings Formed by Ni@Ag Core–Shell Nanoparticles

by Anna Pajor-Świerzy, Radosław Pawłowski, Piotr Sobik, Alexander Kamyshny and Krzysztof Szczepanowicz

Materials 2022, 15(1), 305; https://doi.org/10.3390/ma15010305 - 1 Jan 2022

Cited by 3 | Viewed by 2712

Abstract

Low-cost metallic nanoink based on nickel–silver core–shell nanoparticles (Ni@Ag NPs) was used for the formation of conductive metallic coatings with low sintering temperature, which can be successfully applied for replacement of currently used silver-based nanoinks in printed electronics. The effect of oxalic acid [...] Read more.

Low-cost metallic nanoink based on nickel–silver core–shell nanoparticles (Ni@Ag NPs) was used for the formation of conductive metallic coatings with low sintering temperature, which can be successfully applied for replacement of currently used silver-based nanoinks in printed electronics. The effect of oxalic acid (OA) on the sintering temperature and conductivity of coatings formed by Ni@Ag NPs was evaluated. It was found that the addition of OA to the ink formulation and post-printing treatment of deposited films with this acid provided a noticeable decrease in the sintering temperature required for obtaining conductive patterns that is especially important for utilizing the polymeric substrates. The obtained resistivity of metallic coatings after sintering at temperature as low as 100 °C was found to be 30 µΩ·cm, only ~4 times higher compared to the resistivity of bulk Ni that is promising for future application of such materials for fabrication of low-cost flexible printed patterns. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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13 pages, 6932 KiB

Open AccessArticle

Mass Production of 3D Connective Graphene Networks by Fluidized Bed Chemical Vapor Deposition and Its Application in High Performance Lithium-Sulfur Battery

by Rongzheng Liu, Jian Zhao, Xu Yang, Malin Liu, Jiaxing Chang, Youlin Shao and Bing Liu

Nanomaterials 2022, 12(1), 150; https://doi.org/10.3390/nano12010150 - 31 Dec 2021

Cited by 9 | Viewed by 3311

Abstract

Three−dimensional (3D) graphene with novel nano−architectures exhibits many excellent properties and is promising for energy storage and conversion applications. Herein, a new strategy based on the fluidized bed chemical vapor deposition (FB−CVD) process was proposed to prepare 3D graphene networks (3DGNs) with various [...] Read more.

Three−dimensional (3D) graphene with novel nano−architectures exhibits many excellent properties and is promising for energy storage and conversion applications. Herein, a new strategy based on the fluidized bed chemical vapor deposition (FB−CVD) process was proposed to prepare 3D graphene networks (3DGNs) with various nano−architectures. Specially designed SiC−C@graphene core/shell nanoparticles were prepared taking the advantages of the FB−CVD system, and 3DGNs with hierarchical nanostructures were obtained after removing the SiC core. The 3DGNs performed well as electrodes of lithium–sulfur batteries. The C–S cathode showed good rate performance at the current density of 0.1–2.0 C, and an initial discharge capacity of 790 mAhg⁻¹ cathode was achieved at a current density of 0.2 C. The Li−S batteries showed stabilized coulombic efficiency as high as 94% and excellent cyclic performance with an ultra low cyclic fading rate of 0.075% for the initial 280 cycles at a current density of 1.0 C. The improved electrochemical performance was ascribed to the enhanced conductivity by the connective graphene networks and the weakened shuttle effect by the special outer graphene layers. Mass production of the products was realized by the continuous FB−CVD process, which opens up new perspectives for large scale application of 3D graphene materials. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 2209 KiB

Open AccessArticle

Dimensional Optimization of TiO₂ Nanodisk Photonic Crystals on Lead Iodide (MAPbI₃) Perovskite Solar Cells by Using FDTD Simulations

by Lilik Hasanah, Adryan Ashidiq, Roer Eka Pawinanto, Budi Mulyanti, Chandra Wulandari, Wiendartun and Ahmad Rifqi Md. Zain

Appl. Sci. 2022, 12(1), 351; https://doi.org/10.3390/app12010351 - 30 Dec 2021

Cited by 11 | Viewed by 3720

Abstract

Perovskite solar cells (PSC) are currently exhibiting reproducible high efficiency, low-cost manufacturing, and scalable electron transport layers (ETL), which are becoming increasingly important. The application of photonic crystals (PC) on solar cells has been proven to enhance light harvesting and lead solar cells [...] Read more.

Perovskite solar cells (PSC) are currently exhibiting reproducible high efficiency, low-cost manufacturing, and scalable electron transport layers (ETL), which are becoming increasingly important. The application of photonic crystals (PC) on solar cells has been proven to enhance light harvesting and lead solar cells to adjust the propagation and distribution of photons. In this paper, the optimization of a two-dimensional nanodisk PC introduced in ETL with an organic-inorganic lead-iodide perovskite (methylammonium lead-iodide, MAPbI₃) as the absorber layer was studied. A finite-difference time-domain (FDTD) simulation was used to evaluate the optical performance of PSC with various lattice constants and a radius of nanodisk photonic crystals. According to the simulation, the optimum lattice constant and PC radius applied to ETL are 500 nm and 225 nm, respectively. This optimum design enhances PSC absorption performance by more than 94% of incident light. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 2036 KiB

Open AccessArticle

Preparation and Characterization of Acrylic Pressure-Sensitive Adhesives Crosslinked with UV Radiation-Influence of Monomer Composition on Adhesive Properties

by Karolina Mozelewska, Zbigniew Czech, Marcin Bartkowiak, Małgorzata Nowak, Paulina Bednarczyk, Piotr Niezgoda, Janina Kabatc and Agnieszka Skotnicka

Materials 2022, 15(1), 246; https://doi.org/10.3390/ma15010246 - 29 Dec 2021

Cited by 11 | Viewed by 3923

Abstract

In this study, syntheses of acrylate copolymers were performed based on the monomers butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), and acrylic acid (AA) and the second-type unsaturated photoinitiator 4-acryloyloxybenzophenone (ABP). The structure of the obtained copolymers was confirmed via FT-IR spectroscopic analysis, and [...] Read more.

