Nanoscale Science and Technology Research Group, BUET

The pollution of water resources with pharmaceutical substances poses a critical threat to global health and environmental stability. This study demonstrates a highly effective method for removing ciprofloxacin, a broad-spectrum antibiotic and pharmaceutical contaminant, from aqueous solutions using sulfonated graphene oxide (SGO) as an adsorbent. Comprehensive experiments, supported by density functional theory (DFT) analysis, confirm the strong interaction between ciprofloxacin and SGO through microscopy, spectroscopy, and theoretical techniques. The study rigorously evaluates the impacts of adsorption time, medium pH, adsorbent quantity, ciprofloxacin concentration, inorganic cations, and temperature on adsorption performance, providing compelling evidence of SGO’s superior performance in mitigating this pressing environmental issue. Results reveal that the adsorption process follows a pseudo-second-order kinetic model and aligns with the Langmuir isotherm, underscoring SGO’s high affinity for ciprofloxacin. SGO achieved a significant maximum uptake capacity of 1000.00 μmol/g within 240 min at a low adsorbent dose of 0.2 g/L and optimal pH of 4.0. Thermodynamic assessments indicate that ciprofloxacin adsorption on SGO is both spontaneous and endothermic. Additionally, ciprofloxacin release from antibiotic-loaded SGO was notably high (99.14%) in a solution of 1 M HCl in DMF, and SGO retained over 95.78% of its initial adsorption capacity after five adsorption–desorption cycles, demonstrating its robustness and reusability. These findings strongly position SGO among graphene oxide and their derivatives as a promising and sustainable adsorbent for removing pharmaceutical contaminants, particularly ciprofloxacin, from aqueous solutions. This offers significant potential for advancing water purification technologies in healthcare and environmental applications.

"Exploring the Adsorption Efficiency of Sulfonated Graphene Oxide for Ciprofloxacin Removal from Aqueous Solution: Insights from Density Functional Theory, Kinetics, Thermodynamics and Reusability"

To Read: https://doi.org/10.1021/acsomega.4c11231
Published by American Chemical Society

The relentless miniaturization of field-effect transistors (FETs) necessitates the development of novel materials and architectures to address the challenges posed by short-channel effects (SCEs) and power inefficiencies. This investigation examines the performance of sub-5-nm monolayer α -CS and SiP double-gated (DG) n-type FETs utilizing underlayer (UL) modulation, an approach that has not been previously explored for these materials at such scales. Through the application of density functional theory (DFT) and nonequilibrium Green’s function (NEGF) simulations, we illustrate that the integration of UL significantly enhances the subthreshold swing (SS), on–off ratio ( Ion/Ioff ), delay ( τ ), and power delay product (PDP). The integration of UL helps achieve the International Technology Roadmap for Semiconductor (ITRS) HP device requirements and improves the overall performance of the sub-5-nm monolayer α -CS and SiP DG n-type FETs. For devices with a gate length of 3-nm and 2-nm UL modulation achieves an ( Ion/Ioff ) of 1.34×104 for α -CS and 1.57×104 for SiP, with SS values as low as 108mV/dec for α -CS and 101mV/dec for SiP. These findings exceed the ITRS 2028 Horizon targets, positioning α -CS and SiP as premier candidates for high-performance (HP) logic applications. The study offers essential insights into UL-driven electrostatic control, thereby addressing a critical challenge in the design of ultrascaled 2-D n-type FETs.

