Papers by Varishetty Madhu Mohan
Development of an efficient ammonia gas sensor based on Al doped tin oxide at room temperatureo
Inorganic chemistry communications/Inorganic chemistry communications (Online), Jun 1, 2024
Investigation on Sb-doped SnO2 as an efficient sensor for the detection of formaldehyde
Materials Today Communications
The applicability of antimony-doped tin dioxide (Sb-doped SnO 2) as a very precise sensor for det... more The applicability of antimony-doped tin dioxide (Sb-doped SnO 2) as a very precise sensor for detecting formaldehyde (HCHO) gas is investigated in this study. The sol-gel method was used to prepare pure SnO 2 and Sbdoped SnO 2 nanostructures, which resulted in better structural and morphological properties. The prepared samples were analyzed using several characterization techniques, including X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). A structural investigation indicated the presence of a tetragonal SnO 2 phase with a clear preference for the (110) orientation. Furthermore, the crystallite size reduced as the quantity of Sb doping rose. According to FE-SEM analysis, both the undoped (SnO 2) and Sb-doped SnO 2 samples had polyhedral structures. FTIR analysis verified the presence of organic functional groups in the prepared powder samples. The optical band gap (Eg) values decreased with an increasing concentration of Sb doping in the SnO 2 nanostructures. XPS was used to determine the chemical elements of the prepared powder samples. In the gas sensing study, those based on 8 wt% Sb-doped SnO 2 (referred to as ATO-8) outperformed the others. At room temperature, the ATO-8 sample demonstrated stronger sensor response, faster response and recovery durations (98 s/74 s), and linear behavior. These enhancements can be attributable to an increase in adsorbed oxygen species caused by Sb doping, highlighting ATO-8's potential as a substance for detecting HCHO. This study emphasizes the potential of ATO-8 as a significant resource for practical use in the detection of HCHO, with benefits such as improved indoor air quality, increased industrial safety, and advancements in environmental monitoring.
Green synthesis of cotton flower shaped nickel oxide nanoparticles: Anti-bacterial and tribological studies
Inorganic Chemistry Communications
The goal of this study was to synthesize nickel oxide nanoparticles (NiO-NPs) by the sol-gel meth... more The goal of this study was to synthesize nickel oxide nanoparticles (NiO-NPs) by the sol-gel method, which involved the use of Cassia Fistula is a herbal and medicinal plant. The Cassia Fistula (CF) plant extract acts as a stabilizing and capping agent. Further, NiO-NPs were characterized using UV-Visible spectroscopy (UV-Vis), Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX). According to the results of UV-Visible, the absorption spectroscopy has displayed that the band gap is 3.5 eV. The biological properties were studied for prepared NiO-NPs. The antibacterial testes were examined using different bacterial strains such as Escherichia coli, Staphylococcus aureus and Staphylococcus Epidermis and dose-dependent inhibition response was reported. The tribological tests are carried out using four ball testers in accordance with ASTM D4172-18 requirements. NiO-NPs are utilised as lubricating additives in poly alpha olefin (PAO4) base oil. NiO-NPs in PAO4 at a concentration of 0.5 wt% improved the coefficient of friction, and positive results are observed.
Journal of Solid State Electrochemistry, Apr 15, 2010
This paper aimed to improve the electrochemical activity of a pitch-derived open-pore graphite fo... more This paper aimed to improve the electrochemical activity of a pitch-derived open-pore graphite foam (GF) by an electrochemical coating of reduced graphene oxide (RGO) and platinum particles without significantly affecting its 3D-structure. RGO was synthesized using cyclic voltammetry (CV) from a 3 g L −1 GO and 0.1 M LiClO 4 solution. For the electrodeposition of Pt particles, an alternating current method based on electrochemical impedance spectroscopy (EIS) was used. A sinusoidal voltage from a fixed potential Ei was varied following a selected amplitude (∆E ac = ± 0.35 V) in a frequency range of 8 Hz ≤ f i ≤ 10Hz, where i = 500. This method proved its efficiency when compared to the traditional CV by obtaining more highly electroactive coatings in less synthesis time. For samples' characterization, physical measures included permeability, pressure drop, and nitrogen adsorption isotherms. The electrochemical characterization was performed by CV. The surface morphology and chemical composition were examined using field emission electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. RGO improved the electron transfer rate constant of GF, and a more homogeneous coating distribution of reduced size Pt particles was obtained.
