Faculty Publications
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Item Solar exfoliated graphene and its application in supercapacitors and electrochemical H2O2 sensing(Elsevier Ltd, 2015) Moolayadukkam, M.; Huang, N.M.; Nagaraja, H.S.In the present study, graphene nanosheets are synthesized using sunlight irradiation focussed onto graphite oxide. The morphological characteristics of graphene are examined using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Raman spectroscopy and X-ray diffraction (XRD) are used for the structural characterization of the sample. The electrochemical performance is evaluated using cyclic voltammetry (CV), charge-discharge characteristics and impedance spectroscopy. A high specific capacitance value of 223 F g-1 is obtained using cyclic voltammetry. The electrochemical detection of H2O2, a common biological species using solar graphene is demonstrated. The impedance spectroscopy and CV are used to study the electrocatalytic activity of the material. High sensitivity of 64.79 ?A mM-1 cm-2 is reported. © 2015 Elsevier Ltd. All rights reserved.Item An adaptive reactive power perturbation based hybrid islanding detection method for distributed generation systems(Acta Press journals@actapress.com, 2016) Krishnan, G.; Gaonkar, D.N.The intentional islanding operation of distributed generation (DG) systems can bring many benefits to the DG owner, distribution network operators and customers. One of the requirements for intentional islanding operation is the successful detection of the grid events which can lead to islanding of the DG system. This paper presents the hybrid islanding detection method based on adaptive reactive power variation with a passive algorithm that relies on the transient response characteristics for facilitating islanding detection. The proposed method presented in this paper can overcome the problems in the reactive power variation based methods. Extensive studies are conducted for differentiating the transient characteristic features for islanded and non-islanded systems. In this study the adaptive reactive power sequence is modified to enhance the performance under sudden load changes. The proposed method proved to detect all probable islanding situations with minimum run-on time. The performance of the method is evaluated using simulation results obtained from MATLAB/SIMPOWERSYSTEMS software considering wind power based DG system.Item Properties of CdxZn1-xO thin films and their enhanced gas sensing performance(Elsevier Ltd, 2017) Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.CdxZn1-xO(0 ? x ? 0.20) thin films with different Cd concentrations were successfully deposited on glass substrate using spray pyrolysis technique. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX) were used for structural, surface morphological and compositional characterization. The XRD analysis revealed that the synthesized films were hexagonal in structure with (002) orientation. The SEM studies confirm the formation of homogeneous and uniform films. Optical transmittance and electrical conductivity of the films were evaluated using UV–Visible spectroscopy and two probe method respectively. The optical studies showed that the CdxZn1-xO thin films have optical transmittance in entire visible region. The resistivity of undoped films were very high and it decreases with addition of cadmium. The gas sensing properties were investigated at optimal temperature of 350 °C for various volatile organic compounds like acetone, ethanol and methanol. The CdxZn1-xO thin films with 10 at. % cadmium concentration showed the sensitivity of 50% for 1 ppm ethanol. © 2017 Elsevier B.V.Item Enhanced gas sensing properties of indium doped ZnO thin films(Academic Press, 2018) Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.Indium doped ZnO (InxZn1-xO, 0 ? x ? 0.05) thin films were deposited on to soda lime glass substrate by employing spray pyrolysis as deposition technique. Effect of doping concentration on characteristics of thin films were examined by XRD, SEM, UV-Visible spectroscopy, electrical and gas sensing measurements. XRD analysis demonstrates polycrystalline nature of thin films and also shows the shift in orientation from (002) to (101) crystal plane with increase in indium doping concentration. Surface morphological analysis shows the formation of homogeneous particle like nanostructures. Optical transmittance determined from UV-Visible spectroscopy was in the range of 80–95%, which was decreasing with increase in indium doping concentration. Maximum electrical conductivity was achieved at an optimal indium doping concentration of 3 at.%. The gas sensing properties were examined for different concentration of volatile organic compounds like acetone, ethanol and methanol for different doping levels. In0.03Zn0.97O thin films showed good sensitivity towards ethanol, with sensitivity of 30% towards 25 ppm of ethanol. © 2018 Elsevier LtdItem A scalable screen-printed high performance ZnO-UV and Gas Sensor: Effect of solution combustion(Elsevier Ltd, 2020) Manjunath, G.; Pujari, S.; Patil, D.R.; Mandal, S.In the present study, scalable screen-printed Zinc Oxide (ZnO) based sensor was demonstrated to sense ultra-violet irradiation and gases such as ammonia (NH3), ethanol (C2H5OH), liquefied petroleum gas (LPG), chlorine (Cl2) and hydrogen sulphide (H2S). A facile solution combustion synthesis (SCS) route was adopted to synthesize high purity, homogeneous, nanocrystalline and highly reactive ZnO with favourable morphologies, microstructural parameters for the sensing performance using low-cost and less-violent fuels such as urea, citric acid and glycine. Fuel impacts on uniform particle size distribution, bond length, grain size, lattice strain enhanced the gas sensing potential in the synthesized powders. Films were fabricated by depositing synthesized powders on the glass substrate via screen printing approach using Na-carboxy methyl cellulose as a binder, water as a solvent and annealed at 500 °C for 2 h in ambient. Non-stoichiometric, phase pure and adhered thick films with optical band gap (3.17-3.25 eV) imparted gas sensing properties because of recombination of an electron-hole pair and intrinsic defects. ZnO films obtained from glycine-fuel system exposed to 100 ppm of NH3, C2H5OH, Cl2 and 50 ppm of H2S, exhibited good gas sensitivity of ~8, 5, 3 and 10 at an operating temperature of 50, 100, 200 and 100 °C respectively with a faster response and recovery speed. But, high sensitivity ~6 to 100 ppm of LPG at 350 °C in ZnO films from citric acid fuel-system. ZnO films obtained from glycine fuel system showed a high response to UV irradiation for exposing time of 90s. Low cost, high-performance sensor can be fabricated for the dual applications - alarming to prolonged exposure to harmful UV radiation and detection of a series of toxic and damaging gases. © 2019 Elsevier LtdItem High sensitivity detection of chemicals based on sinusoidally apodized structured grating assisted liquid filled directional coupler(Springer, 2021) Raghuwanshi, S.K.; Singh, Y.; Singh, M.; Chack, D.; Kumar, R.; Prakash, O.The grating has a significant role in sensing applications. Similarly, the grating-assisted coupler has excellent potential in chemical sensing applications. The power coupling between two closely coupled waveguide couplers can be significantly tuned by incorporating grating between them. The grating has been taken of silica material with sinusoidal shape in variation. The grating layer is assumed to be embedded within the sensing layer while considering a changeable effective refractive index depending on the sensing layer substances. In the present paper, grating assisted directional coupler has been numerically analysed using its own developed MATLAB-based algorithm of finite difference method (FDM) scheme. FDM method has been applied to solve the Eigenvalue equation to obtain allowed Eigenvalues and corresponding Eigen vectors (TE and TM cases). In FDM, the analysis domain has been fine discretized into the mesh of 1-D equal spacing for reasonable accurate computation results. In experimental validation, Fibre Bragg grating (FBG) has been suspended between two high refractive index coupler regions, which act as a power coupling zone. Also, the coupling length has been changed from 5 to 20 ? m for tuning purposes and then optimized for grating parameters viz. length, period, etc. The whole structure is 2-Dimensional (x and y directions) with invariant in the y-direction. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item From fundamental to CO2 and COCl2 gas sensing properties of pristine and defective Si2BN monolayers(Royal Society of Chemistry, 2022) Thomas, S.; Madam, A.K.; Asle Zaeem, M.In this work, the capability of Si2BN monolayers (Si2BN-MLs) to sense CO2 and COCl2 molecules was investigated by analyzing the structural, electronic, mechanical and gas sensing properties of defect-free and defective Si2BN-ML structures. Electronic property analysis revealed that the Si2BN-ML retains its metallicity in the presence of vacancy defects. The computed vacancy formation energies of Si, B and N monovacancies are 3.25 eV, 2.27 eV and 2.55 eV, respectively, which indicate that the B monovacancy is thermodynamically more feasible. Besides, both pristine and defective Si2BN-ML structures show good mechanical stability. To validate the gas sensing properties, the adsorption energy and charge transfer were analysed, showing that both pristine and defective Si2BN-ML structures receive considerable charges from the CO2 and COCl2 molecules via a stable physisorption process. The work function analysis revealed that a minute increase <0.10 eV is responsible for the enhanced selectivity and sensitivity of Si2BN-ML structures in detecting CO2 and COCl2 molecules. The low adsorption energies of both CO2 and COCl2 gas molecules during the interaction with Si2BN-ML structures signify the possibility of a large number of adsorption-desorption cycles with an ultra-low recovery time, 0.174 ns for CO2 and 0.016 ns for COCl2, suitable for efficient gas sensing applications. © the Owner Societies.Item Flexible and cost effective CNT coated cotton fabric for CO gas sensing application(Elsevier B.V., 2023) D.s, A.K.; Chauhan, S.S.; Krishnamoorthy, K.; P, D.B.; Bharathi, K.D.; Ravikumar, A.; Rahman, M.R.In this paper, a low-cost and room temperature flexible carbon monoxide (CO) gas sensor is presented using multi-walled carbon nanotubes coated cotton fabric. A dip and drying