Optical, photoconducting, thermal and anisotropic mechanical behaviours of Benzimidazolium salicylate single crystals

Protonated organic single crystals of Benzimidazolium salicylate (BSL) were successfully grown by the slow evaporation solution technique at room temperature. The crystal structure and lattice parameters of the as-grown single crystal have been identified and calculated by the powder X-ray diffraction (PXRD) method. Microanalysis has confirmed the elemental compositions and the Fourier transform infrared (FTIR) spectroscopy technique has revealed vibrations of the functional groups in these crystals. The optical band gap was calculated indicating that the as-grown crystal exhibits 75% of optical transparency in the 350-800 nm range. Fluorescence study has suggested the blue emission nature of the crystal. The thermal stability of the as-grown crystal has been elaborated from the thermogrativity differential thermo-analysis (TG-DTA) technique. Vickers hardness measurement has revealed the mechanically soft nature of the crystal, which is driven by the reverse indentation size effect (RISE) and shows an anisotropic behaviour. A linear increase of the photocurrent on illumination suggests the positive photoconductivity of the crystal. The third-order non-linear optical property characteristics, such as the absorption coefficient (β), the refractive index (n2) and the susceptibility (χ(3)) have been examined using the Z-scan technique.