Astrophysical Applications of Aluminum, Strontium Lanthanate Phosphors Doped with Terbium and Europium
International Journal of Advanced Research in Science, Communication and Technology, Dec 31, 2021
Al2Sr2La2O8 doped (ASL) with terbium and europium ion was synthesized by solid state reaction und... more Al2Sr2La2O8 doped (ASL) with terbium and europium ion was synthesized by solid state reaction under air atmosphere. Its characterization was systematically analyzed by SEM, X-ray diffraction (XRD) and photoluminescence spectra (PL). Photoluminescence emission spectra having excitations at around 254, 268, 278nm revealed that Eu ions were present in trivalent oxidation states. The emission peaks are found at 540(green), 588,(Yellow) and 626nm(red) are observed. Scanning Electron Microscopy (SEM) was implemented to investigate the surface morphology of present phosphor. The obtained results on Al2Sr2La2O8: Tb, Eu is suitable for green-red light source using UV light as the primary excitation. In addition with Aluminum, Strontium Lanthanate phosphors are used for lighting can work to minimize electricity usage, and decreases the excess light pollution, minimizing light pollution has benefits for people and for the surrounding ecosystems. The best example of ASL is lighting use is around Peurto Mosquito, a bioluminescent bay on vieques, peurto rico ,the bioluminescence is more visible and healthier, and people's eyes get a few more minutes to adjust to the dark. Another use of the ASL is lighting is around the lowell astrophysical observatory. Astrophysical observatories require low lighting to properly see stars and often use best practices in light-pollution safe lighting. Now the observatory is lined with paths that glow at night. Researchers and visitors to safely find their way in the dark, without the use of bright electric lights.
Structure, electrical and optical properties of (PVA/LiAsF<sub>6</sub> ) polymer composite electrolyte films
Polymer Engineering and Science, Nov 30, 2009
ABSTRACT In this work, Li+ ion conducting polymer composite electrolyte films (PECs) were prepare... more ABSTRACT In this work, Li+ ion conducting polymer composite electrolyte films (PECs) were prepared based on poly (vinyl alcohol) (PVA), lithium hexafluoro arsenate (LiAsF6), and ceramic filler TiO2 using solution cast technique. The XRD and FTIR spectra were used to determine the complexation of the PVA polymer with LiAsF6 salt. The ionic conductivities of the (PVA + LiAsF6) and (PVA + LiAsF6 + TiO2) films have been determined by the A.C. impedance measurements in the temperature range 320–440 K. The maximum conductivity was found to be 5.10 × 10−4 S cm−1 for PVA:LiAsF6 (75:25) + 5 wt% TiO2 polymer composite film at 320 K. The calculation of Li+ ion transference number was carried out by the combination of A.C. impedance and D.C. polarization methods and is found to be 0.52 for PVA:LiAsF6 (75:25) + 5 wt% TiO2 film. Optical properties such as direct energy gap, indirect energy gap, and optical absorption edge values were investigated in pure PVA and salt complexed PVA films from their optical absorption spectra in the wavelength range of 200–600 nm. The absorption edge was found at 5.76 eV for undoped film, while it is observed at 4.87 and 4.70 eV for 20 and 25 wt% LiAsF6 doped films, respectively. The direct band gaps for these undoped and salt doped PVA films were found to be 5.40, 5.12, and 4.87 eV, respectively, whereas the indirect band gaps were determined as 4.75, 4.45, and 4.30 eV. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers
International Journal of Polymeric Materials, Mar 15, 2007
The structural, electrical, and optical characteristics of nanometric Fe 2 O 3−x films fabricated... more The structural, electrical, and optical characteristics of nanometric Fe 2 O 3−x films fabricated on ͗100͘ Si and SiO 2 substrates by ablating an iron target with a KrF excimer laser in low pressure ͑0.05-1.0 Pa͒ O 2 atmosphere are reported. The thickness of films fabricated with 4000 laser pulses is ϳ80 nm for samples deposited at the lowest pressure ͑0.05 Pa͒ and decreases gradually to 50 nm at the highest used pressure ͑1.0 Pa͒. The film mean composition results close to FeO at lower pressures ͑0.05-0.10 Pa͒ and to Fe 2 O 3 at higher pressures ͑0.5-1.0 Pa͒. From glazing incidence x-ray diffraction spectra, it was inferred that deposits are poorly crystallized, especially the ones prepared at relatively high oxygen pressures ͑0.5-1.0 Pa͒. Scanning electron microscopy inspections show that surfaces are plane and uniform, with very rare ͑Ͻ0.1 m −2 ͒ submicron droplets. From x-ray reflectivity spectra, surface roughness results very low ͑0.1-0.5 nm, increasing with O 2 pressure͒. The films present a semiconductor behavior, with electrical energy gaps increasing from 0.43 to 0.93 eV with increasing O 2 pressure, while the optical energy gap varies from 1.60 eV ͑0.05 Pa͒ to 1.74 eV ͑1.0 Pa͒. Very high thermoelectromotive force coefficient values were measured ͑up to 1.65 mV/K͒. It is also shown that films present promising gas sensing properties.
