Synthesis growth and characterization of pyridine and imidazole derivative organic nlo single crystals

Abstract

Crystal growth research in organic crystals shows much importance in a wide range of applications such as optoelectronics, photonics, nonlinear optical and other technological applications. Hence a need for the inevitable growth of good quality single crystals arises for the further development of research and technology. The growth of a single crystal is primarily based on the ease of use, nature of the precursors and their physico-chemical properties. In the last few decades, the search for new organic Nonlinear Optical (NLO) materials has been increasing due to their wide applications in optical modulation, signal processing, switching, data storage devices, etc. It is used for phase conjugation, image reconstruction, etc. Therefore much work has been focused in search of optimal molecular crystalline materials composed of stable chromophoric molecules with large molecular hyperpolarizabilities with an optimized orientation for large macroscopic NLO effects. In the recent years, intensive research has been carried out to explore the third order nonlinear optical phenomena in organic and inorganic single crystals, which has limited exposure compared to second order NLO materials. The third order NLO materials from the organo-metallic, organic, inorganic and semi organic single crystalline compounds are the great deal of attention due to their potential applications in optical switching, optical information storage, laser technology, etc. Picric acid forms crystalline picrates of various organic molecules through hydrogen bonding and and#960;-and#960; interactions. Picric acid acts as an acidic ligand to form salts through specific electrostatic or hydrogen bond interactions apart from being an acceptor to form various and#960; -stacking complexes with other aliphatic and aromatic molecules. The present thesis is divided into seven chapters, Chapter 1 is the introduction part which gives the detailed information about fundamentals of crystals, its advantages, various crystal growing methods and the properties of nonlinear materials. Chapter 2 summarises about the various instruments used to characterize the grown crystals. Chapter 3 explains the growth and characterizations of organic Nonlinear Optical (NLO) single crystal of 4-aminopyridinium 4-nitrophenolate 4-nitrophenol (4AP4NP) grown using the slow evaporation solution growth technique. The unit cell parameters and space group were estimated using single crystal XRD analysis. The presence of functional groups were analysed by FT-IR and FT-Raman spectral studies. The lower or minimum cut-off wavelength of 4AP4NP crystal was calculated from UV-Vis-NIR studies is 474 nm. Kurtz-Perry powder technique reveals the NLO efficiency of the crystal. The four independent dielectric permittivity tensor coefficients of 4AP4NP which were estimated using dielectric measurements were and#949;11 = 25.09, and#949;22 = 25.84, and#949;33 = 26.69 and and#949;13 = 0.8. The laser damage threshold study showed the withstanding capacity to the laser radiation up to 3.67 GW cmand#8722;2 . TGA / DTA analyses revealed that 4AP4NP was thermally stable up to 175 °C. Specific heat capacity of 4AP4NP was found to be 3.9135 J g-1 K -1 at 33 °C. In Chapter 4, synthesis and characterization of Benzimidazole benzimidazolium picrate (BZP) crystal have been discussed. A single crystal of 38 and#61620;and#61472;10 and#61620; 4 mm3 was grown by a slow evaporation solution growth newline