Browsing by Author "Kumar, H"
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Item Co3O4 quantum dot decorated polypyrrole nanocomposites as a flexible, conducting, anticorrosive and antibacterial agent: sustainable experimental and theoretical approach†(2023-02) Kumar, H; Luthra, MSelf-assembled cobalt oxide quantum dots (QDs) were prepared by the inverse micelle technique. Polypyrrole (PPy) was synthesized by the chemical-oxidative method. Co3O4 QD-based PPy nanocomposites (NCs) were prepared by an in situ method. The Co3O4 QDs, PPy, and Co3O4@PPy NCs were characterized by TEM, FTIR, X-ray diffraction, and UV-visible techniques. The size of Co3O4 QDs, PPy, and Co3O4@PPy NCs was obtained by powder XRD and TEM methods. Computational (DFT) and adsorption (Langmuir and Henry) studies were carried out to support experimental data. Co3O4@PPy NCs show a maximum of 81.58% protection to mild steel in an acidic medium. The antibacterial activity of Co3O4@PPy NCs was comparable to that of Hexa disk (standard antibiotics). The Co3O4@PPy NCs were proven to be flexible, conducting, corrosion inhibiting, and possess antibacterial properties. The NCs find applications in soft electronics, the pharmaceutical industry, corrosion inhibitors for metals and their alloys, and flexible (moldable) display devices for sustainable developments.Item Co3O4 quantum dot decorated polypyrrole nanocomposites as a flexible, conducting, anticorrosive and antibacterial agent: sustainable experimental and theoretical approach†(2023-02) Kumar, H; Luthra, M; Punia, M; Kaur, PSelf-assembled cobalt oxide quantum dots (QDs) were prepared by the inverse micelle technique. Polypyrrole (PPy) was synthesized by the chemical-oxidative method. Co3O4 QD-based PPy nanocomposites (NCs) were prepared by an in situ method. The Co3O4 QDs, PPy, and Co3O4@PPy NCs were characterized by TEM, FTIR, X-ray diffraction, and UV-visible techniques. The size of Co3O4 QDs, PPy, and Co3O4@PPy NCs was obtained by powder XRD and TEM methods. Computational (DFT) and adsorption (Langmuir and Henry) studies were carried out to support experimental data. Co3O4@PPy NCs show a maximum of 81.58% protection to mild steel in an acidic medium. The antibacterial activity of Co3O4@PPy NCs was comparable to that of Hexa disk (standard antibiotics). The Co3O4@PPy NCs were proven to be flexible, conducting, corrosion inhibiting, and possess antibacterial properties. The NCs find applications in soft electronics, the pharmaceutical industry, corrosion inhibitors for metals and their alloys, and flexible (moldable) display devices for sustainable developmentsItem Cool green-emissive Y2Si2O7:Tb3+ nanophosphor: auto-combustion synthesis and structural and photoluminescence characteristics with good thermal stability for lighting applications†(2024-05) Kumar, P; Singh, D; Kadyan, S; Kumar, H; Kumar, RA cheap, versatile, sustainable and energy-efficient gel-combustion method was applied to develop a series of green-emitting down-converted Y2Si2O7:Tb3+ (YPS:Tb3+) nanophosphors. Employing XRD-based Rietveld refinement approach, the phase purity and crystallographic evaluation of the produced phosphor were conducted, revealing a triclinic crystal with P 1 space group. EDX and TEM analyses were performed on the synthesized samples to determine their elemental composition and morphological properties. Diffuse reflectance spectra yielded 5.61 eV and 5.79 eV optical energy band gaps for the host and the optimized (0.04 mole of Tb3+) sample, respectively. UV light has the ability to excite the nanocrystalline phosphor in an efficient manner, leading to significant luminosity qualities attributed to the radiative relaxation of 5 D4 / 7 FJ (J = 6, 5, 4, 3). The bi-exponential decay function was derived by the PL decay curves. With an activation energy of 0.2206 eV, the Y1.96Si2O7:0.04Tb3+ phosphor exhibits good thermal quenching capabilities. Improved photometric attributes including CIE coordinates, CCT and color purity confirmed the green glow, indicating a strong competitor for cool-green emission in lighting applicationsItem Corrosion inhibition and adsorption mechanism of Morus nigra on mild steel in acidic medium: A sustainable and green approach(2021-12) Kumar, H; Sharma, S; Kumari, RMorus nigra (Mulberry leaves) was tested as a green inhibitor for mild steel (MS) in 0.5 M HCl by theoretical, surface study, and experimental techniques. The impedance, polarization, microscopy, Langmuir, and DFT (computational) techniques were used for the adsorption and corrosion inhibition study. The experimental and theoretical study supports each other results. Adsorption parameters were observed by Langmuir, Gaussian09W (DFT), and BIOVIA Materials Studio Softwares. The surface study was carried out by metallurgical microscopy technique. The theoretical study includes chemical potential, electron-donating power, chemical hardness, HOMO, LUMO, metal inhibitor interaction energy, adsorption energy, etc. UV-visible, NMR, and FTIR studies show that aspartic acid is the major constituent present in the mulberry leaves extract. A 91.62 % corrosion protection was provided by the Morus nigra at 1000 ppm. Polarization study proved mixed inhibition. The green inhibitor follows both physical and chemical modes of adsorption. The