In this study, syntheses of acrylate copolymers were performed based on the monomers butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), and acrylic acid (AA) and the second-type unsaturated photoinitiator 4-acryloyloxybenzophenone (ABP). The structure of the obtained copolymers was confirmed via FT-IR spectroscopic analysis, and the viscosity and the content of non-volatile substances were determined. The adhesive films were then coated and cross-linked using ultraviolet radiation in the UV-C range at various doses (5–50 mJ/cm²). Due to the dependence of the self-adhesive properties of the adhesive layer on the basis weight, various basis weights of the layer in the range of 30–120 g/m² were tested. Finally, the self-adhesive properties were assessed: tack, peel adhesion, shear strength (cohesion) at 20 °C and 70 °C, as well as the SAFT test and shrinkage. The aim of the study was to determine the effect of the type of monomer used, the dose of ultraviolet radiation, and the basis weight on the self-adhesive and usable properties of the obtained self-adhesive tapes. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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18 pages, 4083 KiB

Open AccessEditor’s ChoiceArticle

Quantification of STEM Images in High Resolution SEM for Segmented and Pixelated Detectors

by Ivo Konvalina, Aleš Paták, Martin Zouhar, Ilona Müllerová, Tomáš Fořt, Marek Unčovský and Eliška Materna Mikmeková

Nanomaterials 2022, 12(1), 71; https://doi.org/10.3390/nano12010071 - 28 Dec 2021

Cited by 1 | Viewed by 2929

Abstract

The segmented semiconductor detectors for transmitted electrons in ultrahigh resolution scanning electron microscopes allow observing samples in various imaging modes. Typically, two standard modes of objective lens, with and without a magnetic field, differ by their resolution. If the beam deceleration mode is [...] Read more.

The segmented semiconductor detectors for transmitted electrons in ultrahigh resolution scanning electron microscopes allow observing samples in various imaging modes. Typically, two standard modes of objective lens, with and without a magnetic field, differ by their resolution. If the beam deceleration mode is selected, then an electrostatic field around the sample is added. The trajectories of transmitted electrons are influenced by the fields below the sample. The goal of this paper is a quantification of measured images and theoretical study of the capability of the detector to collect signal electrons by its individual segments. Comparison of measured and ray-traced simulated data were difficult in the past. This motivated us to present a new method that enables better comparison of the two datasets at the cost of additional measurements, so-called calibration curves. Furthermore, we also analyze the measurements acquired using 2D pixel array detector (PAD) that provide a more detailed angular profile. We demonstrate that the radial profiles of STEM and/or 2D-PAD data are sensitive to material composition. Moreover, scattering processes are affected by thickness of the sample as well. Hence, comparing the two experimental and simulation data can help to estimate composition or the thickness of the sample. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 20974 KiB

Open AccessArticle

Quantum Hall Effect across Graphene Grain Boundary

by Tuan Khanh Chau, Dongseok Suh and Haeyong Kang

Materials 2022, 15(1), 8; https://doi.org/10.3390/ma15010008 - 21 Dec 2021

Cited by 1 | Viewed by 4892

Abstract

Charge carrier scattering at grain boundaries (GBs) in a chemical vapor deposition (CVD) graphene reduces the carrier mobility and degrades the performance of the graphene device, which is expected to affect the quantum Hall effect (QHE). This study investigated the influence of individual [...] Read more.

Charge carrier scattering at grain boundaries (GBs) in a chemical vapor deposition (CVD) graphene reduces the carrier mobility and degrades the performance of the graphene device, which is expected to affect the quantum Hall effect (QHE). This study investigated the influence of individual GBs on the QH state at different stitching angles of the GB in a monolayer CVD graphene. The measured voltage probes of the equipotential line in the QH state showed that the longitudinal resistance (R_xx) was affected by the scattering of the GB only in the low carrier concentration region, and the standard QHE of a monolayer graphene was observed regardless of the stitching angle of the GB. In addition, a controlled device with an added metal bar placed in the middle of the Hall bar configuration was introduced. Despite the fact that the equipotential lines in the controlled device were broken by the additional metal bar, only the R_xx was affected by nonzero resistance, whereas the Hall resistance (R_xy) revealed the well-quantized plateaus in the QH state. Thus, our study clarifies the effect of individual GBs on the QH states of graphenes. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 1435 KiB

Open AccessArticle

Characterization of Graphenic Carbon Produced by Pulsed Laser Ablation of Sacrificial Carbon Tapes

by Igor V. Ershov, Anatoly A. Lavrentyev, Natalia V. Prutsakova, Olga M. Holodova, Irina V. Mardasova, Tatiana P. Zhdanova and Alexey T. Kozakov

Appl. Sci. 2021, 11(24), 11972; https://doi.org/10.3390/app112411972 - 16 Dec 2021

Cited by 7 | Viewed by 2316

Abstract

This paper reports on the pulsed laser deposition of nanocarbon films on metal and dielectric substrates, using high-purity sacrificial carbon tape as a carbon source on a neutral gas background. The films were characterized by X-ray diffraction (XRD), photoelectron (XPS) and Raman spectroscopy. [...] Read more.