Energy Advances
This research article reports on a systematic approach to developing polymer gel electrolytes (PG... more This research article reports on a systematic approach to developing polymer gel electrolytes (PGE) for the applications of dye-sensitized solar cells (DSSC). The authors prepared poly(acrylonitrile) (PAN) and poly(ethylene glycol)...
Studies in thin films investigations on electrical properties of pure and doped peo polymer electrolyte films for solid state battery applications
Suppressing the Recombination Rate on DSSC by Forming Blocking Layer (シリコン材料・デバイス)
Polymers for Advanced Technologies, 2017
We have synthesized eco-friendly, economic, and equally efficient polysulfobetaine-based gel elec... more We have synthesized eco-friendly, economic, and equally efficient polysulfobetaine-based gel electrolyte to the alternative of liquid electrolyte in the fabrication of dye-sensitized solar cells (DSSCs) for the first time. This nitrogen-rich and highly conductive polysulfobetaine was synthesized by an easy and facile method without the use of any catalyst and explored for its DSSC application. The synthesized polymer gel electrolyte exhibited good ionic conductivity about 6.8 × 10 À3 Scm À1 at ambient temperatures. DSSCs were fabricated based on this polysulfobetaine gel electrolyte and studied for their performance based on photovoltaic parameters. The DSSC photovoltaic results were appreciable and are Voc = 0.82 V, Jsc = 11.49 mA/cm 2 , FF = 66%, and PCE = 6.26% at 1 sun intensity. These values are slightly lower than conventional liquid electrolyte-based DSSC shown as Voc = 0.78 V, Jsc = 12.90 mA/cm 2 , FF = 69%, and PCE = 7.07%, both at 100 mWcm À2. Conductivity and photovoltaic parameters of the device reveals that as prepared polysulfobetaine-based polymer gel electrolyte may be useful in the fabrication of DSSC and other electrochemical devices.
Preparation and Characterization of Polymer-Based Spherical Activated Carbons
Chinese Journal of Polymer Science, 2008
A series of spherical activated carbons (SACs) with different pore structures were prepared from ... more A series of spherical activated carbons (SACs) with different pore structures were prepared from chloromethylated polydivinylbenzene by ZnCl2 activation. The effects of activation temperature and retention time on the yield and textural properties of the resulting SACs were studied. All the SACs are generated with high yield of above 65% and exhibit relatively high mesopore fraction (me%) of 35.7%−43.6% compared with conventional activated carbons. The sample zlc28 prepared at 800°C for 2 h has the largest BET surface area of 891 m 2 g −1 and pore volume of 0.489 cm 3 g −1 . SEM and XRD analyses of zlc28 verify the presence of developed porous structure composed of disordered micrographite stacking with large amounts of interspaces in the order of nanometers.
The goal of this study was to synthesize nickel oxide nanoparticles (NiO-NPs) by the sol-gel meth... more The goal of this study was to synthesize nickel oxide nanoparticles (NiO-NPs) by the sol-gel method, which involved the use of Cassia Fistula is a herbal and medicinal plant. The Cassia Fistula (CF) plant extract acts as a stabilizing and capping agent. Further, NiO-NPs were characterized using UV-Visible spectroscopy (UV-Vis), Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX). According to the results of UV-Visible, the absorption spectroscopy has displayed that the band gap is 3.5 eV. The biological properties were studied for prepared NiO-NPs. The antibacterial testes were examined using different bacterial strains such as Escherichia coli, Staphylococcus aureus and Staphylococcus Epidermis and dose-dependent inhibition response was reported. The tribological tests are carried out using four ball testers in accordance with ASTM D4172-18 requirements. NiO-NPs are utilised as lubricating additives in poly alpha olefin (PAO4) base oil. NiO-NPs in PAO4 at a concentration of 0.5 wt% improved the coefficient of friction, and positive results are observed.