To Read: https://doi.org/10.1109/TED.2025.3602761
Published by IEEE

The memristor is a cornerstone for developing novel non-volatile memory devices that enable brain-like efficient processing and storage capabilities. Two-dimensional transition metal dichalcogenide (TMDC)-based memristors are gaining increasing attention due to the advantages they present over their bulk counterparts. In this work, we employed first-principles calculations to demonstrate that dopants play a significant role in reducing the cycle-to-cycle variability and in lowering the contact resistance in monolayer WS2-based memristor. The possibility of reduced cycle-to-cycle variability is reflected by the attractive nature of the calculated interaction energy between dopant metal atoms and a sulphur monovacancy in the WS2 monolayer. The potential for reduced contact resistance is evident from the reduced tunneling barrier heights and increased tunneling probabilities at the electrode/WS2 interface upon doping. Additionally, extra states are found to appear in the density of states upon doping, which can prove useful for adjusting the conductance of a doped WS2-based memristor as required. Finally, the obtained features are used to outline dopant selection criteria based on the valence electron configuration of dopants. The obtained characteristics and outlined criteria can serve as guidelines for the future design of optimized WS2-based memristive devices, possessing lower contact resistance and reduced variation in device performance.

To Read: https://doi.org/10.1039/D5RA02473K
Published by Royal Society of Chemistry

In this study, we analyze the optical, thermodynamic, and electronic properties of 2D MoGe2P4 from the first principle calculation. 2D MoGe2P4 demonstrates superior optical absorption in the NIR-I biological window (750–1000 nm) with a peak near 808 nm and excellent thermal conductivity (63 W/m/K). Finite-difference time-domain (FDTD) simulations and heat simulations demonstrate that 2D MoGe2P4 possesses efficient photothermal conversion under low laser power (0.5 W/cm2), which is operated at 808 nm. Theoretical investigation shows rapid temperature elevation (ΔT = 24.8°C) of the 2D MoGe2P4 within 2 min and photothermal stability over multiple laser cycles, achieving temperatures suitable for effective photothermal therapeutic applications. Photothermal therapy (PTT) is an emerging tumor treatment technique that utilizes photothermal agents (PTAs) to convert near-infrared (NIR) light into localized heat for tumor ablation. To enhance biocompatibility, we analyze the PEGylation of 2D MoGe2P4 nanosheets through molecular dynamics simulation. PEGylation at human body temperature was stable, which signifies 2D MoGe2P4’s prospect in therapeutic applications. This research highlights the potential of 2D MoGe2P4 as an emerging material for PTA, establishing a foundation for experimental and clinical trials.

To Read: http://dx.doi.org/10.1002/nano.70028
Published by Wiley and available as Open Access

This study evaluates the potential of transition metal dichalcogenide (TMD) nanoribbons, specifically MoTe2, TaS2, WTe2, NbSe2, and TaSe2 as nanoscale interconnects to address scaling challenges in semiconductor technology. Six configurations, 1T′ MoTe2, 1T TaS2, 1T′ WTe2, 1T NbSe2, and 2H TaSe2 (in both armchair and zigzag orientations), are assessed in terms of key performance metrics such as propagation delay, crosstalk-induced delay, noise performance, energy-delay product (EDP), stability, and frequency response. To ensure a comprehensive analysis of structural variations, three distinct edge termination configurations have been investigated for each of the TMD (MX2) materials: C1, with both edges terminated by metal (M) atoms; C2, with one edge terminated by a M atom and the other by a chalcogen (X) atom; and C3, with both edges terminated by X atoms. Interconnect behavior is simulated using a π-type equivalent single conductor (ESC) model in conjunction with a driver-interconnect-load (DIL) setup. The ESC circuit parameters, derived from the number of conducting channels and Fermi velocity calculated via first-principles simulations, facilitated detailed delay and noise calculations, while the open-loop transfer function provided insights into frequency response, Nyquist plots, and damping factors. In addition to our six proposed configurations (each with three distinct edge configurations), nine configurations reported in the literature are compared in terms of the same performance parameters, thereby evaluating a total of twenty-seven configurations. Among these, TaS2 nanoribbon-based configurations outperformed the others overall, with MoTe2, WTe2, and NbSe2 also showing competitive performance; TaSe2 configurations, despite their poorer interconnect performance, demonstrated superior stability. These findings indicate that TaS2, along with NbSe2, WTe2, and MoTe2, is a promising candidate for future nanoscale interconnect applications at reduced dimensions.

