Chemical analysis, FTIR and microhardness study to find out nonlinear optical property of L-asparagine lithium chloride: a semiorganic crystal

In recent times semiorganic nonlinear optical material is a forefront of current research because of its importance to providing key functions of frequency conversion, light modulations and optical memory storage. Most of the organic materials have inadequate transparency, poor optical quality and low laser damage threshold. Inorganic materials have excellent mechanical and thermal properties but they possess relatively modest nonlinearity. Semiorganic materials which have combined properties of both organic and inorganic materials. In this coordination complex the organic ligand plays an important role for the nonlinear optical property. Nowadays, amino acids are more suitable organic materials for nonlinear optical applications because they contain dipolar nature due to the presence of a protonated amino group (NH3+) and deprotonated carboxylic group (COO-). In the present study L-asparagine lithium chloride (LALC) was grown from aqueous solution by slow evaporation method. The crystalline perfection of the material was confirmed by powder X-ray diffraction. The lattice parameters were calculated by single crystal X-ray diffraction and it was found to be the LALC crystallized in orthorhombic crystal system with noncentro symmetric space group of Pna2(1) which is one of the essential parameters in nonlinear optical materials. The optical transparency was analyzed by UV-vis transmission spectral study and it was found to be of lower cut off wavelength of the grown crystal which is 234 nm. The presence of functional groups was identified by FTIR spectral analysis. The percentage of carbon, hydrogen and nitrogen in the crystal was calculated by chemical analysis and compared with its theoretical values. The mechanical strength was calculated by Vickers microhardness tester. The nonlinear optical efficiency of the crystal was estimated by using Kurtz Perry powder technique and it was found to be 2.08 times that of potassium dihydrogen phosphate (KDP) due to noncentro symmetric space group of good nonlinear optical material. Hence, LALC crystal is more suitable for the fabrication of optoelectronic devices. (C) 2013 Elsevier B.V. All rights reserved.