Microplasma-assisted growth of colloidal Ag nanoparticles for point-of-use surface-enhanced Raman scattering applications

The authors present a facile, rapid, one-step process to synthesize Ag nanoparticle for surface-enhanced Raman scattering (SERS) applications. Aqueous metal ions are electrochemically reduced by a microplasma to nucleate nanoparticles at ambient conditions (room temperature and atmospheric pressure) without any chemical reducing agents or stabilizer molecules. The nanoparticles are characterized by UV-visible absorbance and transmission electron microscopy, and found to be spherical, crystalline, and uniform with an average diameter of approximately 10 nm. Preparing nanoparticles with only a target analyte molecule present in solution allows intimate interaction between the metal particle surface and the analyte. Raman analysis shows that the scattered signal from a test molecule, crystal violet, is dependent on the process time and maximized after nanoparticles are grown for 20 min. This optimal SERS signal is large and permits detection of an analyte down to 10-10 M concentrations.