Browsing by Author "Sanjay Kumar Srivastava"

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A contemporary overview on quantum dots-based fluorescent biosensors: Exploring synthesis techniques, sensing mechanism and applications
(Elsevier B.V., 2025) Anushka Yadav; Priyanka Dogra; Pinky Sagar; Monika Srivastava; Amit Kumar Srivastava; Rajneesh Kumar; Sanjay Kumar Srivastava
In the epoch of bioinformatics, pivotal biomedical scrutiny and clinical diagnosis hinge upon the unfolding of highly efficacious biosensors for intricate and targeted identification of specific biomolecules. In pursuit of developing robust biosensors endowed with superior sensitivity, precise selectivity, rapid performance, and operational simplicity, semiconductor QDs have been acknowledged as pivotal and advantageous entities. In this review, we present a comprehensive analysis of the latest unfolding within the domain of QDs used in fluorescent biosensors for the detection of diverse biomolecular entities, encompassing proteins, nucleic acids, and a range of small molecules, with an emphasis on the synthesis methodologies of QDs employed and mechanism behind sensing. Additionally, this review delves into several pivotal facets of QD-based fluorescent biosensors in detail, such as surface functionalization methodologies aimed at enhancing biocompatibility and improving target specificity. The challenges and future perspectives of QD-based fluorescent biosensors are also considered, emphasizing the necessity of ongoing multidisciplinary research to realize their full potential in enhancing personalized medicine and biomedical diagnostics. © 2025 Elsevier B.V.
A dual epitope-imprinted polymer@AuNP-MoS2 nanosheets-EQCM sensor for antibody free detection of SipD protein of Salmonella typhi bacteria with high selectivity
(Elsevier B.V., 2025) Akriti Srivastava; Ashish Kumar Kushwaha; Pinky Sagar; Anirban Parida; Roop Shikha Singh; Sanjay Kumar Srivastava; Richa Raghuwanshi; Gopal Nath; Meenakshi K. Singh
Dual-epitope imprinted EQCM sensor for selective and sensitive detection of Salmonella typhi bacterial protein is fabricated on gold nanoparticle decorated MoS2 nanosheets (AuNPs-MoS2NSs). Salmonella invasive protein D (SipD) binds to the needle protein and appears capable of interacting with the translocon complex to infect the host. Potential B cell antigenic epitope sequences from bacterial tip protein, SipD were intentionally tagged with cysteine and are used as dual templates to fabricate MIP sensor using methacryloyloxyethyl phosphorylcholine (MPC), benzyl methacrylate (BMA) and methacrylic acid (MAA) as monomers and N , N ′-methylene- bis -acrylamide as a crosslinker. The monomers chosen through docking produced a DEIP-EQCM sensor. The sensor was able to show specific binding towards the blood samples of infected patients, even in the presence of ‘matrix’ of ‘real’ samples and other plasma proteins. It has shown excellent specificity, sensitivity and selectivity in sensing range of 100–1000 nM with detection limit 1.65 nM (Epitope I) and 0.025 nM (Epitope II) and limit of quantification as 5.03 nM (Epitope I) and 0.075 nM (Epitope II) for the two epitope sequences imprinted. Sip D protein binding was substantiated by SDS-PAGE analysis. The repetitive experimental runs could not mutilate the specific geometries of respective imprinted cavities and the DEIP-EQCM sensor can be proposed for antibody free detection of Sip D protein. © 2025 The Authors.
