Browsing by Author "Govind Gupta"

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Effect of Mn2+ doping and DDAB-assisted postpassivation on the structural and optical properties of CsPb(Cl/Br)3 halide perovskite nanocrystals
(Institute of Physics, 2024) Charu Dubey; Anjana Yadav; Santosh Kachhap; Sunil Kumar Singh; Govind Gupta; Satendra Pal Singh; Akhilesh Kumar Singh
Cesium lead halide perovskite (CsPbX3; X = Cl, Br, I) nanocrystals showing intense band-edge emission and high photoluminescence quantum yield are known to be a potential candidate for application in optoelectronic devices. However, controlling toxicity due to the presence of Pb2+ in lead-based halide perovskites is a major challenge for the environment that needs to be tackled cautiously. In this work, we have partially replaced Pb2+ with Mn2+ ions in the CsPb(Cl/Br)3 nanocrystals and investigated their impact on the structural and optical properties. The Rietveld refinement shows that CsPbCl2Br nanocrystals possess a cubic crystal structure with Pm 3 ̅ m space group, the Mn2+ doping results in the contraction of the unit cell. The CsPb(Cl/Br)3: Mn nanocrystals show a substantial change in the optical properties with an additional emission band at ∼588 nm through a d-d transition, changing the emission color from blue to pink. Here, a didodecyldimethylammonium bromide (DDAB) ligand that triggers both anion and ligand exchange in the CsPb(Cl/Br)3: Mn nanocrystals have been used to regulate the exchange reaction and tune the emission color of halide perovskites by changing the peak position and the PL intensities of band-edge and Mn2+ defect states. We have also shown that oleic acid helps in the desorption of oleylamine capping from the CsPb(Cl/Br)3: Mn nanocrystal surfaces and DDAB, resulting in the substitution of Cl− with Br− as well as provides capping with shorter branched length ligand which led to increase in the overall PL intensity by many folds. © 2024 IOP Publishing Ltd.
Evaluation of Wastewater Quality Using Multivariate Analysis and Water Quality Index for its Sustainable Management in Urban Area
(University of Tehran, 2024) Govind Gupta; Jabbar Khan; Naveen Kumar Singh; Vivek Narayan Bhave; Vinay Bharadwaj; Rajeev Pratap Singh
In present study, wastewater quality was evaluated applying multivariate analysis (PCA) and water quality index with respect to the Indian standards in the selected urban areas of Jaipur region, Rajasthan, India. Maximum average values of BOD5, TDS, chloride and fluoride were recorded as 21 mg/L, 1501 mg/L, 285.0 mg/L and 1.8 mg/L, respectively, along with metal concentration in order of Zn (6.31 mg/L )> Fe (0.52 mg/L )> Mn (0.25 mg/L), Cu (0.16 mg/L)> Pb (0.11 mg/L)> Ni (0.02 mg/L). PCA indicates four components extracted with a total variance of 78.48% from the water quality parameters. Wastewater Quality Index (WWQI) analysis emphasis level of pollution load at different sites which revealed 40% of the selected sites were inappropriate for reuse without treatment, however, 60% of the sites with moderate pollution load could be suitably reuse in agricultural and aquaculture. Findings of the present study conclude that multivariate analysis and wastewater quality index could be used as an effective tool for environmental monitoring, assessing, and categorizing wastewater to opt appropriate treatment, reuse and recycling options for sustainable wastewater management. © 2024 University of Tehran. All rights reserved.
Fabrication of sensitive bioelectrode based on atomically thin CVD grown graphene for cancer biomarker detection
(Elsevier Ltd, 2018) Vijay K. Singh; Saurabh Kumar; Sumit Kumar Pandey; Saurabh Srivastava; Monu Mishra; Govind Gupta; B.D. Malhotra; R.S. Tiwari; Anchal Srivastava
Motivation behind the present work is to fabricate a cost effective and scalable biosensing platform for an easy and reliable detection of cancer biomarker Carcinoembryonic antigen (CEA). Here, we report the sensitive and selective detection of CEA using graphene based bio-sensing platform. Large sized (~ 2.5 × 1.0 cm2), uniform, continuous, single and few layers graphene films have been grown on copper (Cu) substrate employing chemical vapor deposition (CVD) technique using hexane as a liquid precursor. Functional group has been created over Graphene/Cu substrate through π-π stacking of 1- pyrenebutanoic acid succinimidyl ester (PBSE). Further, to make the sensor specific to CEA, antibody of CEA (anti-CEA) has been covalently immobilized onto PBSE/Graphene/Cu electrode. Selective and sensitive detection of CEA is achieved by anti-CEA/PBSE/Graphene/Cu electrode through electrochemical impedance spectroscopy (EIS) measurements. Under optimal condition, the fabricated sensor shows linear response in the physiological range 1.0–25.0 ng mL−1 (normal value ~ 5.0 ng mL−1), revealing sensitivity 563.4 Ω ng−1 mL cm−2 with a correlation coefficient of 0.996 and limit of detection (LOD) 0.23 ng mL−1. In this way, one step electrode fabrication with high specific surface area provides a light weight, low cost, reliable and scalable novel biosensing platform for sensitive and selective detection of CEA. We believe that this bioelectrode equipped with specific recognition elements could be utilized for detection of other biomolecules too. © 2018 Elsevier B.V.
High yield synthesis of electrolyte heating assisted electrochemically exfoliated graphene for electromagnetic interference shielding applications
(Royal Society of Chemistry, 2015) Prashant Tripathi; Ch. Ravi Prakash Patel; Abhishek Dixit; Avanish Pratap Singh; Pawan Kumar; M.A. Shaz; Ritu Srivastava; Govind Gupta; S.K. Dhawan; Bipin Kumar Gupta; O.N. Srivastava
Herein, we demonstrate a facile one pot synthesis of graphene nanosheets by electrochemical exfoliation of graphite. In the present study, we report a significant increase in the yield of graphene by electrolyte heating assisted electrochemical exfoliation method. The obtained results of heating assisted electrochemically exfoliated graphene (utilizing H2SO4 + KOH + DW) synthesis clearly exhibit that the yield increases ∼4.5 times i.e. from ∼17% (room temperature) to ∼77% (at 80°C). A plausible mechanism for the enhanced yield based on lattice expansion and vibration of intercalated ions has been put forward and discussed in details. The quality of graphene was examined by Raman, XPS, FTIR, AFM, SEM, TEM/HRTEM and TGA techniques. The Raman as well as morphogenesis results confirm the quality of the graphene nanosheets. We have used this graphene as electromagnetic interference shielding material where a comparatively large quantity of graphene is required. This graphene exhibits enhanced shielding effectiveness (46 dB at 1 mm thickness of stacked graphene sheets in frequency region 12.4 to 18 GHz) as compared to conventional electromagnetic interference shielding materials, which is greater than the recommended limit (∼30 dB) for techno-commercial applications. Thus the present work is suggestive for future studies on enhancement of yield of high quality graphene by proposed method and the use of synthesized graphene in electromagnetic interference shielding and other possible applications. © The Royal Society of Chemistry 2015.