Confined Crystals, Quantum Dots, and Nano Crystals

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 29766

Special Issue Editors


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Guest Editor
1. Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, NC 27606, USA
2. Comparative Medicine Institute, North Carolina State University, Raleigh, NC 27606, USA
Interests: bio-nano crystals; transmission electron microscopy; fluorescent microscopy; quantum-dot imaging

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Lockheed Martin Corporation, Bethesda, MD 20817, USA
Interests: photonic materials, energy storage, transmission electron microscopy

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Department of Mechanical and Aerospace Engineering, Oklahama State University, Stillwater, OK 74078-5016, USA
Interests: nanodiamonds; thin film synthesis; electron energy-loss spectroscopy
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Special Issue Information

Dear Colleagues,

The interesting physics behind the quantum confinement of electronic excitations in quantum dots and nanocrystals has fascinated scientists in recent decades. The diverse applications and tunability in properties that have become available through this confinement have brought multidisciplinary fields together. Currently, quantum dots are being used in light-emitting diodes, photovoltaics, photoconductors and detectors, biomedicine and environment, catalysis, memories, etc.

Due to the ongoing appeal of quantum confinement to a broad community of investigators, we invite researchers to contribute to the Special Issue on Confined Crystals, Quantum Dots, and Nanocrystals. This issue focus is on the multidisciplinary aspect to bring scientists of all fields together to advance the field further and explore untouched potential and applications of confined crystals.

The potential topics include, but are not limited to:

- Synthesis and growth of nano crystals

- Characterization of nanocrystals

- The basic science studies including the physics behind the phenomenon

- Simulations and quantifications related to confinement and its applications

- Exploitation of the fascinating properties of nanocrystals in various existent and emerging applications

- The combinations of the existing properties to create a novel application

- Enhancing the current applications further for better tunability

- Applying the existing property in one field of science to another field

- Review on the diverse applications of quantum dots in multidisciplinary fields

Dr. Adele Moatti
Dr. Jeffery A. Aguiar
Prof. Dr. Ritesh Sachan
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Confined crystals
  • Quantum dots
  • Nano crystals
  • Confined electronic excitations
  • One dimensional crystals
  • Two dimensional crystals
  • Physics of confinement

Published Papers (9 papers)

