One-step formation of nanostructured gold layers via a galvanic exchange reaction for surface enhancement Raman scattering

Gold films with various nanostructures on porous silicon substrates have been created in one step by using a galvanic exchange reaction approach. In this approach, the formation of gold films is initiated by the formation of metal nuclei via an exchange reaction in which both the oxidation of silicon and reduction of gold complex occur simultaneously. Results show that the deposition of gold film is diffusion controlled, and its apparent activation energy was determined to be 28.57?kJ?mol?1. Therefore, gold nanostructures with text structure, clusters, and dendrites with leaf-like or branch-like structure can be prepared by adjusting the diffusion conditions such as system temperature, concentration of gold salt, ultrasonic vibration, and addition of additives. The SERS activity of the various porous silicon supported gold nanostructures was evaluated using pyridine and adenine as molecular probes. Amongst the various porous silicon supported gold nanostructures, the gold films with leaf-like structures show the highest SERS activity due to the presence of surface active sites in the nanostructures. The present method is promising for the fabrication of stable gold nanostructures for ultrasensitive analytical measurements.