method is used to fabricate a lightweight, and high-performance fabric based CO gas sensor using different concentrations of multi-walled carbon nanotubes (MWCNTs). Transmission electron microscopy (TEM) is utilized for examining the deagglomeration of MWCNTs in the presence of a sufficient amount of surfactant. The field-emission scanning electron microscopy (FESEM) is used to evaluate the formation of a uniform network of MWCNTs on the cotton fabric. Fourier transform infrared (FTIR) spectroscopy is used to confirm the presence of functional groups which plays an important role in CO gas sensing. The fabricated cotton fabric coated with MWCNTs (CCM) sensors are tested with different concentrations of CO gas ranging from 25 ppm to 100 ppm at room temperature. It is found that in comparison to all other sensors, the CCM sensor coated with the higher concentration of MWCNTs (0.5 mg/ml) shows a maximum response of 9.11 % at 25 ppm and 15.2 % at 100 ppm concentration of CO gas respectively. The CCM 4 sensor shows the fastest response and recovery within 49s for 25–100 ppm of CO gas. Moreover, the fabricated CCM sensor exhibited good repeatability, reproducibility, and selectivity. These sensors are suitable for low-cost smart textile applications. © 2023 Elsevier B.V.Item Effect of microwave treatment on structural characteristics and energy bandgap of electrochemically synthesized hydrated tungsten oxide quantum dots(Elsevier Ltd, 2024) Salot, M.; Santhy, K.; Pramanick, A.K.; Rajasekaran, B.; Awasthi, G.; Singh, S.G.; Chaudhury, S.K.Quantum Dots (QDs) of hydrated tungsten oxide were synthesized via electrolysis using sintered tungsten carbide-6 wt% cobalt (WC–6Co) scrap as anode, Ti plate as cathode, and sulfuric acid as electrolyte at room temperature. The as-synthesized powder was characterized using X-ray diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Electron paramagnetic resonance spectroscopy (EPR), and Ultraviolet–visible spectroscopy (UV–Vis). The XRD analysis confirmed the formation of orthorhombic hydrated tungsten oxide (WO3.H2O) QDs via electrochemical oxidation of WC. As-synthesized WO3.H2O QDs were thermally-treated using microwave radiation and conventional furnace at 150 °C for 8 min and 45 min, respectively. Thermal treatment of as-synthesized QDs produced partially dehydrated powder consisting of both orthorhombic WO3.H2O and cubic WO3.H0.5 crystal structures. The TEM analysis showed that the average particle size of QDs was 7.60 nm. Further, an increase in lattice strain was observed on microwave treatment owing to the non-equilibrium phase transformation (i.e., rapid heating) from orthorhombic to cubic crystal structure resulting in the generation of oxygen vacancies. The increase in oxygen vacancy concentrations in QDs on microwave heating was confirmed by XPS, FTIR, EPR, and Raman spectroscopy. The energy bandgaps of as-synthesized and thermally-treated QDs were in the range of 2.4307–2.4979 eV. The relatively low energy bandgap of QDs is attributed to the change in crystal structure and increase in the oxygen vacancy concentration. An improved CO gas sensing characteristics of microwave-treated QDs was noted. © 2024 Elsevier Ltd and Techna Group S.r.l.Item Conductive nano nickel oxide/hydroxide paper electrochemical sensor for serotonin detection in genetically engineered Drosophila(Royal Society of Chemistry, 2025) Prashanth, S.; Kadandelu, M.; Raghu, S.V.; Prasad, K.S.; Vasudeva Adhikari, A.V.Serotonin is considered an integral part in neuropsychiatric diseases, such as major depressive disorder, schizophrenia, post-traumatic stress disorder, obsessive-compulsive disorder, anxiety disorder, and substance use disorder. Understanding the levels of serotonin under different disease conditions is important. Herein, we explored the development of an efficient electrochemical sensor utilizing sustainable paper electrode integrated with nanocomposites through a simultaneous electrochemical deposition strategy. The as-developed sensor is further investigated with surface and electrochemical studies to understand the robust fabrication of the sensor as well as the electrochemical characteristics to show the improved electron transfer kinetics and detection capabilities even in the presence of common interfering biomolecules. The sensor demonstrated a broad linear range from 0.007 nM to 500 ?M, with an impressive limit of detection of 0.024 nM for the low concentration range (0.007-0.48 nM) and 383.7 nM for the high concentration range both falling well within the clinically relevant detection levels of serotonin. To evaluate the practical performance, the developed sensor was tested on brain homogenates obtained from genetically modified Drosophila melanogaster models with different serotonin levels. The sensor effectively detected the in vivo changes in serotonin level, and the results were validated against gold-standard HPLC analysis and immunohistochemical staining experiments. The sensors’ notable stability, selectivity, and sensitivity towards serotonin make them a valuable tool for neurochemical research and clinical applications, particularly in studying serotonin-related neurological conditions and advancing personalized treatments. © 2025 The Royal Society of Chemistry.