Synthesis, experimental and computational approach to optical, electronic and structural studies of N-acetyl l-alanine crystal

Abstract

Single-crystal N-acetyl-l-alanine (NALA), a semi-organic crystal, has been synthesized by slow evaporation growth technique in aqueous medium. An experimental study proves that it has the space group of P2₁2₁2 and orthorhombic crystal system. The unit-cell parameters of NALA crystal were identified using single-crystal XRD analysis. UV–vis analysis has been used to find out the cut-off wavelength of the crystal. The calculated Urbach energy and the related optical constant values support the non-linear optics (NLO) nature of NALA crystal. SEM and EDAX experiments were carried out to find the surface and elemental characteristics of the NALA crystal. Vickers micro-hardness studies have been utilized to probe the mechanical stability of the crystal. Kurtz–Perry Simple Harmonic Generation (SHG) study has suggested 1.4 times greater NLO efficiency of NALA crystal than that of standard KDP. Thermal stability of the crystal is demonstrated by TGA and DTA analysis. Glass transition (T_g) temperature is achieved through DSC analysis. Coats–Redfern method has been used to explain the thermodynamic parameters. The theoretical calculation done by density functional theory (DFT) and the computed values of polarizability calculations of NALA are compared and justifiable with the standard values. Polarizability and first-order hyperpolarizability (both static and dynamic) are calculated to see the potential application in non-linear optics and it is observed that the values are found to be 2.7 times greater than those of prototype at the same theoretical functional. The frontier study of HOMO–LUMO is used to interpret the global chemical molecular descriptors and indicate the applicability of the NALA crystal toward optical device fabrication.

Graphical Abstract

Hydrogen bonding graphical extract