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Nanomaterials, Volume 9, Issue 9 (September 2019)

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Open AccessArticle
Vertically Aligned NiCo2O4 Nanosheet-Encapsulated Carbon Fibers as a Self-Supported Electrode for Superior Li+ Storage Performance
Nanomaterials 2019, 9(9), 1336; https://doi.org/10.3390/nano9091336 - 18 Sep 2019
Abstract
Binary transition metal oxides (BTMOs) have been explored as promising candidates in rechargeable lithium-ion battery (LIB) anodes due to their high specific capacity and environmental benignity. Herein, 2D ultrathin NiCo2O4 nanosheets vertically grown on a biomass-derived carbon fiber substrate (NCO [...] Read more.
Binary transition metal oxides (BTMOs) have been explored as promising candidates in rechargeable lithium-ion battery (LIB) anodes due to their high specific capacity and environmental benignity. Herein, 2D ultrathin NiCo2O4 nanosheets vertically grown on a biomass-derived carbon fiber substrate (NCO NSs/BCFs) were obtained by a facile synthetic strategy. The BCF substrate has superior flexibility and mechanical strength and thus not only offers a good support to NCO NSs/BCFs composites, but also provides high-speed paths for electron transport. Furthermore, 2D NiCo2O4 nanosheets grown vertically present a large contact area between the electrode and the electrolyte, which shortens the ions/electrons transport distance. The nanosheets structure can effectively limit the volume change derived from Li+ insertion and extraction, thus improving the stability of the electrode material. Therefore, the synthesized self-supporting NCO NSs/BCFs electrode displays excellent electrochemical performance, such as a large reversible capacity of 1128 mA·h·g−1 after 80 cycles at a current density of 100 mA·g−1 and a good rate capability of 818.5 mA·h·g−1 at 1000 mA·g−1. Undoubtedly, the cheap biomass carbon source and facile synthesis strategy here described can be extended to other composite materials for high-performance energy-storage and conversion devices. Full article
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Open AccessArticle
A Label-Free Electrochemical Immunosensor for Detection of the Tumor Marker CA242 Based on Reduced Graphene Oxide-Gold-Palladium Nanocomposite
Nanomaterials 2019, 9(9), 1335; https://doi.org/10.3390/nano9091335 - 18 Sep 2019
Abstract
As a tumor marker, carbohydrate antigen 24-2 (CA242) is a highly accurate and specific diagnostic indicator for monitoring pancreatic and colorectal cancers. The goal of this study was to create a novel label-free electrochemical immunosensor using a nanocomposite glassy carbon electrode for the [...] Read more.
As a tumor marker, carbohydrate antigen 24-2 (CA242) is a highly accurate and specific diagnostic indicator for monitoring pancreatic and colorectal cancers. The goal of this study was to create a novel label-free electrochemical immunosensor using a nanocomposite glassy carbon electrode for the detection of CA242. Graphene oxide (GO) and polyvinyl pyrrolidone were chosen as the dopants for the preparation of a high-performance reduced-GO-gold-palladium (rGO-Au-Pd) nanocomposite. RGO-Au-Pd was characterized using X-ray diffraction and transmission electron microscopy, revealing that the material exhibited superior electrochemical redox activity and electron transfer ability. The effects of the synthesis method, material concentration, reduction cycle, and pH were investigated to optimize the performance of the immunosensor. As a result of the catalytic activity and biocompatibility of rGO-Au-Pd, the prepared CA242 immunosensor displayed a wide linear range of detection from 0.001 U/mL to 10,000 U/mL with a detection limit of 1.54 × 10−3 U/mL and a sensitivity of 4.24 μA (log10CCA242)−1. More importantly, the immunosensor exhibited satisfactory reproducibility and selectivity when detected CA242 in PBS or human serum. The results of our study provide a platform for the development of novel bioassays for use in early cancer diagnosis and promote the application of biosensing technology in the medical field. Full article
(This article belongs to the Special Issue Biosensors Based on Nanostructure Materials)
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Open AccessArticle
Ni0.5Cu0.5Co2O4 Nanocomposites, Morphology, Controlled Synthesis, and Catalytic Performance in the Hydrolysis of Ammonia Borane for Hydrogen Production
Nanomaterials 2019, 9(9), 1334; https://doi.org/10.3390/nano9091334 - 18 Sep 2019
Abstract
The catalytic hydrolysis of ammonia borane (AB) is a promising route to produce hydrogen for mobile hydrogen‒oxygen fuel cells. In this study, we have successfully synthesized a variety of Ni0.5Cu0.5Co2O4 nanocomposites with different morphology, including nanoplatelets, [...] Read more.
The catalytic hydrolysis of ammonia borane (AB) is a promising route to produce hydrogen for mobile hydrogen‒oxygen fuel cells. In this study, we have successfully synthesized a variety of Ni0.5Cu0.5Co2O4 nanocomposites with different morphology, including nanoplatelets, nanoparticles, and urchin-like microspheres. The catalytic performance of those Ni0.5Cu0.5Co2O4 composites in AB hydrolysis is investigated. The Ni0.5Cu0.5Co2O4 nanoplatelets show the best catalytic performance despite having the smallest specific surface area, with a turnover frequency (TOF) of 80.2 molhydrogen·min−1·mol−1cat. The results reveal that, in contrast to the Ni0.5Cu0.5Co2O4 nanoparticles and microspheres, the Ni0.5Cu0.5Co2O4 nanoplatelets are more readily reduced, leading to the fast formation of active species for AB hydrolysis. These findings provide some insight into the design of high-performance oxide-based catalysts for AB hydrolysis. Considering their low cost and high catalytic activity, Ni0.5Cu0.5Co2O4 nanoplatelets are a strong candidate catalyst for the production of hydrogen through AB hydrolysis in practical applications. Full article
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Open AccessArticle
[email protected] Nanoparticles Functionalized with Oligonucleotides: A Prominent Tool for the Detection of the Methylated Reprimo Gene in Gastric Cancer by Dynamic Light Scattering
Nanomaterials 2019, 9(9), 1333; https://doi.org/10.3390/nano9091333 - 18 Sep 2019
Abstract
Reprimo (RPRM) is a tumor suppressor gene involved in the development of gastric cancer. Hypermethylation of the RPRM promoter region has been found in tumor tissue and plasma samples from patients with gastric cancer. These findings suggest that circulating methylated DNA [...] Read more.
