Bi2S3–Bi2O3 composites were synthesized by a facile hydrothermal method with surfactant as template. The structure and morphology of the as-synthesized products were characterized in detail. The photosensitive behavior of the Bi2S3–Bi2O3 composites was investigated carefully. Under the illumination of a 650 nm laser in air or vacuum, the device displayed enhanced photosensitive performance compared to the pure Bi2S3, pure Bi2O3 and mechanical mixture of Bi2S3 and Bi2O3 based devices. The photoswitch ratio (Iphoto/Idark) was as high as 30 in a vacuum with fast photoresponse speed, which indicated their potential applications in manufacturing photodetectors and optoelectronic devices. The possible mechanism of enhanced photosensitivity was also proposed.

Here, we report a novel intermediate state (core–shell MoO3–MoS2 nanowires) in the synthesis of large area few-layer or monolayer MoS2 films on Si/SiO2 substrates coated with 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) using a chemical vapour deposition (CVD) method. In our experiments, water vapor present in the carrier gas (N2) should help enhance the interaction between PTCDA and MoO3. In the intermediate state, the morphology of the nuclei is controlled to be nanowires with 20–180 nm diameters and 30–70 μm lengths. We investigate the formation mechanism of the nucleation-controlled intermediate state and the formation process of monolayer MoS2 using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), photoluminescence (PL), Raman spectroscopy and transmission electron microscopy (TEM) measurements. We also describe a method to control the diameter of the nanowires and the stacking of the nanowires into MoS2 nanosheets on the substrate, which is meaningful for producing large area and highly crystalline MoS2 monolayers.

Various stacking patterns have been predicted in few-layer MoS2, strongly influencing its electronic properties. Bilayer MoS2 nanosheets have been synthesized by vapor phase growth. It is found that both A-B and A-A′ stacking configurations are present in bilayer MoS2 nanosheets through optical images, and the different stacking patterns exhibit distinctive line shapes in the Raman spectra. By theory calculation, it is also concluded that the A-B and A-A′ stacking are the most stable and lowest-energy stacking in the five predicted stacking patterns of bilayer MoS2 nanosheets, which proves the experimental observations.

Tungsten oxide (WO3) nanostructures such as nanowires, nanorod bundles and nanotube bundles are synthesized by a facile hydrothermal method. The ultraviolet (UV) photoresponse characteristics of devices containing these WO3 nanostructures are investigated for the first time and new photosensitive mechanisms involving both photo-generated electron–hole pairs and reversible electrochemical reactions are proposed. We find that h-WO3 nanowires with large specific surface areas and fewer defects exhibit excellent UV photoresponse properties with switch ratios (defined as Iphoto/Idark) as high as 60, which is due to the existing large tunnels serving as channels and intercalation sites for mobile ions and active electrochemical reactions, and our findings provide a new family and more selectivity for UV photosensitive nanomaterials in the future.

First-principles calculations have been performed to study Au-decorated silicene (Au/silicene) as a high-activity catalyst for CO oxidation. The high binding strength of the Au/silicene system and the high diffusion-energy barrier of Au adsorbates, as well as the assisted Coulomb repulsion effect, jointly prevent the formation of Au clusters. Au/silicene transfers many more electrons to O2 than to CO, thus facilitating CO oxidation first by the Langmuir–Hinshelwood (LH) mechanism (CO + O2 → OOCO → CO2 + O) and then by Eley–Rideal (ER) mechanism (CO + O → CO2). The two reaction processes have quite low catalytic energy barriers of 0.34 and 0.32 eV, respectively. The underlying mechanism of high catalytic oxidation of CO can be attributed to electronic-state hybridization among Au d orbitals and CO and O2 2π* antibonding states around the Fermi energy. These findings enrich the applications of Si-based materials to the high-activity catalytic field.

Tungsten oxide (WO3) nanostructures such as nanowires, nanorod bundles and nanotube bundles are synthesized by a facile hydrothermal method. The ultraviolet (UV) photoresponse characteristics of devices containing these WO3 nanostructures are investigated for the first time and new photosensitive mechanisms involving both photo-generated electron–hole pairs and reversible electrochemical reactions are proposed. We find that h-WO3 nanowires with large specific surface areas and fewer defects exhibit excellent UV photoresponse properties with switch ratios (defined as Iphoto/Idark) as high as 60, which is due to the existing large tunnels serving as channels and intercalation sites for mobile ions and active electrochemical reactions, and our findings provide a new family and more selectivity for UV photosensitive nanomaterials in the future.