Fluorescence emission spectra of silver and silver/cobalt nanoparticles

Various aqueous solutions of silver and silver/cobalt nanoparticles (Ag and Ag/Co NPs) were obtained, and their fluorescence emission spectra have been studied. First, colloidal Ag NPs were prepared by an electrochemical method under different time intervals and at different rotation speeds of rotating electrode. Next, in a reduction method, Ag/Co core–shell NPs were prepared, using Ag NPs as a core. The core–shell structure of Ag/Co NPs has been demonstrated by the Transmission Electron Micrograph (TEM) and X-Ray Diffraction (XRD) pattern. The fluorescence emission spectra of Ag and Ag/Co NPs, at different ranges of excitation wavelength, were investigated, which revealed two kinds of fluorescence emission peak. The shorter emission peak was fixed at about 485 (for Ag NPs) and 538 nm (for Ag/Co NPs). For both NPs, with an increase in excitation wavelength, the latter emission peak becomes red-shifted. The effect of duration time and rotation speed of the rotating electrode, in the electrochemical preparation of Ag NPs, on its fluorescence emission spectra, has also been investigated.