Browsing by Author "Amritanshu Pandey"

Now showing 1 - 12 of 12

A curious observation of Pauli-Blocking in MoS2-quantum dots/graphene hybrid system
(American Institute of Physics Inc., 2018) Amulya Nemoori; Himanshu Mishra; Vijay Kumar Singh; P.K. Shukla; Anchal Srivastava; Amritanshu Pandey
In this study, Pauli-Blocking has been observed in a 0D/2D MoS2 quantum dots/graphene (MoS2-QDs/graphene) hybrid system. For the observation of room temperature Pauli-Blocking in the 0D/2D system, a photodetector device based on n-type MoS2-QDs and CVD grown graphene has been fabricated using a facile and lithography free technique. The current-voltage characteristics of the device have been performed at room temperature. The fabricated device shows a negative response under visible light (λ ∼ 400 to 700 nm) illumination. The dark to photo current ratio of the device shows variation up to two orders of magnitude. This negative response, which results decrease in current under visible light illumination, may be attributed to the Pauli-Blocking due to high absorbance of photon energy in visible light range. Furthermore, it is believed that the present study may provide an insight into understanding the Pauli-Blocking in 0D/2D hybrid system at room temperature. © 2018 Author(s).
A Highly Sensitive Ag/MG-CQDs/ZnO NP Ultraviolet Photodetector
(Institute of Electrical and Electronics Engineers Inc., 2022) Anil Kumar; Prashant Kumar Gupta; Monika Srivastava; Amritanshu Pandey; Amit Srivastava; S.K. Srivastava
This article reports the fabrication of marigold flower-derived carbon quantum dots (MG-CQDs) and ZnO nanoparticle (NP)-layered thin-film-based ultraviolet (UV) photodetector (PD) on Si/SiO2 substrates. The MG-CQDs have been green synthesized from natural biomass marigold (MG) flowers by a facile, low-cost hydrothermal synthesis method. The ZnO NPs have been prepared through a rapid sol-gel process. The Ag/MG-CQDs/ZnO NP-layered thin-film-based fabricated UV PDs have good responsivity ({R} ), external quantum efficiency (EQE), and detectivity ({D}{ast } ) values 42.78 A/W, 14535.54%, and {1.99}times {10}{{13}} jones, respectively, under UV radiation (365 nm). The response time of Ag/MG-CQDs/ZnO NP-fabricated UV PD shows adequate rise time (0.213 s) and fall time (0.085 s). © 2001-2012 IEEE.
A sensitive SPR biosensor for glucose detection using MoS2 quantum dots
(Elsevier Inc., 2025) Awadhesh Kumar; A. Sameer Ruban Kumar; Pinky Sagar; Monika Srivastava; Amritanshu Pandey; Rajiv Prakash; Sanjay Kumar Srivastava
Diabetes patients require continuous blood glucose monitoring throughout the year. In this study, we present a highly sensitive surface plasmon resonance (SPR) biosensor for glucose detection, utilizing molybdenum disulfide quantum dots (MoS2 QDs). The proposed biosensor is based on the Kretschmann configuration, consisting of sequentially deposited layers of chromium (Cr), gold (Au), L-cysteine (Cys), and MoS2 QDs on a BK-7 glass substrate through a coating technique. A self-assembled monolayer (SAMs) of Cys is employed to covalently bond the amine groups to the Au surface, ensuring strong adhesion. The sensor demonstrates a linear detection range of 0.5–10 mM for glucose, with a limit of detection (LOD) of 0.31 mM. The experimental results align well with theoretical predictions calculated using the transfer matrix method, indicating strong agreement between the two. Additionally, the biosensor exhibits excellent selectivity in the presence of other biomolecules, specifically showing a high affinity for glucose. The proposed SPR biosensor is highly promising for blood D-glucose detection in diabetic patients due to its miniaturization, high sensitivity, and stability. This work highlights its potential for application in real-time glucose monitoring devices. © 2025 Elsevier B.V.
