Microwave assisted hydrothermal synthesis of Au@TiO2 core–shell nanoparticles for high temperature CO sensing applications

Au@TiO2 core–shell nanoparticles (NPs) were synthesized by microwave assisted hydrothermal method in 1 h. Au NPs with 40 ± 5 nm size were synthesized by colloidal method. TiO2 shell layer with 60 ± 10 nm shell thickness was deposited on Au NPs by microwave assisted hydrothermal method. The average particle size of primary TiO2 NPs was 15 ± 3 nm. The surface plasmon (SP) band of Au NPs was red-shifted from 521 nm to 565 nm after TiO2 shell formation. There was no phase transition from anatase to rutile even these Au@TiO2 core–shell NPs were sintered at 900 °C. The sensor response of Au@TiO2 core–shell NPs was higher than bare TiO2 NPs. The response of Au@TiO2 core–shell NPs increased with increasing CO concentration. The response further increased with increasing testing temperature but decreased with increasing sintering temperature.