A graphene oxide assisted surface plasmon resonance sensor for chloroquine phosphate detection: A theoretical and experimental study
(Elsevier Ltd, 2025) Anil V.S. kumar; Awadhesh Kumar; Monika Srivastava; Rajiv Prakash; Sanjay Kumar Srivastava
The present work deals with a surface plasmon resonance (SPR) sensor that gives real-time and label-free detection of chloroquine phosphate (CQ) with graphene oxide (GO) in water as well as real samples. In this work, theoretical and experimental analysis are performed for present SPR biosensor for the detection of CQ. Furthermore, a self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) is utilized for the attachment of GO over the gold layer, which works as a good probe for the detection of CQ. The present biosensor detects micromolar concentrations of CQ in water and real samples (blood serum) with a limit of detection (LOD) value of 0.21 μM and 0.34 μM, respectively. Furthermore, other biomolecules like urea, L-cysteine, D-glucose and glycine are also tested and it shows maximum sensitivity towards CQ. © 2025 Elsevier Ltd
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.
A smartphone-enabled colorimetric sensor based on VS2 quantum dots for Rapid and on-site detection of ferric ions
(Elsevier B.V., 2025) Anushka Yadav; Pinky Sagar; Monika Srivastava; Amit Kumar Srivastava; Rajneesh Kumar; Sanjay Kumar Srivastava
This research delves into the holistic hydrothermal synthesis of VS2 QDs and their subsequent utilization as a fluorescent probe for the subtle detection of ferric ions (Fe3+) in practical sample matrices. The detection paradigms harness a colorimetric sensing mechanism, amplified by smartphone-enabled analytical integration for improved precision and real-time monitoring. A comprehensive suite of analytical characterization techniques has been employed, revealing that the as-synthesized VS2 QDs feature a surface densely populated with functional groups. While the VS2 QDs showcase interactions with multifarious metal ions in aqueous media, they set forth a pronounced and selective fluorescent quenching response toward Fe3+ ions, markedly surpassing their interactions with other metal ions. The developed sensing probe exhibits a linear detection range spanning from 0 – 90 μM, with a LOD as low as 2.25 μM, also exhibits exceptional sensitivity (KD ∼ 0.8 × 104 M−1) and remarkable selectivity for Fe3+ ions, harnessing the intrinsic photoluminescent characteristics of VS2 QDs. In addition, a sophisticated portable smartphone platform, integrated with a radiometric fluorescence probe specifically tailored for in-situ detection of Fe3+ at the point of care, exhibits a LOD of approximately 5.05 μM, a value that resides below the prescribed safety threshold. Thus, the proposed probe stands to function as an exceptionally potent sensing apparatus for the precise quantification of Fe3+ in complex real-world samples. © 2024 Elsevier B.V.
Alkali metal ion codoped Eu3+ activated yttrium orthovanadate with tunable photoluminescence properties for LEDs and anti-counterfeiting applications
(Elsevier Ltd, 2025) Anuradha; Arpita Dwivedi; Satyam Upadhyay; Amit Kumar Srivastava; Monika Srivastava; Rajneesh Kumar; Sanjay Kumar Srivastava
The present experimental report articulates a comprehensive investigation on the synthesis, structural, and photoluminescence characteristics of M0.05,Eu0.05:Y0.90VO4 (M = Li+, Na+, K+) nanophosphors synthesised by auto-combustion approach, for optical display and anticounterfeiting technologies. Various characterization tools such as X-ray diffractometer (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), Fourier transform infra-red (FTIR) Spectroscope, and Raman spectroscope have been employed to understand the morphology and crystal structure of M0.05,Eu0.05:Y0.90VO4 (M = Li+, Na+, K+) nanophosphor, which reveals the formation of a pure tetragonal structure and well crystalline phase. Moreover, the UV–Vis spectra, suggests that the as-synthesised material substantiated to possess an energy band gap of ∼3.6 eV conjecturing it as a wide-band material, and the refractive index (n) of the prepared samples has been deduced as ∼ 2.1. Among all alkali ions, Li+-codoped sample exhibits the most intense PL spectra. The enhancement in PL intensity has been observed due to the energy transfer of VO43−→Eu3+ and the codoping of lithium ions acts as a good charge compensator. For the optimized sample CIE coordinates has been found as (0.59, 0.39) and CCT value as 1712 K, which suggest it as a prospective candidate for the warm LEDs. The optimized sample has further been investigated for the visualization of Latent fingerprint on glass slide and as security ink. It displays efficient applicability as a well-defined ridge features up to level III. Henceforth, the as-synthesised Li0.05,Eu0.05:Y0.90VO4 nanophosphor may potentially be applied for multipurpose applications. © 2024 Elsevier Ltd and Techna Group S.r.l.