biochemical and chemical oxygen demand of unused acid left after the gravimetric study was found in an acceptable range.Item Developments in conducting polymer-, metal oxide-, and carbon nanotube-based composite electrode materials for supercapacitors: a review(2024-03) Tundwal, A; Kumar, H; Binoj, B; Sharma, R; Kumar, G; Kumari, R; Dhayal, A; Yadav, A; Singh, D; Kumar, PSupercapacitors are the latest development in the field of energy storage devices (ESDs). A lot of research has been done in the last few decades to increase the performance of supercapacitors. The electrodes of supercapacitors are modified by composite materials based on conducting polymers, metal oxide nanoparticles, metal–organic frameworks, covalent organic frameworks, MXenes, chalcogenides, carbon nanotubes (CNTs), etc. In comparison to rechargeable batteries, supercapacitors have advantages such as quick charging and high power density. This review is focused on the progress in the development of electrode materials for supercapacitors using composite materials based on conducting polymers, graphene, metal oxide nanoparticles/nanofibres, and CNTs. Moreover, we investigated different types of ESDs as well as their electrochemical energy storage mechanisms and kinetic aspects. We have also discussed the classification of different types of SCs; advantages and drawbacks of SCs and other ESDs; and the use of nanofibres, carbon, CNTs, graphene, metal oxide– nanofibres, and conducting polymers as electrode materials for SCs. Furthermore, modifications in the development of different types of SCs such as pseudo-capacitors, hybrid capacitors, and electrical double-layer capacitors are discussed in detail; both electrolyte-based and electrolyte-free supercapacitors are taken into consideration. This review will help in designing and fabricating high-performance supercapacitors with high energy density and power output, which will act as an alternative to Li-ion batteries in the future.Item A green light emissive LaSr2AlO5:Er3+ nanocrystalline material for solid state lighting: crystal phase refinement and down-conversion photoluminescence with high thermal stability(2024-09) Kumar, P; Singh, D; Kumar, HThe present study reveals the structural and optoelectronic characteristics of a down-converted (DC) green luminous Er3+ doped LaSr2AlO5 phosphor that was produced by employing an efficient and reliable gel combustion process assisted with urea as a fuel. Using Rietveld refinement of diffraction data, the crystal structure and phase formation were examined. The surface morphology and elemental configuration of the phosphor were analyzed via TEM and EDX spectroscopy, respectively. The band gap of LaSr2AlO5 (5.97 eV) and optimized La0.96Sr2AlO5:4 mol% Er3+ (5.51 eV) classify the optimized sample as a direct band-gap material. The PL peaks located in the visible range corresponding to transitions 2 H9/2 / 4 I15/2 (406 nm), 2 H11/2 / 4 I15/2 (520 nm), 4 S3/2 / 4 I15/2 (550 nm), and 4 F9/ 2 / 4 I15/2 (665 nm) were revealed by photoluminescence spectroscopy under 377 nm excitation. Above 4 mol% Er3+ doping, concentration quenching was observed, which was controlled by the quadrupole–quadrupole interaction. Based on the findings of the double exponential fitting of lifetime curves acquired from the emission spectra at lex = 377 nm and lem = 550 nm, the average lifetime of the excited levels of considered nanomaterials was estimated. The temperature-dependent emission spectra of the La0.96Sr2AlO5:4 mol% Er3+ sample were collected in the range 298–498 K. The considered phosphor was found to have a high thermal stability as evidenced by the luminous intensity being sustained at 74.29% at 498 K compared to the intensity at ambient temperature (298 K) with an activation energy of 0.1453 eV. The calculated color purity and superb chromaticity coordinates indicates that the phosphors have a high degree of color purity, which further supports its applicability as a green component in solid-state lighting.Item Metal oxide decorated polyaniline based multifunctional nanocomposites: An experimental and theoretical approach(2023-05) Yadav, A; Kumar, H; Sharma, RWhen combined with metal oxide nanoparticles, conducting polymers may result in unique or synergistic effects in their properties. Fe/Mn/CuO/PANI (FMC/PANI) based nanocomposites (NCs) were explored for five different novel applications. FTIR, UV–visible, XRD, Raman, and FESEM methods were used to identify the NCs. The anti corrosive, photocatalytic, magnetic, antibacterial, and electrical properties were investigated by experimental and theoretical (DFT) methods. The computational technique was used for frequency, geometry optimization, and energy study. Different thermodynamic, kinetic, and molecular orbital parameters were investigated by the DFT study for the NCs. The anti-corrosive, photocatalytic, antibacterial, electrical, and magnetic properties of NCs were investigated at different concentrations. The FMC/PANI NCs show a maximum of 85 ± 0.2% CIE for MS in 1.0 M HCl solution. The magnetic study proves the paramagnetic nature of NCs. The photocatalytic activity of FMC/PANI NCs was investigated against MO dye under UV light. The antibacterial property of FMC nano particles (NPs) was investigated against gram-positive