This paper reports on the pulsed laser deposition of nanocarbon films on metal and dielectric substrates, using high-purity sacrificial carbon tape as a carbon source on a neutral gas background. The films were characterized by X-ray diffraction (XRD), photoelectron (XPS) and Raman spectroscopy. The XRD and Raman structural analyses revealed that the synthesized films have a graphenic nanocrystalline turbostratic structure, with sp² clusters about 15–18 nm in size, depending on the laser fluence. A significant decrease in the oxygen and hydrogen contents in the films, in comparison with the target material, was established using XPS, as well as a significant decrease in the sp³ carbon content. The deposited films were found to be similar to reduced graphene oxide (rGO) in composition, with a surprisingly low number of defects in the sp²-matrix. The method proposed in the work may have good prospects of application in the production of energy storage and nonvolatile memory devices. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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13 pages, 3043 KiB

Open AccessArticle

Enhanced Photocurrent of the Ag Interfaced Topological Insulator Bi₂Se₃ under UV- and Visible-Light Radiations

by Chih-Chiang Wang, Pao-Tai Lin, Fuh-Sheng Shieu and Han-Chang Shih

Nanomaterials 2021, 11(12), 3353; https://doi.org/10.3390/nano11123353 - 10 Dec 2021

Cited by 14 | Viewed by 3576

Abstract

Bi₂Se₃ is a topological quantum material that is used in photodetectors, owing to its narrow bandgap, conductive surface, and insulating bulk. In this work, Ag@Bi₂Se₃ nanoplatelets were synthesized on Al₂O₃(100) substrates in a [...] Read more.

Bi₂Se₃ is a topological quantum material that is used in photodetectors, owing to its narrow bandgap, conductive surface, and insulating bulk. In this work, Ag@Bi₂Se₃ nanoplatelets were synthesized on Al₂O₃(100) substrates in a two-step process of thermal evaporation and magnetron sputtering. X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) revealed that all samples had the typical rhombohedral Bi₂Se₃. Field-emission scanning electron microscopy (FESEM)-energy dispersive x-ray spectroscopy (EDS), XPS, and HRTEM confirmed the presence of the precipitated Ag. The optical absorptance of Bi₂Se₃ nanoplatelets in UV-visible range decreased with the Ag contents. Results of photocurrent measurements under zero-bias conditions revealed that the deposited Ag affected photosensitivity. A total of 7.1 at.% Ag was associated with approximately 4.25 and 4.57 times higher photocurrents under UV and visible light, respectively, than 0 at.% Ag. The photocurrent in Bi₂Se₃ at 7.1 at.% Ag under visible light was 1.72-folds of that under UV light. This enhanced photocurrent is attributable to the narrow bandgap (~0.35 eV) of Bi₂Se₃ nanoplatelets, the Schottky field at the interface between Ag and Bi₂Se₃, the surface plasmon resonance that is caused by Ag, and the highly conductive surface that is formed from Ag and Bi₂Se₃. This work suggests that the appropriate Ag deposition enhances the photocurrent in, and increases the photosensitivity of, Bi₂Se₃ nanoplatelets under UV and visible light. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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11 pages, 4001 KiB

Open AccessArticle

Structural Disorder in Layered Hybrid Halide Perovskites: Types of Stacking Faults, Influence on Optical Properties and Their Suppression by Crystallization Engineering

by Andrei S. Tutantsev, Ekaterina I. Marchenko, Natalia N. Udalova, Sergey A. Fateev, Eugene A. Goodilin and Alexey B. Tarasov

Nanomaterials 2021, 11(12), 3333; https://doi.org/10.3390/nano11123333 - 8 Dec 2021

Cited by 8 | Viewed by 3759

Abstract

Layered hybrid halide perovskites (LHHPs) are an emerging type of semiconductor with a set of unique optoelectronic properties. However, the solution processing of high-quality LHHPs films with desired optical properties and phase composition is a challenging task, possibly due to the structural disorder [...] Read more.

Layered hybrid halide perovskites (LHHPs) are an emerging type of semiconductor with a set of unique optoelectronic properties. However, the solution processing of high-quality LHHPs films with desired optical properties and phase composition is a challenging task, possibly due to the structural disorder in the LHHP phase. Nevertheless, there is still a lack of experimental evidence and understanding of the nature of the structural disorder in LHHPs and its influence on the optical properties of the material. In the current work, using 2D perovskites (C₄H₉NH₃)₂(CH₃NH₃)_n−1Pb_nI_3n+1 (further BA₂MA_n−1Pb_nI_3n+1) with n = 1–4 as a model system, we demonstrate that deviations in LHHPs optical properties and X-ray diffraction occur due to the presence of continuous defects—Stacking Faults (SFs). Upon analyzing the experimental data and modeled XRD patterns of a possible set of stacking faults (SFs) in the BA₂MAPb₂I₇ phase, we uncover the most plausible type of SFs, featured by the thickness variation within one perovskite slab. We also demonstrate the successful suppression of SFs formation by simple addition of BAI excess into BA₂MA_n−1Pb_nI_3n+1 solutions. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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7 pages, 1610 KiB

Open AccessArticle

Enhancement of InSe Field-Effect-Transistor Performance against Degradation of InSe Film in Air Environment

by Yadong Zhang, Xiaoting Sun, Kunpeng Jia, Huaxiang Yin, Kun Luo, Jiahan Yu and Zhenhua Wu

Nanomaterials 2021, 11(12), 3311; https://doi.org/10.3390/nano11123311 - 6 Dec 2021

Cited by 9 | Viewed by 3450

Abstract

The degradation of InSe film and its impact on field effect transistors are investigated. After the exposure to atmospheric environment, 2D InSe flakes produce irreversible degradation that cannot be stopped by the passivation layer of h-BN, causing a rapid decrease for InSe FETs [...] Read more.

