Rapid construction of interfacial plasmonic nanoarray for SERS sensing of flavonoids

A rapid, low-cost and reliable interfacial plasmonic nanoarray is presented as surface-enhanced Raman scattering (SERS) sensing platform for preliminary quantification and identification of flavonoids. Here, CTAB-modified Au colloidal nanoparticles self-assemble at the cyclohexane/acetone-water interface to form a uniform interfacial plasmonic nanoarray. The target hydrophobic analytes including organic dye methyl red and water-insoluble flavonoids, are effectively captured at the air-water interface and enter the "hot spots" between nanoparticles during the evaporation of the oil phase, which contributes to sensitive and reproducible SERS signals. Furthermore, this remarkable SERS performance enables the quantitative determination of water-insoluble flavonoids such as kaempferol, luteolin and naringenin with low detection limits of 10^-10 M, and an approximately linear correlation between SERS signals and analytical concentrations, as well as rapid multiplex analysis of flavonoids with similar structural characteristics. Additionally, directly relative content detection of crude extracts from lingonberry (Vaccinium vitis-idaea L.) is achieved on the plasmonic nanoarray, serving as a proof-of-concept demonstration for practical applications. Compared to conventional analyses of flavonoids, the proposed SERS platform circumvents complex and time-consuming pretreatments, thereby opening avenues for the analysis of oil-soluble samples and other secondary metabolites, which will facilitate widespread evaluation of quality and medical value.