A Study of Sensitivity Improved Probe Using Hyperbolic Metamaterial for Optical Fiber SPR (OFSPR)-based Refractive Index Sensor
(Springer, 2022) Sarvesh Kumar Dubey; Anil Kumar; Amritanshu Pandey; Amit Pathak; S.K. Srivastava
In this work, we theoretically study the plasmonic behavior of Ag and Au with a hyperbolic metamaterial (HMM) and propose a numerical simulation of a D-shaped surface plasmon resonance (SPR)-based refractive index sensor in the near-infrared (NIR) region using the finite element method (FEM). The design of the sensing probe consists of a grating structure of metal (Ag/Au) coated with an alpha-phase molybdenum trioxide (α-MoO3) HMM layer. The sensing layer of α-MoO3 over Ag/Au is responsible for the enhanced sensitivity of the optical fiber SPR sensor. This is attributed to the better SPR generation with a metal-dielectric layer. Numerical results show that the proposed sensor is able to detect a refractive index over a large dynamic range of 1.33 to 1.4. With the help of the optimized structure, we achieve maximum sensitivity of 8.31 μm /RIU and 9.89 μm /RIU for the Ag-α-MoO3- and Au-α-MoO3-based grating structure, respectively. These results show excellent response in comparison with other reported works. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Analysis of ternary layer photonic band gap tunable filters for wavelength division multiplexing applications
(American Scientific Publishers, 2017) Amritanshu Pandey; Archana Tripathi; Raghavi; S.K. Srivastava; S. Jit
In this paper, we have proposed a ternary layer photonic band gap structure as a versatile optical filter for various WDM applications. The design of a versatile optical filter has been done using Photonic Band Gap (PBG) structure for all Wavelength Division Multiplexing (WDM) applications including Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). The proposed optical filter is a one-dimensional ternary periodic structure with a linearly periodic refractive index profile. It can be tuned by varying lattice parameters and angle of incidence. The filters are designed in the S band of EM spectrum, around 1310 nm wavelength, which can be used in CWDM applications at transmitter and receiver side of the network. Similarly in the C-Band of EM spectrum, near 1550 nm wavelength, filter with 0.4 nm pass band are designed. For DWDM applications, separation between neighboring wavelength channels is less than 1 nm and so the width of the pass band of an individual filter must be less than 0.5 nm. Therefore the filter designed for the C band can be used in DWDM applications. Thus the proposed filter design technique covers all the different ranges of WDM applications. © Copyright 2017 by American Scientific Publishers.
CuO NPs Blended WS2-QDs/Si (0D/3D) Vertical Heterojunction for Uniform and Spectrally Enhanced Broadband Photodetection
(American Chemical Society, 2025) Yashwant Puri Goswami; Prashant Kumar Gupta; Amritanshu Pandey
Broadband photodetectors (i.e., sensing units) within the sensor node are a crucial component that plays a critical role in efficiently embedding cutting-edge technologies like the Internet of Things. Compared to other fabrication techniques, 2D layered material’s hybrid structure-based broadband photodetectors (PDs) may be more helpful in effectively deploying these technologies, as they can eliminate fabrication challenges such as complex device fabrication, low operating temperature requirements, and the toxic fabrication environment. Despite the above fabrication eases, the issue of nonuniform spectral response across the operating wavelength, adversely impacting PD efficacy, still needs to be addressed. The present work demonstrates a cost-effective and facile approach for achieving a substantially uniform spectral response across the broadband. The comparative investigation of WS2-QDs-based PD fabricated with and without CuO NPs blending revealed that by blending WS2-QDs with CuO NPs, the spectral response’s uniformity has been improved in addition to the quantitative improvement in the responsivity. The blended heterojunction PD structure demonstrated a broadband response between 365 and 950 nm at a low operating voltage of −1.5 V, with a peak responsivity of 111.84 A/W, EQE of 37993.74%, and detectivity of 2.13 × 1014 Jones. The PD’s temporal response was similarly found to be sufficiently fast, with rise and fall times of 40.83 and 39.76 ms, respectively. © 2025 American Chemical Society.