Lithiated CuO (Li-CuO) micro-structures were synthesized by the hydrothermal method using KOH as ... more Lithiated CuO (Li-CuO) micro-structures were synthesized by the hydrothermal method using KOH as a reactive solution. The structural properties of pure Li-CuO and other KOH-reacted CuO samples were characterized by XRD analysis. Various vibrational bands were observed by FTIR spectra analysis. The SEM images indicated the formation of Li-CuO hexagonal rods of 1-2 mm dimension. The cyclic efficiencies of pure Li-CuO and 12 M KOH surfactant Li-CuO microstructures were observed to be 78.5% and 91.2%, respectively. The battery discharge characteristics revealed that after 50 cycles, the specific capacity of the battery based on a pure Li-CuO microstructure electrode showed 97 mAh g À1 whereas KOH surfactant Li-CuO microstructures electrode showed 150 mAh g À1 at a constant current density of 17.79 mA g À1 with a 1.0-4.0 V vs. Li/Li + potential range. The enhancement of specific capacity and its stability due to a well-defined hexagonal crystal structure leads to increase Li + ion kinetics during the insertion and extraction processes of batteries. 65 tubes, and graphene demonstrated extensively well with 66 superior electrochemical properties. Deng et al. [11] 67 demonstrated that CuO nanosheets with porous structures 68 and enhanced interface contact lead to an improvement in 69 electrical conductivity, thereby reducing polarization in a 70 cyclic process. During the charge and discharge processes of 71 Al ion batteries, Zhang et al. [12] demonstrated porous-72 CuO microspheres with high cyclic stability and fast ion 73 transport. Zamani et al. [13] reported that the RP/Co 3 O 4-74 CuO nanostructured hybrid anode has good cyclic stability 75 and also exhibited an initial Coulombic efficiency of 99.8% 76 with a current density of 50 mA g À1. Wang et al. [14] 77 demonstrated that the CuO nanochain-based anodes 78 exhibit thermodynamic stability and rate performance 79 due to the easy conversion reactions of Li ions with the 80 nano-inorganic alloys. Cao et al. [15] demonstrated CuO
This research article reports on a systematic approach to the development of polymer gel electrol... more This research article reports on a systematic approach to the development of polymer gel electrolytes (PGEs) for the applications of dye-sensitized solar cells (DSSCs). The authors prepared PGE blend using poly(acrylonitrile) (PAN) and poly(ethylene glycol) (PEG) polymers along with three different ionic salts. They demonstrated a good ionic conductivity of 1.52 Â 10 À2 S cm À1 , which improved PV performance. The conduction mechanism of the (PAN/PEG) PGE is based on the interaction of three cations of distinct sizes, Hex 4 N + , K + , and Li + ions, with the polymer host. The rapid diffusion of I À /I 3 À iodide ions through the pores formed by PEG in the PGE is the primary cause of improved ionic conductivity. Various compositions of (PAN/PEG) have been optimized to obtain a sufficient porous structure and improved photon conversion efficiency (PCE) of the cell, achieving 8.6% in this research. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), impedance spectroscopy, incident photon conversion efficiency (IPCE) and finally current density voltage (J-V) characterization techniques are used to analyze and compare the results with those of liquid electrolyte-based cells.
Electrical and optical properties of pure and KClO3-doped P(MMA-CO-4VPNO) polymer electrolyte films
Ionics, Oct 24, 2008
... Sharma AK, Ramu Ch (1991) J Matt Sci Lett 10:1217 19. Yoshino K, Manada Y, Sawada K, Morita S... more ... Sharma AK, Ramu Ch (1991) J Matt Sci Lett 10:1217 19. Yoshino K, Manada Y, Sawada K, Morita S, Takahashi H, Sugimoto R, Onoda M (1989) J Phys Soc Jpn 58:1320 20. Uma Devi C, SharmaAK, Narasimha Rao VVR (2002) Mater Lett 56:167 21. Mansingh A, Kumar S ...