The degradation of InSe film and its impact on field effect transistors are investigated. After the exposure to atmospheric environment, 2D InSe flakes produce irreversible degradation that cannot be stopped by the passivation layer of h-BN, causing a rapid decrease for InSe FETs performance, which is attributed to the large number of traps formed by the oxidation of 2D InSe and adsorption to impurities. The residual photoresist in lithography can cause unwanted doping to the material and reduce the performance of the device. To avoid contamination, a high-performance InSe FET is achieved by a using hard shadow mask instead of the lithography process. The high-quality channel surface is manifested by the hysteresis of the transfer characteristic curve. The hysteresis of InSe FET is less than 0.1 V at V_d of 0.2, 0.5, and 1 V. And a high on/off ratio of 1.25 × 10⁸ is achieved, as well relative high I_on of 1.98 × 10⁻⁴ A and low SS of 70.4 mV/dec at V_d = 1 V are obtained, demonstrating the potential for InSe high-performance logic device. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 2437 KiB

Open AccessCommunication

hBN Flake Embedded Al₂O₃ Thin Film for Flexible Moisture Barrier

by Wonseok Jang, Seunghun Han, Taejun Gu, Heeyeop Chae and Dongmok Whang

Materials 2021, 14(23), 7373; https://doi.org/10.3390/ma14237373 - 1 Dec 2021

Cited by 3 | Viewed by 2994

Abstract

Due to the vulnerability of organic optoelectronic devices to moisture and oxygen, thin-film moisture barriers have played a critical role in improving the lifetime of the devices. Here, we propose a hexagonal boron nitride (hBN) embedded Al₂O₃ thin film as [...] Read more.

Due to the vulnerability of organic optoelectronic devices to moisture and oxygen, thin-film moisture barriers have played a critical role in improving the lifetime of the devices. Here, we propose a hexagonal boron nitride (hBN) embedded Al₂O₃ thin film as a flexible moisture barrier. After layer-by-layer (LBL) staking of polymer and hBN flake composite layer, Al₂O₃ was deposited on the nano-laminate template by spatial plasma atomic layer deposition (PEALD). Because the hBN flakes in Al₂O₃ thin film increase the diffusion path of moisture, the composite layer has a low water vapor transmission ratio (WVTR) value of 1.8 × 10⁻⁴ g/m² day. Furthermore, as embedded hBN flakes restrict crack propagation, the composite film exhibits high mechanical stability in repeated 3 mm bending radius fatigue tests. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 1300 KiB

Open AccessEditor’s ChoiceArticle

The High Coercivity Field in Chemically Bonded WSe₂/MoSe₂ Powder

by Shiu-Ming Huang, Pin-Cyuan Chen and Pin-Cing Wang

Nanomaterials 2021, 11(12), 3263; https://doi.org/10.3390/nano11123263 - 1 Dec 2021

Cited by 3 | Viewed by 2484

Abstract

We studied the magnetic properties of WSe

_{2}

/MoSe

_{2}

powder. The coercivity field reaches 2600 Oe at 5 K, 4233 Oe at 100 K and 1300 Oe at 300 K. These are the highest values reported for two-dimensional transition metal dichalcogenides. This [...] Read more.

We studied the magnetic properties of WSe

_{2}

/MoSe

_{2}

powder. The coercivity field reaches 2600 Oe at 5 K, 4233 Oe at 100 K and 1300 Oe at 300 K. These are the highest values reported for two-dimensional transition metal dichalcogenides. This study is different from the widely reported vacancy and zigzag structure-induced ferromagnetism studies. Importantly, a Raman peak red shift was observed, and that supports the chemical bonding at the interface between WSe

_{2}

and MoSe

_{2}

. The large coercivity field originates from the chemical bonding-induced structural distortion at the interface between WSe

_{2}

and MoSe

_{2}

. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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17 pages, 3478 KiB

Open AccessArticle

NanoTraPPED—A New Method for Determining the Surface Energy of Nanoparticles via Pickering Emulsion Polymerization

by Andrei Honciuc and Oana-Iuliana Negru

Nanomaterials 2021, 11(12), 3200; https://doi.org/10.3390/nano11123200 - 25 Nov 2021

Cited by 10 | Viewed by 3264

Abstract

Surface energy with its polar and disperse components describes the physicochemical state of nanoparticles’ (NPs) surfaces, and can be a valuable parameter for predicting their bulk behavior in powders. Here, we introduce a new method, namely, Nanoparticles Trapped on Polymerized Pickering Emulsion Droplets [...] Read more.

Surface energy with its polar and disperse components describes the physicochemical state of nanoparticles’ (NPs) surfaces, and can be a valuable parameter for predicting their bulk behavior in powders. Here, we introduce a new method, namely, Nanoparticles Trapped on Polymerized Pickering Emulsion Droplets (NanoTraPPED), for measuring the surface energy of a series of silica NPs bearing various surface functional groups. The method consists in creating Pickering emulsions from vinyl bearing monomers, immiscible with water, whereas NPs of interest have a stabilizing role, and in the process, become trapped at the monomer/water interface of emulsion droplets. The Pickering emulsion is polymerized, and polymer microspheres (colloidosomes) decorated with NPs are obtained. NanoTraPPED relies on measuring contact angles from the immersion depth of nanoparticles at the interface of various polymer colloidosomes with the electron microscope. The contact angle values are used as input for the Owens-Wendt-Rabel-Kaelble (OWRK) model, to quantitatively determine the total surface energy with water γ_NP/water, air γ_NP, and the corresponding polar and dispersive interaction components of NPs carrying -NH₂, -SH, -OH, -CN and -C8 surface functional groups, ranking these according to their polarity. Our findings were confirmed independently by calculating the interfacial desorption energies of NPs from contact angles. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 2956 KiB

Open AccessArticle

Synthesis of SDS-Modified Pt/Ti₃C₂T_x Nanocomposite Catalysts and Electrochemical Performance for Ethanol Oxidation

by Beibei Yang, Tian Qin, Ziping Bao, Wenqian Lu, Jiayu Dong, Duan Bin and Hongbin Lu

Nanomaterials 2021, 11(12), 3174; https://doi.org/10.3390/nano11123174 - 23 Nov 2021

Cited by 7 | Viewed by 2635

Abstract

It is well-known that platinum (Pt) is still the preferred material of anode catalyst in ethanol oxidation, however, the prohibitive high cost and CO poisoning of Pt metal impede the commercialization of fuel cells. Therefore, improving the utilization rate of catalysts and reduce [...] Read more.

It is well-known that platinum (Pt) is still the preferred material of anode catalyst in ethanol oxidation, however, the prohibitive high cost and CO poisoning of Pt metal impede the commercialization of fuel cells. Therefore, improving the utilization rate of catalysts and reduce the cost of catalyst become one of the most concerned focus in the construction of fuel cells. In this work, the Pt-based catalysts are synthesized by using different content of sodium dodecyl sulfate (SDS) modified-Ti₃C₂T_x support, and the dispersion regulation function of SDS modified-Ti₃C₂T_x supported on Pt nanoparticles is investigated. The structure, composition and morphology of different catalysts are characterized by X-ray diffraction (XRD), X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and high-resolution TEM, respectively. It is found that the Pt nanoparticles in pure Ti₃C₂T_x surface are serious aggregated and show poor dispersion, whereas the Pt nanoparticles in SDS modified-Ti₃C₂T_x have a better dispersion. The electrochemical results revealed that SDS modified-Ti₃C₂T_x supported Pt nanoparticles has higher electrocatalytic activity and stability in both acidic and alkaline ethanol oxidation when the dosage of SDS increases to 100 mg. These findings indicate that the SDS-Ti₃C₂T_x/Pt catalysts show a promising future of potential applications in fuel cells with modification of Ti₃C₂T_x support. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 3831 KiB

Open AccessArticle

Computational Study of the Curvature-Promoted Anchoring of Transition Metals for Water Splitting

by Weiwei Liu, Youchao Kong, Bo Wang, Xiaoshuang Li, Pengfei Liu, Alain R. Puente Santiago and Tianwei He

Nanomaterials 2021, 11(12), 3173; https://doi.org/10.3390/nano11123173 - 23 Nov 2021

Cited by 7 | Viewed by 2821

Abstract

Generating clean and sustainable hydrogen from water splitting processes represent a practical alternative to solve the energy crisis. Ultrathin two-dimensional materials exhibit attractive properties as catalysts for hydrogen production owing to their large surface-to-volume ratios and effective chemisorption sites. However, the catalytically inactive [...] Read more.

Generating clean and sustainable hydrogen from water splitting processes represent a practical alternative to solve the energy crisis. Ultrathin two-dimensional materials exhibit attractive properties as catalysts for hydrogen production owing to their large surface-to-volume ratios and effective chemisorption sites. However, the catalytically inactive surfaces of the transition metal dichalcogenides (TMD) possess merely small areas of active chemical sites on the edge, thus decreasing their possibilities for practical applications. Here, we propose a new class of out-of-plane deformed TMD (cTMD) monolayer to anchor transition metal atoms for the activation of the inert surface. The calculated adsorption energy of metals (e.g., Pt) on curved MoS₂ (cMoS₂) can be greatly decreased by 72% via adding external compressions, compared to the basal plane. The enlarged diffusion barrier energy indicates that cMoS₂ with an enhanced fixation of metals could be a potential candidate as a single atom catalyst (SAC). We made a well-rounded assessment of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), which are two key processes in water splitting. The optimized Gibbs free energy of 0.02 for HER and low overpotential of 0.40 V for OER can be achieved when the proper compression and supported metals are selected. Our computational results provide inspiration and guidance towards the experimental design of TMD-based SACs. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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9 pages, 2928 KiB

Open AccessArticle

PVP-Assisted Shellac Nanofiber Membrane as Highly Efficient, Eco-Friendly, Translucent Air Filter

by Shanshuai Lu, Congling Li, Rui Liu and Aifeng Lv

Appl. Sci. 2021, 11(23), 11094; https://doi.org/10.3390/app112311094 - 23 Nov 2021

Cited by 10 | Viewed by 2748

Abstract

Particulate matter (PM), composed of tiny solids and liquid droplets in polluted air, poses a serious threat to human health. Traditional air filters usually cause secondary pollution due to their poor degradability. Here, shellac, as an environmentally friendly natural organic material, was successfully [...] Read more.

