Investigation of gamma-ray irradiation on molecular structure, optical properties and mass attenuation coefficients of colloidal gold nanoparticles

In this research, colloidal gold NPs were synthesized by turkevich method. XRD spectrum after irradiation showed the different peaks but the most important distinctive was related to (111) peaks at (2θ = 38.41°) which give an indication that the structure is cubic. The Raman spectroscopy results indicated that the intensity of peaks with the wave number of 3450 cm−1was increased in the colloidal gold NPs irradiated due to improvement of the crystalline properties of colloidal gold NPs. SEM images showed significant changes in the morphology and size of gamma irradiated colloidal gold NPs. For 10 kGy dose, gamma-ray irradiated crystals, the optical absorption increases compared to that of before irradiation which may be the consequence of the formation of point defects due to gamma-rays. Comparing nonlinear studies, the magnitude of nonlinear refraction index, n2 and nonlinear absorption coefficient, β increase after gamma-ray irradiation. The measurement of mass attenuation coefficients result shows that the gamma-ray irradiation has an influence on radiation absorption coefficients of colloidal gold NPs. It is an evidence which shows that in addition to the atomic mass number of elements, the molecular structure may affect on the attenuation coefficients and nonlinear optical properties.