and gram-negative bacterial strains, that is, B. subtilis and E. coli, respectively. The ZOI was compared with six standard antibiotics and found to be comparable with common antibiotics. The FMC/PANI-based NCs were proven to be perfect photocatalytic, magnetic, antibacte rial, electrical conductors, and anti-corrosive agents.Item PANI encapsulated α-MnO2 nanocomposites as photocatalytic, antibacterial and anticorrosive agents: Sustainable experimental and theoretical studies(2023-06) Kumar, H; Luthra, M; Punia, M; Yadav, AMetal nanoparticles and conducting polymers have applications in the fields like purification, separation, adsorption, photocatalytic, antibacterial, sensors, electrical conductivity, etc. The α-MnO2 nanoparticles, and polyaniline (PANI) were synthesized by the reverse micelle and chemical oxidative techniques, respectively. An in-situ technique was used for the synthesis of α-MnO2/PANI nanocomposites (NCs). The characterization of α-MnO2 nanoparticles and NCs was carried out by XRD, TEM, FTIR, and UV–visible techniques. The experimental data was supported by a theoretical (computational) study. Corrosion inhibition, antibacterial, and photo catalytic activity of α-MnO2/PANI NCs were explored. The NCs show a maximum of 87 ± 0.1% corrosion in hibition efficiency. The NCs (100 ppm concentration) degrade 89.15 ± 1.1% of methyl orange dye after 3 h of UV exposure. The photodegradation of dye follows pseudo-first order kinetics with a rate constant of 0.0657 min− 1 . The mechanism of photodegradation is supported by potentiostatic photocurrent measurement, imped ance spectroscopy, pH variation, and chemical oxygen demand. The antibacterial property of NCs was compared to standard Hexa disk against Gram-positive and Gram-negative bacterial strains. The NCs show 18.5 mm and 15.3 mm Zone of Inhibition (1000 ppm) for S. epidermis and E. coli, respectively. The α-MnO2/PANI NCs show very good anti-corrosive, antibacterial, and photocatalytic properties.Item Realization of a green-emitting pyrosilicate structured Er3+-activated Y2Si2O7 phosphor: a systematic study of opto-electronic characteristics and thermal stability for lighting applications(2024-05) Kumar, P; Singh, D; Singh, S; Kumar, H; Kumar, RA series of green-emitting Y2−xSi2O7:xEr3+ phosphors (x = 1–7 mol%) have been successfully synthesized using a straightforward gel-combustion method facilitated by urea. X-ray diffraction analysis provided specific patterns for samples, confirming a consistent triclinic phase across erbium-doped structures compared to undoped structures. Studies using TEM and EDX were conducted to identify the surface related characteristics and chemical composition of the synthesized nanophosphor, respectively. The band gap was determined to be 5.55 eV and 5.80 eV for the host material and optimal sample, respectively. The primary peak of excitation, observed at 379 nm, represents the highly sensitive electric dipole transition from the 4 I15/2 state to the 4 G11/2 level, suggesting that the prepared phosphors could effectively absorb NUV light for activation. The PL profiles of Y2−xSi2O7:xEr3+ (x = 1–7 mol%) phosphors demonstrate characteristic emissions at 409 nm (2 H9/2 / 4 I15/2), 522 nm (2 H11/2 / 4 I15/2), 553 nm (4 S3/2 / 4 I15/2) and 662 nm (4 F9/2 / 4 I15/2). In accordance with Dexter's theory, luminescence quenching observed at a concentration of 4 mol% Er3+ is attributed to dipole-quadrupole interactions. The optimal sample demonstrates excellent thermal stability, indicated by its luminescence at different temperatures and activation energy of 0.2641 eV. Additionally, the CIE, color purity and CCT values of the fabricated nanomaterials make it ideal for use in lighting applications.Item Remediation of toluidine blue O dye from aqueous solution using surface functionalized magnetite nanoparticles(2024) Jangra, A; Kumar, R; Singh, D; Kumar, H; Kumar, J; Kumar, P; Kumar, SIn the current study, tannic acid-functionalized iron oxide nanoparticles have been synthesized using a cost-effective co-pre cipitation method and subsequently characterized using various instrumentation techniques such as Fourier transform infrared spectroscopy, X-ray diffractometer, field emission scanning electron microscopy, and thermal gravimetric analysis. Further, these surface-modified magnetite nanoparticles have been used for the adsorption of toluidine dye from an aqueous solution. The adsorption process was accompanied using batch procedure, and influences of several factors such as adsorbent dose, contact time, pH, temperature, and initial concentration of adsorbate were inspected concurrently. The maximum adsorp tion capacity of tannic acid-functionalized magnetite nanoparticles was found to be 50.68 mg/g. The adsorption process was observed to follow the Temkin isotherm model, whereas the kinetic study was well described by pseudo-second order. The thermodynamic study revealed the adsorption process to be endothermic and spontaneous in nature with a high degree of freedom between adsorbent and adsorbate. Therefore, the study indicated that the tannic acid-functionalized magnetite nano particles have promising adsorption capability and can be used as an excellent adsorbent for the removal of toluidine blue O dye from the aqueous solution.