Combined experimental and theoretical studies on 4-(2-hydroxy-3-morpholin-4-yl-propoxy)-chromen-2-one
(World Scientific Publishing Co. Pte Ltd, 2016) Priyanka; Sanjay Kumar Srivastava; Diksha Katiyar
The FTIR, UV-Vis and NMR spectra of 4-(2-hydroxy-3-morpholin-4-yl-propoxy)-chromen-2-one (4-HMPC) have been recorded and analyzed. The optimized geometry and harmonic vibrational frequencies of 4-HMPC were obtained by the Hartree-Fock (HF) and density functional theory (DFT) using B3LYP functional with 6-311++G basis set. The 1H and 13C NMR chemical shifts were calculated by the GIAO method in chloroform. The absorption spectra of 4-HMPC were computed in ethanol and water solutions using TD-B3LYP/6-311++G(d,p) approach. The correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the molecule. The results obtained from the studies of HOMO and LUMO were used to calculate the conceptual-DFT-based global reactivity descriptors such as electronic chemical potential, electronegativity, chemical hardness, global softness and electrophilicity index of the compound. © 2016 World Scientific Publishing Company.
Comprehensive analysis of structural, morphological, surface chemistry, and optical traits of multifaceted SrTiO3 for enhanced photocatalytic and DSSC applications
(Elsevier Ltd, 2025) Satyam Upadhyay; Monika Srivastava; Pradyum Patel; Amit Kumar Srivastava; Dhananjay Kumar; Somnath C. Roy; Sanjay Kumar Srivastava
The present study underlines the facile synthesis of SrTiO3 nanoparticles through sol-gel approach and subsequently its dual applicability as photocatalyst for methylene blue degradation and photoanode in dye-sensitized solar cell fabrication. Structural and optical characterizations, including XRD with Rietveld refinement, SEM, TEM, XPS, Raman, UV–Vis, and PL spectroscopy, confirms a cubic perovskite phase with an optical bandgap of ∼3.24 eV. The ST NPs demonstrates enhanced photocatalytic activity under visible light, degrading ∼56.13 % of 10 ppm MB in 120 min. Kinetic studies under UV light further validated the degradation mechanism. As photoanodes in DSSCs, the ST NPs exhibit enhance photocurrent responses, especially when combined with natural pomegranate dye, suggesting their viability for renewable energy devices. These findings highlight the potential of strontium titanate nanoparticles for both photocatalytic applications and dye-sensitized solar cell fabrication, offering an eco-friendly and effective solution to address energy and environmental challenges. © 2025 Elsevier Ltd
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.
Electrochemical investigation of Irbesartan drug molecules as an inhibitor of mild steel corrosion in 1 M HCl and 0.5 M H2SO4 solutions
(Elsevier B.V., 2017) Monika Srivastava; Preeti Tiwari; Sanjay Kumar Srivastava; Rajiv Prakash; Gopal Ji
Inhibition effects of Irbesartan drug on mild steel corrosion in 1 M HCl and 0.5 M H2SO4 solutions have been investigated by open circuit potential (OCP) curves, Tafel polarization curves, linear polarization curves and electrochemical impedance spectroscopy (EIS) along with cyclic voltammetry (CV), UV–visible, FTIR and NMR spectroscopy techniques. Maximum corrosion inhibition of 94% and 83% have been achieved at 300 mg L− 1 Irbesartan concentration in 1 M HCl and 0.5 M H2SO4, respectively. Adsorption of Irbesartan on mild steel surface is studied by SEM and various isotherm models, which follows Langmuir isotherm. The effects of rise in temperature and acid concentration on the corrosion behavior of mild steel in both acid solutions are also studied by weight loss method. Corrosion inhibition by Irbesartan is explained on the basis of experimental results as well as frontier molecular orbitals estimated by CV and UV–visible spectroscopic measurements. © 2017 Elsevier B.V.
