Nanostructured titania films sensitized by quantum dot chalcogenides

The optical and structural properties of cadmium and lead sulfide nanocrystals deposited on mesoporous TiO(2 )substrates via the successive ionic layer adsorption and reaction method were comparatively investigated by reflectance, transmittance, micro-Raman and photoluminescence measurements. Enhanced interfacial electron transfer is evidenced upon direct growth of both CdS and PbS on TiO(2 )through the marked quenching of their excitonic emission. The optical absorbance of CdS/TiO(2 )can be tuned over a narrow spectral range. On the other side PbS/TiO(2 )exhibits a remarkable band gap tunability extending from the visible to the near infrared range, due to the distinct quantum size effects of PbS quantum dots. However, PbS/TiO(2 )suffers from severe degradation upon air exposure. Degradation effects are much less pronounced for CdS/TiO(2 )that is appreciably more stable, though it degrades readily upon visible light illumination.