Growth and spectroscopic, thermodynamic and nonlinear optical studies of L-threonine phthalate crystal

• L-threonine phthalate, an organic material was grown successfully.
• The material possesses a wide transparent range.
• The spectroscopic analysis of the material was made using FTIR and FT-Raman spectra.
• The thermodynamic parameters were evaluated to analyze thermal behavior of the material.
• The material is an excellent NLO material to find optoelectronic, photonic and holographic applications.

L-threonine phthalate (LTP) single crystal has been grown using a solution growth technique at room temperature. Single crystal X-ray diffraction analysis reveals that LTP crystallizes in monoclinic crystal system with space group C2/c. The optical absorption studies show that the crystal is transparent in the entire visible region with a cut-off wavelength 309 nm. The optical band gap is found to be 4.05 eV. The functional groups of the synthesized compound have been identified by FTIR spectral analysis. The functional groups present in the material were also confirmed by FT-RAMAN spectroscopy. Surface morphology and the presence of various elements were studied by SEM–EDAX analysis. The thermal stability of LTP single crystal has been analyzed by TGA/DTA studies. The thermodynamic parameters such as activation energy, entropy, enthalpy and Gibbs free energy were determined for the grown material using TG data and Coats–Redfern relation. Since the grown crystal is centrosymmetric, Z-Scan studies were carried out for analyzing the third order nonlinear optical property. The nonlinear absorption coefficient, nonlinear refractive index and susceptibility have been measured using Z-Scan technique.