Optical properties of ZnO-nanowire/CdSe-colloidal-quantum-dot hybrid structures

One of the research interests in modern nanotechnology is the assembly and study of hybrid heterostructures composed of different materials that offer enhanced properties through the interactions between their different constituents. ZnO nanowires functionalized with colloidal semiconductor quantum dots (QDs) display tailored optical properties due to energy and electron transfer processes between these two components, and have a huge potential for applications in light-emitting and photovoltaic devices. Using a facile method, we synthesized water-soluble CdSe QDs with cadmium acetate and sodium selenosulfate as Cd and Se precursors, respectively. 3-mercaptopropionic acid (MPA) was used to cap the QDs, acting as the stabilizer, making the QDs water soluble and preventing them from agglomeration. TEM measurements demonstrated a narrow size distribution of the as-prepared QDs with the average diameter around 3 nm, consistent with UV-Vis absorption measurements. The carboxylic groups at the outer surface of the MPA-capped CdSe QDs render a tight and uniform attachment onto the surface of ZnO nanowires with high coverage efficiency possible. We studied the optical properties of the hybrid structures by photoluminescence spectroscopy under different temperatures to analyze the energy and electron transfer dynamics between the nanowires and the QDs.