Silver Nano-Dendrite-Plated Porous Silicon Substrates Formed by Single-Step Electrochemical Synthesis for Surface-Enhanced Raman Scattering

Nanostructured layers composed of porous silicon (PSi)-based silver (Ag) nanodendrites have been formed by a simple single-step electrochemical anodic oxidation process on p-type silicon substrate. A mixture of hydrofluoric acid (HF), silver nitrate (AgNO3), and dimethylformamide (DMF) solution was used as the electrolyte to form PSi and nanoscaled Ag structures simultaneously in a few minutes without any post treatment. We studied the influence of the anodization parameters on the morphologies of Ag-PSi structures. The results show that the metallic Ag attached to PSi surfaces completed the conversion from nanoparticles to nanodendrites with the increase of AgNO3 concentrations, along with the increase of the number, size, and the area they covered of dendrites. The sensitivity and stability of the Ag dendrites-coated PSi substrate were evaluated using Rhodamine 6G (R6G) as probe molecule. This Ag-PSi substrate exhibits high surface-enhanced Raman scattering (SERS) response, good reproducibility, and outstanding long-time stability with a detection limit of R6G as low as 10(-11) M. This single-step systhesis technique provides a simple method for preparation of SERS-active substrates with high sensitivity and stability, representing a promising SERS platform for chemical and biomolecule detections.