Yuguo Xia

Electrospun flexible self-standing γ-alumina fibrous membranes and their potential as high-efficiency fine particulate filtration media

Novel self-standing γ-alumina fibrous membranes with good flexibility have been successfully fabricated for the first time using an electrospinning technique. The γ-alumina membranes were composed of randomly arranged nanofibers with a high aspect ratio and small diameter (ca. 230 nm). The γ-alumina membranes show high tensile strength (2.98 MPa) and thermal stability (up to 900 °C), which favor their applications in high temperature conditions. Furthermore, the γ-alumina membranes exhibit good filtration performance for 300 nm dioctyl phthalate fine particulate gas filtration. The filtration efficiency is 99.848% and the pressure drop is 239.12 Pa for the membrane calcined at 700 °C with a basis weight of 9.28 g m−2; and the filtration efficiency could be over 99.97% when the basis weight is over 11.36 g m−2, suggesting that the γ-alumina fibrous membrane is a promising candidate for high temperature, fine particulate filtration applications. This work also provides a novel insight into the electrospinning of flexible self-standing inorganic membranes for applications in the separations field.

Enhanced Catalytic Activity in Liquid-Exfoliated FeOCl Nanosheets as a Fenton-Like Catalyst.

A facile liquid-phase exfoliation method to prepare few-layer FeOCl nanosheets in acetonitrile by ultrasonication is reported. The detailed exfoliation mechanism and generated products were investigated by combining first-principle calculations and experimental approaches. The similar cleavage energies of FeOCl (340 mJ m(-2) ) and graphite (320 mJ m(-2) ) confirm the experimental exfoliation feasibility. As a Fenton reagent, FeOCl nanosheets showed outstanding properties in the catalytic degradation of phenol in water at room temperature, under neutral pH conditions, and with sunlight irradiation. Apart from the increased surface area of the nanosheets, the surface state change of the nanosheets also plays a key role in improving the catalytic performance. The changes of charge density, density of states (DOS), and valence state of Fe atoms in the exfoliated FeOCl nanosheets versus plates illustrated that surface atomistic relationships made the few-layer nanosheets higher activity, indicating the exfoliation process of the FeOCl nanosheets also brought about surface state changes.

Facile synthesis of Cu2O nanocages and gas sensing performance towards gasoline

Facile synthesis of uniform cubic cuprous oxide (Cu2O) nanocages has been realized via an acidic etching method without any surfactant at 35 °C. The edge length of the Cu2O nanocages was 80–90 nm, and the thickness of the walls was about 5 nm. Moreover, the wall thickness of these nanocages could be adjusted by changing the reaction temperature. The formation mechanism of the Cu2O nanocages was investigated. Ascorbic acid played an important role in this experiment. Owing to its reducing action, Cu(OH)2 was first reduced to solid Cu2O nanocubes in an aqueous solution. Almost immediately these nanocubes were etched into hollow ones through the acidic etching effect. Eventually, Cu2O nanocages which had thinner walls and more complete structures than those previously mentioned were produced in the presence of hydrazine hydrate (N2H4·H2O). The as-prepared Cu2O nanocages have superior gas sensing performance toward gasoline comparing with the solid Cu2O nanocubes.

Novel PVP/HTA hybrids for multifunctional rewritable paper

Owing to its benefits to reducing paper production and consumption, ink-free rewritable paper has attracted great attention and it is desirable to develop rewritable paper based on its low-cost, robust, and environmentally benign color switching systems. Herein, we report the fabrication of a rewritable paper based on novel poly(vinylpyrrolidone)/hexatungstic acid (HTA) hybrids with fast dual-mode color switching. As-prepared rewritable paper shows fast and reversible colorless-blue or blue-colorless color switching upon photo- or hydroprinting, owing to the fast redox transformations of the unique HTA clusters. More interestingly, the rewritable paper can be used as a template for noble-metal reduction and the noble metal can be deposited on the reduced area of the paper to form well-ordered patterns in high resolution. This rewritable paper can be produced in large scale, and the composition can be facilely tuned with various polyoxometalates or polymers. It may not only be an attractive alternative to current paper prints but also be potentially used for noble-metal reduction to prepare photolithographic circuits and optoelectronic devices.

Preparation of annular TiO2 nanoparticles constructed by high-energy surfaces and enhanced visible-light photocatalytic activity

Controlling overexposed facets with high energy is pivotal for various applications, particularly catalytic reactions which occur on the surfaces of nanostructures. Herein, we report a combined solvothermal and etching method to synthesize anatase TiO2 nanocrystals with energetic exposed facets, which exhibit enhanced visible light photodegradation activity towards RhB. Electron microscopic photographs revealed that the initially prepared nanocrystals had a hierarchical structure stacked by secondary nanoplates, and time dependent experiments proved that the formation process followed an oriented aggregation mechanism and a subsequent grain growth. In addition, quantum mechanical calculations revealed that the etching process could occur along three directions of TiO2 nanocrystals, and the formation of Ti3+ defects was thermodynamically favorable, which was further demonstrated by XPS spectra. The reasons for the enhanced photodegradation activity are also discussed through the production of reactive oxygen species (ROS), which revealed that the adsorption of surface hydroxyls and H2O may be the main reason for this enhancement.

Facile preparation of Prussian blue analogue Co3[Co(CN)6]2 with fine-tuning color transition temperature as thermochromic material

For thermochromic materials, a fine-tuning thermochromic property is always pursued to in order to realize their full potential. However, to date, realizing the fine-tuning still remains a great challenge and is seldom reported. In the present work, the Prussian blue analogue, Co3[Co(CN)6]2, with fine-tuning color transition temperature is synthesized through a facile wet-chemical method. By simply adjusting the amount of sodium citrate in the system, part of the ligand water molecules coordinated to lattice Co(II) can be substituted by citrate, which is confirmed by DFT calculations and experimental results, resulting in a color transition versus temperature as a response to a coordination environmental change of the Co(II). Finally, a fine-tuning color transition temperature from 40 to 80 °C is realized with the color changing from pink to blue upon heating. In addition to the tunable color transition temperature, a high color transition speed and long term stability were also achieved due to the porous and stable lattice structure of Co3[Co(CN)6]2. To the best of our knowledge, this is the first report of a metal–organic framework (MOF) with a fine-tuning reversible thermochromic property, and the present controlled strategy might be expanded to the preparation of other similar materials.

Enhanced charge carrier separation of manganese(II)-doped graphitic carbon nitride: formation of N–Mn bonds through redox reactions

High photogenerated charge carrier recombination restricts the photoactivity of graphitic carbon nitride (g-C3N4), a promising photocatalyst. Herein, MnII doped g-C3N4, obtained through redox reactions between urea and a permanganate in an inert gas, exhibits significantly enhanced photoinduced charge carrier separation and photoactivity. This work opens a new avenue for doping of g-C3N4.