Enhance photoluminescence properties of Ca-Eu:Y2O3@SiO2 core–shell nanomaterial for the advanced forensic and LEDs applications
(Elsevier B.V., 2023) Arpita Dwivedi; Anuradha; Monika Srivastava; Amit Srivastava; Rajneesh Kumar; Sanjay Kumar Srivastava
The divalent (Ca2+)-doped Eu:Y2O3@SiO2 core–shell luminescent nanophosphors have been synthesised by a cost-effective combustion technique. Various characterizations were carried out to confirm the successful formation of the core–shell structure. The TEM micrograph reveals the thickness of the SiO2 coating over Ca-Eu:Y2O3 as ∼25 nm. The optimal value of silica coating over the phosphor has been obtained as 10 vol%(TEOS) of SiO2, with this value increasing fluorescence intensity by 34 %. Phosphor exhibits CIE coordinates as x = 0.425, y = 0.569 and a CCT value as ∼2115 K with color purity and the respective CRI of 80 % and 98 %, respectively, which make the core–shell nanophosphor suitable for warm LEDs, and other optoelectronic applications. Further, the core–shell nanophosphor has been investigated for the visualisation of latent finger prints and as security ink. The findings point towards the prospective future application of nanophosphor materials for anti-counterfeiting purposes and latent finger prints for forensic purposes. © 2023 Elsevier B.V.
Impact of Eu3 +/Y3+ doping on the structural and optical properties of SrTiO3 perovskite phosphor and multi-functional applications
(Elsevier Ltd, 2025) Satyam Upadhyay; Arpita Dwivedi; Prateek Kumar Yadav; Monika Srivastava; Amit Kumar Srivastava; Chandan Upadhyay; Sanjay Kumar Srivastava
A latent fingerprint (LFP) examination is essential for identifying fingerprints at crime sites, and personal data for legal operations requires economical, eco-friendly, and sensitive new materials. Here, a new composition of intense red-emitting Eu3+ and Y3+ co-doped SrTiO3 perovskites nanophosphor synthesized using a modified sol-gel-assisted combustion technique has been reported. To explore the structural and optical features of the nanophosphors the samples are characterized by various techniques. The powder XRD pattern reveals that the approximate crystallite size is 30 nm, which is consistent with TEM. It is found that with the mid- and near-ultraviolet light excitation, Eu3+ and Y3+ co-doped SrTiO3 nanophosphor displays a strong red emission at 618 nm for optimal concentrations (3 mol% Eu). The CIE (0.656, 0.344), color purity 95 %, CRI 98 %, and CCT values 2435 K, which is less than 5000 K reveals that the Eu3+ and Y3+ co-doped SrTiO3 phosphor was highly useful for the fabrication of warm LED and display device applications. Further, the optimized phosphor was tested (under UV light of 254 nm) for the visualization of LFP and security ink on various material surfaces. The results demonstrated that it provides an effective method for visualizing ridge patterns, offering a promising approach for applications in these areas. Based on the findings, Eu3+ and Y3+ co-doped SrTiO3 show potential for various optoelectronic applications, including WLEDs, LFP detection, security inks, and LEDs. © 2025 Elsevier B.V.
