Browsing by Author "A. Sameer Ruban Kumar"

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A highly responsive UV photodetector based on WO3–ZnO layered thin film
(Elsevier B.V., 2025) Richa Kumari; A. Sameer Ruban Kumar; Sandeep Dahiya; Sanjay Kumar Srivastava; Debanjan Guin; Chandra Shekhar Pati Tripathi
This work focuses on the development of a heterostructure ultraviolet photodetector constructed using tungsten oxide (WO3) nanosheets (NSs) and zinc oxide (ZnO) nanoparticles (NPs), fabricated on Si/SiO2 substrates. For synthesis, a simple, economically feasible hydrothermal for WO3 and sol-gel synthesis approach for ZnO was used. The WO3 NSs/ZnO NPs heterostructure thin-film UV photodetector demonstrates excellent performance, including high responsivity (R), and detectivity (D) of 97.55 A/W, and 6.5 × 1011 Jones, respectively, when exposed to UV light (λ ∼ 365 nm). The working mechanism of the fabricated photodetector explained using a suitable energy band diagram. The WO3 NSs/ZnO NPs heterostructure thin-film UV photodetector exhibits a satisfactory response time, with a rise time of 5.35 s and a fall time of 10.24 s. © 2025 Elsevier B.V.
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.
Beyond graphene basics: A holistic review of electronic structure, synthesis strategies, properties, and graphene-based electrode materials for supercapacitor applications
(Elsevier Ltd, 2025) Sachin Kumar Yadav; A. Sameer Ruban Kumar; Neeraj Mehta
This review presents a comprehensive analysis of graphene-based electrode materials for supercapacitor application, focusing on electronic structure, synthesis strategies, and key attributes. The remarkable 2D-structure of graphene, characterized by sp2 hybridized carbon atoms, confers exceptional electronic mobility (100000 cm2V−1s−1), large specific surface area (2600 m2g-1), and mechanical flexibility (2.4 ± 0.4 TPa), making it an ideal contender for next-generation energy storage devices. We have discussed various synthesis strategies, including CVD, mechanical exfoliation, and chemical reduction, emphasizing their impact on the electrochemical performance of graphene electrodes. The integration of graphene with other nanomaterials, such as metal oxides, TMDs, conducting polymers, and MXenes, is explored to enhance the specific capacitance, cycle stability, and energy density of supercapacitor electrode materials. This review also covers the tunable electronic properties of graphene, addressing charge transport, ion diffusion, and electrochemical performance, which are critical for efficient supercapacitor design. Graphene-based electrodes' flexibility and mechanical stability are examined, highlighting their role in wearable and portable electronic applications. Challenges such as large-scale production, electrode degradation, and cost-effectiveness are also discussed, offering potential solutions through innovative synthesis routes and composite material design. This review provides a holistic perspective on the current advancement of graphene-based electrode materials for supercapacitor applications. © 2025 Elsevier Ltd
Investigation of shielding properties of Se100−y(AgX)y (y = 0, 5 and X = Cl, Br, and I) glass-ceramics
(Royal Society of Chemistry, 2025) A. Sameer Ruban Kumar; Shiv Kumar Pal; Neeraj Mehta
The Se100−y(AgX)y (y = 0, 5 and X = Cl, Br, and I) glass-ceramics were synthesised via melt-quenching, with density measured using Archimedes' principle. Radiation-shielding properties were investigated using Phy-X/PSD across a range of 15 keV to 15 MeV, assessing parameters such as LAC, MAC, MFP, Zeff, Neff, Ceff, Zeq., EABF, EBF, and FNRCS. The Se95(AgBr)5 sample exhibited the lowest HVL, indicating superior photon attenuation compared to other compositions. The attenuation percentage (RPE%) was investigated experimentally across 60 keV, 81 keV, and 100 keV measured using Scanditronix stereotactic field diode (SFD) detectors. Additionally, their shielding performance was compared with commercially used materials, including ordinary concrete and radiation-shielding glasses. Results demonstrate that Se95(AgBr)5 meets key shielding criteria, making it a promising alternative for low-energy radiation protection. Incorporating silver halides significantly influences shielding efficiency, with AgBr proving the most effective. These findings highlight the potential of AgBr-doped selenium glass-ceramics as efficient radiation-shielding materials, offering a viable replacement for traditional options in specific shielding applications. © 2025 The Royal Society of Chemistry.