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Research

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11 pages, 2440 KiB  
Article
Laser Irradiation-Induced Nanoscale Surface Transformations in Strontium Titanate
by Ashish Kumar Gupta, Siddharth Gupta, Soumya Mandal and Ritesh Sachan
Crystals 2022, 12(5), 624; https://doi.org/10.3390/cryst12050624 - 27 Apr 2022
Cited by 5 | Viewed by 1993
Abstract
We studied the structural transformations and atomic rearrangements in strontium titanate (SrTiO3) via nanosecond pulsed laser irradiation-induced melting and ultrafast quenching. Using scanning transmission electron microscopy, we determine that the laser-irradiated surface in single-crystalline SrTiO3 transforms into an amorphous phase [...] Read more.
We studied the structural transformations and atomic rearrangements in strontium titanate (SrTiO3) via nanosecond pulsed laser irradiation-induced melting and ultrafast quenching. Using scanning transmission electron microscopy, we determine that the laser-irradiated surface in single-crystalline SrTiO3 transforms into an amorphous phase with an interposing disordered crystalline region between amorphous and ordered phases. The formation of disordered phase is attributed to the rapid recrystallization of SrTiO3 from the melt phase constrained by an epitaxial relation with the pristine region, which eases up on the surface, leading to amorphous phase formation. With electron energy-loss spectroscopic analysis, we confirm the transformation of Ti+4 to Ti+3 due to oxygen vacancy formation as a result of laser irradiation. In the disordered region, the maximum transformation of Ti+4 is observed to be 16.2 ± 0.2%, whereas it is observed to be 20.2 ± 0.2% in the amorphous region. Finally, we deduce that the degree of the disorder increases from atomically disordered to amorphous transition in SrTiO3 under laser-irradiation. The signatures of short-range ordering remain similar, leading to a comparable fingerprint of electronic structure. With these results, this study addresses the gap in understanding the atomic and electronic structure modified by pulsed laser irradiation and functionalizing pristine SrTiO3 for electronic, magnetic, and optical applications. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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16 pages, 28947 KiB  
Article
Fabrication of Q-Carbon Nanostructures, Diamond and Their Composites with Wafer-Scale Integration
by Nayna Khosla and Jagdish Narayan
Crystals 2022, 12(5), 615; https://doi.org/10.3390/cryst12050615 - 26 Apr 2022
Cited by 10 | Viewed by 3784
Abstract
We report the formation of Q-carbon nanolayers, Q-carbon nanoballs, nanodiamonds, microdiamonds, and their composites by controlling laser and substrate variables. The choice of these parameters is guided by the SLIM (simulation of laser interactions with materials) computer modeling. For a constant film thickness [...] Read more.
We report the formation of Q-carbon nanolayers, Q-carbon nanoballs, nanodiamonds, microdiamonds, and their composites by controlling laser and substrate variables. The choice of these parameters is guided by the SLIM (simulation of laser interactions with materials) computer modeling. For a constant film thickness and initial sp3 content, we obtain different microstructures with increasing pulse energy density as a result of different quenching rate and undercooling. This is related to decreasing undercooling with increasing pulse energy density. The structure of thin film Q-carbon evolves into Q-carbon nanoballs with the increase in laser annealing energy density. These Q-carbon nanoballs interestingly self-organize in the form of rings with embedded nanodiamonds to form Q-carbon nanoballs/diamond composites. We form high quality, epitaxial nano, and micro diamond films at a higher energy density and discuss a model showing undercooling and quenching rate generating a pressure pulse, which may play a critical role in a direct conversion of amorphous carbon into Q-carbon or diamond or their composites. This ability to selectively tune between diamond or Q-carbon or their composites on a single substrate is highly desirable for a variety of applications ranging from protective coatings to nanosensing and field emission to targeted drug delivery. Furthermore, Q-carbon nanoballs and nanodiamonds are utilized as seeds to grow microdiamond films by HFCVD. It is observed that the Q-carbon nanoballs contain diamond nuclei of critical size, which provide available nucleation sites for diamond growth, leading to stress-free, adherent, and denser films, which are needed for a variety of coating applications. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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8 pages, 2494 KiB  
Article
The Growth of Hexagonal Boron Nitride Quantum Dots on Polycrystalline Nickel Films by Plasma-Assisted Molecular Beam Epitaxy
by Nurzal Nurzal, Wei-Cyuan Huang, Cheng-Yu Liu, Su-Hua Chen and Ing-Song Yu
Crystals 2022, 12(3), 347; https://doi.org/10.3390/cryst12030347 - 3 Mar 2022
Cited by 3 | Viewed by 2238
Abstract
In this report, quantum dots of hexagonal boron nitride (h-BN) were fabricated on the surface of polycrystalline Ni film at low growth temperatures (700, 750, and 800 °C) by plasma-assisted molecular beam epitaxy. Reflection high-energy electron diffraction could trace the surface condition during [...] Read more.
In this report, quantum dots of hexagonal boron nitride (h-BN) were fabricated on the surface of polycrystalline Ni film at low growth temperatures (700, 750, and 800 °C) by plasma-assisted molecular beam epitaxy. Reflection high-energy electron diffraction could trace the surface condition during the growth and perform the formation of BN. The observation of surface morphology by scanning electron microscopy and atomic force microscopy showed the nanodots of BN on Ni films. The existence of crystal h-BN quantum dots was determined by the analysis of Raman spectra and Kevin probe force microscopy. The cathodoluminescence of h-BN quantum dots performed at the wavelength of 546 and 610 nm, attributed to the trapping centers involving impurities and vacancies. Moreover, the influence of temperatures for the substrate and boron source cell was also investigated in the report. When the k-cell temperature of boron and growth temperature of substrate increased, the emission intensity of cathodoluminescence spectra increased, indicating the better growth parameters for h-BN quantum dots. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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16 pages, 3458 KiB  