To Read: http://dx.doi.org/10.1021/acsaelm.5c00367
Published by American Chemical Socierty

The emergence of SARS-CoV-2 in 2019 led to the global COVID-19 pandemic, highlighting the urgency for developing cost-effective and non-invasive methods to detect diseases at an early stage. Human breath, rich in volatile organic compounds (VOCs), is promising for cost-effective and rapid disease detection, with specific VOCs like methanol, ethanal, butanone, acetone, and ethyl butyrate linked to COVID-19. Recent advances in biomarker detection and gas sensing with 2D materials, particularly III-As monolayers like BAs, GaAs, and AlAs, offer high sensitivity at low concentrations, providing a novel avenue for exploring their potential in detecting COVID-19 biomarkers. This article aims to examine the effects of adsorption on different properties of III-Arsenide (BAs, GaAs and AlAs) monolayers, particularly in connection with SARS-CoV-2 biomarkers. In order to examine the interaction between the monolayers and biomarkers, first-principles computations within the framework of density functional theory (DFT) are utilized. The present study involves an investigation of the modifications in the band structure, density of states (DOS), work function, electron density difference, and optical properties (reflectance and absorbance) of III-As monolayers, with the aim of assessing their viability for the detection of SARS-CoV-2 biomarkers along with interfering gases such as CO2 and H2O. It is observed that VOCs induce a notable change in the work function of GaAs which serves as an indicator of the presence of these biomarkers. However, the changes in work function are not as substantial as those for AlAs and BAs. Additionally, the chemiresistive sensitivity, optical sensitivity and recovery time of III-As are investigated. The findings suggest that the pristine GaAs monolayer displays a significant level of sensitivity and selectivity towards the SARS-CoV-2 biomarkers, rendering it a material with potential for utilization in sensing applications. Furthermore, it has been observed that the recovery time of the GaAs monolayer subsequent to its exposure to the VOC biomarkers lies within an acceptable threshold. Upon exposure to UV light, the recovery time is further reduced. The outcomes of our study indicate that GaAs monolayers exhibit considerable potential as chemiresistive, work function-based and optical sensors for the precise and discerning identification of VOCs linked to the SARS-CoV-2 virus compared to the other two III-As monolayers.

To Read: http://dx.doi.org/10.1039/D3CP05215J
Published by Royal Society of Chemistry

Our Article on the Cover Page of "𝐍𝐚𝐧𝐨𝐬𝐜𝐚𝐥𝐞 𝐀𝐝𝐯𝐚𝐧𝐜𝐞𝐬", Royal Society of Chemistry

Thin-film silicon solar cells have sparked a great deal of research interest because of their low material usage and cost-effective processing. Despite the potential benefits, thin-film silicon solar cells have low power-conversion efficiency, which limits their commercial usage and mass production. To solve this problem, we design an ultrathin dual junction tandem solar cell with Cu2ZnSnS4 (CZTS) and crystalline silicon (c-Si) as the main absorbing layer for the top and bottom cells, respectively, through optoelectronic simulation. To enhance light absorption in thin-film crystalline silicon, we use silver nanoparticles at the rear end of the bottom cell. We utilize amorphous Si with a c-Si heterojunction to boost the carrier collection efficiency. Computational analyses show that within 9 μm thin-film c-Si, we achieve 28.28% power conversion efficiency with a 220 nm top CZTS layer. These findings will help reduce the amount of Si (∼10 vs. ∼180 μm) in silicon-based solar cells while maintaining high power conversion efficiency.

