Organic NLO Crystals: Synthesis and Growth

SUMMARY AND SUGGESTIONS FOR FUTURE WORK

The main objective of the present investigation is in order to realize the second and third order nonlinear property of the synthesised crystals. Organic crystals formed with benzotriazole compound are identified as potential candidates for NLO applications to replace the inorganic, semi-organic crystals because of their high melting point, thermal and mechanical strengths, but very poor in second and third harmonic generation efficiencies. For many attempts can be made to growing acentric crystals structure by the charge transfer phenomenon of hydrogen bonding interactions.

Good organic NLO responded materials, have higher second and third order hyperpolarizobilities, because of their delocalization length, ? electron conjugated systems and NLO chromophores of the molecules.

In view of this, there has been considerable interest in the synthesis, growth and characterization of organic nonlinear optical crystals. Good quality and inclusion free crystals of Benzotriazole pyridine-2-carboxylic acid(BTPCA), Bis benzotriazole trichloroacetic acid (BBTCA), 4-(dimethylamino)-pyridinium 4-aminobenzoate dihydrate (DMAPAB) and Glycinium 3-carboxy -4-hydroxybenzenesulfonate (CGHBS) have been synthesized and grown by slow evaporation of solvent and these crystals are chosen to demonstrate their use in nonlinear optical applications.

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The synthesized organic optical single crystals are performed for NLO applications using Kurtz powder technique and Z-scan technique.

The synthesis and growth of novel organic Benzotriazole pyridine-2-carboxylic acid (BTPCA) single crystals grown by the slow evaporation solution growth technique. The unit cell parameters of BTPCA crystal were found out by single crystal X-ray diffraction study. The crystallanity of the grown crystals was elucidated by taking the X-ray diffraction pattern of BTPCA.

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UV-Vis-NIR transmission studies confirmed that the grown of BTPCA crystal is transparent in the full-length visible range with a lower optical cut-off wavelength of 306 nm. The presence of molecular vibrations was confirmed by FTIR analysis. From the thermogravimetric and differential thermal analyses, the thermal stability of BTPCA crystal was ascertained to be 194°C. The relative second harmonic generation efficiency of BTPCA was found to be 2.5 times than that of KDP by using Kurtz-Perry technique [15].

The potential organic NLO crystal of bis benzotriazole trichloroacetic acid (BBTCA) and crystals were successfully grown by slow evaporation solution growth technique. The cell parameters of grown crystal were confirmed by single crystal X-ray diffraction analysis and it belongs to the centrosymmetric space group P21/c. UV-Vis-NIR transmittance studies confirmed the optical transparency window of the grown crystal. TGA/DTA thermal measurements reveal that BBTCA is thermally stable up to160oC. The quality of electrical behaviour of the synthesised materials, which is assessed by variation of dielectric constant with frequency at different temperatures, was investigated. Third-order optical nonlinearities of BBTCA crystal were investigated. The mechanical properties of the grown crystal were studied by Vicker's micro hardness technique.

A new organic 4-(dimethylamino)pyridinium 4-aminobenzoate dihydrate (DMAPAB) single crystal grown by employing sloe evaporation technique. 4-Dimethylaminopyridine and 4-aminobenzoic acid are the source materials used for the growth. The grown crystal was characterized by single X-ray diffraction analysis and it shows that 4-(dimethylamino)pyridinium 4-aminobenzoate dihydrate crystallizes in the triclinic space group P1[16]. The lattice parameters of the crystal were also determined by using powder diffraction method. FTIR spectral analysis confirmed the presence of the functional groups of the synthesized compound. The transmission spectrum of DMAPAB shows that the crystal has no absorption in the visible region. In addition to solving crystal structure, the grown crystals were characterized by Vicker'smicrohardness and third harmonic generation studies. The absorbance and the fluorescence spectra of the title compound were analyzed by using UV-Vis and PL spectra. The thermo analytical properties of the crystal were studied by using TGA and DTA studies.

The growth and characterization of third-order nonlinear optical glycinium 3-carboxy-4-hydroxybenzenesulfonate organic single crystal. The crystal was grown by slow evaporation technique with 13x 6x 6 mm3 dimension. From the single crystal X-ray diffraction study, it was observed that GCHBS crystal belongs to monoclinic system with P21/c space group [17]. The quality of the grown crystal was ascertained by using single crystal and powder XRD analysis and found fairly good crystalline perfection. Infrared spectral study was used to confirm the functional groups present in GCHBS compound. TG-DTA thermal studies reveal that grown crystal is thermally stable up to 235oC. UV-visible study showed the good transmission region (350-900 nm) of the grown crystal. The cut-off wavelength and band gap energy were found to be 335 nm and 3.67 eV respectively. The nonlinear optical refractive index, nonlinear absorption coefficient and third-order nonlinear optical susceptibility were calculated by Z-scan technique. The Vicker'smicrohardness test reveals that GCHBS belongs to soft category nonlinear optical crystal.

Suggestions For future work

Investigation on the existing experimental result works have been carried out on organic BTPCA, BBTCA, DMAPAB and GCHBS Crystals. Considerable effort can be made to grow bulk size crystals of BTPCA, BBTCA, DMAPAB and GCHBS single crystals for improved optical quality by unidirectional crystal growth method. Since, effect of dopants with different concentration on the growth can be carried out to improve their NLO efficiency.Attempts could be made in future to investigate the nucleation parameters such as meta stable zone width, induction period, interfacial tension etc,. The laser damage threshold studies could be carried out on the grown crystals with improved optical quality.

Also, laser induced damage threshold studies can be carried out for the above grown crystals in order to find out suitability of the crystal in laser applications. Further, phase matching, density functional theory, heavy ion irradiation and other harmonic studies can be made on the grown crystal. The grown crystals will be subjected by HRXRD analysis to improve the crystalline perfection of the grown crystal.

Other combinational derivatives of the crystal may be synthesized and studied for the improvement on their optical electrical and mechanical properties. The SHG efficiency varies based on the particle size factors. Hence, the grown crystal of BTPCA could be made particle size efficiency. Attempts can be made to study the transport properties such as electrical conductivity and thermal conductivity along various planes. Advanced microscopic techniques such as AFM and TEM could be used to characterize the samples. The etching behaviour on different crystallographic planes can be done using various organic solvents in order to estimate the dislocation density, lattice in homogeneities and growth mechanism.

Updated: Nov 30, 2023
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Organic NLO Crystals: Synthesis and Growth. (2019, Dec 13). Retrieved from https://studymoose.com/synthesised-crystals-essay

Organic NLO Crystals: Synthesis and Growth essay
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