Ruihua Zhao

Self-Assembly of Gridlike Zinc Oxide Lamellae for Chemical-Sensing Applications

Hexagonal gridlike ZnO lamellae (GZL) with uniform thickness are synthesized by the o-phthalic acid-assisted hydrothermal method. Here, a systematic study of the assembly behaviors of gridlike ZnO lamellae obtained by the synergistic effect of urea and o-phthalic acid is presented. The morphology evolution and formation mechanism of GZL are also discussed in detail. The as-synthesized samples were characterized by powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy and electron diffraction spectroscopy. The results show that 2D ZnO lamellae are composed of nanotablets, which are jointed to form grids. The length and width of ZnO lamellae are about 1000 and 500 nm, respectively, and the thickness is about 30 nm. GZL morphology evolves from hexagonal ZnO nanotablets to lamellae with grids. The gas-sensing properties indicate that sensors fabricated from different materials present very different responses to volatile organic compounds. A GZL-based sensor has good response to acetaldehyde, and the response and recovery times are 1 and 6 s, respectively, when it was exposed to 1 ppm of acetaldehyde gas. The possibility of tuning the gas-sensing properties by adjusting the morphology makes GZL a novel candidate for more effective detection of a toxic, volatile gas with low concentration.

Catalytic performance of Mo2C supported on onion-like carbon for dehydrogenation of cyclohexane

Mo2C is a promising substitute for noble metal catalysts. Mo2C unsupported and supported on carbon (Mo2C/C) including activated carbon (AC) and onion-like carbon (OLC) was used for hydrogen production. The activity and stability of the Mo2C based catalysts in the dehydrogenation of cyclohexane were studied. The onion-like carbon supported Mo2C catalyst (Mo2C/OLC) was characterized by XRD, TEM and EDS techniques. The results indicate that the Mo2C/OLC catalyst exhibited high stability and activity by adjusting the Mo contents compared to other catalysts. The structures and morphologies of OLC as well as the dispersion of Mo2C did not change before and after reaction of the Mo2C with 15 wt% Mo, which suggests that onion-like carbon is an effective support and Mo2C/OLC is a potential catalyst substitute for noble metals in dehydrogenation.

Hierarchically Self-Assembled Star-Shaped ZnO Microparticles for Electrochemical Sensing of Amines.

Novel, hierarchically nanostructured, star-shaped ZnO (SSZ) microparticles are synthesized by a hydrothermal synthetic route. The SSZ microparticles serve as effective platforms for electrochemical detection of amines in solution. The morphology and structure of the materials are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and UV/Vis spectroscopy. The as-synthesized SSZ microparticles comprise self-assembled hexagonal prisms that possess nanometer and micrometer pores in their structure and on their surfaces-structural features that are conducive to sensing applications. An electrode fabricated by using the hierarchically nanostructured SSZ materials serve as a sensitive electrochemical sensor for detection of low concentrations of ethylenediamine, with a sensitivity of 2.98×10(-2)  mA cm(-2)  mm(-1) , a detection limit of 2.36×10(-2)  mm, and a short response time of 8 s.