Homogeneous Hot Spots Plasmonic Microcapsules Integrated Enrichment-Detection All-in-One for Sensitive and Repeatable Surface-Enhanced Raman Spectroscopy Analysis

Rapid and accurate analysis of complex samples by surface-enhanced Raman spectroscopy (SERS) still faces challenges. Herein, an enrichment-detection all-in-one strategy within plasmonic microcapsules (PMCs) was proposed for sensitive and repeatable SERS analysis. The PMC had silver nanoparticles (AgNPs) as shells, which were prepared using any immiscible solvents in 1 min. It could not only serve as microreaction chambers for phase separation and rapid enrichment of analytes but also offer homogeneous hot spots and powerful signal enhancement for SERS detection. The PMC showed good SERS performance with a relative standard deviation (RSD) of less than 5.0% for uniformity and less than 7.0% for intrabatch and interbatch stability. Moreover, PMC showed high SERS enhancement for methylene blue (MB), malachite green (MG), and rhodamine 6G (R6G), with enhancement factors (EFs) of 3.4 × 10⁷, 2.1 × 10⁷ and 1.1 × 10⁸, respectively, corresponding to 2 orders of magnitude higher than that of Ag sol method. Subsequently, the selectivity and enhancement mechanisms were studied. MB and T-2 toxin were chosen as model analytes to present two application scenarios. The detection limits of MB and T-2 toxin were 0.03 nmol/L and 1.6 ng/L, respectively. It was applied to the detection of MB in animal-source samples and T-2 toxin in plant-source samples, with recovery rates of 91.5-104% and RSD of 1.0-7.2%. Validation using the high-performance liquid chromatography method with a relative error of -7.1-0.5%. The proposed method shows great potential for the sensitive and repeatable SERS detection of trace analytes.