Stability analysis of silver nanoparticle suspensions by cyclic voltammetry

We report the application of cyclic voltammetry and absorption spectroscopy to the characterization and study of the stability of silver colloids in water. The samples are prepared via chemical reduction and the reactions are catalyzed by irradiation with white light. The electrochemical response is related to the characteristic sample surface plasmon resonance (SPR) in the UV-visible absorption spectra. Cyclic voltammetry shows a characteristic reduction peak whose position is specific to each analyzed sample. Optical analysis of a colloid precursor during a 12 h time span, under low-power white-light irradiation, shows that nanoparticles undergo change in size and surface state (absorption bands splitting and inversion) to attain the "stable" colloidal form. While the absorption spectrum bands of the precursor return almost periodically to similar positions, the cyclic voltammogram characteristic reduction peak is displaced as a function of time. Finally, we follow the SPR changes of one "stable" colloid being subjected to electrolysis, heating, and sunlight irradiation, for environmental remediation purposes. Sunlight exposure produces the most significant SPR intensity drop, but the electrochemical technique shows itself promising as well.