With single-molecule sensitivity, surface-enhanced Raman scattering (SERS) has promised to be a powerful tool from chemical analysis to biosensors. However, problem with large signal fluctuations for reproducibility has impeded SERS from widespread application. The fabrication of SERS substrate with large and uniform enhancement in combination with an effective target analyte-transfer process is crucial for applications of SERS for trace molecule detection. In this study, we performed laser-scanning confocal mapping to characterize 3 SERS substrate samples. The substrate consists of a monolayer of cuboctahedral silver nanocrystals (AgNCs) made with Langmuir-Blodgett technique. The synthesis of the cuboctahedral AgNCs involves the use of polyvinylpyrrolidone (PVP) as a shape-controlling agent that remains on the surface of the nanocrystals. Using PVP as an analyte, we investigate the temporal and spatial variation of PVP SERS signals from the cuboctahedral AgNC Langmuir-Blodgett film. Analyzing the enhancement probability distribution with a model allows quantitative characterization of the cuboctahedral AgNC SERS substrates. The results help to identify important SERS substrate characteristics that influence the performance of the SERS substrate.
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