The photocatalytic properties of SnSe nanostructures (NSs) and SnSe/graphene nanocomposites with different graphene concentrations (5, 10, and 15 wt%/v) were investigated. The products were synthesized by a simple and cost-effective co-precipitation method. The samples obtained demonstrated that graphene concentration at an optimum amount was an important factor in enhancing the photocatalytic performance of the products. The graphene source was graphene oxide (GO) sheets and several characterization results indicated, which were used to remove Methylene blue (MB) dye, that the GO sheets were changed into reduced graphene oxide (rGO) sheets during the synthesis process. The optical properties of the products were studied using a room temperature photoluminescence (PL) spectrometer and it was observed that the near-band-edge (NBE) position of the samples was at the end of the red region between 729 and 756 nm of the electromagnetic spectrum, which was confirmed by a UV-vis spectrometer. The PL spectra of the samples also demonstrated three emissions from the violet, green, and orange regions of the visible spectrum, which were from different defects. The samples were annealed in a hydrogen and air atmosphere at 300 °C and it was found that defect concentrations were increased by annealing for the SnSe/rGO nanocomposites. The photocatalyst studies of the post-annealed samples revealed that the photocatalytic performance of the products was enhanced by annealing in hydrogen, while it was reduced by annealing in air. In addition to MB, the photocatalytic performance of the products for the degradation of phenol as a colorless pollutant was examined. It was observed that rGO in this process also had a significant role in the enhancement of photocatalytic performance. In fact, the electron spin resonance (ESR) test showed the role of rGO in photocatalytic activity very well.

No abstract

In this work, the photoresponse performance of monodisperse PbSe nanocubes in the range of visible and near-infrared (NIR) (400–1500 nm) regions was enhanced by reduced graphene oxide (rGO). A simple cost-effective method is presented to synthesize monodisperse PbSe nanocubes (NCs) that are decorated on the rGO sheets. By the addition of PbSe/rGO nanocomposites with different rGO concentrations, pristine PbSe NCs were synthesized with the same method. Microscopy images showed that the size of NCs was smaller than the exciton Bohr radius (46 nm) of PbSe bulk. Therefore, the UV-Vis-IR spectroscopy result revealed that the PbSe/rGO samples had absorption peaks in the NIR region around 1650 nm and showed a blue shift compared to the absorption peak of the PbSe bulk. J-V measurements of the samples indicated that monodisperse PbSe/rGO nanocomposites had a higher resistance than the other samples under dark condition. On the other hand, the resistance of the monodisperse PbSe/rGO nanocomposites decreased under different light source illuminations while the resistance of the other samples was increased under illumination. Photodetector measurements indicated that the monodisperse morphology of the PbSe NCs enhanced the photoresponse speed and photocurrent intensity. In addition, responsivity (R) and detectivity (D*) of the samples were higher in the NIR region.

The capability of undoped and Zn-doped PbO nanoparticles (NPs) with different Zn concentrations, which were deposited on fluorine-doped tin oxide (FTO) glass, as a photoanode of the photocurrent device based on SnSe NPs, was investigated. An X-ray diffraction pattern of undoped PbO NPs indicated a mixture phase of orthorhombic, tetragonal phases of PbO, and a monoclinic phase of Pb2O3, while Zn-doped PbO NP samples showed a single orthorhombic phase of PbO, and these results were confirmed by Raman spectra results. Room temperature photoluminescence (PL) spectroscopy results of undoped and Zn(2%)-doped PbO NPs showed two emissions in the violet and red regions that belonged to the bandgap and defect, respectively. In addition, PL results indicated an extra emission for the Zn-doped PbO NPs in the green region by increasing Zn concentrations up to 4% and 6%. However, the red emission intensity was reduced by increasing Zn concentrations. Finally, undoped and Zn-doped PbO NPs with FTO glasses were used as photoanodes to measure the photocurrent response of SnSe NPs in the visible and near-infrared (NIR) regions, and the results were compared with FTO/TiO2 as a photoanode, which has been typically used as photoanodes in quantum dot solar cells and dye-sensitized solar cells. It was observed that undoped and Zn-doped PbO NPs caused enhancement of photocurrent performance of the device. However, the responsivity of the device with FTO/Zn(2%)-doped PbO/ under NIR illumination source was higher than the responsivity of other devices under the same illumination source.