Facile microwave fabrication of CdS nanobubbles with highly efficient photocatalytic performances

Abstract

A new fabrication method of CdS nanobubbles with high photocatalytic activity has been explored under ambient conditions using SiO₂ hard templates and microwave irradiation. The one-step Stöber method has been used to produce SiO₂ core nanospheres, onto which CdS shells have been readily and efficiently coated by 10 min microwave irradiation. The acid etching of the SiO₂ cores has produced monodispersive CdS nanobubbles with outer diameters of 300, 370, and 400 nm with a uniform shell thickness of 11 nm. The CdS nanobubbles have been found to photocatalyze the degradation of rhodamine B efficiently under Xe-lamp irradiation via simultaneous reaction pathways of N-deethylation and conjugated-ring attack. It has been found that the degradation rate increases linearly with the concentration increase of the nanocatalyst but decreases nonlinearly with increasing nanobubble diameters. The pseudo-first-order degradation rate constant via the nanobubbles (0.081 min⁻¹) was found to be about 20 times larger than that via the SiO₂@CdS core@shell nanocomposites (0.0044 min⁻¹) due to the nanoreactor confinement effect leading to a decrease in the activation energy of the reaction.