Controlled fabrication of Ag@clay nanomaterials for ultrasensitive and rapid surface-enhanced Raman spectroscopic detectionElectronic supplementary information (ESI) available. See https://doi.org/10.1039/d2ay01262f

The nanostructure of Ag nanoparticles (NPs) plays a critical role in their surface-enhanced Raman scattering (SERS) activity. Despite many efforts to tune the nanostructure of Ag NPs, it remains a great challenge as Ag NPs tend to agglomerate and their nanostructure is difficult to control. Herein, newly-discovered clay-surfactant-Ag+materials and interfacial processes were developed and used to prepare uniform spherical Ag@synthetic hectorite (Ag@Hct) nanomaterials for ultrasensitive SERS assay. Sodium dodecyl sulfate (SDS), an anionic surfactant, acted as a bridge to conjugate the positively charged edge of Hct NPs and Ag+viaelectrostatic interaction to form the bridging nanostructure of Hct-SDS-Ag+, which promoted the uniform dispersion of Hct NPs. Following this, Ag+was reduced to Ag0by the reductant, and Ag0grew on the surface of disc-like Hct NPs to form spherical Ag@Hct nanomaterials with an average particle size of ∼24 nm. The prepared Ag@Hct nanomaterials showed an ultrasensitive SERS response to methylene blue (MB) with a detection limit of 10−12M. The detection limit of MB in sewage was 10−11M. The prepared Ag@Hct nanomaterials also exhibited great SERS enhancement for malachite green and crystal violet. This work provides a novel and simple approach to prepare Ag@Hct nanomaterials with uniform spheres and adjustable particle size, allowing more sensitive and reproducible detection of MB.