Nanozymes-based multifunctional platforms for uric acid detection in patients
(Elsevier, 2024) Ravi Prakash Ojha; Sanjay Kumar Srivastava; Monika Srivastava; Rajiv Prakash
Uric acid (UA), a metabolic by-product arising from purine metabolism, can result in hyperuricemia and related ailments like gout and kidney stones when accumulated excessively. In recent times, nanotechnology's emergence has opened avenues for innovative approaches in diagnostics and therapeutics. Notably, nanozymes, categorized as nanomaterials exhibiting inherent enzyme-like properties, have garnered significant interest for their potential applications in fabricating sensors for monitoring UA levels in patients. Nanozymes boast qualities, such as stability, tunability, cost-effectiveness, specificity, biocompatibility, and resilience, against challenging conditions. These attributes highlight their versatility, making them valuable for applications in sensors for the detection of ions, biomolecules, and disease biomarkers. This chapter comprehensively explores the conceptualization, fabrication, and multifaceted utilities of nanozyme-based platforms tailored for UA detection. © 2024 Elsevier Inc. All rights are reserved including those for text and data mining AI training and similar technologies.
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
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
The study of the green synthesis of Co3O4 nanomaterials and Co3O4/Ce24Co11/CeO2 nanocomposites using Kigelia pinnata fruit extract and their antibacterial potential
(Elsevier B.V., 2025) Anil Kumar Gautam; Ruchi Shankhwar; Snigdha; Ravi Kr Gupta; Sanjay Kumar Srivastava; Gajanan Pandey
In this study the aqueous extract of Kigelia pinnata fruit was used to produce three different nanomaterials; Co3O4 (termed as KpCoO) NPs, Co3O4/Ce24Co11/CeO2 (5 mol % Ce and 95 mol % Co, termed as KpCe@CoO-5) and Co3O4/Ce24Co11/CeO2 (10 mol % Ce and 90 mol % Co, termed as KpCe@CoO-10) nanocomposites. A comparative examination of their antibacterial effectiveness against the harmful bacterial strains S. aureus and P. aeruginosa was conducted using KpCoO NPs and KpCe@CoO-5, KpCe@CoO-10 NCs. Optical and structural properties of the nanomaterials were determined using UV–visible, FTIR, XRD, SEM, EDX, HRTEM, BET and XPS spectroscopy. Crystallography Open Database (COD) and Match software were used to verify the presence of Co3O4 and cerium mixed Co3O4/Ce24Co11/CeO2 nanocomposites with the cubic, trigonal and cubic respectively. The fruit extract's phytochemicals played an important role in the formation as well as stabilization of nanomaterials with capping on the surface of the nanomaterials. The size of the nanomaterials and antibacterial activity are decreased by mixing the cerium salt mole% in copper salts. Overall, the used low-cost and environmentally benign green synthesized novel nanomaterials exhibited antibacterial activity of KpCoO in comparison to its nanocomposites (KpCe@CoO-5 and KpCe@CoO-10) with the Cerium metals. © 2024 Elsevier B.V.
Tunable photoluminescence and energy transfer of Eu3+,Ho3+-doped Ca0.05Y1.93-xO2 nanophosphors for warm white LEDs applications
(Nature Research, 2022) Arpita Dwivedi; Monika Srivastava; Amit Srivastava; Chandan Upadhyay; Sanjay Kumar Srivastava
A series of Eu3+ ions doped Ca0.05Y1.93-xO3:0.02Ho3+ (CYO:Ho3+,xEu3+) nanophosphors having multicolour tuneability have been synthesised by following a simplistic solution combustion approach. The synthesised samples have been characterised by employing X-ray diffraction (XRD), Transmission electron microscope (TEM), and Fourier transforms infrared spectroscopy (FTIR). The optical properties have been engrossed by UV–visible and photoluminescent excitation and emission spectra, and decay lifetimes measurements. The characteristic emission, which occurs due to the f-f transition of Ho3+ and Eu3+ has been observed in emission spectra with excitation of 448 nm. By adjusting the doping ratio of Ho3+/Eu3+, the as-synthesized nanophosphor accomplishes multicolour tunability from green-yellow to red. Emission spectra and decay lifetime curve recommend dipole–dipole interaction causes energy transfer from Ho3+ → Eu3+. The energy transfer process from Ho3+ to Eu3+ has been confirmed through electric dipole–dipole interaction with critical distance 15.146 Å. Moreover, temperature dependent emission spectra show the high thermal stability with an activation energy ⁓ 0.21 eV, with the quantum efficiency of 83.6%. CIE coordinate illustrates that the singly doped Ho3+ and Eu3+ lie in the green and red region, respectively, while the as-synthesized CYO:Ho3+,xEu3+shows tunability from green to red with low CCT and high colour purity values. Hence, the CYO:Ho3+,xEu3+nanophosphor may be a near-UV excited multicolour colour-tunable pertinent candidate with potential prospects for multicolour- display and near-ultraviolet lighting applications. © 2022, The Author(s).
