Nonlinear optical properties of irradiated 1,2-dihydroxyanthraquinone thin films: merged experimental and TD-DFT insights

Irradiating thin films via gamma rays is a facile method to tune their structural and optical properties. In the current study, thin films of Alizarin dye (AZ) are prepared via thermal evaporation technique. Subsequently, the AZ virgin films are irradiated by gamma rays (15–45 kGy). Fourier Transform Infrared spectroscopy (FTIR), the X-ray diffraction (XRD), and UV/Vis spectroscopy are employed to examine the induced changes in the functional groups, crystal structure and optical properties of AZ films. FTIR elucidates that the molecular structure of AZ films is independent of irradiation doses. XRD reveals that the mass density reduces with increasing the irradiation dose while the crystallite size increases. In regard to optical properties, while the refractive index of AZ films decreases with increasing the irradiation dose, the oscillating and dispersion energies increase. Further, the nonlinear optical susceptibility sharply decreases by increasing irradiation dose which gives a preference to the virgin AZ film in the optical applications over the irradiated ones.