Reprimo (RPRM) is a tumor suppressor gene involved in the development of gastric cancer. Hypermethylation of the RPRM promoter region has been found in tumor tissue and plasma samples from patients with gastric cancer. These findings suggest that circulating methylated DNA of RPRM could be a candidate for a noninvasive detection of gastric cancer. We designed a nanosystem based on the functionalization of silica coated gold nanoparticles with oligonucleotides that recognize a specific DNA fragment of the RPRM promoter region. The functionality of the oligonucleotide on the surface of the nanoparticle was confirmed by polymerase chain reaction (PCR). The nanoparticles were incubated with a synthetic DNA fragment of methylated DNA of RPRM and changes in the size distribution after hybridization were evaluated by dynamic light scattering (DLS). A difference in the size distribution of nanoparticles hybridized with genomic DNA from the KATO III gastric cancer cell line was observed when was compared with DNA from the GES-1 normal cell line. These results showed that this nanosystem may be a useful tool for the specific and sensitive detection of methylated DNA of RPRM in patients at risk of developing gastric cancer. Full article
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Open AccessArticle
Ultrafast Oatterning Vertically Aligned Carbon Nanotube Forest on Al Foil and Si Substrate Using Chemical Vapor Deposition (CVD)
Nanomaterials 2019, 9(9), 1332; https://doi.org/10.3390/nano9091332 - 18 Sep 2019
Viewed by 44
Abstract
This study introduces a method of patterning carbon nanotube (CNTs) forests that is both fast and simple. We found that, as commercially available oil-based markers undergo nanotube synthesis, a thin film forms that prevents the catalyst, ferrocene, from coming into contact with the [...] Read more.
This study introduces a method of patterning carbon nanotube (CNTs) forests that is both fast and simple. We found that, as commercially available oil-based markers undergo nanotube synthesis, a thin film forms that prevents the catalyst, ferrocene, from coming into contact with the surface of the test sample. This, thus, blocks CNT growth. Through further deduction, we used styrene maleic anhydride (SMA) to conduct CNT patterning, in addition to analyzing the relationship between the weight percent concentration of the SMA and the extent to which it blocked CNT growth. We developed two separate methods for applying ink to soft and hard substrates: one method involved ink printing and the other laser stripping. In the CNT pattern we produced, a minimum line width of around 10 µm was attained. Full article
(This article belongs to the Special Issue Carbon Nanotube: Synthesis, Characteristics and Applications)
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Open AccessArticle
Mussel-Inspired Fabrication of SERS Swabs for Highly Sensitive and Conformal Rapid Detection of Thiram Bactericides
Nanomaterials 2019, 9(9), 1331; https://doi.org/10.3390/nano9091331 - 17 Sep 2019
Viewed by 135
Abstract
As an important sort of dithiocarbamate bactericide, thiram has been widely used for fruits, vegetables and mature crops to control various fungal diseases; however, the thiram residues in the environment pose a serious threat to human health. In this work, silver nanoparticles (AgNPs) [...] Read more.
As an important sort of dithiocarbamate bactericide, thiram has been widely used for fruits, vegetables and mature crops to control various fungal diseases; however, the thiram residues in the environment pose a serious threat to human health. In this work, silver nanoparticles (AgNPs) were grown in-situ on cotton swab (CS) surfaces, based on the mussel-inspired polydopamine (PDA) molecule and designed as highly sensitive surface-enhanced Raman scattering (SERS) swabs for the conformal rapid detection of bactericide residues. With this strategy, the obtained [email protected]@AgNPs swabs demonstrated highly sensitive and reproducible Raman signals toward Nile blue A (NBA) probe molecules, and the detection limit was as low as 1.0 × 10−10 M. More critically, these [email protected]@AgNPs swabs could be served as flexible SERS substrates for the conformal rapid detection of thiram bactericides from various fruit surfaces through a simple swabbing approach. The results showed that the detection limit of thiram residues from pear, grape and peach surfaces was approximately down to the level of 0.12 ng/cm2, 0.24 ng/cm2 and 0.15 ng/cm2 respectively, demonstrating a high sensitivity and excellent reliability toward dithiocarbamate bactericides. Not only could these SERS swabs significantly promote the collection efficiency of thiram residues from irregular shaped matrices, but they could also greatly enhance the analytical sensitivity and reliability, and would have great potential for the on-site detection of residual bactericides in the environment and in bioscience fields. Full article
(This article belongs to the Special Issue Surface-Enhanced Raman Spectroscopy in the Nano-World)
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Open AccessReview
Carbon-Based Nanomaterials in Sensors for Food Safety
Nanomaterials 2019, 9(9), 1330; https://doi.org/10.3390/nano9091330 - 17 Sep 2019
Viewed by 120
Abstract
Food safety is one of the most important and widespread research topics worldwide. The development of relevant analytical methods or devices for detection of unsafe factors in foods is necessary to ensure food safety and an important aspect of the studies of food [...] Read more.
Food safety is one of the most important and widespread research topics worldwide. The development of relevant analytical methods or devices for detection of unsafe factors in foods is necessary to ensure food safety and an important aspect of the studies of food safety. In recent years, developing high-performance sensors used for food safety analysis has made remarkable progress. The combination of carbon-based nanomaterials with excellent properties is a specific type of sensor for enhancing the signal conversion and thus improving detection accuracy and sensitivity, thus reaching unprecedented levels and having good application potential. This review describes the roles and contributions of typical carbon-based nanomaterials, such as mesoporous carbon, single- or multi-walled carbon nanotubes, graphene and carbon quantum dots, in the construction and performance improvement of various chemo- and biosensors for various signals. Additionally, this review focuses on the progress of applications of this type of sensor in food safety inspection, especially for the analysis and detection of all types of toxic and harmful substances in foods. Full article
(This article belongs to the Special Issue Carbon-Based Nanomaterials for (Bio)Sensors Development)
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Open AccessReview
Developing Protein-Based Nanoparticles as Versatile Delivery Systems for Cancer Therapy and Imaging
Nanomaterials 2019, 9(9), 1329; https://doi.org/10.3390/nano9091329 - 16 Sep 2019
Viewed by 289
Abstract
In recent years, it has become apparent that cancer nanomedicine’s reliance on synthetic nanoparticles as drug delivery systems has resulted in limited clinical outcomes. This is mostly due to a poor understanding of their “bio–nano” interactions. Protein-based nanoparticles (PNPs) are rapidly emerging as [...] Read more.
