Highly ordered Au-Ag alloy arrays with tunable morphologies for surface enhanced Raman spectroscopy

A simple approach combining electrochemical reaction self-assembly and photolithography has been proposed for the controlled and reproducible fabricating the highly ordered Au-Ag alloy arrays for SERS. The nucleation and growth processes of the Au-Ag alloy are adjusted easily via changing the applied voltage and reaction time to obtain the flower-like hierarchy nanostructure, which show the strongest SERS properties due to the wealthy Raman hot spots provided by the corners and edges in much-branched flower structure. Moreover, the maximum SERS is observed for the Au-Ag alloy with a small amount of Au (12%), which can lead to a charge separation and favor the probe molecules adsorption to the silver domains. By using these flower-like Au-Ag alloy arrays, the Rhodamine 6G (R6G) with the concentration of as low as 10(-12) M can be detected easily in this study, which would be very promising for the applications in biosensors and nanodevices with molecule-level detection.