Facile, rapid and efficient doping of amorphous TiO2 by pre-synthesized colloidal CdS quantum dots

Various methods have been developed to reduce the band gap of TiO2 via combining TiO2 with quantum dots (QDs). However, the attainment of high activity and stability of hybrid QDs/TiO2 is still a significant challenge since the poor interface contact between QDs and TiO2. This drawback could be tackled to some extent through optimisation of the preparation technology. The present study suggests a simple hydrolysis route to in situ TiO2 doping by pre-synthesized CdS QDs, which play a role of crystal seeds, pre-planted in liquid titanium alkoxide, for the TiO2 crystallization process. The comprehensive investigation of the CdS/TiO2 composite is carried out by X-ray diffraction, UV-Visible spectroscopy, scanning electron microscopy, photocatalytic activity measurements in the photo oxidation of cyclic aromatic organic compounds. The stability of model TiO2-shell structures on CdS seeds is assessed by means of molecular dynamics simulations. Both experimental and theoretical results confirm the mutual impact of CdS QDs and TiO2 on their crystallinity. The presence of CdS QDs in the solution provokes the formation of amorphous TiO2 clusters, while the high TiO2 content leads to amorphization of CdS QDs. The CdS/TiO2 composite particles consisting of CdS amorphous core and TiO2 amorphous shell demonstrate the highest photocatalytic activity.