Highly Ordered Ag/Cu Hybrid Nanostructure Arrays for Ultrasensitive Surface‐Enhanced Raman Spectroscopy

Abstract

Despite significant progress recently made in this field, the practical application of surface‐enhanced Raman spectroscopy (SERS) is frequently limited by the lack of highly sensitive, reproducible, and cost‐effective substrates. The fabrication of SERS substrates with a consistently high density of hot‐spots is a key step to address this issue. Here, a simple approach is reported for the fabrication of Ag/Cu hybrid nanostructure arrays as highly sensitive and cost‐effective substrates for SERS application. By effectively tuning the gap size between neighboring nanorods to sub‐10 nm and increasing the packing density of nanorods, ordered Cu nanorod arrays can be used as cheap and effective SERS substrates in their own right. After sputtering a very thin layer of Ag nanoparticles on the surface of the Cu nanorods to get sub‐5 nm gaps, further field enhancement is enabled. A cascaded field enhancement has been evidenced by the electromagnetic simulations. The Ag/Cu hybrid nanostructure arrays exhibit a detection limit down to 10 −15 m for nonresonant molecules such as benzenethiol.