PbS nanostructures are synthesized using solvothermal method. Here, EDTA is employed as a chelating agent and PEG–PPG–PEG polymer as a structure directing surfactant. The possible factors behind the formation of nanostructures of various morphologies are explained. Crystalline quality is improved when EDTA is employed in the growth. In the Raman spectra, overtones of the longitudinal optical (LO) phonon peaks are observed. In the I–V characteristics of the photovoltaic devices, both open circuit voltage and short circuit current were improved as compared to the earlier devices made by using a similar mechanical pressing method with PbS nanowires.

We synthesized p-type copper sulfide (CuS) nanowires by hydrothermal method using a polymer as structure directing agent. Single nanowire devices were then fabricated and hole concentration was measured to be ~4×1018cm−3. Schottky contacts between the nanowires and metal electrodes have been distinctively imaged by a scanning photocurrent microscopic method. As the synthesized CuS nanowires were much longer than the diffusion length, the nanowires were intentionally broken down to demonstrate a photovoltaic device utilizing the Schottky contact with Cu electrodes.

We fabricated ZnO nanowires on pre-patterned alumina substrates by using a sonochemical method with Zn(NO3)2 and ZnCl4 precursors, and we studied the optical and the gas sensing properties with thermal treatment for these samples. The yellow emission was found to be decreased with thermal annealing, and the gas response time was reduced with annealing. The NO gas sensitivity of the sample made using ZnCl4 precursors was almost independent of the sensing temperature whereas a significant decrease in the yellow emission was observed with thermal annealing. This can be explained if the oxygen interstitials responsible for the yellow emission do not influence the affinity of the gas molecules significantly because they are located inside the nanowires.

We studied both cw and time-resolved photoluminescence of colloidal CdSe/ZnS core-shell quantum dots capped with chemical ligands. For the trioctylphosphine oxide capped CdSe/ZnS QDs, both the luminescence intensity and lifetime were found to be increased with increasing temperatures, which can be explained by the thermal activation of the carriers trapped at shallow trapping centers. After the ligand exchange into 3-mercaptopropionic acid, the non-radiative recombination rate was increased and the luminescence efficiency was decreased at room temperature. When the QDs were employed in photovoltaic devices, photocurrent was found to be increased after the ligand exchange. The improved photocurrents observed in photovoltaic devices can be explained by the improved tunnelling probability between the neighbouring QDs.

TiO2/CdS core-shell nanowires were synthesized using a simple thermal oxidation treatment of a Ti film, followed by O2 plasma treatment and CdS coating via low-cost chemical bath deposition. The 5 and 20 nm thick CdS films were uniformly coated onto TiO2 nanowires using 200 and 40 ml aqueous solvent, respectively. Time-resolved photoluminescence (PL) measurements on the TiO2/CdS (5 nm) nanowires showed a remarkably increased PL lifetime of 420 ps compared with the 60 ps of the TiO2/CdS (20 nm) nanowires. This result can be attributed to the enhanced electron-hole separation due to the more upshifted quantized electron energy levels of the 5 nm thick CdS film with respect to the TiO2 conduction band edge.

Vertically aligned ZnO nanorods were synthesized on Zn coated Si substrates under various growth conditions by sonochemical method, and the effects of these growth conditions on the nanorods were systematically studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). In the low-temperature PL spectra, we often observed a PL peak at 3.331 eV in addition to a donor-bound exciton peak. The PL peak at 3.331 eV appeared for samples with diameters of similar to 50 nm, and disappeared for samples with larger diameters of similar to 100 nm. This suggests that the peak is associated with the larger surface, consistent with an exciton localized at the surface. We present a discussion on the effects of the mole concentrations of the precursors on the average lengths and diameters of the nanorods. In addition, the Zn thickness dependence of the growth of the ZnO nanorods, as well as the sonochemical growth using ZnCl4 as a precursor instead of Zn(NO3)(2), is discussed.