Article
Materials Science, Multidisciplinary
Vikas Kashyap, Chandra Kumar, Neeru Chaudhary, Navdeep Goyal, Kapil Saxena
Summary: The study investigates the quantum confinement effect in SiNWs fabricated by SIE technique, showing an enhanced optical band gap under UV excitation. The analysis of characteristic features of Raman line-shape helps to understand the mechanism of QC effect, and different models are used to calculate the NCS of SiNWs in the samples. This research suggests a new direction for fabricating optoelectronic devices based on nano-scale light-matter interactions.
Article
Multidisciplinary Sciences
Ovidiu Cojocaru, Ana-Maria Lepadatu, George Alexandru Nemnes, Toma Stoica, Magdalena Lidia Ciurea
Summary: A detailed study on the bandgap dependence of spherical Ge-rich GexSi1-x nanocrystals was conducted using atomistic density functional theory calculations. The results show a composition invariance of the bandgap diameter dependence, with the bandgap of NCs being well described by a power function for a certain diameter range. H-passivation of the NC surface helps accurately determine the NC bandgap by excluding surface states near the band edges.
SCIENTIFIC REPORTS
(2021)
Article
Chemistry, Physical
Lu Zhang, Haiyang Hong, Kun Qian, Songsong Wu, Guangyang Lin, Jianyuan Wang, Wei Huang, Songyan Chen, Cheng Li
Summary: In this study, a highly controllable method for synthesizing GeSn quantum dots in a CMOS compatible way was demonstrated, resulting in high area density, high-Sn fraction, and narrow size distribution of the GeSn quantum dots. The properties of the GeSn quantum dots can be well controlled by adjusting the preparation temperature.
APPLIED SURFACE SCIENCE
(2022)
Review
Chemistry, Multidisciplinary
Yize Su, Chenhao Wang, Zijian Hong, Wei Sun
Summary: Silicon nanocrystals have drawn significant attention in recent decades for their unique luminescent properties, with thermal disproportionation method offering precise control over their size and structure, showing promising industrial applications. Research has shown that factors such as temperature, Si/O ratio, and surface groups play a crucial role in determining the properties of silicon nanocrystals.
FRONTIERS IN CHEMISTRY
(2021)
Article
Chemistry, Analytical
Nur Diyana Halim, Muhammad Safwan Zaini, Zainal Abidin Talib, Josephine Ying Chyi Liew, Mazliana Ahmad Kamarudin
Summary: The effect of temperature on the photoluminescence emission of lead sulfide (PbS) and lead sulfide/manganese tellurite (PbS/MnTe) quantum dots was investigated. The results showed that as the temperature increased, the emission was blue-shifted and the emission bandwidth gradually increased, indicating electron-phonon interactions. Analysis based on the Boson model revealed stronger exciton longitudinal-optical-phonon coupling in the compound structure of PbS/MnTe compared to PbS.
Article
Chemistry, Analytical
Shanshan Wang, Shujia Huang, Jijie Zhao
Summary: The optical properties of silicon nanowire arrays can be controlled by adjusting the structural parameters of the synthesized nanostructure arrays, which are formed by replication of versatile homogeneous Au films using porous anodic aluminum oxide membranes as templates.
Article
Chemistry, Multidisciplinary
Wenqi Hu, Mohammad A. Kher-Elden, Hexu Zhang, Peng Cheng, Lan Chen, Ignacio Piquero-Zulaica, Zakaria M. Abd El-Fattah, Johannes V. Barth, Kehui Wu, Yi-Qi Zhang
Summary: In this study, the tailoring of Shockley surface-state electrons using complex interfacial supramolecular tessellations was investigated. Experimental and modeling results showed the possibility of realizing novel two-dimensional electronic structures through quantum dot coupling, which could provide a complementary and versatile route for controlling surface electronic landscapes.
Article
Chemistry, Multidisciplinary
Yuqin Zhang, Shi He, Honghong Yao, Hao Zuo, Shuang Liu, Chao Yang, Guoying Feng
Summary: Previous studies have shown that the nano-crystallization process affects the luminescence properties of nanocrystals. This project explores the influence of nanocrystal size on the electrical and optical properties of Cr2+:ZnSe nanowires. A first-principles study of Cr2+:ZnSe nanowires with different sizes was conducted. It was found that the Cr2+ ion prefers to reside at the surface of ZnSe nanowires and as the nanocrystal size decreases, a significant short-wave-length shift in absorption was observed.
Article
Materials Science, Multidisciplinary
Vikas Kashyap, Chandra Kumar, Neeru Chaudhary, Navdeep Goyal, Kapil Saxena
Summary: This study focuses on the nanocrystal size (NCS) of aligned silicon nanowires (SiNWs) array fabricated by metal induced chemical etching using different resistivity of Si wafer. The microstructural analysis of SiNWs has been carried out through FESEM and XRD, showing visible photoluminescence emission under UV excitation due to quantum confinement (QC) effect. QC effect has been further analyzed using Raman spectroscopy, revealing red shift and asymmetry ratio of Raman band observed from SiNWs as compared to its bulk counterpart, along with a comparative study of NCS using various QC based models like Brus model, Yorikawa-Muramatsu (Y-M) model and bond-polarizability (BP) model.
