Multifunctional Ag-coated CuO microbowl arrays for highly efficient, ultrasensitive, and recyclable surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) has been demonstrated to be an ultrasensitive and real-time analysis technique for detection of analytes with its specific fingerprint-identification feature. However, most traditional SERS-active substrates are suffering from their high expense, intricate fabrication processes and non-recyclability, which seriously hinder the applicable universality of SERS analytical technique. Thus, it is highly desired to develop highly sensitive SERS-active substrates that can be recovered in an easy way. Herein, we present a facile and inexpensive approach for fabrication of photocatalytically active Ag-coated CuO (denoted as CuO@Ag) microbowl array substrate, applicable for the highly efficient, ultrasensitive, and recyclable SERS detection. In this approach, a multifunctional CuO@Ag microbowl array is achieved based on the pre-synthesis of a quasi-2D CuO microbowl array by employing the colloidal lithography on Cu foil combined with the subsequent chemical oxidation reaction, and followed by the sputtering deposition of Ag layer on the CuO microbowl array. Importantly, this CuO@Ag microbowl array can serve as SERS-active substrate with extra advantageous feature of excellent photocatalytic activity, which enables self-degradation of analytes after the SERS-detection under visible light illumination. Remarkably, this allows for recyclable SERS detection. In the detection of model probe molecules, e.g., methylene blue (LOD: 1.3 × 10−16 M) and Aflatoxin B1 (LOD: 6.5 × 10−15 M), approximate femtomolar level can be reached. Impressively, this substrate allows multi-detection without compromising the SERS activity. The present research provides a new and cost-effective strategy for synthesizing recyclable SERS-active substrates, which suggests plausible ways in the design of multi-functional SERS-active substrates.