Single crystals of functionalized nanoparticles as a medium for structural and spectroscopic studies of photosensitizer dyes on semiconductor surfaces

Single crystals of semiconductor nanoparticles functionalized with technologically relevant ligands offer the opportunity to obtain structural information that can be combined with theoretical calculations. The latter are based on the experimental geometry and used to interpret spectroscopic and other information. A series of Ti/O clusters with diameters up to approximately 2.0 nm have been synthesized and functionalized with a variety of small molecule ligands which exhibit distinct binding modes. DFT calculations complement spectroscopic measurements which examine the band gap of the nanoparticles pre- and post-functionalization and elucidate the influence of adsorbate geometry as well as size quantization effects on the band structure. The detailed structure of the nanoparticles deviates significantly from that of anatase, which is commonly used as a structural model for the substrate used in photovoltaic cells. The structures for the first time unambiguously reveal the different binding modes of the adsorbant molecules.