T. Xian

Sonocatalytic degradation of RhB over LuFeO3 particles under ultrasonic irradiation.

LuFeO3 particles with an average particle size of ∼200 nm were synthesized via a polyacrylamide gel route. The sonocatalytic activity of LuFeO3 particles was evaluated by the degradation of Rhodamine B (RhB) under ultrasonic irradiation, revealing that they exhibit a good sonocatalytic activity. The effects of various experimental factors including ultrasonic frequency (f), reaction solution temperature (T), catalyst dosage (Ccatalyst), initial RhB concentration (CRhB), and pH value on the sonocatalysis efficiency were investigated. It is found that the former four factors have an important influence on the sonocatalytic degradation of RhB, where the best degradation conditions are obtained to be f=60 kHz, T=40 °C, Ccatalyst=4 g L(-1), and CRhB=5 mg L(-1). The pH value has a relatively small effect on the sonocatalytic degradation of RhB compared with other experimental factors. Hydroxyl (·OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing that they are produced over the ultrasonic-irradiated LuFeO3 particles. The addition of ethanol leads to a quenching of ·OH radicals and a simultaneous decrease in the RhB degradation. This indicates that ·OH radicals are the primary active species responsible for the dye degradation.

Fabrication of 0-3 type manganite/insulator composites and manipulation of their magnetotransport properties

In order to promote the technological applications of perovskite manganites, a great fundamental interest has been devoted to tailoring and/or enhancing their magnetotransport properties. Design and fabrication of manganite-based nanocomposites offer great potential to tailor the magnetotransport properties. In this work, we illustrate the promising concept of 0-3 type manganite/insulator composites (where manganite nanoparticles are uniformly and discretely embedded in a three-dimensional-connectivity insulator matrix) through the example of the La0.67Ca0.33MnO3 (LCMO)/MgO system. We present a promising strategy, which is based on the creation of core (LCMO)–shell (MgO) composite powders, for the synthesis of 0-3 type LCMO/MgO composites. A modified polyacrylamide gel method has been developed to prepare the core-shell structured LCMO/MgO composite powders. Besides its ability to create well-defined core-shell composite structures, the present gel method also allows the production of nanopowders with uni...

Preparation of BiFeO 3 -graphene nanocomposites and their enhanced photocatalytic activities

BiFeO3 nanoparticles were prepared via a polyacrylamide gel route. BiFeO3-graphene nanocomposites were fabricated by mixing BiFeO3 nanoparticles and graphene into absolute ethanol solution followed...BiFeO3 nanoparticles were prepared via a polyacrylamide gel route. BiFeO3-graphene nanocomposites were fabricated by mixing BiFeO3 nanoparticles and graphene into absolute ethanol solution followed by thermal drying. The TEM observation demonstrates that the BiFeO3 nanoparticles are well anchored onto graphene sheets. The photocatalytic activities of the as-prepared samples were evaluated by the degradation of methyl orange (MO) under simulated sunlight irradiation. Compared to bare BiFeO3 nanoparticles, BiFeO3-graphene nanocomposites exhibit enhanced photocatalytic activity. The outstanding photocatalytic performance is mainly ascribed to the efficient transfer of photogenerated electrons from BiFeO3 to graphene, thus leading to an increased availability of h+ for the photocatalytic reaction. In addition, hydroxyl (ċOH) radicals were detected by the photoluminescence technique using terephthalic acidas a probe molecule and are found to be produced on the irradiated BiFeO3 and BiFeO3-graphene nanocomposites; in particular, an enhanced yield is observed for the latter.

Graphene-assisted enhancement of photocatalytic activity of bismuth ferrite nanoparticles

Bismuth ferrite (Bi2Fe4O9) nanoparticles were synthesized via a polyacrylamide gel route. Bi2Fe4O9–graphene nanocomposites were fabricated by mixing Bi2Fe4O9 nanoparticles and graphene into absolute ethanol solution followed by thermal drying. Transmission electron microscope observation reveals that Bi2Fe4O9 nanoparticles are well assembled onto graphene sheets. The photocatalytic activity of the prepared samples was evaluated by the degradation of methyl orange under simulated sunlight irradiation, revealing that Bi2Fe4O9–graphene nanocomposites exhibit an enhanced photocatalytic activity compared to bare Bi2Fe4O9 nanoparticles. This can be explained by the fact that the photogenerated electrons are captured by graphene, leading to an increased availability of h+ for the photocatalytic reaction. In addition, it is found that hydroxyl (·OH) radicals, detected by the photoluminescence technique using coumarin as a probe molecule, are produced on the irradiated Bi2Fe4O9 and Bi2Fe4O9–graphene nanocomposite; especially, an enhanced yield is observed for the latter.

Enhanced photocatalytic activity of CaTiO3-graphene nanocomposites for dye degradation

Calcium titanate (CaTiO3) nanoparticles with an average size of 36 nm were synthesized by a polyacrylamide route. CaTiO3-graphene composites were fabricated by mixing CaTiO3 particles and graphene into absolute ethanol, followed by thermal drying. The prepared samples were characterized by x-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and UV-visible diffuse reflectance spectroscopy. Methyl orange (MO) was chosen as the target pollutant to evaluate the photocatalytic activity of the samples under UV irradiation. Our results show that CaTiO3-graphene composites exhibit enhanced photocatalytic activity compared to bare CaTiO3 particles. This can be explained by the effective suppression of electron–hole pair recombination due to the transfer of photogenerated electrons from the conduction band of CaTiO3 to graphene sheets. Hydroxyl (•OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing an enhanced yield on the irradiated CaTiO3-graphene composites. Ethanol was used as a •OH scavenger to investigate its effect on photocatalytic efficiency as well as on •OH radical yields. Based on the experimental results, we suggest that •OH radicals are the dominant active species responsible for the dye degradation.

