Sonocatalytic activity of Yb, B, Ga-codoped Er3+:Y3Al5O12/TiO2 in degradation of organic dyes

A series of Yb, B and Ga doped Er3+:Y3Al5O12 (Er:YAG) as up-conversion luminescence agents were synthesized using sol–gel method. After that, their corresponding TiO2 coated composites (Er3+:Y3Al5O12/TiO2 (Er:YAG/TiO2), Yb-doped Er3+:Y3Al5O12/TiO2 (YbEr:YAG/TiO2), Yb and B-doped Er3+:Y3Al5O12/TiO2 (YbEr:(B)YAG/TiO2), Yb and Ga doped Er3+:Y3Al5O12/TiO2 (YbEr:(Ga)YAG/TiO2) and Yb, B and Ga doped Er3+:Y3Al5O12/TiO2 (YbEr:(B,Ga)YAG/TiO2)) as sonocatalysts were prepared by sol–gel coating process. The up-conversion luminescence agents and their coated composites were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). And that, the sonocatalytic activities were detected through the degradation of some organic dyes as model pollutants by UV–vis spectroscopy under ultrasonic irradiation. The influencing factors such as heat-treated temperature and heat-treated time on the sonocatalytic activity of YbEr:(B,Ga)YAG/TiO2 coated composite were studied. In addition, the effects of ultrasonic irradiation time and initial dye concentration on the sonocatalytic degradation were also reviewed. The experimental results showed that the doping of Yb, B and Ga into Er:YAG/TiO2 significantly enhanced its up-conversion luminescence capability, therefore, improved the sonocatalytic activity of Er:YAG/TiO2 coated composite in the degradation of organic dyes. Particularly, YbEr:(B,Ga)YAG/TiO2 coated composites with 3:7 mass ratio heat-treated at 550 °C for 60 min displayed the highest sonocatalytic activity. At last, the experiments indicated that the YbEr:(B,Ga)YAG/TiO2 coated composite has also a good sonocatalytic activity to degrade other organic dyes under ultrasonic irradiation.