Ionics, Jan 22, 2012
In this paper, we report the hydrothermal synthesis of VO 2 , poly(ethylene oxide) (PEO)/VO 2 ,V ... more In this paper, we report the hydrothermal synthesis of VO 2 , poly(ethylene oxide) (PEO)/VO 2 ,V 3 O 7 •nH 2 O and PEO/V 3 O 7 •nH 2 O nanobelts by using 1,2-propylene carbonate (1,2-PC (C 4 H 6 O 3)) and poly(ethylene glycol) (PEG) as templates, respectively. Structure and morphology of the samples were investigated by XRD, FTIR, SEM, and TEM. The vanadium oxide (VO 2) nanobeltcomposite show the initial specific capacity 152 mA h g −1 , whereas PEO/VO 2 shows 182 mA h g −1. The pure V 3 O 7 •nH 2 O nanobelts shows the initial specific capacity 192 mA h g −1 , while PEO/ V 3 O 7 •nH 2 O nanobelts show 297 mA h g −1. It was found that PEO/VO 2 and PEO/V 3 O 7 •nH 2 O nanocomposites show better cyclic performance and high discharge stability compared to pure vanadium oxide nanomaterials. The role of the polymeric PEO component of the hybrid material seems to be the stabilization and improvement of the specific capacity due to probable homogeneous distribution between the nanobelts. The TEM images indicate that PEO works as a surfactant to decrease the dimensions of nanobelts. Keywords Hydrothermal synthesis. VO 2 and V 3 O 7. nH 2 O nanobelts. Poly(ethylene oxide). Cathode material. Electrochemical properties
Hydrothermal growth of bilayered rutile-phased TiO2 nanorods/micro-size TiO2 flower in highly acidic solution for dye-sensitized solar cell
Journal of Sol-Gel Science and Technology, Jan 20, 2015
Aligned rutile-phased TiO2 (r-TNRs) nanorods and micro-size rutile-phased TiO2 flowers (r-TFs) fi... more Aligned rutile-phased TiO2 (r-TNRs) nanorods and micro-size rutile-phased TiO2 flowers (r-TFs) films were prepared on fluorine-doped tin oxide (FTO) substrate using highly acidic solution by two steps of hydrothermal process. The hydrothermal process was done at 150 °C in 5 h for the first step and 2 h for the second step. These films were used as a photoelectrode in dye-sensitized solar cell (DSC) application. Aligned r-TNRs and r-TFs were prepared using one-step and two-step hydrothermal processes, respectively. At the end of second step hydrothermal process, micro-size rutile-phased TiO2 flowers (r-TFs) were observed on top of r-TNRs (FTO/r-TNRs/r-TFs). Power conversion efficiencies for both aligned r-TNRs and r-TNRs/r-TFs were compared. From the results, DSC made of r-TNRs only produced energy conversion efficiency of 1.52 % and DSC made of r-TNRs/r-TFs gave excellent energy conversion efficiency (η) of 4.27 %.
Pure TiO 2 and surface-modified TiO 2 (SMT) films have been developed using zinc acetate solution... more Pure TiO 2 and surface-modified TiO 2 (SMT) films have been developed using zinc acetate solution on fluorine-doped SnO 2 (FTO) substrates via spray pyrolysis technique for the application in dye-sensitized solar cells (DSSCs). X-ray diffraction (XRD) profiles indicate that pure TiO 2 and SMT exhibit the same crystal structure. Optical absorption studies reveal that there is no significant absorption difference between SMT and pure TiO 2. Impedance measurements show that ZnO layer-covered TiO 2 nanoparticles particularly increase the impedance and also suppress the reverse transmission of photoinduced electrons ejected from SMT electrode to the electrolyte. Surface morphological and elemental studies have been performed using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) respectively. The photoelectrochemical (J-V curves) values of DSSCs for pure TiO 2 and SMT thin films have been compared. The results show that the photoelectric current (J SC) of pure TiO 2 increased from 16.73 to 18.09 mA cm-2. Additionally, open-circuit voltage (V OC) of DSSCs containing SMT thin films appreciably changed from 0.71 to 0.75 V. This indicates that the ZnO layer on TiO 2 nanoparticles contributes to the surface resistance, which impedes the flow of back-scattered electrons to the electrolyte significantly. The incident light conversion into power efficiency of the DSSCs has been increased from 8.25 to 9.3%.
Structural, electrical and optical characterization of InGaN layers grown by MOVPE
Chinese Physics B, 2009
We present a study on n-type ternary InGaN layers grown by atmospheric pressure metalorganic vapo... more We present a study on n-type ternary InGaN layers grown by atmospheric pressure metalorganic vapour phase epitaxy (MOVPE) on GaN template/(0001) sapphire substrate. An investigation of the different growth conditions on n-type Inx Ga1 − x N (x = 0.06 − 0.135) alloys was done for a series of five samples. The structural, electrical and optical properties were characterized by high resolution x-ray diffraction (HRXRD), Hall effect and photoluminescence (PL). Experimental results showed that different growth conditions, namely substrate rotation (SR) and change of total H2 flow (THF), strongly affect the properties of InGaN layers. This case can be clearly observed from the analytical results. When the SR speed decreased, the HRXRD scan peak of the samples shifted along a higher angle. Therefore, increasing the SR speed changed important structural properties of InGaN alloys such as peak broadening, values of strain, lattice parameters and defects including tilt, twist and dislocation density. From PL results it is observed that the growth conditions can be changed to control the emission wavelength and it is possible to shift the emission wavelength towards the green. Hall effect measurement has shown that the resistivity of the samples changes dramatically when THF changes.
Uploads
Papers by Varishetty Madhu Mohan