Browsing by Author "Gopal Krishna Gupta"

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Excellent supercapacitive performance of graphene quantum dots derived from a bio-waste marigold flower (Tagetes erecta)
(Elsevier Ltd, 2021) Gopal Krishna Gupta; Pinky Sagar; Monika Srivastava; Ashwani Kumar Singh; Jai Singh; S.K. Srivastava; Amit Srivastava
Marigold flower (MG; Tagetes erecta) derived Graphene quantum dots (GQDs) have been successfully reported for the fabrication of supercapacitor electrodes in charge storage devices. The GQDs have been synthesized through a hydrothermal route using biomass viz. Waste material (MG) without adding any hazardous chemicals. The successful formation of GQDs as elaborated has been confirmed by various analytical characterization techniques. The as-synthesized GQDs have been electrodeposited on the Ni foil (working electrode) with the help of PVDF (binder) and subsequently, cyclic voltammetry (CV) has been conducted to access specific capacitance, energy density, and other parameters. Moreover, the galvanometric charge/discharge (GCD) technique has been employed due to its accuracy and reliability. Maximum areal specific capacitance has been found as 1.6008 F/cm2 with the current density of 2.0 A/g even after loading a little amount of material on the electrode. The high magnitude of columbic efficiency (160.08), energy density (17.78 Wh/kg), and specific capacitance of 200 F/g at current density 2.0 A/g within a voltage range of −0.55 V to +0.25 V in 2 M KOH electrolyte solution indicate a good electrocapacitive performance of the as-synthesized material. Moreover, the as-synthesized GQDs have shown excellent capacitive retention after 1000th cycles which clearly embarks its sustainable electrocapacitive nature and henceforth offers outstanding potential for the applications in energy storage devices like supercapacitors. © 2021
Hydrothermally synthesized nickel ferrite nanoparticles integrated reduced graphene oxide nanosheets as an electrode material for supercapacitors
(Springer, 2024) Gopal Krishna Gupta; Pinky Sagar; Monika Srivastava; Ashwani Kumar Singh; Jai Singh; S.K. Srivastava; Amit Srivastava
In the present study, we have employed an integrative strategy to synthesize a three-dimensional hierarchical electrode material consisting of NiFe2O4/r-GO nanostructures using a simple hydrothermal process and subsequently explored its electrocapacitive performance. The structural and morphological characteristics of the as-synthesized NiFe2O4/r-GO nanostructure have been accessed through X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and X-ray photospectrometer (XPS). The electrocapacitive performances of the as-synthesized sample have been evaluated by galvanostatic charge–discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) using a three-electrode system with 3-M KOH electrolyte solution. As-prepared hierarchical electrode material exhibits specific capacity ∼ 362.46 F g−1 at a current density of 0.65 A g−1, suggesting good rate capability. Furthermore, NiFe2O4/r-GO-nanostructured electrode material displays a significant high energy ∼ 36.37 Wh/kg and power density as ∼ 276.22 W/kg. Moreover, the as-synthesized nanocomposite harvests a superior cycling stability over 5000 cycles without obvious capacitance attenuation. The NiFe2O4/r-GO provides rapid pathways for electron transfer and diminishes the ion diffusion routes due to NiFe2O4 over r-GO sheets, which ultimately results in exceptional electrochemical properties. Henceforth, NiFe2O4/r-GO nanocomposite which renders a new reasonable design to manifest more energy density and deliver maximum power may be enrooted as a promising/prospective electrode material due to its unique morphological properties, superior conductivity, and favorable cyclic stability in the field of energy storage applications. © 2024, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
In Situ Fabrication of Activated Carbon from a Bio-Waste Desmostachya bipinnata for the Improved Supercapacitor Performance
(Springer, 2021) Gopal Krishna Gupta; Pinky Sagar; Sumit Kumar Pandey; Monika Srivastava; A.K. Singh; Jai Singh; Anchal Srivastava; S.K. Srivastava; Amit Srivastava
Herein, we demonstrate the fabrication of highly capacitive activated carbon (AC) using a bio-waste Kusha grass (Desmostachya bipinnata), by employing a chemical process followed by activation through KOH. The as-synthesized few-layered activated carbon has been confirmed through X-ray powder diffraction, transmission electron microscopy, and Raman spectroscopy techniques. The chemical environment of the as-prepared sample has been accessed through FTIR and UV–visible spectroscopy. The surface area and porosity of the as-synthesized material have been accessed through the Brunauer–Emmett–Teller method. All the electrochemical measurements have been performed through cyclic voltammetry and galvanometric charging/discharging (GCD) method, but primarily, we focus on GCD due to the accuracy of the technique. Moreover, the as-synthesized AC material shows a maximum specific capacitance as 218 F g−1 in the potential window ranging from − 0.35 to + 0.45 V. Also, the AC exhibits an excellent energy density of ~ 19.3 Wh kg−1 and power density of ~ 277.92 W kg−1, respectively, in the same operating potential window. It has also shown very good capacitance retention capability even after 5000th cycles. The fabricated supercapacitor shows a good energy density and power density, respectively, and good retention in capacitance at remarkably higher charging/discharging rates with excellent cycling stability. Henceforth, bio-waste Kusha grass-derived activated carbon (DP-AC) shows good promise and can be applied in supercapacitor applications due to its outstanding electrochemical properties. Herein, we envision that our results illustrate a simple and innovative approach to synthesize a bio-waste Kusha grass-derived activated carbon (DP-AC) as an emerging supercapacitor electrode material and widen its practical application in electrochemical energy storage fields. © 2021, The Author(s).
Tagetes erecta as an organic precursor: Synthesis of highly fluorescent CQDs for the micromolar tracing of ferric ions in human blood serum
(Royal Society of Chemistry, 2021) Pinky Sagar; Gopal Krishna Gupta; Monika Srivastava; Amit Srivastava; S.K. Srivastava
The present article illustrates the green synthesis of novel carbon quantum dots (CQDs) from biomass viz. Tagetes erecta (TE), and subsequently fabrication of a metal ion probe for the sensing of Fe3+ in real samples. TE-derived CQDs (TE-CQDs) have been synthesized by a facile, eco-friendly, bottom-up hydrothermal approach using TE as a carbon source. The successful synthesis and proper phase formation of the envisaged material has been confirmed by various characterization techniques (Raman, XRD, XPS, TEM, and EDS). Notably, the green synthesized TE-CQDs show biocompatibility, good solubility in aqueous media, and non-toxicity. The as-synthesized TE-CQDs show an intense photoluminescence peak at 425 nm and exhibit excitation dependent photoluminescence behavior. The proposed TE-CQD-based probe offers a remarkable fluorescence (FL) quenching for Fe3+ with high selectivity (Kq ∼ 10.022 × 1013 M-1 s-1) and a sensitive/rapid response in a linear concentration range 0-90 μM (regression coefficient R2 ∼ 0.99) for the detection of Fe3+. The limit of detection (LOD) of the probe for Fe3+ has been found as 0.37 μM in the standard solution. It has further been applied for the detection of Fe3+ in real samples (human blood serum) and displays good performance with LOD ∼ 0.36 μM. The proposed TE-CQD-based ion sensing probe has potential prospects to be used effectively in biological studies and clinical diagnosis. This journal is © The Royal Society of Chemistry.