Hydrogen-bond-regulated optical band-gap engineering and transparency in semi-organic L-glycine succinate crystals

Semi-organic amino acid-based crystals have great potential to be used as optical materials because configurationally tunable hydrogen-bond networks and natural molecular polarity can be utilised. Nevertheless, a mechanistic understanding of the hydrogen bond interaction with the band gap is still scarce in detail. In this work, we discuss L-glycine succinate dihydrate (LGSD) as a model hydrogen-bond regulated optical system and intend to discuss how full proton transfer is responsible for electronics decoupling and transparency enhancement. Amino salt structure and properties. Spectroscopic and structural studies confirm the formation of a stabilised amino-salt that contains NH₃⁺ and COO^- moieties that give a sharp optical cutoff at ~ 200 nm and a wide-transfer transparency interval in the visible range. Tauc analysis suggests a direct band gap of 6.42 eV, which indicates a wide gap optical insulator with no absorption in the mid gap. Thermogravimetric, differential thermal analysis and diffraction measurements were performed to ascertain solvent-free lattice stabilisation and superior crystallinity of the material to validate the optical reliability.

LGSD crystals were obtained by slow evaporation of a stoichiometric aqueous solution of L-glycine and succinic acid. The structural, optical and thermal properties of the processed nanomaterials were characterised using Fourier-transform infrared spectroscopy, ultraviolet-visible-near-infrared spectroscopy (Tauc analysis), fluorescence spectroscopy, thermogravimetric analysis/differential thermal analysis/powder X-ray diffraction and scanning electron microscopy.