Dual-mode fluorescence–SERS sensor for sensitive and selective detection of uranyl ions based on satellite Fe3O4-Au@CdTe nanostructure

Abstract Increasingly serious uranium pollution necessitates a new method for rapid qualitative and quantitative uranium detection. Some methods based on fluorescence spectroscopy and surface-enhanced Raman scattering (SERS) have been reported to detect uranyl ions (UO22+), the main species of uranium. However, various factors affect the fluorescence selectivity and SERS quantitative analysis. Herein we report on a composite material for a dual-mode fluorescence–SERS detection protocol for simultaneous quantitative and qualitative analysis of UO22+, based on a layer-by-layer assembly strategy, combining the advantages of the two complementary techniques. The composite material consists of a Fe3O4@SiO2 core coated by gold nanoparticles (FA) via electrostatic adsorption. The CdTe quantum dots (CdTe QDs) outside the FA are linked with amide bonds to form a satellite Fe3O4-Au@CdTe nanostructure (FA-CdTe). The fluorescence signal of FA-CdTe was selectively quenched by UO22+, with a detection limit as low as 1.2 nM; the material was also used as a SERS substrate to detect the Raman mode of uranyl at 828 cm-1. Furthermore, this method has been applied for UO22+ detection in seawater, river water, and tap water, demonstrating the broad application prospects and providing novel development concepts.