Faculty Publications
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Item The measurement of electrical conductivity for the investigation of the number of water molecules present in the mixed crystals of barium copper oxalate and barium ammonium oxalate lattice have been carried out in the temperature range 30 to 450 °C. The dehydration temperature and the number of water molecules removed out of the structure at a particular temperature is estimated from the sharp increase in conductivity at these points. The almost steep increase of conductivity is attributed to the increase in the number of mobile charge carriers H+ and OH– ions generated from the escaping water molecules. The study of electrical conductivity in association with the thermal behaviour has been used to understand the mechanism of conduction. Copyright © 1995 WILEY?VCH Verlag GmbH & Co. KGaA(Electrical Conductivity and Thermal Dehydration Studies of Mixed Single Crystals of BaCu(C2O4)2 · 6 H2O, Ba1–xCuxC2O4 · 4 H2O and Ba1–2x(NH4)2xC2O4 · 4 H2O) Kasthuri, V.B.; Mohan Rao, P.1995Item Semiconducting thin films of cadmium telluride, both p-type and n-type, have been prepared by conventional thermal evaporation technique. The influence of various growth parameters such as the rate of deposition, deposition temperature, post-deposition heat treatment, and source material composition has been investigated. The films deposited at high deposition rates and low substrate temperatures exhibited an excess of tellurium and showed a p-type conductivity, whereas those deposited at high substrate temperature and low deposition rates contained excess cadmium and are n-type in nature. An intrinsic bandgap of 1.49 eV for stoichiometric films obtained by both electrical and optical characterization is reported.(Growth and characterization of vacuum deposited cadmium telluride thin films) Shreekanthan, K.N.; Kasturi, V.B.; Shivakumar, G.K.2003Item Crystal structure of semiorganic antimony thiourea bromide monohydrate crystals: a redetermination(2009) Upadhya, M.K.; Udayashankar, N.K.The growth of antimony thiourea bromide monohydrate (ATBM) single crystals by evaporation technique at room temperature is reported here. Antimony thiourea bromide monohydrate crystallizes in the orthorhombic space group Cmca with unit cell parameters a = 12.320(7) A, b = 11.668(7) A, c = 18.615(11), and z = 8. The structure has been solved by direct methods and refined to a final R value of 0.0239.Item Supramolecular synthons in noncovalent synthesis of a class of gelators derived from simple organic salts: Instant gelation of organic fluids at room temperature via in situ synthesis of the gelators(2009) Das, U.K.; Trivedi, D.R.; Adarsh, N.N.; Dastidar, P.(Chemical Equation Presented) The supramolecular synthon approach has been employed to synthesize noncovalently a series of low molecular mass organic gelators (LMOGs) derived from benzylammonium salts of variously substituted benzoic acids. The majority of the salts (75%) prepared showed interesting gelation properties. Instant gelation of an organic fluid, namely methyl salicylate, was achieved at room temperature by using most of the gelator salts by in situ synthesis of the gelators. Table top rheology and scanning electron microscopy (SEM) were used to characterize the gels. Single crystal X-ray diffraction studies revealed the presence of both 1D and 2D supramolecular synthons. X-ray powder diffraction (XRPD) studies indicated the presence of various crystalline phases in the fibers of the xerogels. By using these data, a structure-property correlation has been attempted and the working hypothesis for designing the gelator has been reinforced. © 2009 American Chemical Society.Item The third-order nonlinear optical properties of novel styryl dyes(2009) Shettigar, S.; Umesh, G.; Poornesh, P.; Manjunatha, K.B.; Asiri, A.M.The third-order nonlinear optical properties of two novel styryl dyes, namely, 1,3-diethyl-5-(4-methoxybenzylidene)-2-thioxodihydropyrimidine-4,6(1H,5H)-dione and 5-(3,4-dimethoxybenzylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione were studied using the Z-scan technique employing 7 ns laser pulses at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, magnitude of effective third-order susceptibility and coupling factor were determined. The optical power limiting behavior of the colorants was ascribed to two-photon absorption phenomenon. Nonlinear absorption cross-section increased with increase in ? electron density and the effective two-photon absorption cross-section was two orders of magnitude larger than those of commercially available azo compounds. The results suggest that these colorants offer promise as nonlinear optical materials for device applications. © 2009 Elsevier Ltd. All rights reserved.Item Synthesis, characterization and nonlinear optical properties of 2-[(E)-2-(4-ethoxyphenyl)ethenyl]-1-methylquinolinium 4-substitutedbenzenesulfonate compounds(2010) Ruanwas, P.; Kobkeatthawin, T.; Chantrapromma, S.; Fun, H.