Faculty Publications
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Item Nonlinear optical studies of newly synthesized polythiophenes containing pyridine and 1,3,4-oxadiazole units(John Wiley and Sons Inc., 2009) Poornesh, P.; Hegde, P.K.; Manjunatha, M.G.; Umesh, G.; Vasudeva Adhikari, A.V.We report measurements of the third-order nonlinear optical properties of a newly synthesized thiophene- based copolymer. The nonlinear transmission measurements were performed on the copolymer dissolved in tetrahydrofuran by employing the single beam Z-scan technique. Q-switched laser output at 532-nm wavelength was used for this purpose. The nonlinear absorption coefficient, β, nonlinear refractive index, n2, and the real and imaginary parts of third-order susceptibility, x(3), were, 18.93 cm/GW, 3.037 x 10 -17 m2/W (1.022 x 10-10 esu), 1.512 x 10-20 m2/V2(-1.080 x 10 -12 esu) and 0.399 x 10-20 2m/V2 (0.285 x 10 -12 esu), respectively. The excited state absorption crosssection σexc, was found to be larger than the ground state absorption crosssection σg, indicating reverse saturable absorption (RSA) in the copolymer sample. The co- polymer exhibits an optical power limiting threshold of about 120 μJ and saturated output of less than 80 μJ. Hence, the copolymer seems to be a promising material for photonic device applications. © 2008 Society of Plastics Engineers.Item Photoalignment of nematic liquid crystal by thin films of bishydrazones derived from 3,4 dipropyloxythiophene(2010) Alla, R.A.; Hegde, G.; Ravi, K.; Vasudeva Adhikari, A.V.; Vishnumurthy, K.A.; Komitov, L.Photoalignment of nematic liquid crystals (LC) promoted by thin films of bishydrazone derived from 3, 4 dipropyloxythiophene is studied. Experimental results show that bishydrazone without methyl group in their structure is promoting planar alignment parallel to the polarization direction of the actinic light whereas the ones with methyl group in the structure are promoting planar alignment perpendicular to light polarization direction. © 2010 ITE and SID.Item A new nonlinear optically active donor-acceptor-type conjugated polymer: Synthesis and electrochemical and optical characterization(2010) Manjunatha, M.G.; Vasudeva Adhikari, A.V.; Hegde, P.K.; Suchand Sandeep, C.S.S.; Philip, R.A new donor-acceptor-type poly[3-{5-[3,4-didodecyloxy-5-(1,3,4-oxadiazol- 2-yl)thiophen-2-yl]-1,3,4-oxadiazol-2-yl}-9-dodecyl-9H-carbazole] (P) has been synthesized through multistep reactions. The new polymer P exhibited good thermal stability and film-forming behavior. The electrochemical band gap is estimated to be 2.15 eV. The polymer emits intense green fluorescence in the solid state. Third-order nonlinear optical (NLO) studies showed that the strong absorptive nonlinearity observed for the polymer is of the optical limiting type, which is due to an "effective" three-photon absorption (3PA) process. This 3PA process can have potential applications in photonic devices. The studies revealed that the new polymer P is a promising material for development of efficient optoelectronic devices. © 2010 TMS.Item Nonlinear optical properties of a newly synthesized thiophene based conjugated polymer(2011) Sunitha, M.S.; Vasudeva Adhikari, A.V.; Vishnumurthy, K.A.; Philip, R.We have synthesized a new donor-acceptor (D-A) conjugated polymer containing 3,4-aralkyloxy and alkoxy substituted thiophene and 1,3,4-oxadiazole as donor and acceptor moieties respectively, through precursor polyhydrazide route. The required polyhydrazide was synthesized from 3,4-dihydroxythiophene diester through multistep reaction. The new polymer was characterized by using FTIR, 1H NMR spectroscopy, followed by Elemental analysis. The average molecular weight of the polymer was determined by Gel Permeation Chromatography. The band gap of the polymer was calculated by using UV-visible and cyclic voltametry. Further, its NLO properties in THF solution were investigated both by the Z-scan and degenerate four-wave mixing (DFWM) techniques using 532 nm, 7 nanosecond laser pulses. The results indicate that they exhibit good optical limiting behavior due to effective two-photon absorption (TPA). Values of the effective TPA coefficient (β), third-order non-linear optical susceptibility (χ(3)) and figure of merit (F) were calculated. The optical and electrochemical properties reveal that the polymer is a promising candidate for opto-electronic applications. © 2011 American Institute of Physics.Item Synthesis and characterization of a new conjugated polymer bearing pyrazole and thiophene moieties as potent NLO material(2011) Vishnumurthy, K.A.; Vasudeva Adhikari, A.V.; Sunitha, M.S.; Philip, R.In this communication we describe the design and synthesis of a new conjugated polymer (P) carrying 3,4-dialkoxythiophene, 1,3,4 oxadiazole and pyrazole units, from its monomers through condensation polymerization method. The structure of newly synthesized polymer was established by FT-IR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. Further, its electrochemical, linear and nonlinear optical properties of the polymer have been investigated. The optical and electrochemical band gap was found to be 2.39 eV. Z-scan results reveal that the polymer exhibits strong optical limiting behavior