Growth and Characterization of the NLO Crystal 4-Dimethylamino-N-methyl-4-stilbazolium Tosylate (DAST)

Abstract

In order to satisfy present day technological requirements, one has to search the new organic nonlinear optical (NLO) materials with good efficiency. In this article, the title compound (4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST)) belongs to the class of organic NLO materials, and it is one of the highest of the nonlinear materials among all the known NLO single crystals. In the present study, we have reported the synthesis, solubility, metastable zone width, and induction period of the DAST single crystal. The crystal has been grown by the slope nucleation technique by optimizing the growth conditions, and it has been characterized by different instrumentation methods. The crystal system and lattice constants were found from powder X-ray diffractometry (XRD). Nuclear magnetic resonance (13C NMR) studies confirm the presence of functional groups. The crystalline perfection is moderately good as observed from the high-resolution X-ray diffractometry (HRXRD). A low-angle internal structural grain boundary was observed from this analysis, which seems to be formed by the segregation of solvent molecules at the boundary due to entrapment of solvent molecules during the growth process. Entrapment of solvent molecules in the crystalline matrix has been confirmed by differential scanning calorimetry (DSC). The Kurtz powder second-harmonic generation (SHG) reveals that the SHG efficiency of grown DAST is about 141 times that of urea. From the microhardness measurements, the Meyer's index and Young's modulus have been calculated.