Quan Deng

Ag nanoparticle decorated nanoporous ZnO microrods and their enhanced photocatalytic activities.

Nanostructured Ag nanoparticles (Ag-NPs)/nanoporous ZnO micrometer-rods (n-ZnO MRs) have been synthesized by a two-step method. The n-ZnO MRs was initially prepared by solvothermal-assisted heat treatment. The rods had the diameter ranged from 90 to 150 nm and length between 0.5 and 3 μm. They were found to be porous and were composited of ZnO nanopartiles with size of about 20 nm. In the second stage, Ag-NPs with a diameter of 20-50 nm were anchored onto the surface of the as-prepared n-ZnO MRs by a photoreduction method. The Ag-NPs/n-ZnO MRs were evaluated for their ability to degrade methylene blue (MB) solution under visible to ultraviolet (UV) light irradiation. The rate of degradation of the as-prepared Ag-NPs/n-ZnO MRs was more than twice and nearly 5.6 times faster than that of using bare n-ZnO MRs under the UV and solar light irradiation, respectively. The formation of Schottky barriers in the regions between the Ag-NPs and n-ZnO MRs had improved the charge separation and consequently enhanced the efficiency of the degradation process. Moreover, the as-prepared hybrid structure exhibited high photostability, and 98% of degradation efficiency could be maintained even after being used five times. This endurance was attributed to the retardation of photocorrosion of ZnO as a result of the low concentration of surface defects in the as-prepared n-ZnO MRs. It also minimized the surface defects of the as-prepared n-ZnO MRs and consequently further inhibited the photocorrosion of ZnO when the deposited Ag-NPs were much more inclined to combine with the chemisorbed oxygen.

Microwave-Assisted Fabrication of Nanoparticulate TiO2 Microspheres for Synergistic Photocatalytic Removal of Cr(VI) and Methyl Orange

High yield production of micro/nanostructured nanoparticulate TiO2 microspheres (NTMs) via a facile microwave-assisted hydrothermal approach was investigated. The rapid and uniform microwave heating could reduce the reaction time to 30 min, an order of magnitude shorter than that of conventional hydrothermal methods. The characterization data confirmed that the resultant NTMs were highly uniform in size, having an average diameter of ∼0.5 μm. The obtained NTMs were found to be constructed by well-crystallized anatase phase nanoparticles ranging from 5 to 10 nm that can be readily controlled by the microwave radiation temperature. Nitrogen sorption isotherm analysis revealed that the obtained NTMs possessed abundant mesoporous structures with a high specific surface area of 124 m(2) g(-1). An in situ self-aggregation formation process under controllable pH in presence of urea was proposed. The results obtained from the application of NTMs for simultaneous photocatalytic decontamination of Cr(VI) and methyl orange (MO) demonstrated a strong synergistic effect that dramatically enhanced both Cr(VI) reduction and MO oxidation removal efficiencies. This work not only enriched the synthesis methods of the micro/nanostructured TiO2, but also provided a new means to improve the photocatalytic efficiency via structural-induced synergistic effect, applicable to the other catalysis systems.

A Versatile Method for Controlled Synthesis of Porous Hollow Spheres

A versatile method was developed to synthesize nickel silicate, silica, and silica-nickel composite porous hollow spheres by using silica spheres as templates. In the preparation, silica spheres were treated with a mixture of NiSO(4)·6H(2)O and NH(3)·H(2)O. The nickel-based ingredient reacted with the silica to form a shell while the alkaline solution could remove the silica core, thus forming the nickel silicate hollow spheres. After these spheres were further treated with hydrogen in reduction or with HCl in etching, they became silica-nickel hollow spheres or silica hollow spheres, respectively. The sizes of these hollow spheres depended on the concentration of the precursor. Our investigation also found that their surface properties or magnetic properties could be tailored by adjusting the fabrication parameters.

Synthesis and characterization of nanostructured Fe3O4 micron-spheres and their application in removing toxic Cr ions from polluted water

We present a simple and effective method for the synthesis of nanostructured Fe(3)O(4) micron-spheres (NFMSs) by annealing hydrothermally formed FeCO(3) spheres in argon. The phase structure, particle size, and magnetic properties of the product have been characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and by means of a superconducting quantum interference device (SQUID). The results have shown that the as-obtained NFMSs have a diameter of about 5 μm and are composed of nanometer-sized porous lamellae. The NFMSs have a large specific surface area (135.9 m(2) g(-1)), reductive Fe(2+) incorporated into their structure, and intense magnetic properties. These properties suggest that NFMSs have potential application in removing toxic Cr(6+) ions from polluted water. At 25°C, each gram of NFMSs product can remove 43.48 mg of Cr(6+) ions, as compared to just 10.2 mg for nanometer-sized Fe(3)O(4) and 1.89 mg for micron-sized Fe(3)O(4). The enhanced removal performance can be ascribed to the structural features. Moreover, the Cr(6+) ion removal capacity of the NFMSs can reach up to 71.2 mg g(-1) at 50°C. The influencing parameters in the removal of Cr(6+) ions, such as contact time, pH, and temperature, have been evaluated. The Cr(6+)-removal mechanism has been investigated. We have found that the NFMSs product not only serves as an effective adsorbent to remove toxic Cr(6+) ions from polluted water, but also as an effective reductant in reducing the adsorbed toxic Cr(6+) ions to much less toxic Cr(3+) through the Fe(2+) incorporated into its structure.

A facile synthesis of single crystal TiO2 nanorods with reactive {100} facets and their enhanced photocatalytic activity

High-energy {100} faceted single crystal TiO2 nanorods were synthesized by a facile hydrothermal method. An interesting phase transition from the orthorhombic hydrogen titanate to anatase TiO2 was observed during the reaction process. A structural formation model of the TiO2 nanorods was proposed based on experimental evidence. The resultant {100} faceted TiO2 nanorods exhibited considerably enhanced photocatalytic activity towards degradation of organic pollutants and removal of heavy metal ions owing to the special one-dimensional structure with the reactive {100} facets, thus showing a great potential in the field of water treatment. At the same time, the synthetic route provided guidance for the synthesis of high-energy {100} facets using EDTA and urea as effective modifiers. This approach may be extended to synthesize other functional oxide crystals with well-defined morphologies and to increase the percentages of certain exposed facets.

Photocatalytic degradation of 2,4,4′-trichlorobiphenyl into long-chain alkanes using Ag nanoparticle decorated flower-like ZnO microspheres

Toxic 2,4,4′-trichlorobiphenyl (PCB28) was photocatalytically degraded by the action of Ag nanoparticle decorated nanosheet-assembled ZnO microspheres via a new photocatalytic degradation pathway. The outright degradation into long-chain alkanes via ring-opening reactions was demonstrated by gas chromatography-mass spectrometry.

Micro/Nanostructured α-Fe2O3 with Structural Enhanced Removal Capacity of Cr(VI) Ions

We have succeeded in preparing micro/nanostructured α-Fe2O3 spheres (MNFSs). The resulted MNFSs have an average diameter of about 5 µm, and are constructed by subunits of interlinked and elongated particles with a diameter of 20~60 nm. MNFSs show an obviously structural enhanced Cr(VI) removal capacity (5.88 mg/g) compared with nanoscaled (0.81 mg/g) and microscaled α-Fe2O3 (0.1 mg/g) due to its high specific surface area together with the special porous structure. Moreover, MNFSs show good availability of reusing to remove Cr(VI) ions.