In recent years, it has become apparent that cancer nanomedicine’s reliance on synthetic nanoparticles as drug delivery systems has resulted in limited clinical outcomes. This is mostly due to a poor understanding of their “bio–nano” interactions. Protein-based nanoparticles (PNPs) are rapidly emerging as versatile vehicles for the delivery of therapeutic and diagnostic agents, offering a potential alternative to synthetic nanoparticles. PNPs are abundant in nature, genetically and chemically modifiable, monodisperse, biocompatible, and biodegradable. To harness their full clinical potential, it is important for PNPs to be accurately designed and engineered. In this review, we outline the recent advancements and applications of PNPs in cancer nanomedicine. We also discuss the future directions for PNP research and what challenges must be overcome to ensure their translation into the clinic. Full article
(This article belongs to the Special Issue Optical Nanomaterials for Diagnosis and Therapy)
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Open AccessArticle
Solution-Processed PEDOT:PSS/MoS2 Nanocomposites as Efficient Hole-Transporting Layers for Organic Solar Cells
Nanomaterials 2019, 9(9), 1328; https://doi.org/10.3390/nano9091328 - 16 Sep 2019
Viewed by 153
Abstract
An efficient hole-transporting layer (HTL) based on functionalized two-dimensional (2D) MoS2-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composites has been developed for use in organic solar cells (OSCs). Few-layer, oleylamine-functionalized MoS2 (FMoS2) nanosheets were prepared via a simple and cost-effective solution-phase exfoliation method; [...] Read more.
An efficient hole-transporting layer (HTL) based on functionalized two-dimensional (2D) MoS2-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composites has been developed for use in organic solar cells (OSCs). Few-layer, oleylamine-functionalized MoS2 (FMoS2) nanosheets were prepared via a simple and cost-effective solution-phase exfoliation method; then, they were blended into PEDOT:PSS, a conducting conjugated polymer, and the resulting hybrid film (PEDOT:PSS/FMoS2) was tested as an HTL for poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) OSCs. The devices using this hybrid film HTL showed power conversion efficiencies up to 3.74%, which is 15.08% higher than that of the reference ones having PEDOT:PSS as HTL. Atomic force microscopy and contact angle measurements confirmed the compatibility of the PEDOT:PSS/FMoS2 surface for active layer deposition on it. The electrical impedance spectroscopy analysis revealed that their use minimized the charge-transfer resistance of the OSCs, consequently improving their performance compared with the reference cells. Thus, the proposed fabrication of such HTLs incorporating 2D nanomaterials could be further expanded as a universal protocol for various high-performance optoelectronic devices. Full article
(This article belongs to the Special Issue Advances in Emerging Solar Cells)
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Open AccessArticle
Strain-Mediated Bending of InP Nanowires through the Growth of an Asymmetric InAs Shell
Nanomaterials 2019, 9(9), 1327; https://doi.org/10.3390/nano9091327 - 16 Sep 2019
Viewed by 163
Abstract
Controlling nanomaterial shape beyond its basic dimensionality is a concurrent challenge tackled by several growth and processing avenues. One of these is strain engineering of nanowires, implemented through the growth of asymmetrical heterostructures. Here, we report metal–organic molecular beam epitaxy of bent InP/InAs [...] Read more.
Controlling nanomaterial shape beyond its basic dimensionality is a concurrent challenge tackled by several growth and processing avenues. One of these is strain engineering of nanowires, implemented through the growth of asymmetrical heterostructures. Here, we report metal–organic molecular beam epitaxy of bent InP/InAs core/shell nanowires brought by precursor flow directionality in the growth chamber. We observe the increase of bending with decreased core diameter. We further analyze the composition of a single nanowire and show through supporting finite element simulations that strain accommodation following the lattice mismatch between InP and InAs dominates nanowire bending. The simulations show the interplay between material composition, shell thickness, and tapering in determining the bending. The simulation results are in good agreement with the experimental bending curvature, reproducing the radius of 4.3 µm (±10%), for the 2.3 µm long nanowire. The InP core of the bent heterostructure was found to be compressed at about 2%. This report provides evidence of shape control and strain engineering in nanostructures, specifically through the exchange of group-V materials in III–V nanowire growth. Full article
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Open AccessArticle
Buckling Behavior of Nanobeams Placed in Electromagnetic Field Using Shifted Chebyshev Polynomials-Based Rayleigh-Ritz Method
Nanomaterials 2019, 9(9), 1326; https://doi.org/10.3390/nano9091326 - 16 Sep 2019
Viewed by 225
Abstract
In the present investigation, the buckling behavior of Euler–Bernoulli nanobeam, which is placed in an electro-magnetic field, is investigated in the framework of Eringen’s nonlocal theory. Critical buckling load for all the classical boundary conditions such as “Pined–Pined (P-P), Clamped–Pined (C-P), Clamped–Clamped (C-C), [...] Read more.
In the present investigation, the buckling behavior of Euler–Bernoulli nanobeam, which is placed in an electro-magnetic field, is investigated in the framework of Eringen’s nonlocal theory. Critical buckling load for all the classical boundary conditions such as “Pined–Pined (P-P), Clamped–Pined (C-P), Clamped–Clamped (C-C), and Clamped-Free (C-F)” are obtained using shifted Chebyshev polynomials-based Rayleigh-Ritz method. The main advantage of the shifted Chebyshev polynomials is that it does not make the system ill-conditioning with the higher number of terms in the approximation due to the orthogonality of the functions. Validation and convergence studies of the model have been carried out for different cases. Also, a closed-form solution has been obtained for the “Pined–Pined (P-P)” boundary condition using Navier’s technique, and the numerical results obtained for the “Pined–Pined (P-P)” boundary condition are validated with a closed-form solution. Further, the effects of various scaling parameters on the critical buckling load have been explored, and new results are presented as Figures and Tables. Finally, buckling mode shapes are also plotted to show the sensitiveness of the critical buckling load. Full article
(This article belongs to the Special Issue Advanced Mechanical Modeling of Nanomaterials and Nanostructures)
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Open AccessArticle
A Mechanochemical Route for ZnS Nanocrystals, and Batch Sorting along Size Distribution
Nanomaterials 2019, 9(9), 1325; https://doi.org/10.3390/nano9091325 - 15 Sep 2019
Viewed by 189
Abstract
The assistances of sodium dodecyl benzene sulfonate (SDBS) and aging treatment were introduced to further improve the room-temperature mechanochemical synthesis of the quantum-sized zinc sulfide (ZnS) nanocrystals. As a result, a green strategy for synthesizing the monodisperse nanocrystals with tunable size and crystallinity [...] Read more.
The assistances of sodium dodecyl benzene sulfonate (SDBS) and aging treatment were introduced to further improve the room-temperature mechanochemical synthesis of the quantum-sized zinc sulfide (ZnS) nanocrystals. As a result, a green strategy for synthesizing the monodisperse nanocrystals with tunable size and crystallinity was developed, holding convenient, highly efficient and low pollution. Size evolution shows a gradually increasing trend along the aging-temperature. A model that the independent reaction cells constructed by SDBS-wrapped reactant packages (solid state vesicles, SSVs) for the confined growth of ZnS nanocrystals was proposed to access the formation mechanism of ZnS quantized crystal in a solid-state synthesis system. The band gaps and band-edge luminescent emissions of as-prepared ZnS nanocrystals experienced the size-dependent quantum confinement effect, while the trap-state emissions exhibited the lattice integrity-dependence. Furthermore, ZnS quantum-sized nanocrystals with narrower size distribution can be obtained by a batch-sorting process through adjusting the centrifugal speed. Full article
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Open AccessArticle
SnSe2 Quantum Dots: Facile Fabrication and Application in Highly Responsive UV-Detectors
Nanomaterials 2019, 9(9), 1324; https://doi.org/10.3390/nano9091324 - 15 Sep 2019
Viewed by 207
Abstract
Synthesizing quantum dots (QDs) using simple methods and utilizing them in optoelectronic devices are active areas of research. In this paper, we fabricated SnSe2 QDs via sonication and a laser ablation process. Deionized water was used as a solvent, and there were [...] Read more.
Synthesizing quantum dots (QDs) using simple methods and utilizing them in optoelectronic devices are active areas of research. In this paper, we fabricated SnSe2 QDs via sonication and a laser ablation process. Deionized water was used as a solvent, and there were no organic chemicals introduced in the process. It was a facile and environmentally-friendly method. We demonstrated an ultraviolet (UV)-detector based on monolayer graphene and SnSe2 QDs. The photoresponsivity of the detector was up to 7.5 × 106 mAW−1, and the photoresponse time was ~0.31 s. The n–n heterostructures between monolayer graphene and SnSe2 QDs improved the light absorption and the transportation of photocarriers, which could greatly increase the photoresponsivity of the device. Full article
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Open AccessArticle
Amorphous Sb2S3 Nanospheres In-Situ Grown on Carbon Nanotubes: Anodes for NIBs and KIBs
Nanomaterials 2019, 9(9), 1323; https://doi.org/10.3390/nano9091323 - 15 Sep 2019
Viewed by 204
Abstract
Antimony sulfide (Sb2S3) with a high theoretical capacity is considered as a promising candidate for Na-ion batteries (NIBs) and K-ion batteries (KIBs). However, its poor electrochemical activity and structural stability are the main issues to be solved. Herein, amorphous [...] Read more.
Antimony sulfide (Sb2S3) with a high theoretical capacity is considered as a promising candidate for Na-ion batteries (NIBs) and K-ion batteries (KIBs). However, its poor electrochemical activity and structural stability are the main issues to be solved. Herein, amorphous Sb2S3 nanospheres/carbon nanotube (Sb2S3/CNT) nanocomposites are successfully synthesized via one step self-assembly method. In-situ growth of amorphous Sb2S3 nanospheres on the CNTs is confirmed by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. The amorphous Sb2S3/CNT nanocomposites as an anode for NIBs exhibit excellent electrochemical performance, delivering a high charge capacity of 870 mA h g−1 at 100 mA g−1, with an initial coulomb efficiency of 77.8%. Even at 3000 mA g−1, a charge capacity of 474 mA h g−1 can be achieved. As an anode for KIBs, the amorphous Sb2S3/CNT nanocomposites also demonstrate a high charge capacity of 451 mA h g−1 at 25 mA g−1. The remarkable performance of the amorphous Sb2S3/CNT nanocomposites is attributed to the synergic effects of the amorphous Sb2S3 nanospheres and 3D porous conductive network constructed by the CNTs. Full article
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Open AccessArticle
A Highly Efficient and Durable Fluorescent Paper Produced from Bacterial Cellulose/Eu Complex and Cellulosic Fibers
Nanomaterials 2019, 9(9), 1322; https://doi.org/10.3390/nano9091322 - 15 Sep 2019
Viewed by 193
Abstract
The general method of producing fluorescent paper by coating fluorescent substances onto paper base faces the problems of low efficiency and poor durability. Bacterial cellulose (BC) with its nanoporous structure can be used to stabilize fluorescent particles. In this study, we used a [...] Read more.
The general method of producing fluorescent paper by coating fluorescent substances onto paper base faces the problems of low efficiency and poor durability. Bacterial cellulose (BC) with its nanoporous structure can be used to stabilize fluorescent particles. In this study, we used a novel method to produce fluorescent paper by first making Eu/BC complex and then processing the complex and cellulosic fibers into composite paper sheets. For this composting method, BC can form very stable BC/Eu complex due to its nanoporous structure, while the plant-based cellulosic fibers reduce the cost and provide stiffness to the materials. The fluorescent paper demonstrated a great fluorescent property and efficiency. The ultraviolet absorbance or the fluorescent intensity of the Eu-BC fluorescent paper increased with the increase of Eu-BC content but remained little changed after Eu-BC content was higher than 5%. After folding 200 times, the fluorescence intensity of fluorescent paper decreased by only 0.7%, which suggested that the Eu-BC fluorescent paper has great stability and durability. Full article
(This article belongs to the Special Issue Nanocelluloses: Synthesis, Modification and Applications)
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Open AccessArticle
Tuning the Supramolecular Structures of Metal-Free Porphyrin via Surfactant Assisted Self-Assembly to Enhance Photocatalytic Performance
Nanomaterials 2019, 9(9), 1321; https://doi.org/10.3390/nano9091321 - 15 Sep 2019
Viewed by 220
Abstract
Metal-free porphyrin with good planarity is beneficial to π–π stack interactions, which promotes electron coupling and the separation and transfer of photogenerated carriers. It is necessary to develop metal-free porphyrin-based photocatalysts and exploit the photocatalytic mechanism. Herein, metal–free porphyrin (5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, TCPP) was self-assembled [...] Read more.
Metal-free porphyrin with good planarity is beneficial to π–π stack interactions, which promotes electron coupling and the separation and transfer of photogenerated carriers. It is necessary to develop metal-free porphyrin-based photocatalysts and exploit the photocatalytic mechanism. Herein, metal–free porphyrin (5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, TCPP) was self-assembled through an acid-based neutralization reaction and mixing dual-solvents under surfactants to form different aggregates. Morphology structures, optical and optoelectronic properties of the TCPP aggregates were characterized in detail. TCPP self-assemblies showed higher photocatalytic activities for the degradation of phenol under visible light than untreated TCPP powders, and the aggregates of nanorods formed through the acid-based neutralization reaction in the presence of hexadecyl trimethyl ammonium bromide (CTAB) possessed 2.6 times more activity than the nanofiber aggregates formed through mixing dual-solvents. It was proved that self-assembly methods are crucial for controlling the aggregation of porphyrins to form different aggregations, which have a profound impact on the photocatalytic activity. Full article
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Open AccessArticle
Graphene−Perfluoroalkoxy Nanocomposite with High Through-Plane Thermal Conductivity Fabricated by Hot-Pressing
Nanomaterials 2019, 9(9), 1320; https://doi.org/10.3390/nano9091320 - 15 Sep 2019
Viewed by 229
Abstract
With the rapid development of electronics and portable devices, polymer nanocomposites with high through-plane thermal conductivity (TC) are urgently needed. In this work, we fabricated graphene nanosheets−perfluoroalkoxy (GNs−PFA) composite sheets with high through-plane TCs via hot-pressing followed by mechanical machining. When the GNs [...] Read more.
With the rapid development of electronics and portable devices, polymer nanocomposites with high through-plane thermal conductivity (TC) are urgently needed. In this work, we fabricated graphene nanosheets−perfluoroalkoxy (GNs−PFA) composite sheets with high through-plane TCs via hot-pressing followed by mechanical machining. When the GNs content exceeded 10 wt%, GNs were vertically aligned in the PFA matrix, and the through-plane TCs of nanocomposites were 10–15 times higher than their in-plane TCs. In particular, the composite with 30 wt% GNs exhibited a through-plane TC of 25.57 W/(m·K), which was 9700% higher than that of pure PFA. The composite with 30 wt% GNs was attached to the surface of a high-power light-emitting diode (LED) to assess its heat-dissipation capability. The composite with vertically aligned GNs lowered the LED surface temperature by approximately 16 °C compared with pure PFA. Our facile, low-cost method allows for the large-scale production of GNs–PFA nanocomposites with high through-plane TCs, which can be used in various thermal-management applications. Full article
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Open AccessArticle
Sustainable Desalination by 3:1 Reduced Graphene Oxide/Titanium Dioxide Nanotubes (rGO/TiONTs) Composite via Capacitive Deionization at Different Sodium Chloride Concentrations
Nanomaterials 2019, 9(9), 1319; https://doi.org/10.3390/nano9091319 - 15 Sep 2019
Viewed by 229
Abstract
The capability of novel 3:1 reduced graphene oxide/titanium dioxide nanotubes (rGO/TiONTs) composite to desalinate using capacitive deionization (CDI) employing highly concentrated NaCl solutions was tested in this study. Parameters such as material wettability, electrosorption capacity, charge efficiency, energy consumption, and charge-discharge retention were [...] Read more.
The capability of novel 3:1 reduced graphene oxide/titanium dioxide nanotubes (rGO/TiONTs) composite to desalinate using capacitive deionization (CDI) employing highly concentrated NaCl solutions was tested in this study. Parameters such as material wettability, electrosorption capacity, charge efficiency, energy consumption, and charge-discharge retention were tested at different NaCl initial concentrations—100 ppm, 2000 ppm, 15,000 ppm, and 30,000 ppm. The rGO/TiONTs composite showed good material wettability before and after CDI runs with its contact angles equal to 52.11° and 56.07°, respectively. Its two-hour electrosorption capacity during CDI at 30,000 ppm NaCl influent increased 1.34-fold compared to 100 ppm initial NaCl influent with energy consumption constant at 1.11 kWh per kg with NaCl removed. However, the percentage discharge (concentration-independent) at zero-voltage ranged from 4.9–7.27% only after 30 min of desorption. Repeated charge/discharge at different amperes showed that the slowest charging rate of 0.1 A·g−1 had the highest charging time retention at 60% after 100 cycles. Increased concentration likewise increases charging time retention. With this consistent performance of a CDI system utilizing rGO/TiONTs composite, even at 30,000 ppm and 100 cycles, it can be a sustainable alternative desalination technology, especially if a low charging current with reverse voltage discharge is set for a longer operation. Full article
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Open AccessArticle
Zinc Oxide Nanoparticles Cytotoxicity and Release from Newly Formed PMMA–ZnO Nanocomposites Designed for Denture Bases
Nanomaterials 2019, 9(9), 1318; https://doi.org/10.3390/nano9091318 - 15 Sep 2019
Viewed by 247
Abstract
The goal of the study was to investigate the level of zinc oxide nanoparticles (ZnO NPs) release from polymethyl methacrylate (PMMA)–ZnO nanocomposites (2.5%, 5%, and 7.5% w/w), as well as from the ZnO NPs layer produced on pure PMMA, and [...] Read more.
The goal of the study was to investigate the level of zinc oxide nanoparticles (ZnO NPs) release from polymethyl methacrylate (PMMA)–ZnO nanocomposites (2.5%, 5%, and 7.5% w/w), as well as from the ZnO NPs layer produced on pure PMMA, and the impact of the achieved final ZnO NPs concentration on cytotoxicity, before the potential use as an alternative material for denture bases. The concentration of ZnO nanoparticles released to the aqueous solution of Zn2+ ions was assessed using optical emission spectrometry with inductively coupled plasma (ICP-OES). In the control group (pure PMMA), the released mean for ZnO was 0.074 mg/L and for individual nanocomposites at concentrations of 2.5%, 5%, and 7.5% was 2.281 mg/L, 2.143 mg/L, and 3.512 mg/L, respectively. The median for the ZnO NPs layer produced on PMMA was 4.878 mg/L. In addition, in vitro cytotoxicity of ZnO NPs against the human HeLa cell line was determined through the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) dye. The cytotoxicity studies demonstrate that ZnO nanoparticles in the concentrations up to 20 mg/L have no adverse effect on HeLa cells. When compared with the released and cytotoxic concentrations of ZnO NPs, it can be expected that ZnO released from dental prostheses to the oral cavity environment will have no cytotoxic effect on host cells. Full article
(This article belongs to the Special Issue Nanomaterials and Nanotechnology in Dentistry)
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Open AccessCommunication
A Portable Electrospinner for Nanofiber Synthesis and Its Application for Cosmetic Treatment of Alopecia
Nanomaterials 2019, 9(9), 1317; https://doi.org/10.3390/nano9091317 - 14 Sep 2019
Viewed by 190
Abstract
A portable, handheld electrospinning apparatus is designed and constructed using off-the-shelf components and 3D-printed parts. The portable electrospinner is used to generate nanofibers with diameters ranging from 85 to 600 nm; examination of these fibers is achieved with scanning electron microscopy. This portable [...] Read more.
A portable, handheld electrospinning apparatus is designed and constructed using off-the-shelf components and 3D-printed parts. The portable electrospinner is used to generate nanofibers with diameters ranging from 85 to 600 nm; examination of these fibers is achieved with scanning electron microscopy. This portable electrospinner has similar capabilities to standard stationary benchtop electrospinners in terms of the diversity of polymers the device is able to spin into nanofibers and their resulting size and morphology. However, it provides much more ambulatory flexibility, employs current-limiting measures that allow for safer operation and is cost effective. As a demonstration of the device’s unique application space afforded by its portability, the device is applied in direct-to-skin electrospinning to improve the aesthetics of simulated hair loss in a mouse model by electrospinning dyed polyacrylonitrile nanofibers that mimic hair. The superficial nanofiber treatment for thinning hair is able to achieve an improvement in appearance similar to that of a commercially available powder product but outperforms the powder in the nanofiber’s superior adherence to the affected area. The portable electrospinning apparatus overcomes many limitations of immobile benchtop electrospinners and holds promise for applications in consumer end-use scenarios such as the treatment of alopecia via cosmetic hair thickening. Full article
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Open AccessArticle
Exploring the Effect of the Irradiation Time on Photosensitized Dendrimer-Based Nanoaggregates for Potential Applications in Light-Driven Water Photoreduction
Nanomaterials 2019, 9(9), 1316; https://doi.org/10.3390/nano9091316 - 14 Sep 2019
Viewed by 193
Abstract
Fourth generation polyamidoamine dendrimer (PAMAM, G4) modified with fluorescein units (F) at the periphery and Pt nanoparticles stabilized by L-ascorbate were prepared. These dendrimers modified with hydrophobic fluorescein were used to achieve self-assembling structures, giving rise to the formation of nanoaggregates in water. [...] Read more.
Fourth generation polyamidoamine dendrimer (PAMAM, G4) modified with fluorescein units (F) at the periphery and Pt nanoparticles stabilized by L-ascorbate were prepared. These dendrimers modified with hydrophobic fluorescein were used to achieve self-assembling structures, giving rise to the formation of nanoaggregates in water. The photoactive fluorescein units were mainly used as photosensitizer units in the process of the catalytic photoreduction of water propitiated by light. Complementarily, Pt-ascorbate nanoparticles acted as the active sites to generate H2. Importantly, the study of the functional, optical, surface potential and morphological properties of the photosensitized dendrimer aggregates at different irradiation times allowed for insights to be gained into the behavior of these systems. Thus, the resultant photosensitized PAMAM-fluorescein (G4-F) nanoaggregates (NG) were conveniently applied to light-driven water photoreduction along with sodium L-ascorbate and methyl viologen as the sacrificial reagent and electron relay agent, respectively. Notably, these aggregates exhibited appropriate stability and catalytic activity over time for hydrogen production. Additionally, in order to propose a potential use of these types of systems, the in situ generated H2 was able to reduce a certain amount of methylene blue (MB). Finally, theoretical electronic analyses provided insights into the possible excited states of the fluorescein molecules that could intervene in the global mechanism of H2 generation. Full article
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Open AccessArticle
Catechol-Loading Nanofibrous Membranes for Eco-Friendly Iron Nutrition of Plants
Nanomaterials 2019, 9(9), 1315; https://doi.org/10.3390/nano9091315 - 14 Sep 2019
Viewed by 153
Abstract
Modern agriculture requires more efficient and low-impact products and formulations than traditional agrochemicals to improve crop yields. Iron is a micronutrient essential for plant growth and photosynthesis, but it is mostly present in insoluble forms in ecosystems so that it is often limiting [...] Read more.
Modern agriculture requires more efficient and low-impact products and formulations than traditional agrochemicals to improve crop yields. Iron is a micronutrient essential for plant growth and photosynthesis, but it is mostly present in insoluble forms in ecosystems so that it is often limiting for plants. This study was aimed at combining natural strategies and biodegradable nanostructured materials to create environmentally friendly and low-toxic bioactive products capable of both supplying iron to Fe-deficient plants and reducing the impact of agricultural products on the environment. Consequently, free-standing electrospun nanofibrous polycaprolactone/polyhydroxybutyrate thin membranes loaded with catechol (CL-NMs) as an iron-chelating natural agent (at two concentrations) were fabricated on purpose to mobilize Fe from insoluble forms and transfer it to duckweed (Lemna minor L.) plants. The effectiveness of CL-NMs in providing iron to Fe-deficient plants, upon catechol release, tested in duckweeds grown for 4 days under controlled hydroponic conditions, displayed temporal variations in both photosynthetic efficiency and biometric parameters measured by chlorophyll fluorescence and growth imaging. Duckweeds supplied with CL-NMs hosting higher catechol concentrations recovered most of the physiological and growth performances previously impaired by Fe limitation. The absence of short-term toxicity of these materials on duckweeds also proved the low impact on ecosystems of these products. Full article
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Open AccessArticle
Ultrawide Color Gamut Perovskite and CdSe/ZnS Quantum-Dots-Based White Light-Emitting Diode with High Luminous Efficiency
Nanomaterials 2019, 9(9), 1314; https://doi.org/10.3390/nano9091314 - 14 Sep 2019
Viewed by 165
Abstract
We demonstrate excellent color quality of liquid-type white light-emitting diodes (WLEDs) using a combination of green light-emitting CsPbBr3 and red light-emitting CdSe/ZnS quantum dots (QDs). Previously, we reported red (CsPbBr1.2I1.8) and green (CsPbBr3) perovskite QDs (PQDs)-based [...] Read more.