Dual-side polished optical fiber SPR biosensor for enhanced sensitivity and versatile detection
(Springer, 2025) Ajit Kumar; Amritanshu Pandey; Sanjay Kumar Srivastava
In this study, we introduce a highly sensitive biosensor design utilizing a dual-side polished photonic crystal fiber (PCF) structure, evaluated through finite element method (FEM) simulations. The dual-side polishing approach enhances interaction with the evanescent field, thereby improving sensitivity while retaining the mechanical integrity of the structure. The sensor functions efficiently across a wide refractive index (RI) range of 1.21–1.40, making it suitable for detecting various biological fluids, gases, and chemical substances. It operates over a broad wavelength spectrum, spanning from 0.42 m in the visible region to 1.0 m in the near-infrared (NIR) region. The integration of gold (Au) as the plasmonic layer significantly extends both the sensitivity and dynamic detection range compared to traditional SPR-based PCF sensors. Simulation results demonstrate a peak amplitude sensitivity of 2535 (1/RIU) and a maximum wavelength sensitivity of 9500 (nm/RIU), achieving a high sensing resolution of. © The Author(s), under exclusive licence to The Optical Society of India 2025.
Effects of annealing temperature on the structural, optical, and electrical properties of ZnO thin films grown on n-Si〈100〉 substrates by the sol-gel spin coating method
(Chinese Society for Metals, 2014) Aniruddh Bahadur Yadav; Amritanshu Pandey; S. Jit
The effects of annealing temperature on the sol-gel-derived ZnO thin films deposited on n-S〈100〉 substrates by sol-gel spin coating method have been studied in this paper. The structural, optical, and electrical properties of ZnO thin films annealed at 450, 550, and 650 °C in the Ar gas atmosphere have been investigated in a systematic way. The XRD analysis shows a polycrystalline nature of the films at all three annealing temperatures. Further, the crystallite size is observed to be increased with the annealing temperature, whereas the positions of various peaks in the XRD spectra are found to be red-shifted with the temperature. The surface morphology studied through the scanning electron microscopy measurements shows a uniform distribution of ZnO nanoparticles over the entire Si substrates of enhanced grain sizes with the annealing temperature. Optical properties investigated by photoluminescence spectroscopy shows an optical band gap varying in the range of 3.28-3.15 eV as annealing temperature is increased from 450 to 650 °C, respectively. The four-point probe measurement shows a decrease in resistivity from 2.1 × 10 -2 to 8.1 × 10-4 ω cm with the increased temperature from 450 to 650 °C. The study could be useful for studying the sol-gel-derived ZnO thin film-based devices for various electronic, optoelectronic, and gas sensing applications. © 2014 The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.
Nanopetal-Assembled SnS Flower-Based Vis-NIR Photodetector
(American Chemical Society, 2024) Prashant Kumar Gupta; Yashwant Puri Goswami; Amritanshu Pandey
This paper reports a simple, low-cost, and high-performance two-dimensional (2D) nanopetal-assembled three-dimensional (3D) SnS flowers/Si heterojunction-based visible-near-infrared (vis-NIR) photodetector (PD). A modified chemical bath deposition (CBD) method was used to grow a uniform and closely spaced array of SnS flowers on a Si substrate. This type of nanostructure offers a large photoactive area, thus generating a large number of carriers. The high-performance parameters of the fabricated PD (responsivity, 68.21 A/W; external quantum efficiency (EQE), 1.32 × 104%; detectivity, 6.87 × 1013 Jones; rise time, 193.91 ms; and fall time, 94.19 ms at 635 nm) are attributed to the heterojunction characteristics resulting from closely spaced nanopetal-assembled SnS flowers on silicon. © 2024 American Chemical Society.