Particulate matter (PM), composed of tiny solids and liquid droplets in polluted air, poses a serious threat to human health. Traditional air filters usually cause secondary pollution due to their poor degradability. Here, shellac, as an environmentally friendly natural organic material, was successfully applied to fabricate biodegradable air filters. Since pure shellac fiber shows poor mechanical properties and bad light transmittance, we then introduced a small amount of polyvinylpyrrolidone (PVP) in the shellac solution to prepare highly efficient air filter membranes by the electrospinning method. The prepared PVP-assisted shellac nanofiber membrane (P-Shellac FME) demonstrated improved filtration efficiencies as high as 95% and 98% for PM_2.5 and PM₁₀, respectively. The P-Shellac FME also showed good stability, with filtration efficiencies still above 90% and 95% for PM_2.5 and PM₁₀ even after six hours of air filtering under high PM concentrations. The pressure drop going through the filter was only 101 Pa, which is also comparable to the value of 76 Pa obtained using commercial polypropylene nanofibers (PP nanofibers, peeled off from the surgical mask), indicating good air permeability of P-Shellac FME. Additionally, P-Shellac FME also showed the advantages of translucence, biodegradability, improved mechanical properties, and low cost. We believe that the P-Shellac FME will make a significant contribution in the application of air filtration. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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12 pages, 3982 KiB

Open AccessArticle

Hydrothermal Synthesis of 1T-MoS₂/Pelagic Clay Composite and Its Application in the Catalytic Reduction of 4-Nitrophenol

by Nan Li, Qiwei Sun, Peiping Zhang and Shubo Jing

Materials 2021, 14(22), 7020; https://doi.org/10.3390/ma14227020 - 19 Nov 2021

Cited by 7 | Viewed by 2189

Abstract

Pelagic clay is an emerging marine resource with strong hydrophilicity, fine particles and a large specific surface area. In this work, a 1T-MoS₂/pelagic clay composite was fabricated by hydrothermal synthesis. In the composite, 1T-MoS₂ nanosheets are evenly dispersed on the [...] Read more.

Pelagic clay is an emerging marine resource with strong hydrophilicity, fine particles and a large specific surface area. In this work, a 1T-MoS₂/pelagic clay composite was fabricated by hydrothermal synthesis. In the composite, 1T-MoS₂ nanosheets are evenly dispersed on the surface of the clay minerals, significantly reducing the agglomeration of MoS₂. Compared with pure 1T-MoS₂, the 1T-MoS₂ nanosheets generated on the surface of pelagic clay have significantly smaller lateral dimensions and thicknesses. Moreover, the specific surface area is much larger than that of the pure 1T-MoS₂ nanosheets fabricated by the same method, indicating that the active sites of the MoS₂ sheets are fully exposed. In addition, the composite exhibited excellent hydrophilicity, leading to a high dispersibility in aqueous solutions. In this work, the composite was used as a catalyst in the reduction of 4-nitrophenol (4-NP), and the conversion of 4-NP reached up to 96.7%. This result shows that the 1T-MoS₂/pelagic clay composite is a promising catalyst in a variety of reactions. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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18 pages, 5143 KiB

Open AccessArticle

Factors Influencing the Hydration, Dimensional Stability, and Strength Development of the OPC-CSA-Anhydrite Ternary System

by Zhenzhen Yang, Hansong Ye, Qiang Yuan, Baiyun Li, Yuelin Li and Dajun Zhou

Materials 2021, 14(22), 7001; https://doi.org/10.3390/ma14227001 - 18 Nov 2021

Cited by 22 | Viewed by 3134

Abstract

Due to the advantages of high early strength and rapid setting, ternary systems consisting of ordinary Portland clinker (OPC), calcium sulphoaluminate (CSA) clinker, and anhydrite have broad application prospects. However, further studies need to be undertaken to find a more optimal mixing proportion [...] Read more.

Due to the advantages of high early strength and rapid setting, ternary systems consisting of ordinary Portland clinker (OPC), calcium sulphoaluminate (CSA) clinker, and anhydrite have broad application prospects. However, further studies need to be undertaken to find a more optimal mixing proportion of this ternary binder in order to meet basic performance requirements. In this paper, isothermal calorimetric tests, chemical shrinkage tests, drying shrinkage tests, and compressive strength tests were carried out to systematically identify the effect of the OPC/CSA ratio and anhydrite dosage on the hydration, mechanical property development, and dimensional stability of ternary binders. It was found that a higher CSA content leads to a higher cumulative hydration heat, a shorter acceleration period, and a delayed induction period, which can be ascribed to the retardation of C₃S at a high aluminate concentration. However, a higher addition of anhydrite can retard the main peak of hydration despite promoting the intermediate peak and improving the hydration reaction rate. The drying shrinkage of blends decreases first along with the CSA proportion and then increases. Moreover, a higher anhydrite content mitigates the drying shrinkage and hinders the strength development. Finally, considering the properties of both the fresh and hardened binder, the ternary blends with 5% anhydrite and OPC/CSA ratios ranging from 3/7 to 2/8 were identified as most suitable for applications that require a high early strength, stable late strength, and small level of shrinkage. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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16 pages, 5225 KiB

Open AccessArticle

Self-Assembled Polyaniline/Ti₃C₂T_x Nanocomposites for High-Performance Electrochromic Films

by Tao Lin, Wenlong Liu, Bin Yan, Jing Li, Yi Lin, Yinghui Zhao, Zheng Shi and Sheng Chen

Nanomaterials 2021, 11(11), 2956; https://doi.org/10.3390/nano11112956 - 4 Nov 2021

Cited by 26 | Viewed by 4449

Abstract

Electrochromic materials and devices are attracting intense attention because of their low energy consumption and open-circuit memory effect. Considering the difficult processing characteristics of electrochromic conductive polymers, we developed a facile and scalable strategy to prepare solution processable polyaniline (PANI)-based nanocomposites by introducing [...] Read more.

