Au-coated Fe3O4@SiO2 core-shell particles with photothermal activity

Abstract Metal nanoparticles can be used in the advanced applications in catalysis due to their multi-functionality and easy tunable of catalyst size. Especially, gold nanoparticles exhibit valuable properties such as localized surface plasmon resonance (LSPR), which was the result of absorption of resonant light. Therefore, herein, we tried to improve the catalytic performance through the photothermal effects via LSPR of NPs. Au-coated (second shell) nanoparticles with core-shell structures, which comprised magnetite cores (diameter: about 100 nm) and silica shells (first shell; thickness: about 20 nm), were synthesized by a sol-gel method. To enhance the photothermal conversion efficiency of these core-shell particles, Au nanoparticle (NP) seeds prepared by the citrate reduction method were deposited on the silica-coated substrates. Then, the resulting particles were coated with Au (2nd shell, thickness: about 40 nm). The plasmonic resonance peak of the Au-coated particles were red-shifted, which caused an enhancement in the photothermal performance and photothermal conversion efficiency. The prepared samples were used for 4-nitrophenol reduction. Interestingly, the first-order reaction rate constant significantly increased upon irradiation with 808 nm laser was irradiated. Namely, the catalytic performance of Au-coated core-shell particles was 4.5 times enhanced after NIR-irradiation due to the photothermal effect.