We demonstrate excellent color quality of liquid-type white light-emitting diodes (WLEDs) using a combination of green light-emitting CsPbBr3 and red light-emitting CdSe/ZnS quantum dots (QDs). Previously, we reported red (CsPbBr1.2I1.8) and green (CsPbBr3) perovskite QDs (PQDs)-based WLEDs with high color gamut, which manifested fast anion exchange and stability issues. Herein, the replacement of red PQDs with CdSe/ZnS QDs has resolved the aforementioned problems effectively and improved both stability and efficiency. Further, the proposed liquid-type device possesses outstanding color gamut performance (132% of National Television System Committee and 99% of Rec. 2020). It also shows a high efficiency of 66 lm/W and an excellent long-term operation stability for over 1000 h. Full article
(This article belongs to the Special Issue Quantum Dots and Micro-LED Display)
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Open AccessArticle
Pitch-Derived Activated Carbon Fibers for Emission Control of Low-Concentration Hydrocarbon
Nanomaterials 2019, 9(9), 1313; https://doi.org/10.3390/nano9091313 - 14 Sep 2019
Viewed by 135
Abstract
The unburned hydrocarbon (HC) emissions of automobiles are subject to strong regulations because they are known to be converted into fine dust, ozone, and photochemical smog. Pitch-based activated carbon fibers (ACF) prepared by steam activation can be a good solution for HC removal. [...] Read more.
The unburned hydrocarbon (HC) emissions of automobiles are subject to strong regulations because they are known to be converted into fine dust, ozone, and photochemical smog. Pitch-based activated carbon fibers (ACF) prepared by steam activation can be a good solution for HC removal. The structural characteristics of ACF were observed using X-ray diffraction. The pore characteristics were investigated using N2/77K adsorption isotherms. The butane working capacity (BWC) was determined according to ASTM D5228. From the results, the specific surface area and total pore volume of the ACF were determined to be 840–2630 m2/g and 0.33–1.34 cm3/g, respectively. The butane activity and butane retentivity of the ACF increased with increasing activation time and were observed to range between 15.78–57.33% and 4.19–11.47%, respectively. This indicates that n-butane adsorption capacity could be a function not only of the specific surface area or total pore volume but also of the sub-mesopore volume fraction in the range of 2.0–2.5 nm of adsorbents. The ACF exhibit enhanced BWC, and especially adsorption velocity, compared to commercial products (granules and pellets), with lower concentrations of n-butane due to a uniformly well-developed pore structure open directly to the outer surface. Full article
(This article belongs to the Special Issue Nanotechnology for Environmental and Biomedical Research)
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Open AccessArticle
A Bilayer 2D-WS2/Organic-Based Heterojunction for High-Performance Photodetectors
Nanomaterials 2019, 9(9), 1312; https://doi.org/10.3390/nano9091312 - 13 Sep 2019
Viewed by 161
Abstract
Two-dimensional (2D) tungsten disulfide (WS2) has inspired great efforts in optoelectronics, such as in solar cells, light-emitting diodes, and photodetectors. However, chemical vapor deposition (CVD) grown 2D WS2 domains with the coexistence of a discontinuous single layer and multilayers are [...] Read more.
Two-dimensional (2D) tungsten disulfide (WS2) has inspired great efforts in optoelectronics, such as in solar cells, light-emitting diodes, and photodetectors. However, chemical vapor deposition (CVD) grown 2D WS2 domains with the coexistence of a discontinuous single layer and multilayers are still not suitable for the fabrication of photodetectors on a large scale. An emerging field in the integration of organic materials with 2D materials offers the advantages of molecular diversity and flexibility to provide an exciting aspect on high-performance device applications. Herein, we fabricated a photodetector based on a 2D-WS2/organic semiconductor materials (mixture of the (Poly-(N, N'-bis-4-butylphenyl-N, N'-bisphenyl) benzidine and Phenyl-C61-butyric acid methyl ester (Poly-TPD/PCBM)) heterojunction. The application of Poly-TPD/PCBM organic blend film enhanced light absorption, electrically connected the isolated WS2 domains, and promoted the separation of electron-hole pairs. The generated exciton could sufficiently diffuse to the interface of the WS2 and the organic blend layers for efficient charge separation, where Poly-TPD was favorable for hole carrier transport and PCBM for electron transport to their respective electrodes. We show that the photodetector exhibited high responsivity, detectivity, and an on/off ratio of 0.1 A/W, 1.1 × 1011 Jones, and 100, respectively. In addition, the photodetector showed a broad spectral response from 500 nm to 750 nm, with a peak external quantum efficiency (EQE) of 8%. Our work offers a facile solution-coating process combined with a CVD technique to prepare an inorganic/organic heterojunction photodetector with high performance on silicon substrate. Full article
(This article belongs to the Special Issue Quantum Dots and Micro-LED Display)
Open AccessArticle
Mg Doped CuCrO2 as Efficient Hole Transport Layers for Organic and Perovskite Solar Cells
Nanomaterials 2019, 9(9), 1311; https://doi.org/10.3390/nano9091311 - 13 Sep 2019
Viewed by 199
Abstract
The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO2 (CCO) nanoparticles and their performance [...] Read more.
The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO2 (CCO) nanoparticles and their performance as HTLs in OSCs and PSCs. CCO and Mg doped CCO (Mg:CCO) nanoparticles were hydrothermally synthesized. The nanoparticles were characterized by various experimental techniques to study the effect of Mg doping on structural, chemical, morphological, optical, and electronic properties of CCO. We found that Mg doping increases work function and decreases particle size. We demonstrate CCO and Mg:CCO as efficient HTLs in a variety of OSCs, including the first demonstration of a non-fullerene acceptor bulk heterojunction, and CH3NH3PbI3 PSCs. A small improvement of average short-circuit current density with Mg doping was found in all systems. Full article
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Open AccessArticle
Electric Field Assisted Self-Assembly of Viruses into Colored Thin Films
Nanomaterials 2019, 9(9), 1310; https://doi.org/10.3390/nano9091310 - 13 Sep 2019
Viewed by 141
Abstract
Filamentous viruses called M13 bacteriophages are promising materials for devices with thin film coatings because phages are functionalizable, and they can self-assemble into smectic helicoidal nanofilament structures. However, the existing “pulling” approach to align the nanofilaments is slow and limits potential commercialization of [...] Read more.