Article
Materials Science, Multidisciplinary
Mohammad Kamal Hossain, Roberto dos Reis, Wayesh Qarony, Yuen Hong Tsang, Johnny C. Ho, Kin Man Yu
Summary: This study presents a non-catalytic approach for growing all-inorganic CsPbX3 perovskite nanowires using chemical vapor deposition, revealing a growth mechanism involving nucleation of halide nanoparticles, structural transformations, and eventual formation of complete nanowires. Spectroscopic measurements show that nanoscale features at different growth stages have similar material properties as the final nanowires, suggesting potential applications in novel optoelectronic devices.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)
Article
Multidisciplinary Sciences
Deniz Yazicioglu, Sebastian Gutsch, Margit Zacharias
Summary: The effect of an externally applied electric field on exciton splitting and carrier transport in Si nanocrystals embedded in SiO2 superlattices was investigated. The role of surface defects in enhancing this effect was analyzed. The findings provide insights for the design and application of photon detection and tandem solar cells.
SCIENTIFIC REPORTS
(2022)
Review
Spectroscopy
Rajesh Kumar, Manushree Tanwar
Summary: Raman spectroscopy is a versatile tool for material characterization, capable of extracting information about materials across various scientific fields, and has been applied to almost all areas. By studying silicon as an example, factors influencing Raman line shapes can be understood, and important information about the material can be obtained from the analysis of these shapes.
JOURNAL OF RAMAN SPECTROSCOPY
(2021)
Article
Biochemistry & Molecular Biology
Ziyi Liu, Fei Li, Yi Luo, Ming Li, Guanghui Hu, Xianjuan Pu, Tao Tang, Jianfeng Wen, Xinyu Li, Weitao Li
Summary: High-photoluminescence graphene quantum dots were synthesized through a simple one-pot hydrothermal process and separated using dialysis bags of different molecular weights, resulting in four GQDs with varying sizes. As the size of the separated GQDs decreased, the intensity of the emission peak became stronger, with the smallest GQDs showing the most energetic PL intensity among the four separated GQDs. The PL energy of all separated GQDs shifted slightly, as supported by density functional theory calculations.
Article
Optics
Y. Luo, X. Yang, L. Yue, D. S. Ren, J. R. Chen
Summary: The luminescence intensity of silicon nanocrystals (Si-NC) can be enhanced by phosphorus (P) doping. In-situ P-doped Si-NC exhibited higher luminescence intensity compared to ex-situ P-doped Si-NC, with an order of magnitude increase compared to undoped Si-NC.
Article
Nanoscience & Nanotechnology
Chia-Ching Huang, Yingying Tang, Marco van der Laan, Jorik van de Groep, A. Femius Koenderink, Katerina Dohnalova
Summary: The study directly assessed the size dependence of the optical band gap and found that the optical band gap is given by the amorphous shell. It proposes that structural disorder might be the reason behind the limited emission tunability from various Si-NPs. The results suggest a pressing need for development and broader use of direct correlative single-dot microscopy methods.
ACS APPLIED NANO MATERIALS
(2021)
Article
Spectroscopy
Shailendra K. Saxena, Rupnayan Borah, Vivek Kumar, Hari Mohan Rai, Ravikiran Late, V. G. Sathe, Ashisha Kumar, Pankaj R. Sagdeo, Rajesh Kumar
JOURNAL OF RAMAN SPECTROSCOPY
(2016)
Article
Chemistry, Physical
Shailendra K. Saxena, Vivek Kumar, Hari M. Rai, Gayatri Sahu, Ravikiran Late, Kapil Saxena, A. K. Shukla, Pankaj R. Sagdeo, Rajesh Kumar
Article
Chemistry, Physical
Priyanka Yogi, Suryakant Mishra, Shailendra K. Saxena, Vivek Kumar, Rajesh Kumar
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2016)
Article
Chemistry, Physical
Priyanka Yogi, Deepika Poonia, Suryakant Mishra, Shailendra K. Saxena, Swarup Roy, Vivek Kumar, Pankaj R. Sagdeo, Rajesh Kumar
JOURNAL OF PHYSICAL CHEMISTRY C
(2017)
Article
Materials Science, Multidisciplinary
T. Anusuya, J. Prakash, Devesh K. Pathak, Kapil Saxena, Rajesh Kumar, Vivek Kumar
Summary: An easy and efficient method for synthesizing porous graphene network (PGN) from reduced graphene oxide under ambient conditions has been developed, showing promise for various applications. The structural transformation during reduction of GO was investigated using X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. The results demonstrate a convenient and general protocol for synthesizing PGN from GO.
