Ag/Periodic Mesoporous Organosilica Yolk–Shell Nanostructures for Ratiometric Cu²⁺ Fluorescent Sensors

The creation of yolk–shell nanoparticles (YS NPs) with a movable core and periodic mesoporous organosilica (PMO) shell has been simplified using a “ self-template” strategy. In this method, the knitting of the PMO shell and the formation of the interlayer cavity co-occur. This benefit contributes to the simplification of preparation processes and the realization of greater YS NP preparation efficiency with varied functional cores. By incorporating a silver nanocore into the YS NP (Ag-PMO-YS), a ratiometric Cu 2+ fluorescence sensor is created by the “like dissolves like” principle driving the self-assembly of fluorescein derivatives and Cu 2+ ligands within the surfactant micelles. Due to the coordination of Cu 2+ and its ligands and their impact on the emission of fluorescein derivatives, which take part in the fluorescence resonance energy transfer (FRET) process with carbon dots (CDs), this sensor system demonstrates extraordinary detection sensitivity to Cu 2+ (10 –7 M). Additionally, the movable Ag nanocore’s metal-enhanced fluorescence (MEF) effect strengthens the high detection sensitivity and stability.