Advanced SERS\nPlatform for Uniform and Reliable Molecular\nDetection

Signal uniformity is crucial for reliable and quantifiable\nsurface-enhanced\nRaman scattering (SERS) measurements. However, challenges arise due\nto the continuous impact of localized hottest spots and the coffee\nring effect on signal uniformity. In response to this, we developed\na platform featuring a hierarchical structure with Ag nanopores and\nmicrobowls (HANM) and incorporated superhydrophobic/superhydrophilic\n(SHB/SHL) treatments. This design enhances the hottest spot area,\nensuring a strong and consistent electromagnetic field while mitigating\nthe coffee ring effect, which leads to an even analyte distribution.\nThis was demonstrated by analyzing rhodamine 6G (R6G, 4 μL,\n10<sup>–9</sup> M to 10<sup>–12</sup> M) molecules at\ndifferent concentrations. The 2D mapping of the SERS signal intensities\nfrom the entire dried droplet exhibited excellent uniformity. The\nrelative standard deviation of the intensities from 200 randomly selected\npoints was calculated to be just 3.81%, laying the foundation for\nthe quantitative detection capability. Additionally, through bisphenol\nA (BPA) detection in water samples collected from five different locations,\nthe HANM-SHB/SHL structure consistently detected BPA with a uniform\nsignal intensity across all water samples. In conclusion, we proposed\na dual-function SERS platform featuring an improved hottest spot region\nand the ability to avoid the coffee ring effect, offering precise\nand reliable molecular analysis.