MATERIALS TODAY COMMUNICATIONS
(2021)
Article
Engineering, Electrical & Electronic
T. Anusuya, D. Prema, Vivek Kumar
Summary: Reduction of graphene oxide improves the physical and electronic characteristics of reduced graphene oxide (rGO) through de-oxygenation and restoration of pi-conjugation. The changes in conductivity during reduction process are governed by desorption of water and OH groups as well as restoration of graphene sp(2) network. This process is suitable for applications including flexible electronics, TCO layer in solar cells, and gas/temperature sensors.
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
(2022)
Article
Chemistry, Physical
Devesh K. Pathak, Manushree Tanwar, Chanchal Rani, Suchita Kandpal, Tanushree Ghosh, Priyanka Yogi, T. Anusuya, Puspen Mondal, Anjali Chaudhary, Vivek Kumar, Rajesh Kumar
Summary: The study introduces a new inclusive approach for analyzing size-dependent field emission properties of silicon nanowires. By using boost factor and field emission power density as parameters, it quantifies the size-dependent field emission and proposes an empirical formula to represent the power density. This framework complements the traditional Fowler-Nordheim methodology for more efficient analysis of nanomaterials.
Article
Environmental Sciences
T. Anusuya, Veeresh Kumar, Vivek Kumar
Summary: Efforts are being made to develop fast, cost-effective and sensitive sensors to detect water contamination by toxic heavy metal ions, using oxygenated functional groups decorated graphene quantum dots (GQDs) which effectively enhance aqueous solubility. The fluorescence quenching results showed that the synthesized GQDs are efficient fluorescent probes for heavy metal ions, with detection limits for Hg2+, Cd2+ and Pb2+ being 1.171 mu M, 2.455 mu M, and 2.011 mu M respectively.
Article
Materials Science, Multidisciplinary
Vikas Kashyap, Chandra Kumar, Vivek Kumar, Neeru Chaudhary, Kapil Saxena
Summary: In this study, the effect of crystal size and aspect ratio on the field emission properties of silicon nanowires fabricated using metal-induced chemical etching was investigated. The results showed that smaller crystal size resulted in a lower turn-on voltage for field emission.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2022)
Article
Physics, Multidisciplinary
Tanushree Ghosh, Suchita Kandpal, Manushree Tanwar, Devesh K. Pathak, Chanchal Rani, T. Anusuya, Vivek Kumar, Rajesh Kumar, Anjali Chaudhary
Summary: This article introduces a flexible electrode based on a carbon cloth substrate, consisting of RGO and nano-WO3, for flexible supercapacitor electrodes. Compared to the standalone nano-WO3 electrode, this hybrid electrode exhibits improved supercapacitor behavior and higher stability.
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS
(2022)
Article
Physics, Condensed Matter
Vikas Kashyap, Chandra Kumar, Vivek Kumar, Neeru Chaudhary, Kapil Saxena
Summary: The study investigates the reflection and absorption characteristics of random silicon nanowires arrays with different lengths and doping types. It explores the comparative study of light trapping in Si-NWs fabricated by using n-type and p-type Si wafer, and finds that the reflectance can be modified due to light absorption driven by multiple scattering inside the structure. The measurement results of current-voltage curves indicate that the dopant types have significant influences on the photovoltaic parameters, with p-type doped Si-NWs exhibiting the highest power conversion efficiency.
PHYSICA B-CONDENSED MATTER
(2022)
Article
Chemistry, Physical
T. Anusuya, D. K. Pathak, Rajesh Kumar, Vivek Kumar
Summary: This study utilizes first order Raman scattering to investigate the structural modifications and quantification of defects in graphene oxide (GO) and thermally reduced GO (rGO). The research reveals that estimating defect density and determining the degree of reduction and quality of GO and rGO solely based on the intensity ratios of graphitic (G) and defect (D) Raman peaks can lead to over or underestimation of results due to the presence of intermixed defects inherent in the synthesis process. To overcome this, the integrated first order G and D-peak Raman intensities of GO and rGO annealed at different temperatures are analyzed with the theoretical defect diagram to extract information about defect contribution and the nature of disorder during structural evolution.
Article
Chemistry, Physical
K. Karthick Raja, T. Anusuya, Vivek Kumar
Summary: Hydrogen adsorption on pristine graphene, graphene with defect, and transition metal doped graphene has been studied using density functional theory. The results show that transition metal-doped graphene with defects exhibits better hydrogen adsorption properties, especially the Fe/GD system, which shows higher adsorption energy and stability. The study also suggests that hydrogen concentration can be predicted by measuring conductivity changes.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Navraj Poudel, T. Anusuya, Kapil Saxena, Rajesh Kumar, Vivek Kumar
ADVANCES IN MATERIALS AND PROCESSING TECHNOLOGIES
(2019)
Article
Chemistry, Multidisciplinary
Vivek Kumar, Deepak Gupta, Rajesh Kumar