To Read: http://dx.doi.org/10.1039/D2NA00826B
Published by Royal Society of Chemistry

MoSi2N4 is a recently fabricated 2-dimensional indirect bandgap semiconductor material that has attracted interest in various fields due to its promising properties. A defect-based thorough and reliable investigation of its physical properties is indispensable in this regard to explore its industrial applications in the future. In this work, a comprehensive vacancy defect-based analysis of the electronic and mechanical characteristics of this material is conducted with varying defect percentages. We have analyzed the gradual change in electronic properties of MoSi2N4 by performing first-principles density functional theory-based investigation and presented a detailed analysis for point vacancies ranging from 0.297% to 14.29%, revealing the transition of this monolayer from the semiconductor to metal phase. The gradual change in mechanical properties due to the defect introduction has also been reported and analyzed, where the Young's modulus, Poisson ratio, elastic constant, etc. are calculated by the stress–strain method using Matrix Sets (OHESS). Further, we extend the investigation to the exploration of thermal and topological characteristics and report the triviality of the MoSi2N4 material as well as the effect on specific heat, entropy, and free energy with respect to temperature. We believe that the results presented in this study could assist the process of incorporating MoSi2N4 in future 2D electronics.

To Read: http://dx.doi.org/10.1039/D2RA07483D
Published by Royal Society of Chemistry

GaN-based electronics have witnessed an increase in both research and industrial activities, first spurred by the successful demonstration of GaN LEDs, and are now expanding into transistors and photovoltaic cells. In addition, GaN/GaAs heterojunction devices are currently receiving much interest. In this study, we conduct rigorous optoelectronic computational analysis of cubic phase GaN (c-GaN)/GaAs heterojunction solar cells for a comprehensive understanding of the cell. We utilize a compositionally graded GaAs1–xNx buffer layer to reduce defect states at the heterojunction interface caused by a significant lattice mismatch between c-GaN and GaAs. Furthermore, we enhance the performance of the cell by optimizing GaAs absorber layer thickness and c-GaN buffer layer doping concentration. Moreover, we examine the effects of GaAs1–xNx/GaAs interface recombination velocity (IRV) on the cell. Overall, we achieve ~23% power conversion efficiency within 1.25- μm thin-film GaAs at low GaAs1–xNx/GaAs IRV. The analyses and results presented in this study demonstrate the vast application potential of c-GaN/GaAs heterojunction in high-efficiency solar cells.

To Read: http://dx.doi.org/10.1109/TED.2023.3237995
Published by IEEE

We report the design, optimization, and performance analysis of three axial junction nanowire solar cells (NW SCs) based on cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and copper zinc tin sulfide (CZTS) with significant improvement in their optical and electrical characteristics compared to their planar counterparts. It is shown that the performance of these NW SCs can be further improved by incorporating a hemispherical indium doped tin oxide (ITO) forward scatterer on top of the ITO front contact of the solar cells. We also compare forward scatterer incorporated NW SCs with forward scatterer incorporated planar solar cells (PSCs) and observe that forward scatterers significantly enhance the absorption in both cases. We further study the optimum size and arrangement of ITO hemispheres that result in improved photocurrent. In optimum cases, the incorporation of forward scatterers leads to absorption enhancement of 7.8%, 5.36%, and 8.8% in PSCs, and 21.4%, 7.36%, and 6.02% in NW SCs, respectively, for CdTe, CIGS, and CZTS absorbers in the same order. From the absorption profile at various wavelengths, it is found that forward scatterers enhance absorption in the 450–600 nm wavelength range, while nanowires improve absorption in the 600–800 nm range, and their combination results in an improved absorption profile for the entire visible wavelength range. We also observe increased electron–hole-pair (EHP) generation rate due to increased field-scattering and light concentration at the center of the nanowire below forward scattering hemispheres, leading to 46%, 32%, and 82.5% improvement in power conversion efficiency (PCE) for the three absorber layers, respectively. The effects of Al2O3 and SiO2 passivation layers surrounding the nanowires of the optimized cells are observed, and we conclude that the CIGS absorber benefits the most when the SiO2 passivation layer is used, increasing its PCE from 29.72% to 32.43%, while the PCEs of CdTe and CZTS are unaffected by the passivation layer due to competing effects of reduced absorption and reduced surface recombination.

To Read: http://dx.doi.org/10.1039/D1RA09392D
Published by Royal Society of Chemistry