Breathing Raman modes in Ag₂S nanoparticles obtained from F9 zeolite matrix

Ag₂S nanoparticles were synthesized with a combination of synthetic F9, silver nitrate (AgNO₃) and monohydrated sodium sulfide (Na₂S₉H₂O). An ionic exchange was achieved via hydrothermal reaction. Nanoparticles with a predominant size ranging from 2 to 3 nm were obtained through Transmission Electron Microscopy (TEM). The nanoparticles feature a phase P21/n (14) monoclinic structure. A Raman band can be observed at around 250 cm^-1 in the nanoparticles. Furthermore, the vibrational properties and stability parameters of the clusters (AgS)_n, (with n = 2-9) were studied by the Density Functional Theory (DFT). The approximation levels used with DFT were: Local Spin Density Approximation (LSDA) and Becke's three-parameter and the gradient corrected functional of Lee, Yang and Puar (B3LYP) in combination with the basis set LANL2DZ (the effective core potentials and associated double-zeta valence). The Radial Breathing Mode (RBM) for B3LYP was found between 227 and 295 cm^-1 as well as in longer wavelengths for LSDA.