Xiguang Han

Synthesis of Titania Nanosheets with a High Percentage of Exposed (001) Facets and Related Photocatalytic Properties

Anatase TiO(2) nanosheets with highly reactive (001) facets exposed have been successfully synthesized by a facile hydrothermal route, taking advantage of a specific stabilization effect of fluorine ion on (001) facets. The percentage of highly reactive (001) facets in such TiO(2) nanosheets is very high (up to 89%). In addition, the as-prepared TiO(2) nanosheets exhibit excellent activity in the photocatalytic degradation of organic contaminants.

Synthesis of Tin Dioxide Octahedral Nanoparticles with Exposed High-Energy {221} Facets and Enhanced Gas-Sensing Properties

National Natural Science Foundation of China [20725310, 20721001, 20673085, 20801045]; National Basic Research Program of China [2007CB15303, 2009CB939804]

Enhancing the Photocatalytic Activity of Anatase TiO2 by Improving the Specific Facet-Induced Spontaneous Separation of Photogenerated Electrons and Holes

Recently, it has been proven that directional flow of photogenerated charge carriers occurs on specific facets of TiO(2) nanocrystals. Herein, we demonstrate that the photocatalytic activity of anatase TiO(2) nanocrystals in both photoreduction and photooxidation processes can be enhanced by selectively depositing Pt nanoparticles on the {101} facets, which strengthens spontaneously surface-induced separation between photogenerated electrons and holes in the photocatalysis process. An optimal ratio of the oxidative {001} facets to the reductive {101} facets exists with regard to the photocatalysis of the faceted TiO(2) nanocrystals, and this is crucial for balancing the recombination and redox reaction rates of photogenerated electrons and holes. The present work might help us gain deeper insight into the relation between the specific surface of semiconductor photocatalysts and their photocatalytic activities and provides us with a new route to design photocatalysts with high photocatalytic activity.

Solid state precursor strategy for synthesizing hollow TiO2 boxes with a high percentage of reactive {001} facets exposed

Three-dimensional, hollow, anatase TiO(2) boxes, each was enclosed by six single-crystalline TiO(2) plates exposed with highly reactive {001} facets, were facilely obtained by calcining a cubic TiOF(2) solid precursor at 500-600 °C. The formation of such particular nanostructures is attributed to the hard self-template restriction and the adsorption of F(-) ions from the TiOF(2).

Synthesis of Concave Palladium Nanocubes with High‐Index Surfaces and High Electrocatalytic Activities

National Natural Science Foundation of China[20725310, 21021061, 21073145]; National Basic Research Program of China[2007CB815303, 2011CBA00508]

Controlled Synthesis and Enhanced Catalytic and Gas‐Sensing Properties of Tin Dioxide Nanoparticles with Exposed High‐Energy Facets

A morphology evolution of SnO(2) nanoparticles from low-energy facets (i.e., {101} and {110}) to high-energy facets (i.e., {111}) was achieved in a basic environment. In the proposed synthetic method, octahedral SnO(2) nanoparticles enclosed by high-energy {111} facets were successfully synthesized for the first time, and tetramethylammonium hydroxide was found to be crucial for the control of exposed facets. Furthermore, our experiments demonstrated that the SnO(2) nanoparticles with exposed high-energy facets, such as {221} or {111}, exhibited enhanced catalytic activity for the oxidation of CO and enhanced gas-sensing properties due to their high chemical activity, which results from unsaturated coordination of surface atoms, superior to that of low-energy facets. These results effectively demonstrate the significance of research into improving the physical and chemical properties of materials by tailoring exposed facets of nanomaterials.

Carbonate ions-assisted syntheses of anatase TiO2 nanoparticles exposed with high energy (001) facets

Anatase TiO2 nanoparticles exposed with a remarkable amount (60%) of high-energy (001) facets were synthesized via a fluorine-free hydrothermal route, using K-titanate nanowires as a precursor and urea as a surface regulator. The carbonate ions were found to play a key role in the formation of the exposed (001) facets.

Controlling the morphologies of WO3 particles and tuning the gas sensing properties

The monodisperse triclinic WO3 nanoparticles with exposed (001), (100) and (010) facets have been successfully synthesized via a simple hydrothermal route with the assistance of tartaric acid. The percentage of exposed facets can be regulated by changing the amount of tartaric acid. On the bases of the structural analysis and gas sensing results, we indicated that the monodisperse WO3 nanoparticles with exposed more percentage of (010) facets exhibit better gas sensing to 1-butylamine.

Control of Anatase TiO2 Nanocrystals with a Series of High-Energy Crystal Facets via a Fuorine-Free Strategy

The shape of it: A series of anatase TiO(2) nanocrystals with exposed high-energy {001} facets or high-index {103}, {102} facets and/or low-energy {101} facets were successfully synthesized via a fluorine-free route, and crystal-facet-dependent photodegradation activities were found to follow the sequence of {001}>{102}≈{103}>{101} (see picture; the scale bars are 200 nm).

Intense and wavelength-tunable photoluminescence from surface functionalized MgO nanocrystal clusters

We report fancy brilliant photoluminescence (PL) from surface functionalized MgO nanocrystal clusters (NCs). Single-crystal-like MgO NCs were prepared by a simple one-pot pyrolysis method in the mixed organic solvent of octylamine (OTA) and oleic acid (OA) using magnesium acetate as a precursor. Under the chemical equilibrium of etching and re-growth with the assistance of OA, the MgO products were surface functionalized. It was found that such surface functionalized MgO NCs exhibited intense visible light PL with high PL thermal-stability, and the apparent quantum yield was as high as 19 ± 1%. In addition, through controlling the synthetic temperature and the reaction time, the functionalized surfaces of MgO NCs were facilely tuned, resulting in the tuneable wavelength of the PL from blue-violet to yellow. Different low-coordinated oxygen sites, capping OA and carbonate species on the surface of the MgO nanocrystals were thought to be the origin of PL at different wavelengths. Considering the intense PL, high PL stability at ambient conditions, low cost and low toxicity, such MgO NCs might have potential applications in medicine and biology as a new kind of fluorescent label.