due to effective three-photon absorption (3PA). The value of 3PA coefficient was found to be 1.1×10-20m3/W2, which is comparable to that of good optical limiting materials. The fluorescence quantum yield of the polymer in solution was determined using quinine sulfate as standard and it was found to be 42%. © 2011 American Institute of Physics.Item Synthesis and mesomorphism of new 2-methoxy-3-cyanopyridine mesogens(2012) Ahipa, T.N.; Vasudeva Adhikari, A.V.In the present paper, we describe the synthesis and characterization of six new bent -shaped molecules carrying the 2-methoxy-3-cyanopyridine as a core possessing an outer phenylene unit at the lengthening arm with different alkoxy chain lengths (C-10 and C-12). Mesomorphic behaviors of the new compounds were investigated using optical polarizing microscope and DSC studies. Also, the effect of structural variables on mesogenic properties was studied. All the new cyanopyridine derivatives showed good liquid crystalline properties and exhibit smectic phase. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).Item Recent developments in photoalignment technology: Alignment properties of a thiophene based bis-hydrazone derivative(2012) Hegde, G.; Srivastava, A.K.; Vasudeva Adhikari, A.V.; Vishnumurthy, K.A.; Mohd Yusoff, M.M.; Chigrinov, V.G.; Kwok, H.S.Liquid crystal photoalignment on bis-hydrazones derived from thiophene derivatives is reviewed. Proposed material shows excellent alignment properties which is highly promisable for future applications. This photoalignment is based on reorientation phenomena attributed to thiophenes.Item Synthesis, Characterization and Performance Studies of a New Metal-Free Organic Sensitizer for DSSC application(Elsevier Ltd, 2018) Naik, P.; Babu, D.D.; Su, R.; El-Shafei, A.; Vasudeva Adhikari, A.V.In this present work we report, design, synthesis and performance studies of a new metal-free organic dye (N, N'-PABA) based on N,N-dimethyl-4-vinyl aniline carrying 4-amino benzoic acid as acceptor, as sensitizers for sensitizing photoanode (TiO2). In the sensitizers, N,N-dimethylaniline ring acts as anelectron donorwhile para amino benzoic acid function as electron acceptor/anchoring units. It was synthesized via condensation reaction starting from simple 4-(N,N-dimethyl amino)benzaldehyde and their structures were confirmed using spectral techniques like FTIR, 1HNMR, 13CNMR, MS and elemental analysis. Further, it was subjected to electrochemical and optical characterization in order to evaluate their band gap and absorption/emission behavior. Further, DFT studies were performed using turbo mole V6.6 software package to evaluate their optimized geometry and FMO levels. Finally, DSSC devices were fabricated using this dye under simulated solar radiation AM1.5G and result revealed that it shows a conversion efficiency of 1%. © 2018 Elsevier Ltd.Item Molecular Engineering of a New Organic Chromophore with D-Ï€-A Architecture for Dye-Sensitized Solar Cells(Elsevier Ltd, 2018) Naik, P.; Vasudeva Adhikari, A.V.Herein, we report design and synthesis of a new metal-free organic dye N1 derived from (Z)-3-(9-hexyl-9H-carbazol-3-yl)-2-(thiophen-2-yl) acrylonitrile scaffold. In this design, the electron rich carbazole unit is connected to rhodanine-3-acetic acid via cyano vinyl thiophene as Ï€-spacer. Its molecular structure was confirmed by FTIR, NMR, Mass spectral and elemental analyses. The dye was subjected to optical and electrochemical studies in order to investigate their absorption/emission behaviour as well as HOMO/LUMO energies. The DFT studies were performed using Turbomole 7.1V software and the results indicated the existence of proper charge separation between its HOMO and LUMO energy levels. © 2018 Elsevier Ltd. All rights reserved.Item “Dental Cements Based on Acid Degradable Glasses/Ion Leachable Glasses” – A Review(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2016) Nagaraja Upadhya, P.; Ginjupalli, K.; Srinivasan, K.K.; Vasudeva Adhikari, A.V.; Satapathy, L.N.Glass ionomer cement (GIC) is one of the most versatile cements used in dentistry. It came into existence in the late 1960s mainly to overcome the drawbacks of its predecessor material ‘dental silicate cements’. Since then, it has undergone several improvisations and modifications to meet the requirements of various dental applications. The GIC consists of basic glass powder and acidic polyacids, which sets by an acid-base reaction between the components. The glass component of GIC plays a major role in the clinical performance of the material. It provides the source of ions for the cement formation, controls the strength, imparts translucency and provides a therapeutic benefit by releasing fluoride. Glass structure-reactivity-processing are the three main aspects to be considered when designing the glass compositions for cement formation. From the conventional calcium fluoroaluminosilicate glass to the current aluminium free glasses, GIC has received significant attention in the recent past to further extend its applications in various fields. The purpose of this article is to provide relevant discussion on the scientific development of the GIC from the glass science and technology point of view. © 2016 The Indian Ceramic Society.