Green synthesis and electrophoretic deposition of Ag nanoparticles on SiO2/Si(100).

Plasmonic substrates were prepared by electrophoretic deposition of Ag nanoparticles on SiO2/Si(100). The Ag nanoparticles were obtained using [Ag(NH3)2](+) as the Ag precursor and d-glucose as the reducing agent. Under optimized conditions, this simple and green synthesis method furnished a suspension of Ag nanoparticles with a narrow dimensional dispersion (centered around 27 nm) and a negative z-potential, suitable for electrophoretic deposition. Samples were chemically, optically and morphologically characterized by photoemission and UV-vis spectroscopy and electron microscopy, and tested as substrates for surface enhanced Raman spectroscopy. Despite being a very simple procedure, good enhancement factors were measured thanks to the formation of hot spots, formed by sandwiching the analyte (benzenethiol) between sequentially deposited Ag nanoparticles.

Growth and optical properties of silver nanostructures obtained on connected anodic aluminum oxide templates.

Ag nanostructures are grown by AC electrodeposition on anodic alumina oxide (AAO) connected membranes acting as templates. Depending on the thickness of the template and on the voltage applied during the growth process, different Ag nanostructures with different optical properties are obtained. When AAO membranes about 1 µm thick are used, the Ag nanostructures consist in Ag nanorods, at the bottom of the pores, and Ag nanotubes departing from the nanorods and filling the pores almost for the whole length. When AAO membranes about 3 µm thick are used, the nanostructures are Ag spheroids, at the bottom of the pores, and Ag nanowires that do not reach the upper part of the alumina pores. The samples are characterized by angle resolved x-ray photoelectron spectroscopy, scanning electron microscopy and UV-vis and Raman spectroscopies. A simple NaOH etching procedure, followed by sonication in ethanol, allows one to obtain an exposed ordered array of Ag nanorods, suitable for surface-enhanced Raman spectroscopy, while in the other case (3 µm thick AAO membranes) the sample can be used in localized surface plasmon resonance sensing.