Rapid, large-scale, sonochemical synthesis of 3D nanotextured silver microflowers as highly efficient SERS substrates

This paper reports a simple, sonochemical, surfactant-free synthesis of three-dimensional (3D) silver microflowers with high yield and good size distribution at ambient temperature. The shape, size and surface structure (controlled roughness of the surface topography) of the Ag microflowers could be tuned by controlling the experimental parameters. The special structural features with nanoscale corrugations of 3D silver microflowers make a significant contribution to the high sensitivity of SERS to Rhodamine 6G (R6G) and 4-mercaptobenzoic acid (MBA) molecules. The rougher Ag microflowers display a higher SERS activity compared to the smooth ones, which demonstrates the crucial role of nanoscale surface texturing in the plasmonic response of Ag microflowers. Raman results show that the detection limits for R6G and MBA of the optimized Ag microflower substrate are as low as 10−17 M and 10−12 M, respectively, which can meet the requirements for ultratrace detection of analytes. Furthermore, when the Ag microflower substrate is applied to detect biomolecules of bovine serum albumin (BSA), it also exhibits a high detection sensitivity and the detection concentration of BSA is as low as 10−12 M. This facile, large-scale, low-cost, and green chemistry synthesized Ag substrate with high SERS activity and sensitivity make it a perfect choice for practical SERS detection applications.