Synergistic SERS Enhancement in GaN‐Ag Hybrid System toward Label‐Free and Multiplexed Detection of Antibiotics in Aqueous Solutions

Noble metal‐based surface‐enhanced Raman spectroscopy (SERS) has enabled the simple and efficient detection of trace‐amount molecules via significant electromagnetic enhancements at hot spots. However, the small Raman cross‐section of various analytes forces the use of a Raman reporter for specific surface functionalization, which is time‐consuming and limited to low‐molecular‐weight analytes. To tackle these issues, a hybrid SERS substrate utilizing Ag as plasmonic structures and GaN as charge transfer enhancement centers is presented. By the conformal printing of Ag nanowires onto GaN nanopillars, a highly sensitive SERS substrate with excellent uniformity can be fabricated. As a result, remarkable SERS performance with a substrate enhancement factor of 1.4 × 1011 at 10 fM for rhodamine 6G molecules with minimal spot variations can be realized. Furthermore, quantification and multiplexing capabilities without surface treatments are demonstrated by detecting harmful antibiotics in aqueous solutions. This work paves the way for the development of a highly sensitive SERS substrate by constructing complex metal‐semiconductor architectures. The synergistic interplay of the electromagnetic and chemical enhancement of Raman signals is achieved in an Ag nanowire/GaN nanopillar‐based hybrid SERS structure to maximize signal intensities. Using the solvent‐assisted nanotransfer printing technique, highly ordered metal nanostructures are fabricated conformally on a nanopatterned semiconductor substrate. Therefore, several antibiotics dissolved in aqueous solutions are detected without any Raman reporters.