Synthesis of spherical Bi 2 WO 6 nanoparticles by a hydrothermal route and their photocatalytic properties

Spherical Bi2WO6 nanoparticles were synthesized by a hydrothermal route. SEM observation shows that the size of the particles ranges from 60 to 120 nm and the average particle size is ∼85 nm. TEM investigation shows that the particles are made up of subgrains with size of 5-10 nm. The bandgap energy of the particles is measured to be 2.93 eV by ultraviolet-visible diffuse reflectance spectroscopy. RhB was chosen as the target pollutant to evaluate the photocatalytic activity of the particles under irradiation of simulated sunlight, revealing that they exhibit an obvious photocatalytic activity. The effects of ethanol, KI, and BQ on the photocatalytic efficiency of Bi2WO6 particles towards the RhB degradation were investigated. It is observed that ethanol has no effect on the photocatalytic degradation of RhB, whereas KI and BQ exhibit a substantial suppression of RhB degradation. No hydroxyl (•OH) is found, by the photoluminescence technique using terephthalic acid as a probe molecule, to be produced over the irradiated Bi2WO6 particles. Based on the experimental results, photoexcited hole (h+) and superoxide (•O2-) are suggested to be the two main active species responsible for the dye degradation, while •OH plays a negligible role in the photocatalysis.

A new photocatalyst of LuFeO3 for the dye degradation

A polyacrylamide gel route was introduced to synthesize LuFeO3 particles, where the effects of calcination temperature, calcination time and chelating agent on the products were investigated. By varying the experimental conditions, several LuFeO3 samples with sphere-, ellipsoid- and worm-like morphologies and average particle sizes of 200?270 nm were prepared. The photocatalytic activity of LuFeO3 samples was evaluated by degrading rhodamine B (RhB) under simulated-sunlight irradiation, revealing that they exhibit a pronounced photocatalytic activity. The effects of p-benzoquinone (BQ), ethanol and oxalic acid (OA) on the photocatalytic efficiency were investigated. It is observed that BQ has almost no effect on the photocatalytic degradation of RhB, ethanol exhibits a substantial suppression of RhB degradation, while OA significantly enhances the photocatalytic efficiency. Hydroxyl (?OH) radicals were examined by fluorimetry using terephthalic acid as a probe molecule, and are found to be produced over the simulated-sunlight irradiated LuFeO3 particles. The addition of ethanol leads to a quenching of ?OH radicals, whereas the yield of ?OH radicals is highly increased on addition of OA. Based on the experimental results, ?OH radicals are suggested to be the dominant active species responsible for the dye degradation, while superoxide (?O2?) radicals play a negligible role in the photocatalysis.

Growth of BiFeO 3 microcylinders under a hydrothermal condition

BiFeO3 microcylinders were synthesized via a hydrothermal condition. SEM observation reveals that with increasing the hydrothermal reaction time from 6 to 15 h, the microcylinders grow from ∼0.7 to ∼4.1 µm in height, whereas their diameter remains to be 3.7-3.8 µm with a minor change. The microcylinders are mainly made up of sphere-like grains of 100-150nm in size. A possible growth mechanism of the BiFeO3 microcylinders is proposed. The photocatalytic activity of the as-prepared BiFeO3 samples was evaluated by the degradation of acid orange 7 under simulated sunlight irradiation, revealing that they possess an appreciable photocatalytic activity. Magnetic hysteresis loop measurement shows that the BiFeO3 microcylinders exhibit a typical antiferromagnetic behavior at room temperature.

Polyacrylamide Gel Preparation, Photocatalytic Properties, and Mechanism of BiVO 4 Particles: Polyacrylamide Gel Preparation, Photocatalytic Properties, and Mechanism of BiVO 4 Particles

BiVO4 particles were prepared by a polyacrylamide gel method and characterized by X-ray diffraction, scanning electron micros- copy, and ultraviolet-visible diffuse reflectance spectroscopy.The results demonstrate that the as-prepared BiVO4 particles crystallize in a monoclinic scheelite-type structure, are regularly shaped like spheres with a uniform size of ～400 nm, and have a bandgap energy of 2.49 eV. The photocatalytic activity of BiVO4 particles was evaluated by the degradation of methylene blue under simulated sunlight irradiation. The effects of O2, N2, ethanol, and KI on the photocatalytic efficiency were investigated. Hydroxyl radicals (·OH) formed on the catalyst under simulated sunlight irradiation were detected by photoluminescence spectroscopy using terephthalic acid as a probe molecule. The photocatalytic degradation mechanism involved is discussed in detail. Based on the photocatalytic results, hydroxyl radicals and photogenerated h+ are suggested to be the two main active species toward the photocatalytic degradation of methylene blue by BiVO4.

Synthesis and magnetoresistance properties of La 2/3 Ca 1/3 MnO 3 /MgO core-shell nanocomposites

In this work, (1−x)La2/3Ca1/3MnO3(LCMO)/xMgO (x=0, 0.1, 0.2, 0.3, 0.4, 1) core-shell composite particles were first synthesized by a polyacrylamide gel route, and then the obtained composite particles were pelletized and sintered into the bulk composite samples. It is believed that the MgO phase was self-welded to form a three-dimensional-connectivity matrix and the LCMO particles were discretely embedded in the MgO matrix without adhesion. The magnetoresistance (MR) properties of the composite samples were investigated. It is demonstrated that the MR value increases with raising MgO concentration x at low temperatures (T<80 K), and also the low-field sensitivity of MR, defined as d(MR)/dH, gets enhanced for the composites. The enhancement in MR can be attributed to the enhanced spin-polarized tunneling of conduction electrons at the grain boundaries in the composite samples.