Growth characterisation and theoretical investigations on 4 dimethylamino pyridinium p chlorophenolate 4 dimethylamino pyridinium p bromophenolate and dimethylamino pyridinium p bromo chlorophenolate single crystals

Abstract

Nonlinear optical (NLO) materials are considered as an integral part of nonlinear optics and have attained an indispensable role in today s technological advancements especially in the field of telecommunications and the development of optical computing. Efforts are being made for the identification and development of materials exhibiting vast nonlinearities with broad range of transparency, quick response and huge damage threshold which could be considered advantageous for device fabrication. The large packing density of chromophore, steady positioning and excellent photochemical permanence makes single crystals advantageous than polymers. Organic NLO crystals having centrosymmetric space group are of great importance in Third Harmonic Generation (THG) due to its application in sensors, optical communication network, signal processing, integrated optics and optical communication network. Single crystals of 4-Dimethylamino pyridinium p-chlorophenolate (4DMAPCP), 4-Dimethylamino pyridinium p-bromophenolate (4DMAPBP) and Dimethylamino pyridinium p-bromo-chlorophenolate (DMAPBCP) grown by slow evaporation solution growth method were subjected to various characterizations studies to discover the properties and appropriateness for device fabrications. The first chapter deals with the fundamental crystal growth methods and a brief outline on the various requirements of solution growth technique. Various characterization techniques which were carried out on the grown crystal to understand the different properties exhibited have been dealt in a detailed manner. The second chapter discusses in elaborate, the growth and characterisation of 4DMAPCP crystals. The grown crystals were subjected to single crystal X-ray diffraction studies to determine the structure. 4DMAPCP crystal exhibits monoclinic crystal system with centrosymmetric space group P21/c. The observed lattice parameters are a = 9.68 Å, b = 12.84 Å, c = 11.60 Å, Z = 4 and V = 1353 Å3 . The morphology of the grown crystal exhibit eight faces. The composition of various elements in the grown crystal were confirmed through CHN analysis. Functional groups present in the grown crystal were confirmed by FT IR and FT Raman spectral studies. The optical band gap calculated from UV studies was found to be 3.73 eV. Thermal analysis reveals that decomposition of the compound takes place beyond 250ºC. Dielectric loss and dielectric constant measurements as a function of frequency and temperature were measured for the grown crystal. The mechanical analysis by Vicker s hardness test showed that 4DMAPCP belongs to soft category. The laser induced surface damage threshold of the grown crystal was much greater than that of KDP. The third order nonlinear optical coefficients were estimated by using the single beam Z-scan studies. The photoluminescence spectrum showed clear and high intense emission peaks at 367, 428, 493 nm. newline