Plasmon-enhanced photoluminescence of carbon dots–silica hybrid mesoporous spheres

Abstract

Ag-enhanced fluorescent carbon dot–silica hybrid mesoporous spheres (Ag-CDSiMs) with high surface areas (>300 m² g⁻¹) have been prepared by a facile process. The incorporation of the silver nanoparticles (NPs) at a concentration of 0.34 at% considerably improved the photoluminescence (PL) of these spheres. The enhancement factor (EF) was very sensitive to the excitation wavelength, and the largest EF (∼3.4-fold) appeared when applying an excitation wavelength of 370 nm. XPS measurements revealed that the incorporation of silver NPs led to an increase of the O binding energy, indicating that they selectively linked to the SiO₂ domain using Ag–O bonds. In this case, the electron transfer between carbon dots and the Ag NPs became impossible, which induced an enhancement of the local electromagnetic field and a plasmon coupling effect between the SPR absorption of Ag NPs and emission of Ag-CDSiMs, along with enhancement of the luminescence of the carbon dots covalently bonded to the mesoporous SiO₂.