Growth of 4-N,N-Dimethylamino-4 '-N '-methyl-stilbazolium Tosylate (DAST) Organic Single Crystals Controlled by Oleic Acid

4-N,N-Dimethylamino-4'-N'-methyl-stilbazolium Tosylate (DAST) organic single crystals controlled by (Z)-Octadec-9-enoic acid (oleic acid, OA) was grown by a slow-cooling method. The as-grown DAST single crystals were systematically characterized by FTIR, X-ray diffraction, second harmonic generation, and UV-vis spectroscopy. Results indicate that addition of OA into the DAST solutions leads to the controlled growth of DAST single crystals and consequently, the crystal quality and optical properties can be modified. Particularly, the DAST crystals grown under the control of OA exhibit larger sizes, higher crystallinities, and better optical qualities with higher optical band gaps and lower defect density, compared with those grown in the absence of OA. These results are helpful for better understanding the controlled growth of DAST organic single crystals and modifying their properties for practical applications.