Square & H metasurfaces for SPR Increasing in long Wave-IR absorber
(Elsevier B.V., 2025) Sarvesh Kumar Dubey; Awadhesh Kumar; A. Sameer Ruban Kumar; Amit Pathak; Sanjay Kumar Srivastava
In the long-wave infrared (LWIR) spectrum, this paper suggests an electromagnetic (EM) waveband absorber design based on metamaterials. Germanium, gold, and magnesium oxide layers are arranged in a layered structure from top to bottom in the suggested model. Our proposed metamaterial structure's upper surface is composed of metallic metasurfaces with H and square forms from various studies. The finite element method is used to evaluate the metamaterials’ electromagnetic properties in terms of absorbance and reflectance. It is observed that there is a particular size of the metamaterial at which extremely localized electromagnetic resonance occurs. Quantitative findings indicate that the suggested metamaterial design's average absorption reaches 90 % in the 10 μm to 14 μm range across a wide variety of incidence angles (00 to 400 & 00 to 800) for both transverse electric (TE) and transverse magnetic (TM) polarization. It is evident from these data that the suggested model configuration has broad potential applications in many optoelectronic fields of study. © 2024
Study of the uncertainty quantification of the 121Sb(n,γ)122Sb reaction
(Springer Science and Business Media Deutschland GmbH, 2025) Namrata Singh; Mahesh Choudhary; A. Gandhi; Mahima Upadhyay; Ratankumar K. Singh; Akash Hingu; Gaurav P. Mishra; Sukanya De; Laxman Singh Danu; Ajay Vinod Kumar; Renju G. Thomas; Saurav Sood; Sajin Prasad; B. Lalremruata; K. Katovsky; A. Sameer Ruban Kumar
The reaction cross-sections for the 121Sb(n,γ)122Sb reaction were determined at 1.66, 2.65, and 3.05 MeV. The experiment was conducted using the neutron activation technique followed by the offline γ-ray spectrometry. The neutrons were generated using the 7Li(p,n)7Be reaction, and the reaction cross-section for 121Sb(n,γ)122Sb was measured with respect to the 115In(n,n′γ)115Inm monitor reaction cross-section. Wood–Saxon phenomenological optical model potentials (OMP) were used to calculate the uncertainties of the theoretical calculation for the 121Sb(n,γ)122Sb reaction cross-section. The measured reaction cross-section data are compared to the existing data available in the EXFOR database. Additionally, the data are compared to the evaluated data from ENDF/B-VIII.0 and JEFF-3.1/A. TALYS-1.96 nuclear code is used for the theoretical calculations. The measured cross-sections are given along with their uncertainties and covariance matrices. In this work, the theoretical cross-section uncertainties have been estimated using the uncertainties in the level density and optical model parameters. © The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Thermo-mechanical and physicochemical features in Pseudo-binary Se-AgX chalcogenide glassy system
(Elsevier Masson s.r.l., 2025) A. Sameer Ruban Kumar; A. Dahshan; Neeraj Mehta
Micro-indentations were made on new samples of the Se100(AgX)0 and Se95(AgX)5 (where X = Cl, Br, & I) systems to perform hardness measurement studies at different loads. Numerous models and methodologies, such as Meyer's law, the elastic/plastic deformation theory, Hays-Kendall's method, and the energy balance model, were used to assess the gathered Vickers microhardness data. DSC techniques were used to identify events related to thermal glass transition. Essential mechanical qualities that have been assessed include several thermos-mechanical parameters, such as the modulus of elasticity (E), the least micro-void formation energy (Eh), the micro-void volume (Vh), etc. Furthermore, a variety of physicochemical characteristics have been theoretically computed, such as the average coordination number (), average heat of atomization (Hs), total constraints per atom (Nc), and the axial (nβ) and radial (nα) strength of the bonds. The findings highlight that the various thermo-mechanical parameters examined in this work reach their optimized values in the case of the Se95(AgBr)5 sample. Furthermore, molar volume (Vm), compactness (δ), and density (ρ) have been computed both theoretically and experimentally. © 2025 Elsevier Masson SAS
Zinc-induced bandgap modulation and nonlinear optical response in SeTeSn thin films
(Elsevier Ltd, 2025) Vishnu Saraswat; A. Sameer Ruban Kumar; S.S Salah Fouad; H. Atiya; Ishu Sharma; Neeraj Mehta
This work investigates the optical properties of zinc-containing amorphous thin films (TFs) in the multicomponent STS system. Critical optical features relevant to applying chalcogenide glasses (ChGs) in optoelectronics and optics have been thoroughly examined. Experimental spectrum data on transmission and reflection in the wavelength range of 4000 Å to 25,000 Å were used to explore the optical behaviour of the generated TFs. Important metrics, including the absorption and refractive indices, were assessed. Examining the spectrum fluctuation of dispersion characteristics allowed for determining the Urbach energy (Eu) and optical bandgap (Egopt). The optical bandgap exhibited a notable increase across the samples: a rise of 0.23 eV for the STSZ4 sample, 0.22 eV for STSZ6, and 0.16 eV for STSZ2, indicating significant changes in the bandgap with zinc incorporation. Additionally, the Urbach energy showed a substantial increase, particularly in the STSZ4 sample. The study confirms an indirect optical transition, supported by the transition power factor (m). Furthermore, single-oscillator dispersion characteristics and a high dielectric constant (ε′) were determined. The study also investigates how the volume and surface energy loss functions, relaxation time (τ), dissipation factor (tanδ), and real (ε′) and imaginary (ε′′) components of the optical dielectric constant rely on photon energy (ℎν). Notably, the infinite dielectric constant (ε∞) of the parent STS TF (ε∞ = 3.43) increases outstandingly after doping with STSZ2 (ε∞ = 6.78), STSZ4 (ε∞ = 2.03), and STSZ6 (ε∞ = 3.51). For the multicomponent STSZ system, optical and electrical conductivities and Nonlinear optical properties were also investigated. © 2025 Elsevier Ltd and Techna Group S.r.l.