Article
Electromagnetically Modified Wettability and Interfacial Tension of Hybrid ZnO/SiO2 Nanofluids
by Yarima Mudassir Hassan, Beh Hoe Guan, Lee Kean Chuan, Mayeen Uddin Khandaker, Surajudeen Sikiru, Ahmed Halilu, Abdullahi Abbas Adam, Bashir Abubakar Abdulkadir and Fahad Usman
Crystals 2022, 12(2), 169; https://doi.org/10.3390/cryst12020169 - 25 Jan 2022
Cited by 14 | Viewed by 2477
Abstract
Worldwide, reservoirs are having serious challenges on crude oil removal due to various factors affecting its mobility; hence, the approach of oil production needs to be rectified. Recently, various nanoparticles (NPs) were discovered to have aided in oil displacement to improve oil production [...] Read more.
Worldwide, reservoirs are having serious challenges on crude oil removal due to various factors affecting its mobility; hence, the approach of oil production needs to be rectified. Recently, various nanoparticles (NPs) were discovered to have aided in oil displacement to improve oil production by modifying some reservoir conditions thereby reducing interfacial tension (IFT) and rock surface wettability. However, the injected NPs in the reservoir are trapped within the rock pores and become worthless due to high temperature and pressure. Hence, introducing energy to the nanofluids via electromagnetic (EM) waves can improve nanoparticle (NPs) mobility in the reservoir for the attainment of oil displacements. In this work, hybrid ZnO/SiO2 NPs were selected by considering that the combination of two dielectric NPs may produce a single nanofluid that is expected to make the fluids more electrified under EM waves. The result showed that ZnO/SiO2 NPs reduced the IFT (mN/m) from 17.39 to 2.91, and wettability (°) from 141 to 61. Moreover, by introducing the EM waves to the fluids, the IFT was further reduced to 0.02 mN/m from 16.70 mN/m, and solid surface wettability was also reduced from 132° to 58°. The advancement observed during exposure to EM waves was attributed to the energy propagated to the fluids that polarize the free charges of the NPs and consequently activate the fluids by creating disturbances at the fluid/oil interface, which resulted in reduced IFT and wettability. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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10 pages, 3939 KiB  
Article
Atomic-Scale Insights on Large-Misfit Heterointerfaces in LSMO/MgO/c-Al2O3
by Soumya Mandal, Ashish Kumar Gupta, Braxton Hays Beavers, Vidit Singh, Jagdish Narayan and Ritesh Sachan
Crystals 2021, 11(12), 1493; https://doi.org/10.3390/cryst11121493 - 1 Dec 2021
Cited by 7 | Viewed by 2497
Abstract
Understanding the interfaces in heterostructures at an atomic scale is crucial in enabling the possibility to manipulate underlying functional properties in correlated materials. This work presents a detailed study on the atomic structures of heterogeneous interfaces in La0.7Sr0.3MnO3 [...] Read more.
Understanding the interfaces in heterostructures at an atomic scale is crucial in enabling the possibility to manipulate underlying functional properties in correlated materials. This work presents a detailed study on the atomic structures of heterogeneous interfaces in La0.7Sr0.3MnO3 (LSMO) film grown epitaxially on c-Al2O3 (0001) with a buffer layer of MgO. Using aberration-corrected scanning transmission electron microscopy, we detected nucleation of periodic misfit dislocations at the interfaces of the large misfit systems of LSMO/MgO and MgO/c-Al2O3 following the domain matching epitaxy paradigm. It was experimentally observed that the dislocations terminate with 4/5 lattice planes at the LSMO/MgO interface and with 12/13 lattice planes at the MgO/c-Al2O3 interface. This is consistent with theoretical predictions. Using the atomic-resolution image data analysis approach to generate atomic bond length maps, we investigated the atomic displacement in the LSMO/MgO and MgO/c-Al2O3 systems. Minimal presence of residual strain was shown at the respective interface due to strain relaxation following misfit dislocation formation. Further, based on electron energy-loss spectroscopy analysis, we confirmed an interfacial interdiffusion within two monolayers at both LSMO/MgO and MgO/c-Al2O3 interfaces. In essence, misfit dislocation configurations of the LSMO/MgO/c-Al2O3 system have been thoroughly investigated to understand atomic-scale insights on atomic structure and interfacial chemistry in these large misfit systems. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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17 pages, 21843 KiB  
Article
One-Step Formation of Reduced Graphene Oxide from Insulating Polymers Induced by Laser Writing Method
by Parand R. Riley, Pratik Joshi, Hristo Penchev, Jagdish Narayan and Roger J. Narayan
Crystals 2021, 11(11), 1308; https://doi.org/10.3390/cryst11111308 - 27 Oct 2021
Cited by 11 | Viewed by 4538
Abstract
Finding a low-cost and effective method at low temperatures for producing reduced graphene oxide (rGO) has been the focus of many efforts in the research community for almost two decades. Overall, rGO is a promising candidate for use in supercapacitors, batteries, biosensors, photovoltaic [...] Read more.
