Understanding structure of small TiO 2 nanoparticles and adsorption mechanisms of PbS quantum dots for solid-state applications: a combined theoretical and experimental study

A combined theoretical and experimental study on a series of TiO2, lead sulfide (PbS) and PbS@TiO2 nanocomposites was performed. TiO2 structures were stabilized with simulated annealing using molecular dynamics at the ReaxFF level. A density functional theory study elucidated relevant electronic structure properties.We performed the study for a series of TiO2)n, where n=18, 28, 38, 76 and 114. Band gaps ranging from 1.2 to 2.2 eV were found. This range was attributed to the size of the TiO2 cluster models used in the calculations, and some models became metallic at smaller sizes. We synthesized TiO2 nanoparticles of anatase (101) facet, which were characterized with pair distribution functions, in excellent agreement with the theoretical results. We explored the possibility to anchor a PbS quantum dot with a TiO2 model system.This intermolecular interaction was relevant, since the composite material could be used in solid-state devices' applications, in which stability in the formation of the PbS/TiO2 interface plays an important role for the device performance. The possibility to form a PbS@TiO2 composite material was evidenced, via a covalent interaction, with contributions of the van der Waals type.