Qinliang Li

Enhanced Gas-Sensing Properties of the Hierarchical TiO2 Hollow Microspheres with Exposed High-Energy {001} Crystal Facets

Anatase hierarchical TiO2 with innovative designs (hollow microspheres with exposed high-energy {001} crystal facets, hollow microspheres without {001} crystal facets, and solid microspheres without {001} crystal facets) were synthesized via a one-pot hydrothermal method and characterized. Based on these materials, gas sensors were fabricated and used for gas-sensing tests. It was found that the sensor based on hierarchical TiO2 hollow microspheres with exposed high-energy {001} crystal facets exhibited enhanced acetone sensing properties compared to the sensors based on the other two materials due to the exposing of high-energy {001} crystal facets and special hierarchical hollow structure. First-principle calculations were performed to illustrate the sensing mechanism, which suggested that the adsorption process of acetone molecule on TiO2 surface was spontaneous, and the adsorption on high-energy {001} crystal facets would be more stable than that on the normally exposed {101} crystal facets. Further characterization indicated that the {001} surface was highly reactive for the adsorption of active oxygen species, which was also responsible for the enhanced sensing performance. The present studies revealed the crystal-facets-dependent gas-sensing properties of TiO2 and provided a new insight into improving the gas sensing performance by designing hierarchical hollow structure with special-crystal-facets exposure.

Horizontal growth of MoS2 nanowires by chemical vapour deposition

We describe a single step route for the synthesis of MoS2 wires using a chemical vapour deposition (CVD) method. By tuning the CVD growth parameters, the horizontally oriented MoS2 nanowires on SiO2/Si substrate can be synthesized successfully. The MoS2 nanowire has height of about 93 nm and width of about 402 nm with multilayer structure. Good local photoluminescence (PL) properties can be observed for these horizontal MoS2 nanowires. The successful fabrication and prominent PL effect of the horizontal MoS2 nanowires provide potential applications for the MoS2-based in planar devices.

Monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes with enhanced photoluminescence

The precise control of the morphology and crystal shape of MoS2 nanostructures is of particular importance for their application in nanoelectronic and optoelectronic devices. Here, we describe a single step route for the synthesis of monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes using a chemical vapor deposition method. First-principles calculations demonstrated that the bandgap of the pyramid-like MoS2 nanodot is a direct bandgap. Enhanced local photoluminescence emission was observed in the pyramid-like MoS2 nanodot, in comparison with monolayered MoS2 flakes. The findings presented here provide new opportunities to tailor the physical properties of MoS2via morphology-controlled synthesis.

Tuning strain and photoluminescence of confined Au nanoparticles by hydrogen passivation

Au nanoparticles confined in an Al2O3 matrix are synthesized using pulsed laser deposition method and rapid thermal annealing technique. The confined Au nanoparticles experience a compressive strain during the growth process. It is demonstrated that hydrogen passivation can be used to enhance and tailor the optical properties of confined Au nanoparticles by engineering the strain and defect states of the confined Au nanoparticles. The findings provide an insight and useful methodology to improve the emission efficiency of noble metal nanoparticle based materials for potential application in optoelectronic and photonic devices.