Synthesis and photocatalytic activity of plasmon-enhanced core-shell upconversion luminescent photocatalytic Ag@SiO2@YF3:Ho3+@TiO2 nanocomposites

Abstract

Examination of the local surface plasmon resonance (LSPR) effect of precious metals shows that combining noble metal nanomaterials and upconversion (UC) materials increases the luminescence quantum yield and luminescence stability of UC materials. Furthermore, this combination reduces the luminescence lifetime. In this study, a new type of UC luminescent material, Ag@SiO2@YF3:Ho3+, was synthesized. The SiO2 group was used to protect the YF3:Ho3+ group from Ag. In addition, Ag@SiO2 nuclear shell structure model was constructed using finite-difference time-domain (FDTD) simulation software. Ag particle size and SiO2 shell thickness, the parameters of the LSPR resonance peak that most improved the luminous intensity of the UC material, were calculated theoretically. Finally, the composite photocatalyst, Ag@SiO2@YF3:Ho3+@TiO2, was obtained by combining the LSPR-enhanced UC material with the photocatalyst TiO2. The FDTD simulation results showed that the conditions using a Ag particle radius of 75–125 nm and a SiO2 shell thickness of 20 nm most greatly enhanced the luminescence of the UC material YF3:Ho3+, which was deposited on top of the Ag@SiO2 shell structure. Ag@SiO2@YF3:Ho3+ prepared under these conditions possessed a core-shell structure in which the diameter of the Ag core was 150–250 nm and the composite shell, after loading TiO2, was divided into three layers. Furthermore, the results demonstrated the successful fabrication of the UC materials and composite materials. Finally, degradation experiments showed that a desirable photodegradation effect (76%) was obtained and the degradation rate of the dark reaction was 18%.