Faculty Publications
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Publications by NITK Faculty
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Item Nonlinear optical and optical power limiting studies on a new thiophene-based conjugated polymer in solution and solid PMMA matrix(2010) Poornesh, P.; Hegde, P.K.; Umesh, G.; Manjunatha, M.G.; Manjunatha, K.B.; Vasudeva Adhikari, A.V.An experimental investigation of the third-order nonlinear optical properties of new poly{2-{5-[3,4-ditetradecyloxy-5-(1,3,4-oxadiazol-2-yl)thiophen-2-yl]-1,3,4-oxadiazol-2-yl}pyridine} (P) in tetrahydrofuran (THF) solution and in solid poly(methylmethacrylate) (PMMA) matrix, by Z-scan technique is reported. The Z-scan traces reveal that the composite films exhibit large negative nonlinear refractive index of the order 10-10 esu. The excited-state absorption cross-section was found to be larger than the ground-state absorption indicating that the operating nonlinear process is reverse saturable absorption (RSA). The new polymer P exhibits good optical power limiting properties in the nanosecond regime in solution and as well in solid PMMA matrix. © 2009 Elsevier Ltd. All rights reserved.Item Electrical and magnetic properties of chitosan-magnetite nanocomposites(2010) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.Magnetite powders in nanometer size have been synthesized by the hydrothermal process. Various magnetic films of chitosan and the synthesized magnetite nanopowders containing different concentrations of the latter were prepared by ultrasonication route. The X-ray diffraction (XRD) studies and the transmission electron microscopy (TEM) images showed that the synthesized magnetite particles had 80 nm dimensions. The band gap of the composites was evaluated using the UV-visible Spectroscopy. The influence of magnetite content on the magnetic properties of the composite showed a decrease in the saturation magnetization with the decrease in the magnetic content. The effect of magnetite content on the dielectric properties of the polymer film at different frequencies from 0.01 to 105 Hz was studied using an electrochemical impedance spectroscopy. The possible mechanism for the observed electrical properties of the composite films was discussed. © 2010 Elsevier B.V. All rights reserved.Item Third-order optical nonlinear studies of Cobalt (II) Schiff base complex bearing triphenylphosphine using Differential Optical Kerr Gate and Z-scan studies(2010) Rudresha, B.J.; Badekai Ramachandra, B.; Ramakrishna, D.; Anthony, J.K.; Rotermund, F.The third-order optical nonlinearity of the composite film of coordination complex [CoLPPh3Cl] (L = N-(2-pyridyl)-N?-(salicylidene)hydrazine) and PMMA has been investigated by using Differential Optical Kerr Gate (DOKG) and Z-scan measurements. Large value of the third-order nonlinear optical susceptibility (?(3)) of the order of 10-10 esu was measured and its nonlinear response time was found to be faster than or comparable to the laser pulse width (90 fs) used. The single beam Z-scan technique was used to investigate the nonlinear absorption property of the composite near 800 nm. The sample exhibit saturable absorption. The nonlinear absorption coefficient of sample is found to be -32 cm/GW. © 2010 Elsevier B.V. All rights reserved.Item Crystallinity, conductivity, and magnetic properties of PVDF-Fe 3O4 composite films(2011) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.The formation of Fe3O4 nanoparticles by hydrothermal process has been studied. X-ray Diffraction measurements were carried out to distinguish between the phases formed during the synthesis. Using the synthesized Fe3O4 nanoparticles, poly(vinyledene fluoride)-Fe3O4 composite films were prepared by spin coating method. Scanning electron microscopy of the composite films showed the presence of Fe3O4 nanoparticles in the form of aggregates on the surface and inside of the porous polymer matrix. Differential Scanning calorimetry revealed that the crystallinity of PVDF decreased with the addition of Fe3O4. The conductitivity of the composite films was strongly influenced by the Fe3O4 content; conductivity increased with increase in Fe3O4 content. Vibration sample magnetometry results revealed the ferromagnetic behavior of the synthesized iron oxide nanoparticles with a Ms value of 74.50 emu/g. Also the presence of Fe3O4 nanoparticles rendered the composite films magnetic. © 2010 Wiley Periodicals, Inc.Item Chitosan/NiO nanocomposites: A potential new dielectric material(2011) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.; Tai, C.-W.The study of electrochemical behavior of organic-inorganic nanocomposite materials remains a major challenge for application in energy storage devices. Here, new composite materials of chitosan and NiO nanoparticles have been fabricated. The NiO nanoparticles are well characterized by infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The electrical properties of the films are studied by impedance spectroscopy at different temperatures; and thereby permittivity, electric modulus and conductivity data are obtained. By studying the variations in permittivity and electric modulus spectra with respect to applied frequency signal and temperature, the ionic conductivity of the material is investigated. The Correlated Barrier Hopping model is employed to understand the conduction mechanism. An admirable conductivity of 1.4 × 10-2 S cm -1 is obtained for a nanocomposite with 4 wt% NiO content. The activation energies of the composite films decrease with increase in NiO content, from 16.5 to 4.8 kJ mol-1. © 2011 The Royal Society of Chemistry.Item Nonlinear optical study of palladium Schiff base complex using femtosecond differential optical Kerr gate and Z-scan techniques(2012) Rudresha, B.J.; Badekai