Electrochromic materials and devices are attracting intense attention because of their low energy consumption and open-circuit memory effect. Considering the difficult processing characteristics of electrochromic conductive polymers, we developed a facile and scalable strategy to prepare solution processable polyaniline (PANI)-based nanocomposites by introducing two-dimensional titanium carbon nanosheets (MXene) through a self-assembly approach. The PANI/MXene nanocomposite can be fabricated into porous films via spray-coating process, which show an obvious synergetic effect of both materials, leading to superior electrochromic properties. The optical contrast of the optimized PANI/MXene film reached as high as 55% at =700 nm, and its response times were 1.3 s for coloration and 2.0 s for bleaching, respectively. In addition, the composite film also showed excellent cycle stability (after 500 cycles, the ΔT retention was above 87%). The improved electrochromic properties are owed to the high conductivity of MXene and the formation of the porous composite film structure, which promote the electronic/ionic transfer and migration efficiency. This research suggests that the self-assembly method and the conductive polymer/MXene nanocomposites have a potential application in the fields of electronic functional films and devices. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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15 pages, 4318 KiB

Open AccessArticle

Activated Carbon Derived from Carbonization of Kevlar Waste Materials: A Novel Single Stage Method

by Daniel Karthik, Vijay Baheti, Jiri Militky, Muhammad Salman Naeem, Veronika Tunakova and Azam Ali

Materials 2021, 14(21), 6433; https://doi.org/10.3390/ma14216433 - 27 Oct 2021

Cited by 21 | Viewed by 3293

Abstract

The augmented demands of textile materials over time have brought challenges in the disposal of substantial volumes of waste generated during the processing and end of life of such materials. Taking into consideration environmental safety due to discarding of textile waste, it becomes [...] Read more.

The augmented demands of textile materials over time have brought challenges in the disposal of substantial volumes of waste generated during the processing and end of life of such materials. Taking into consideration environmental safety due to discarding of textile waste, it becomes critical to recuperate useful products from such waste for economic reasons. The present work deals with the preparation of porous and electrically conductive activated carbon fabric by a novel single stage method of simultaneous carbonization and physical activation of Kevlar feedstock material procured from local industries, for effective electromagnetic (EM) shielding applications. The Kevlar fabric waste was directly carbonized under a layer of charcoal without any intermediate stabilization step at 800 °C, 1000 °C, and 1200 °C, with a heating rate of 300 °C/h and without any holding time. The physical and morphological properties of the activated carbon, influenced by carbonization process parameters, were characterized from EDX, X-ray diffraction, SEM analysis, and BET analysis. Furthermore, the electrical conductivity was analyzed. Finally, the potential application of the activated material for EM shielding effectiveness was analyzed at low (below 1.5 GHz) and high (2.45 GHz) frequencies. The phenomena of multiple internal reflections and absorption of electromagnetic radiations was found dominant in the case of activated carbon fabric produced at higher carbonization temperatures. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 15160 KiB

Open AccessArticle

MoTe₂ Field-Effect Transistors with Low Contact Resistance through Phase Tuning by Laser Irradiation

by Geun Yeol Bae, Jinsung Kim, Junyoung Kim, Siyoung Lee and Eunho Lee

Nanomaterials 2021, 11(11), 2805; https://doi.org/10.3390/nano11112805 - 22 Oct 2021

Cited by 14 | Viewed by 4698

Abstract

Due to their extraordinary electrical and physical properties, two-dimensional (2D) transition metal dichalcogenides (TMDs) are considered promising for use in next-generation electrical devices. However, the application of TMD-based devices is limited because of the Schottky barrier interface resulting from the absence of dangling [...] Read more.

Due to their extraordinary electrical and physical properties, two-dimensional (2D) transition metal dichalcogenides (TMDs) are considered promising for use in next-generation electrical devices. However, the application of TMD-based devices is limited because of the Schottky barrier interface resulting from the absence of dangling bonds on the TMDs’ surface. Here, we introduce a facile phase-tuning approach for forming a homogenous interface between semiconducting hexagonal (2H) and semi-metallic monoclinic (1T′) molybdenum ditelluride (MoTe₂). The formation of ohmic contacts increases the charge carrier mobility of MoTe₂ field-effect transistor devices to 16.1 cm² V⁻¹s⁻¹ with high reproducibility, while maintaining a high on/off current ratio by efficiently improving charge injection at the interface. The proposed method enables a simple fabrication process, local patterning, and large-area scaling for the creation of high-performance 2D electronic devices. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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7 pages, 1703 KiB

Open AccessArticle

Hexagonal Boron Nitride Passivation Layer for Improving the Performance and Reliability of InGaN/GaN Light-Emitting Diodes

by Gun-Hee Lee, Tran-Viet Cuong, Dong-Kyu Yeo, Hyunjin Cho, Beo-Deul Ryu, Eun-Mi Kim, Tae-Sik Nam, Eun-Kyung Suh, Tae-Hoon Seo and Chang-Hee Hong

Appl. Sci. 2021, 11(19), 9321; https://doi.org/10.3390/app11199321 - 8 Oct 2021

Cited by 5 | Viewed by 2554

Abstract

We introduce a low temperature process for coating InGaN/GaN light-emitting diodes (LEDs) with h-BN as a passivation layer. The effect of h-BN on device performance and reliability is investigated. At −5 V, the leakage current of the h-BN passivated LED was −1.15 × [...] Read more.