Wireless & portable smartphone assisted electrochemical platform for on-site monitoring of chloramphenicol drug
(Elsevier Ltd, 2025) Priyanka Dogra; Monika Srivastava; Pinky Sagar; Chandra Shekhar Pati Tripathi; Sanjay Kumar Srivastava
Precise detection of antibiotic residues such as chloramphenicol (CAP) remains challenging due to their widespread use in veterinary, food, medical, and environmental sectors. Herein, we report a smartphone-assisted electrochemical sensor with graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) for the sensitive detection of CAP. The system integrates with both a traditional Autolab potentiostat and a pocket size Palmsens potentiostat. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studies of GO@MWCNT nanocomposite exhibited excellent electrocatalytic activity, with a linear detection range of 0–600 μM, a limit of detection (LOD) of 46 nM (S/N = 3), and sensitivity of 1.71 μA μM−1 cm−2. The sensor showed excellent stability (∼90 % retention after 21 days) and reproducibility (RSD <3 %). A strong correlation between Autolab and smartphone-based results validated the reliability of the system. This is the first report of a smartphone-assisted platform for CAP detection, enabling wireless, Bluetooth enabled, and real-time analysis via a user-friendly smart phone application. The sensor performed effectively in milk, tap water, eye drops, capsules, and human blood serum, with good recoveries. A reusability/regeneration study confirmed the potential of the platform as a cost-effective, field-deployable POC diagnostic tool. © 2025 Elsevier B.V.
WS2 nanoparticle integrated MWCNT as an efficient electrode material for electrochemical sensing of chloramphenicol in pharmaceutical samples
(Elsevier Inc., 2025) Pinky Sagar; Ayushi Sahrawat; Monika Srivastava; Priyanka; Pooja Agarwal; Sanjay Kumar Srivastava
Detection of an antibiotic drug chloramphenicol (CPN) in pharmaceutical samples is very essential due to its wide application in food, agriculture and healthcare sector and nanomaterials are gaining significant attention as efficient electrode materials in the realm of CPN residue diagnostics. Among these materials, graphene-based compounds stand out due to their intriguing π–π interaction properties. In this study, we present a facile hydrothermal technique for the synthesis of WS2 nanoparticles which later decorated on multiwalled carbon nanotubes (WS2-MWCNT). This nanocomposite material was then employed for the electrochemical detection of CPN simultaneously by two techniques: cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The WS2-MWCNT based sensor exhibited an impressive low limit of detection of 0.041 nM (CV) and 0.34 nM (DPV), and a remarkable sensitivity of 4.29 μAμM−1cm−2 (CV) and 0.71 μAμM−1cm−2 (DPV), along with excellent performance in terms of selectivity, and reproducibility for CPN detection. Furthermore, the sensor demonstrated successful detection of CPN in pharmaceutical and natural matrices with satisfactory results. This proposed voltammetric sensor presents an inexpensive and promising approach for applications in monitoring pharmaceutical samples, with great opportunities for its miniaturization and detection in real samples. © 2025 Elsevier B.V.