Photocatalytic properties of hybrid structures based on Titania nanoparticles and semiconductor quantum dots

Titania nanoparticles (NPs) demonstrate the highest photocatalytic activity among metal oxides nanoparticles. A combination of Titania nanoparticles with brightly luminescent semiconductor quantum dots (QDs) makes it possible to obtain highly efficient photocatalytic systems activated by visible light due to photoinduced electron transfer. Multilayered Titania NPs/QDs hybrid structures have been formed using Langmuir–Blodgett technique. Photoluminescent properties of the structures have been analyzed taking into account multiexponential decay of QDs' photoluminescence and their nonuniform distribution in the structures. It has been shown that luminescent fractions of QDs are strong electron donors for Titania NPs with electron transfer rate $k_{ET}\ge 4\cdot {10}^{10}{\text{s}}^{-1}$. It allows for electron transfer with 85% efficiency. At the same time, it was observed that average electron transfer efficiency in the structures is $55\pm 5\%$ because of presence of a dark fraction in QDs ensemble. Our results clearly demonstrate that Titania NPs/QDs hybrid structures are prospective generator of reactive oxygen species under visible light and reducing QDs' dark fraction should increase average electron transfer efficiency in the structures.