We introduce a low temperature process for coating InGaN/GaN light-emitting diodes (LEDs) with h-BN as a passivation layer. The effect of h-BN on device performance and reliability is investigated. At −5 V, the leakage current of the h-BN passivated LED was −1.15 × 10⁻⁹ A, which was one order lower than the reference LED’s leakage current of −1.09 × 10⁻⁸ A. The h-BN layer minimizes the leakage current characteristics and operating temperature by acting as a passivation and heat dispersion layer. With a reduced working temperature of 33 from 45 °C, the LED lifetime was extended 2.5 times following h-BN passivation. According to our findings, h-BN passivation significantly improves LED reliability. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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11 pages, 5972 KiB

Open AccessArticle

Switchable Interlayer Magnetic Coupling of Bilayer CrI₃

by Yue Jiang, Yandong Guo, Xiaohong Yan, Hongli Zeng, Liyan Lin and Xinyi Mou

Nanomaterials 2021, 11(10), 2509; https://doi.org/10.3390/nano11102509 - 27 Sep 2021

Cited by 5 | Viewed by 3203

Abstract

Due to the weak van der Waals (vdW) interlayer interaction, interfacial geometry of two-dimensional (2D) magnetic vdW materials can be freely assembled, and the stacking order between layers can be readily controlled, such as laterally shifting or rotating, which may trigger the variation [...] Read more.

Due to the weak van der Waals (vdW) interlayer interaction, interfacial geometry of two-dimensional (2D) magnetic vdW materials can be freely assembled, and the stacking order between layers can be readily controlled, such as laterally shifting or rotating, which may trigger the variation of magnetic order. We investigate the H-type bilayer CrI

_{3}

where the two layers are aligned in anti-parallel directions. Based on first-principles calculations, we propose two states with different interlayer magnetic couplings, i.e., ferromagnetic and antiferromagnetic, and analyze the superexchange mechanism inside. It is found that the two magnetic coupling states are stacking-dependent, and could be switched by applying out-of-plane axial strain and electron doping. Our findings show great application potential in the design of heterostructural and spintronic devices based on 2D magnetic vdW materials. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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18 pages, 4934 KiB

Open AccessArticle

Low-Energy Electron Inelastic Mean Free Path of Graphene Measured by a Time-of-Flight Spectrometer

by Ivo Konvalina, Benjamin Daniel, Martin Zouhar, Aleš Paták, Ilona Müllerová, Luděk Frank, Jakub Piňos, Lukáš Průcha, Tomáš Radlička, Wolfgang S. M. Werner and Eliška Materna Mikmeková

Nanomaterials 2021, 11(9), 2435; https://doi.org/10.3390/nano11092435 - 18 Sep 2021

Cited by 9 | Viewed by 3800

Abstract

The detailed examination of electron scattering in solids is of crucial importance for the theory of solid-state physics, as well as for the development and diagnostics of novel materials, particularly those for micro- and nanoelectronics. Among others, an important parameter of electron scattering [...] Read more.

The detailed examination of electron scattering in solids is of crucial importance for the theory of solid-state physics, as well as for the development and diagnostics of novel materials, particularly those for micro- and nanoelectronics. Among others, an important parameter of electron scattering is the inelastic mean free path (IMFP) of electrons both in bulk materials and in thin films, including 2D crystals. The amount of IMFP data available is still not sufficient, especially for very slow electrons and for 2D crystals. This situation motivated the present study, which summarizes pilot experiments for graphene on a new device intended to acquire electron energy-loss spectra (EELS) for low landing energies. Thanks to its unique properties, such as electrical conductivity and transparency, graphene is an ideal candidate for study at very low energies in the transmission mode of an electron microscope. The EELS are acquired by means of the very low-energy electron microspectroscopy of 2D crystals, using a dedicated ultra-high vacuum scanning low-energy electron microscope equipped with a time-of-flight (ToF) velocity analyzer. In order to verify our pilot results, we also simulate the EELS by means of density functional theory (DFT) and the many-body perturbation theory. Additional DFT calculations, providing both the total density of states and the band structure, illustrate the graphene loss features. We utilize the experimental EELS data to derive IMFP values using the so-called log-ratio method. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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10 pages, 2377 KiB

Open AccessArticle

Energy Gaps in BN/GNRs Planar Heterostructure

by Jinyue Guan and Lei Xu

Materials 2021, 14(17), 5079; https://doi.org/10.3390/ma14175079 - 5 Sep 2021

Cited by 1 | Viewed by 2313

Abstract

Using the tight-binding approach, we study the band gaps of boron nitride (BN)/ graphene nanoribbon (GNR) planar heterostructures, with GNRs embedded in a BN sheet. The width of BN has little effect on the band gap of a heterostructure. The band gap oscillates [...] Read more.

Using the tight-binding approach, we study the band gaps of boron nitride (BN)/ graphene nanoribbon (GNR) planar heterostructures, with GNRs embedded in a BN sheet. The width of BN has little effect on the band gap of a heterostructure. The band gap oscillates and decreases from 2.44 eV to 0.26 eV, as the width of armchair GNRs,

n_{A}

, increases from 1 to 20, while the band gap gradually decreases from 3.13 eV to 0.09 eV, as the width of zigzag GNRs,

n_{Z}

, increases from 1 to 80. For the planar heterojunctions with either armchair-shaped or zigzag-shaped edges, the band gaps can be manipulated by local potentials, leading to a phase transition from semiconductor to metal. In addition, the influence of lattice mismatch on the band gap is also investigated. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials)

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