Ziwei Liu

SnO2 nanocrystal-decorated mesoporous ZSM-5 as a precious metal-free electrode catalyst for methanol oxidation

A novel precious metal-free electrode catalyst SnO2/m-ZSM-5 nanocomposite has been successfully synthesized. This SnO2/m-ZSM-5 nanocomposite shows high and stable electrochemical catalytic activity for methanol oxidation, which is comparable to Pt/C. The high electrochemical performance has been attributed to the synergetic catalytic effects between the mesoporous ZSM-5 matrix and the loaded SnO2 nanocrystals.

Core-shell hierarchical mesostructured silica nanoparticles for gene/chemo-synergetic stepwise therapy of multidrug-resistant cancer

The design and synthesis of hierarchically nanoporous structures for the co-encapsulation and sequential releases of different cargos are still great challenges in biomedical applications. In this work, we report on the elaborate design and controlled synthesis of a unique core-shell hierarchical mesoporous silica/organosilica nanosystem, in which there are large and small mesopores separately present in the shell and core, facilitating the independent encapsulations of large (siRNA) and small (doxorubicin) molecules, respectively. Importantly, the framework of the organosilica shell is molecularly hybridized with disulfide bonds, which enables the unique responsiveness to the reductive tumor microenvironment for the controlled releasing of loaded gene molecules, followed by the subsequent doxorubicin release. The first released large siRNA molecules from the organosilica shell down-regulated the expression of P-gp in the cell membrane and reversed the MDR of cancer cells, thus enhancing the antitumor effect of subsequently released small DOX molecules from the silica core, and in such a synergetic way the MDR tumor growth can be efficiently inhibited. This work shows the significant advantages compared to the traditional small-mesoporous or large-mesoporous nanosystems for drug co-delivery.

On the Mesoporogen‐Free Synthesis of Single‐Crystalline Hierarchically Structured ZSM‐5 Zeolites in a Quasi‐Solid‐State System

Hierarchically structured zeolites (HSZs) have gained much academic and industrial interest owing to their multiscale pore structures and consequent excellent performances in varied chemical processes. Although a number of synthetic strategies have been developed in recent years, the scalable production of HSZs single crystals with penetrating and three-dimensionally (3-D) interconnected mesopore systems but without using a mesoscale template is still a great challenge. Herein, based on a steam-assisted crystallization (SAC) method, we report a facile and scalable strategy for the synthesis of single-crystalline ZSM-5 HSZs by using only a small amount of micropore-structure-directing agents (i.e., tetrapropylammonium hydroxide). The synthesized materials exhibited high crystallinity, a large specific surface area of 468u2005m(2) u2009g(-1) , and a pore volume of 0.43u2005cm(3) u2009g(-1) without sacrificing the microporosity (≈0.11u2005cm(3) u2009g(-1) ) in a product batch up to 11.7u2005g. Further, a kinetically controlled nucleation-growth mechanism is proposed for the successful synthesis of single-crystalline ZSM-5 HSZs with this novel process. As expected, compared with the conventional microporous ZSM-5 and amorphous mesoporous Al-MCM-41 counterparts, the synthesized HSZs exhibited significantly enhanced activity and stability and prolonged lifetime in model reactions, especially when bulky molecules were involved.

Quantitative Analysis of the Relationship Between Microstructures and Thermal Conductivity for YSZ Coatings

The thermal conductivities of as-sprayed yttria-stabilized zirconia thermal barrier coating prepared by atmospheric plasma spraying at different temperatures are investigated based on quantitative microstructural analysis. Multiple linear regression is used to develop quantitative models which describe the relationship between multiple elements such as porosity, grain boundary density, monoclinic phase content, temperature and thermal conductivity. Results reveal that the thermal conductivity of the coating is mainly determined by the porosity and grain boundary density below 300xa0°C and by the monoclinic phase content above 800xa0°C. Furthermore, based on the significance testing analysis, the confidence interval under a confidence level of 95% at different temperatures enables researchers to predict the thermal conductivity based on microstructural information.

Effect of Microstructure on the Thermal Conductivity of Plasma-Sprayed Al2O3-YSZ Coatings

The microstructures of three atmospheric plasma-sprayed (APS) Al2O3-ZrO2 coatings were investigated using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The differences in the microstructures of the three Al2O3-ZrO2 coatings, including their phase compositions, cracks, pores, grain sizes, and solid solutions, were analyzed in detail. A close relationship was observed between the thermal conductivities of the coatings and the microstructures, and the Al2O3-YSZ coatings with more spherical pores, fewer vertical cracks, and finer grains exhibited the lowest thermal conductivity of 0.91xa0W/m·K. Compared with YSZ coatings, Al2O3-YSZ coatings can exhibit lower thermal conductivity, which may be attributed to the formation of an amorphous phase, smaller grains, and Al2O3-YSZ solid solution.