Coencapsulation of Carbon Dots and Gold Nanoparticles over Escherichia coli for Bacterium Assay by Surface-Enhanced Raman Scattering

Carbon dots (C-dots) is a type of fluorescent nanomaterials with excellent properties, which in combination with gold nanoparticles (AuNPs) generate structures that can be applied in various fields of science. This research developed a hybrid nanostructure between C-dots and AuNPs using a layer-by-layer (LbL) assembly to increase the surface-enhanced Raman scattering signals (SERS) for the detection of Escherichia coli. The created nanostructure was denoted as B@C-dots@AuNPs and proved by zeta potential, scanning electron microscopy, and fluorescence assays. The results showed that the introduction of AuNPs greatly enhanced the SERS signals of C-dots. The relative intensities of peaks at 2873 and 3082 cm–1 could be used for the detection of bacterium concentration with a detection limit of ca. 102 cfu/mL. In conclusion, an easy, quick, low-cost, and nontoxic technique for the detection of bacteria was developed through the coencapsulation of C-dots and AuNPs over bacteria. The findings are envisaged to facilitate the application of SERS in microbiology and related fields.