Exploring the spectroscopic, optical, dielectric, and hardness properties of L-histidine methylester dihydrochloride (LHMEDH), a nonlinear optical compound for optoelectronic uses

Abstract

l-histidine methylester dihydrochloride (LHMEDH), a nonlinear optical compound, was obtained using the method of gradual evaporation. The single-crystal XRD investigation showed that LHMEDH was synthesized with the P2₁ space group in a monoclinic structure. Raman spectroscopy was applied to determine the existence of different functionalities and their vibration modes. Nuclear magnetic resonance (NMR) spectroscopy was used to identify the chemical structure of LHMEDH. The UV-Vis-NIR spectrum analysis showed that the LHMEDH exhibits perfect transparency between 260 and 900 nm. The optical measurements yielded optical characteristics, such as bandgap, Urbach energy, extinction coefficient (k), and refractive index (n). Urbach energy and bandgap of LHMEDH were estimated to be 0.076 and 5.35 eV, respectively. Compared to the KDP crystal, the second harmonic generation (SHG) in LHMEDH was estimated to be 1.6 times higher. The LHMEDH sample showed low dielectric loss and significant dielectric constant values at high frequencies. Microhardness measurements indicated that the LHMEDH sample is classified as a hard substance. The DSC experiment showed that the LHMEDH sample is thermally stable up to 213 °C. The SEM micrographs show a few grain boundaries and striations on the flat crystal surface. The LHMEDH sample exhibits intriguing properties for optoelectronic applications due to its good optical traits, relatively high SHG ability, low dielectric loss values, and hardness features.