Filamentous viruses called M13 bacteriophages are promising materials for devices with thin film coatings because phages are functionalizable, and they can self-assemble into smectic helicoidal nanofilament structures. However, the existing “pulling” approach to align the nanofilaments is slow and limits potential commercialization of this technology. This study uses an applied electric field to rapidly align the nanostructures in a fixed droplet. The electric field reduces pinning of the three-phase contact line, allowing it to recede at a constant rate. Atomic force microscopy reveals that the resulting aligned structures resemble those produced via the pulling method. The field-assisted alignment results in concentric color bands quantified with image analysis of red, green, and blue line profiles. The alignment technique shown here could reduce self-assembly time from hours to minutes and lend itself to scalable manufacturing techniques such as inkjet printing. Full article
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Open AccessArticle
Effects of Ultrasound on Zinc Oxide/Vermiculite/Chlorhexidine Nanocomposite Preparation and Their Antibacterial Activity
Nanomaterials 2019, 9(9), 1309; https://doi.org/10.3390/nano9091309 - 13 Sep 2019
Viewed by 174
Abstract
Microbial infection and biofilm formation are both problems associated with medical implants and devices. In recent years, hybrid organic-inorganic nanocomposites based on clay minerals have attracted significant attention due to their application potential in the field of antimicrobial materials. Organic drug/metal oxide hybrids [...] Read more.
Microbial infection and biofilm formation are both problems associated with medical implants and devices. In recent years, hybrid organic-inorganic nanocomposites based on clay minerals have attracted significant attention due to their application potential in the field of antimicrobial materials. Organic drug/metal oxide hybrids exhibit improved antimicrobial activity, and intercalating the above materials into the interlayer of clay endows a long-term and controlled-release behavior. Since antimicrobial activity is strongly related to the structure of the material, ultrasonic treatment appears to be a suitable method for the synthesis of these materials as it can well control particle size distribution and morphology. This study aims to prepare novel, structurally stable, and highly antimicrobial nanocomposites based on zinc oxide/vermiculite/chlorhexidine. The influence of ultrasonic treatment at different time intervals and under different intercalation conditions (ultrasonic action in a breaker or in a Roset’s vessel) on the structure, morphology, and particle size of prepared hybrid nanocomposite materials was evaluated by the following methods: scanning electron microscopy, X-ray diffraction, energy dispersive X-ray fluorescence spectroscopy, carbon phase analysis, Fourier transforms infrared spectroscopy, specific surface area measurement, particle size analysis, and Zeta potential analysis. Particle size analyses confirmed that the ultrasonic method contributes to the reduction of particle size, and to their homogenization/arrangement. Further, X-ray diffraction analysis confirmed that ultrasound intercalation in a beaker helps to more efficiently intercalate chlorhexidine dihydrochloride (CH) into the vermiculite interlayer space, while a Roset’s vessel contributed to the attachment of the CH molecules to the vermiculite surface. The antibacterial activity of hybrid nanocomposite materials was investigated on Gram negative (Escherichia coli, Pseudomonas aeruginosa) and Gram positive (Staphylococcus aureus, Enterococcus faecalis) bacterial strains by finding the minimum inhibitory concentration. All hybrid nanocomposite materials prepared by ultrasound methods showed high antimicrobial activity after 30 min, with a long-lasting effect and without being affected by the concentration of the antibacterial components zinc oxide (ZnO) and CH. The benefits of the samples prepared by ultrasonic methods are the rapid onset of an antimicrobial effect and its long-term duration. Full article
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Open AccessArticle
Highly Dispersed Ag2S Nanoparticles: In Situ Synthesis, Size Control, and Modification to Mechanical and Tribological Properties towards Nanocomposite Coatings
Nanomaterials 2019, 9(9), 1308; https://doi.org/10.3390/nano9091308 - 12 Sep 2019
Viewed by 180
Abstract
A facile in situ synthesis approach and a size control strategy were established to obtain Ag2S nanoparticles in polyimide (PI) composite coatings. Such Ag2S nanoparticles in the composite coatings were characterized, and the effects of the as-obtained Ag2 [...] Read more.
A facile in situ synthesis approach and a size control strategy were established to obtain Ag2S nanoparticles in polyimide (PI) composite coatings. Such Ag2S nanoparticles in the composite coatings were characterized, and the effects of the as-obtained Ag2S nanoparticles of different sizes on the mechanical and tribological properties of the nanocomposite coatings were investigated. Results indicate that the in situ synthesized Ag2S nanoparticles exhibited good dispersibility and bimodal and multimodal size distribution in the nanocomposite coatings. The size of the Ag2S nanoparticles can be effectively controlled by adjusting the substituent alkyl chain length of single-source precursor, and these Ag2S nanoparticles exhibited superior improvement to mechanical and tribological properties of the nanocomposite coatings. More importantly, the Ag2S nanoparticles with the proper grain size and bimodal size distribution provided the optimal mechanical and tribological properties for the nanocomposite coatings, and the excellent tribological properties were attributed to their outstanding mechanical properties and strong ability to form a homogenous and stable protective tribofilm. Full article
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Open AccessCommunication
Effect of the Host on Deep-Blue Organic Light-Emitting Diodes Based on a TADF Emitter for Roll-Off Suppressing
Nanomaterials 2019, 9(9), 1307; https://doi.org/10.3390/nano9091307 - 12 Sep 2019
Viewed by 501
Abstract
To achieve significant efficiency and low roll-off in thermally activated delayed fluorescence (TADF) material organic light-emitting diodes (OLEDs), it is essential to choose a host that has suitable high triplet energy (T1) and bipolar character to boost the TADF characteristics as [...] Read more.
To achieve significant efficiency and low roll-off in thermally activated delayed fluorescence (TADF) material organic light-emitting diodes (OLEDs), it is essential to choose a host that has suitable high triplet energy (T1) and bipolar character to boost the TADF characteristics as a dopant and avoid exciton annihilation. Herein, we present the effect of different host materials on the efficiency of organic light-emitting diodes (OLEDs) based on bis[4-(3,6 dimethoxycarbazole)phenyl]sulfone (DMOC-DPS) deep-blue emitter. The devices with 10 wt.% of an emitter in different electron types of host bis[2-(diphenylphosphino) phenyl] ether oxide (DPEPO), and hole types of host 1,3-bis(N-carbazolyl)benzene (mCP), were fabricated to study the effect on device performance. The results show that an external quantum efficiency (EQE) of 4% and maximum current efficiency (ƞc) up to 5.77 cd/A with high luminescence (lmax) 8185 cd/m2 in DPEPO was achieved, compared to 2.63% EQE, ƞc 4.12 cd/A with lmax 5338 cd/m2 in mCP in a very simple device structure. As a remarkable result, the roll-off is suppressed at 1000 cd/m2, and for maximum brightness, the roll-off is less than 50%. Further general applications are discussed. Full article
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