-K.; Philip, R.; Smijesh, N.; Padaki, M.; Isloor, A.M.In the present investigation, 2-[(E)-2-(4-ethoxyphenyl)ethenyl]-1-methylquinolinium 4-substituted benzenesulfonate (X = CH3 (1), X = OCH3 (2), X = Cl (3), X = Br (4)) have been synthesized and characterized by 1H NMR, UV-Vis and FT-IR spectroscopy methods. In addition compound 3 was also characterized by single crystal X-ray diffraction (XRD) and found that it crystallized out in the monoclinic space group P21 with cell parameters, a = 9.8072(9) Å, b = 6.4848(5) Å, c = 19.4405(16) Å, ? = 90°, ? = 103.421(5)°, ? = 90°, z = 2 and V = 1202.61(17) Å3. The nonlinear optical absorption of the samples has been studied at 532 nm using 5 ns laser pulses, employing the open-aperture z-scan technique. It is found that some of the samples are potential candidates for optical limiting applications. © 2009 Elsevier B.V. All rights reserved.Item Electron irradiation effects on optical properties of semiorganic antimony thiourea bromide monohydrate single crystals(2010) Mahesha Upadhya, K.; Udayashankar, N.K.Antimony thiourea bromide monohydrate (ATBM) single crystals were grown by solution growth technique at room temperature for the first time. The UVvis, FT-IR and fluorescence spectra were recorded and electron irradiation effects on these properties were studied. The optical absorption edge of the UVvis spectrum shifts towards lower wavelength with the increase of irradiation. The fluorescence quantum yield is increased for electron irradiated ATBM crystals. The FT-IR analysis shows that the water of crystallization is weakly bonded in as-grown and electron irradiated ATBM crystals. © 2010 Elsevier B.V. All rights reserved.Item Synthesis, microhardness, FT-IR, and thermal decomposition of semiorganic antimony thiourea bromide monohydrate single crystals(2012) Mahesha Upadhya, K.; Udayashankar, N.K.Antimony thiourea bromide monohydrate (ATBM) single crystals were grown by a solution growth technique at room temperature. Microhardness studies on the grown crystal were carried out using the Vickers microhardness tester to estimate the mechanical strength of the crystal. The FT-IR analysis ascertains the presence of a metal-sulphur bond in ATBM crystals. The thermal decomposition of ATBM crystals was investigated by means of thermogravimetric analysis. © Springer Science+Business Media, LLC 2011.Item Electron irradiation effects on optical properties of semiorganic antimony thiourea tetra chloride single crystals(2012) Mahesha Upadhya, K.; Udayashankar, N.K.; Ganesh, S.Antimony thiourea tetra chloride single crystals were grown by solution growth technique at room temperature. The UV-visible, fourier transform infrared and fluorescence spectra were recorded and electron irradiation effects on these properties were studied. The optical absorption edge of the UV-visible spectrum slightly shifts towards longer wavelength with the increase of irradiation dose. The fluorescence quantum yield is decreased for electron irradiated antimony thiourea tetra chloride crystals. The presence of functional group of the as-grown and electron irradiated complex was confirmed by fourier transform infrared spectral study. © 2012 Elsevier B.V. All rights reserved.Item Nickel(II) complex of p-[N,N-bis(2-chloroethyl)amino]benzaldehyde-4-methyl thiosemicarbazone: Synthesis, structural characterization and biological application(Elsevier Ltd, 2013) Sankaraperumal, A.; Karthikeyan, J.; Nityananda Shetty, A.N.; Lakshmisundaram, R.New complex of Ni(II) with p-[N,N-bis(2-chloroethyl)amino]benzaldehyde-4- methyl thiosemicarbazone (CEAB-4-MTSC) have been synthesized and characterized by elemental analysis, IR, electronic, 1H NMR spectroscopy. The crystal structure of the free ligand and complex has been determined by single crystal X-ray diffraction technique. In the complex, thiosemicarbazone ligand is coordinated to nickel through (1:2 complex) SNNS mode. The complex crystallizes in the triclinic with space group P1?. The complex has been tested for their antibacterial activity against various pathogenic bacteria. From this study, it was found out that the activity of complex reaches the effectiveness of the conventional bacteriocide Streptomycin compared to simple ligand. © 2012 Elsevier Ltd. All rights reserved.