| dc.description.abstract |
Novel semiorganic and organic crystals have been grown by natural slow evaporation process. To grow semiorganic crystals, organic materials L-asparagine monohydrate (LAM) and L-alanine (LA) have been doped with inorganic compounds potassium dihydrogen phosphate (KDP), as well as LAM has been doped with magnesium sulphate heptahydrate (MSHH) and zinc sulphate heptahydrate (ZSHH). This work also covers the growth of organic single crystals of LAM and LA. The different doping concentrations were 0.2, 0.4, 0.8, and 1.0 mol% of LAM and LA. The solubility, metastable zone width (MSZW) and different nucleation kinetics parameters like energy of formation of the critical nucleus (ΔG*), interfacial energy (σ) have been measured. From FT-IR spectroscopy, various functional groups have been identified and bond lengths of the groups have been observed to increase with doping concentration. Strong and sharp x-ray diffraction peaks validate the formation of good crystalline structure. The calculated strain and crystallite size have been observed to enhance with doping concentration. Surface morphology of the grown crystals has been studied by SEM images after etching. From energy dispersive x-ray (EDX) analysis, the constituent elements of the grown crystals have been identified. From microhardness study, the hardness values are observed to reduce with increasing doping level and the doped crystals have been specified as soft category materials. From thermogravimetric analysis (TGA), different stages of thermal decomposition have been observed and the corresponding kinetic and thermodynamic parameters reveal spontaneous reaction mechanism. The different decomposition stages have been confirmed by the negative differential scanning calorimetry (DSC) peak. From dielectric studies, the obtained dielectric loss and dielectric constant indicate normal dielectric behavior of the crystals. From DC conductivity study, an increase in conductivity is observed for the doped samples. UV-Vis spectral analysis reveals enhanced optical transparency for the doped crystals. The optical linear susceptibility χ(1), third order nonlinear susceptibility χ(3) and nonlinear refractive index n2 have been detected to increase with doping concentration. From quantum computational analysis, the frontier molecular orbitals have been drawn and NLO properties were determined by density functional theory (DFT) which are observed to increase for the doped crystals. All findings demonstrate that the semi-organic crystals possess good photo response and favorable nonlinear optical properties. |
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