Optimization of Transmitter Semi-Angle and Ambient Noise Cancellation for Indoor Visible Light Communications
(Greater Mekong Subregion Academic and Research Network, Asian Institute of Technology, 2023) Aanchal Verma; Amritanshu Pandey
Visible light communication (VLC) is unquestionably a viable method for dealing with the ever-increasing traffic on wireless networks. Light-emitting diodes (LEDs), which are used for lighting, can be used to convey high-speed data. The optical power determines the indoor VLC link performance. A fundamental challenge in this regard is to design an optimized design of visible light communication with the uniform power distribution and minimize the interference of the ambient light in the daytime. The optimization of transmitter semi-angle and ambient noise cancellation for indoor visible light communications is discussed in this study. The study shows that lowering the semi-angle improves average received optical power while raising power fluctuations on the receiver's plane. In order to resolve this trade-off, we use a unique and simple optimization method for calculating the appropriate transmitter semi-angle that maximizes received power while reducing power variation around the room. By adjusting the number of LED panels and their placements on the plane of the transmitter, the best configuration based on the optimization function is selected. The effects of utilizing a differential optical receiver on SNR distribution in optimal VLC indoor configuration is discussed, which results in better SNR, and the ability to suppress ambient light and other atmospheric noise. © 2023. All Rights Reserved.
Solution-Processed ZnO/V2O5Heterojunction Thin Films for UV Photodetectors
(American Chemical Society, 2025) Prateek Kumar Yadav; Sandeep Dahiya; Bhola Nath Pal; Amit Kumar Srivastava; Amritanshu Pandey; Sanjay Kumar Srivastava
This study delineates the fabrication and evaluation of a high-performing ultraviolet (UV) photodetector (PD) consisting of a ZnO/V2O5nanoparticle (NP) bilayer thin film deposited on a Si/SiO2substrate through spin coating. Various analytical techniques, such as X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy, have been employed to investigate the structural features and surface morphology of the as-prepared samples. The V2O5NPs were prepared through a facile one-pot solvothermal process, while ZnO NPs were obtained through a rapid sol–gel method. V2O5NPs demonstrate extended absorption with significant absorption in the range of 240–450 nm and exhibit a relatively smaller band gap. The optoelectronic features of as-deposited thin films have primarily been studied through I–V characteristics under dark and UV light conditions with the same external bias of 2 V, and the photocurrent has been found to be 9.13 × 10–5A/cm2, which is ∼2.77 × 103times higher than the dark current. The obtained photocurrent-to-dark current ratio for the ZnO/V2O5device is nearly ∼1.37 × 102times higher than that of the ZnO-only device. Moreover, this bilayer UV PD exhibits a detectivity (D) of ∼3.1 × 1012Jones, a spectral responsivity (R) of ∼4 A/W, and an external quantum efficiency (EQE) of ∼16% under an external potential of 10 V. Furthermore, the findings are analyzed, and an explanation of the detailed photodetection mechanism is outlined in this paper. © 2025 American Chemical Society
WS2 Quantum Dot Graphene Nanocomposite Film for UV Photodetection
(American Chemical Society, 2019) Vijay K. Singh; Sanjeev M. Yadav; Himanshu Mishra; Rahul Kumar; R.S. Tiwari; Amritanshu Pandey; Anchal Srivastava
The development of highly responsive, ultrathin, and cost-effective 0D-2D nanocomposite photodetectors, in which light absorption and carrier transportation may be realized separately and independently, has garnered considerable attention. In the present work, we demonstrate the fabrication of atomically thin UV photodetectors based on a hybrid structure (0D-2D) of semiconducting WS2 quantum dots (0D) with graphene (2D) on SiO2/Si substrate. Graphene and WS2 quantum dots (WS2-QDs) are synthesized through chemical vapor deposition (CVD) and hydrothermal processes, respectively. The proposed photodetector offers a remarkable response to ultraviolet (UV) light of ∼365 nm, owing to the high absorption efficiency of WS2-QDs and excellent charge mobility of graphene. The photodetector exhibits high responsivity of ∼1814 A W-1 under illumination of UV light (365 nm, power density of 50.74 μW cm-2) and a high photodetectivity of ∼7.47 × 1012 Jones (cm Hz1/2 W-1). The photodetector fabricated in this work shows a fast photoresponse time of ∼2 s (rise time) and ∼2.9 s (fall time). We have also elucidated the working principle of the proposed photodetector. Outcomes of the present work are comparable or better than other results available in the literature. Our findings suggest that this nanocomposite structure of WS2-QDs with graphene sheets is a prospective candidate for high-performance optoelectronic devices. © 2019 American Chemical Society.