Floating Ag-NPs@Cu-NW bundles fabricated on copper mesh for highly sensitive SERS detection of uric acid in pretreatment-free urine

The rapid and sensitive detection of ultra-trace marker molecules from biological samples is of great significance for the wide application of surface-enhanced Raman spectroscopy (SERS) methods in clinical diagnosis and disease monitoring. However, the cumbersome biological sample processing procedures and the poor enrichment of target analytes in hot spots hinder the practical applications of SERS methods. In this paper, we synthesized a novel floating SERS substrate by a simple one-step oxidation process, annealing and in situ chemical etching to form Ag-NPs@Cu-NW bundles on copper mesh (CM). In particular, under spontaneous bottom-up capillary action, the pressure difference at different nanogaps drives uric acid molecules to actively enter hot spots, so that the Ag-NPs@Cu-NW bundle nanostructure with the advantages of a light weight CM is capable of preventing the common coffee-ring effect and enhancing the spatial enrichment of analytes. Therefore, this SERS substrate realizes highly sensitive detection of uric acid at a level of 50 nM in pretreatment-free urine. Currently, this portable, flexible, simple, fast and cost-effective SERS substrate has great potential for early screening and clinical diagnosis of diseases in different biofluids.