Ramachandra, B.R.; Ramakrishna, D.; Anthony, J.K.; Lee, H.W.; Rotermund, F.A femtosecond differential optical Kerr gate (DOKG) and Z-scan techniques, have been applied to investigate the third-order optical nonlinearity of composite film of the coordination complex [PdLPPh 3] (L=N-(2-pyridyl)-N'-(salicylidene)hydrazine, PPh 3=triphenylphosphine) . Film exhibits superior nonlinear optical properties in the near-infrared spectral region. The nonlinear response time and third-order nonlinear optical susceptibility of complex were found to be?90 fs and 3.9×10 -10 esu, respectively. The Z-scan result shows that saturable absorption property of the film and its nonlinear absorption coefficient of the sample was found to be -23 cm/GW. © 2011 Elsevier Ltd. All rights reserved.Item Magnetron sputtered MoO3/carbon nanotube composite electrodes for electrochemical supercapacitor(Elsevier B.V., 2013) Aravinda, L.S.; Nagaraja, K.K.; Bhat, K.; Badekai Ramachandra, B.Molybdenum oxide (MoO3) has been deposited on multiwalled carbon nanotubes (MWCNTs) using DC reactive magnetron sputtering of molybdenum for supercapacitor applications. The deposits of MoO3 have been developed under different intervals of time. The structure and surface morphology of the deposits have been characterized by means of X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM). X-ray diffraction peaks of the composite films reveal the formation of crystalline structure of MoO3. The electrochemical performance of the composite films was studied using cyclic voltammetry (CV), galvanostatic charge discharge and electrochemical impedance spectroscopy measurements. The composite film exhibits maximum specific capacitance of 70 F g-1 at a scan rate of 10 mV s-1 in 1 M Na2SO4 electrolyte. The nanocomposite electrode material shows specific capacitance which is almost four fold increase with respect to that of bare MWCNTs. The effect of coating duration on specific capacitance has been studied. The nanocomposite film is found to display good cycleability, even up to 1000 cycles. © 2013 Elsevier Inc. All rights reserved.Item Nonlinear optical and all-optical switching studies of palladium(II) complex(2013) Manjunatha, K.B.; Dileep, R.; Umesh, G.; Badekai Ramachandra, B.Palladium complex with Schiff-base (PdL) was synthesized and composite films were fabricated on glass substrates by the spin coating technique. Z-scan and degenerate four wave mixing (DFWM) studies on the complex were performed using Q-switched Nd:YAG 7 ns laser pulses at 532 nm to reveal the third-order nonlinear optical (NLO) parameters. The third-order NLO susceptibility (?(3)) and second-order hyperpolarizability (?h) in film form are estimated to be of the order of 10-11 and 10 -30 esu respectively. Large nonlinear absorption (NLA) due to reverse-saturable absorption (RSA) in the complex exhibits good optical power limiting (OPL) performance. All-optical switching (AOS) experiments were performed using the pump-probe method. The Z-scan investigations reveal that the switching is caused by excited-state absorption (ESA) of the He-Ne laser. © 2013 Elsevier B.V.Item ZnO/carbon nanotube nanocomposite for high energy density supercapacitors(2013) Aravinda, L.S.; Nagaraja, K.K.; Nagaraja, H.S.; Bhat, K.; Badekai Ramachandra, B.A facile, green and highly efficient method for the decoration of carbon nanotubes with ZnO was developed for the fabrication of binder-free composite electrode for supercapacitor applications. The nano composite was prepared by using reactive magnetron sputtering in Ar/O2 environment. This approach leads to more uniform coating with tuneable thickness, which alters the electrochemical performance of the nano composite electrodes. The structure and surface morphology of the composite film have been studied by means of X-ray diffraction (XRD) analysis, scanning electron microscopy and field emission scanning electron microscopy (FESEM). The XRD study reveals the formation of Wurtzite ZnO structure. The electrochemical performance of nano composite electrode was investigated using cyclic voltammetry, chronopotentiometry and electrochemical impedance measurements in non-aqueous electrolyte. The nano composite electrode shows significant increase in the specific capacitance up to 48 F g-1 with an energy density 13.1 Wh kg-1 in the potential range -2 V to 1 V. © 2013 Elsevier Ltd. All rights reserved.Item Chitosan composites reinforced with nanostructured waste fly ash(Springer Japan, 2017) Patil, A.G.; Poornachandra, S.; Gumageri, R.; Rajkumar, K.; Anandhan, S.This paper outlines the preparation and characterization of chitosan (CS) composites reinforced with mechano-chemically activated fly ash (MCA-FA). A series of composite films was prepared by solution casting method with varying filler content. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses showed good compatibility between the CS matrix and MCA-FA. The surface roughness and irregularity in shape of MCA-FA resulted in its efficient mechanical interlocking with the polymer matrix. This, in turn enhanced the mechanical properties of these composites. All the composite films exhibited a higher tensile strength and a lower percentage of elongation-at-break compared with the pure CS film. The highest tensile strength was observed for the composite films with 1 wt% of filler loading and the reduction in the tensile properties at higher filler loading was due to agglomeration of filler and polymer–filler interface debonding. The tensile strength data were analyzed using Nielsen and Pukanzsky models to understand the interface formation and polymer–filler interactions. Thermal properties showed a marginal improvement due to the incorporation of MCA-FA. Overall, this study indicates that MCA-FA could be used as value added filler in polymer matrix composites. © 2016, Springer Japan.