Narrow Results

The influence of heat treatment on hole transfer (HT) processes from the CdSe/ZnS and CdSe/CdS/ZnS quantum dots (QDs) to 4,4${}^{\prime }$,4${}^{″}$-Tris(carbazol-9-yl)-triphenylamine (TCTA) in QD/TCTA hybrid films has been researched with time-resolved photoluminescence (PL) spectroscopy. The PL dynamic results demonstrated a heat-treatment-temperature-dependent HT process from the core-shell CdSe QDs to TCTA. The HT rates and efficiencies can be effectively increased due to reduced distance between core-shell CdSe QDs and TCTA after heat treatment. The CdS shell exhibited a more obvious effect on HT from the core-shell CdSe QDs to TCTA than on electron transfer to TiO₂, due to higher barrier for holes to tunnel through CdS shell and larger effective mass of holes in CdS than electrons. These results indicate that heat treatment would be an effective means to further optimize solid-state QD sensitized solar cells and rational design of CdS shell is significant.

CdSe semiconducting nanoparticles in the range of 6–7 nm in size were synthesized by a soft chemical procedure at room temperature. The particles were characterized by powder X-ray diffraction, UV–visible optical spectroscopy revealing nanocrystallization, and quantum mechanical electron confinement. Photoluminescence and Raman spectroscopy of these nanocrystalline powders indicated optical phonon confinement. Asymmetric line shapes revealed occurrence of nonzone center phonons. The particles could be successfully deposited on ITO substrate by electrophoresis to obtain self-organized quantum dot array. Scanning electron microscopy, high-resolution scanning electron microscopy, confocal fluorescence microscopy, and atomic force microscopy investigations revealed self-similar deposits.

Here we adopt a convenient green chemical route for synthesis of CdSe quantum dots, their characterization by UV/Vis absorption spectroscopy, X-ray diffraction study and transmission electron microscopy. We carry out photoluminescence and electroluminescence spectroscopy to investigate the variation in electro-optical property with size. By UV/Vis spectroscopy, blue shift is revealed and bandgap is also calculated. X-ray diffraction spectrum reveals cubic structure and transmission electron micrographs show quantum dots of different size distributions (in the range 2–8 nm). Both the luminescence spectroscopies reveal green-orange luminescence depending upon the size distribution and indicate the possibility of using CdSe quantum dots as light emitting devices with better compatibility and faster response.

The optical properties of CdSe quantum dots (QDs) capped by thioglycolic acid (TGA) before and after surface modification with poly (acrylic acid) grafted onto salep (salep-g-PAA), as a biopolymer-based multidentate ligand, were examined. The results showed that the fluorescence intensity as well as the stability of CdSe QDs was incredibly increased after surface modification with the biopolymer-based ligand. To provide more evidence for the occurrence of surface modification, the prepared CdSe–salep-g-PAA QDs were characterized by thermo-gravimetric analysis (TG), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR).