Synthesis Cum Structural, Mechanical, Optical and Piezoelectric Studies of L(+)-Tartaric Acid Crystals Adulterated with Malachite Green and Trypan Blue Dyes

Single crystals of unadulterated, malachite green (MG) dye adulterated (0.01 mol%), and trypan blue (TB) dye adulterated (0.01 mol%) tartaric acid (TA) were grown and characterized. Their structural traits were affirmed by powder X-ray diffraction and refined via EXPO2014 software. UV–Visible spectroscopic measurements confirmed the characteristic absorption at 584 and 624 nm, respectively for TB and MG dye, with relatively decreased transmittance with the cut-off being at 232 nm. Furthermore, the direct band gap increased from 5.31 eV for unadulterated TA to 5.32 eV for MG dye adulterated TA, while it decreased to 5.22 eV for TB dye adulterated TA. Photoluminescence studies further inferred that both MG and TB dye adulteration has decreased the sharpness and reduced the intensity of violet emission, the principal emission band when excited at 250 nm wavelength. Functional groups were further affirmed by Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, it was observed that piezoelectric behaviour was enhanced in TB adulterated TA crystals while the same was, however, reduced in MG adulterated TA crystals. TA crystal has shown the normal indentation size effect behaviour when subjected to a microhardness study. This work concludes the suitability of the entitled crystals for optoelectronic applications.