Growth and characterisation of organic material 4-dimethylaminopyridine single crystals for nonlinear optical applications

Abstract

The aromatic organic 4-dimethylaminopyridine single crystals were grown by the slow evaporation solution growth method. The unit cell parameters of the grown 4-dimethylaminopyridine crystal were studied by single crystal and powder X-ray diffraction (PXRD) studies. The Fourier transform infrared (FTIR) and FT-Raman spectral analyses were used to identify the functional groups of the grown crystal. The UV–Vis–NIR studies reveal that the grown crystal cut-off wavelength is around 345 nm and the band gap was measured as 3.15 eV. The optical parameters such as the absorption coefficient (α), extinction coefficient (K), reflectance (R), refractive index (n), Urbach Energy (E_U)_, Steepness parameter (σ) and Electron–Phonon interaction (E_e–p) were calculated. The photoluminescence (PL) analysis was carried out, which shows the high intensity emission peak observed at 545 nm. The thermal analyses reveal that the grown crystal melting point is 115 °C and the decomposition point is 205 °C. The kinetic and thermodynamic parameters such as the activation energy, enthalpy, entropy and Gibbs free energy were calculated from the TGA data using the Coats–Redfern, Horowitz–Metzger and Piloyan–Novikova methods. The dielectric measurements were carried out with different frequencies at various temperatures using parallel plate capacitor method and the electronic parameters were also calculated. The activation energy was calculated from Arrhenius plot. The Vickers micro-hardness studies were performed to analyse the mechanical strength of the grown crystal. The work hardening coefficient, stiffness constant, yield strength, fracture toughness and brittleness were calculated. The nonlinear optical properties of the grown 4-dimethylaminopyridine single crystal were measured by the Z-scan technique.