Finding a low-cost and effective method at low temperatures for producing reduced graphene oxide (rGO) has been the focus of many efforts in the research community for almost two decades. Overall, rGO is a promising candidate for use in supercapacitors, batteries, biosensors, photovoltaic devices, corrosion inhibitors, and optical devices. Herein, we report the formation of rGO from two electrically insulating polymers, polytetrafluoroethylene (PTFE) and meta-polybenzimidazole fiber (m-PBI), using an excimer pulsed laser annealing (PLA) method. The results from X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy confirm the successful generation of rGO with the formation of a multilayered structure. We investigated the mechanisms for the transformation of PTFE and PBI into rGO. The PTFE transition occurs by both a photochemical mechanism and a photothermal mechanism. The transition of PBI is dominated by a photo-oxidation mechanism and stepwise thermal degradation. After degradation and degassing procedures, both the polymers leave behind free molten carbon with some oxygen and hydrogen content. The free molten carbon undergoes an undercooling process with a regrowth velocity (<4 m·s−1) that is necessary for the formation of rGO structures. This approach has the potential for use in creating future selective polymer-written electronics. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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11 pages, 10382 KiB  
Article
Controlled Synthesis of Au Nanoparticles by Modified Polyol Methods: Determination of Their Size, Shape, and Crystal Structure
by Nguyen Thi Nhat Hang, Yong Yang, Nguyen Quang Thanh Nam, Masayuki Nogami, Le Hong Phuc, Nguyen Huu Tri, Ho Van Cuu and Nguyen Viet Long
Crystals 2021, 11(11), 1297; https://doi.org/10.3390/cryst11111297 - 26 Oct 2021
Cited by 6 | Viewed by 3196
Abstract
We successfully prepared Au nanoparticles using the modified polyol methods and design of experiments. The desirable crystal structure and particle size of Au nanoparticles with various kinds of polyhedral and spherical shapes as well as various kinds of their morphologies or complete and [...] Read more.
We successfully prepared Au nanoparticles using the modified polyol methods and design of experiments. The desirable crystal structure and particle size of Au nanoparticles with various kinds of polyhedral and spherical shapes as well as various kinds of their morphologies or complete and rough spherical crystal surfaces were experimentally predicted in TEM and XRD measurements according to the theoretical calculation and data. The fine crystal formation of Au nanostructures by modified polyol methods with EG, PVP, and NaBH4 is of great importance to their practical applications. Our research shows that the critical nucleation, growth, and formation of sizes, shapes, and morphologies of Au nanoparticles were experimentally discussed in modified polyol methods and design of experiments. In this context, our particle size calculation can hold the greatest attraction for researchers in the field of nanoparticles. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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8 pages, 1915 KiB  
Article
Controlled Morphology and Its Effects on the Thermoelectric Properties of SnSe2 Thin Films
by Muhammad Siyar, Maroosha Farid, Haad Khan, Malik Adeel Umar, Waqas Hassan Tanveer and Amna Safdar
Crystals 2021, 11(8), 942; https://doi.org/10.3390/cryst11080942 - 13 Aug 2021
Cited by 4 | Viewed by 3702
Abstract
In the last few years, the thermoelectric properties of tin selenide (SnSe) have been explored in much detail due to its high efficiency and green nature, being free of Te and Pb. In the same chalcogenide family, SnSe2 is also a layered [...] Read more.
In the last few years, the thermoelectric properties of tin selenide (SnSe) have been explored in much detail due to its high efficiency and green nature, being free of Te and Pb. In the same chalcogenide family, SnSe2 is also a layered structured material, but its thermoelectric potential has not been widely explored experimentally. Since SnSe2 has the layered structure, its electrical transport properties may strongly be affected by its microstructure and morphology. Here, we report the effect of reaction time on the structure, phase, and morphology of the SnSe2 during solvothermal synthesis process. We have studied four SnSe2 samples with different reaction times. The sample obtained after 16 h of reaction time was named as M1, for 20 h M2, similarly for 24 h was M3 and for 48 hours’ time, the sample was named as M4. We investigated its thermoelectric properties and found that phase purity and morphology can affect the thermoelectric performance of the synthesized samples. The peak power factor (PF) value along the ab plane was (0.69 μWcm−1K−2) for the M4 sample at 575 K, which was the highest among all the measured samples. The comparatively larger PF value of sample M4 can be related to the increase in its electrical conductivity due to increase in phase purity and band gap reduction. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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Review

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14 pages, 3307 KiB  
Review
Cellulose Nanomaterials as a Future, Sustainable and Renewable Material
by Hoang Thi Phuong, Nguyen Kim Thoa, Phung Thi Anh Tuyet, Quyen Nguyen Van and Yen Dao Hai
Crystals 2022, 12(1), 106; https://doi.org/10.3390/cryst12010106 - 14 Jan 2022
Cited by 14 | Viewed by 3718
Abstract
Cellulose nanomaterials (CNs) are renewable, bio-derived materials that can address not only technological challenges but also social impacts. This ability results from their unique properties, for example, high mechanical strength, high degree of crystallinity, biodegradable, tunable shape, size, and functional surface chemistry. This [...] Read more.
Cellulose nanomaterials (CNs) are renewable, bio-derived materials that can address not only technological challenges but also social impacts. This ability results from their unique properties, for example, high mechanical strength, high degree of crystallinity, biodegradable, tunable shape, size, and functional surface chemistry. This minireview provides chemical and physical features of cellulose nanomaterials and recent developments as an adsorbent and an antimicrobial material generated from bio-renewable sources. Full article
(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)
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