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The heterostructure Ag@WO3–x(x=0.1 or 1) composites with high selectivity for breaking azo-bond were obtained by in situ reduction of Ag2WO4. The crystal structure and morphology of Ag@WO3–x were characterized by X-ray powder diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscope(TEM). The residue solution of methyl orange(MO) after degradation was tested by gas chromatograph mass spectrometer (GCMS) to analyze the exact components. The results indicate that the products after degradation are N,N-dimethylaniline, N,N-dimethyl-p-phenylenediamine and sulfanilic acid. This is caused by specific breaking of azo-bond in MO. The azo-bond breaking of MO by Ag@WO3–x could occur in dark without any light illumination. Therefore, we proposed a possible mechanism for this azo-bond breaking reaction based on the reaction condition and results.

Magnetic Fe3O4 nanospheres with a average diameter of (201±0.5) nm were synthesized at 200 °C via a solvothermal method. The as-synthesized Fe3O4 nanospheres performed an efficiency in the Fenton degradation of xylenol orange with a degradation rate of 90%—95%. Additionally, the catalyst was easily recyclable and the recovery rate was greater than 90%. Moreover, the catalyst could be regenerated under an ultrasonic treatment, and the degradation performance remained essentially the same. More importantly, the degradation rate varied with respect to the amount of H2O2 and the pH of the best reaction process. And the reaction efficiency was achieved with 1.5 mL of H2O2 in an acidic environment.

A facile approach was developed to prepare highly dispersed TiO2 nanoparticles with selected phase. The crystallization phase of the nanoparticles can be easily tuned from anatase to rutile by the dosage of hydrochloric acid in the reaction system. The crystallite size of the as-prepared anatase TiO2 nanoparticles was ca. 3.2 nm with high dispersion. A transparent TiO2 colloid was obtained by dispersing the as-prepared anatase TiO2 nanoparticles in deionized water without any organic additives added. The concentration of TiO2-H2O colloid can be as high as 1600 g/L. The optical transmittance of TiO2-H2O colloid with a low concentration was nearly 100% in the visible region. Furthermore, anatase TiO2 nanoparticles(TiO2-NPs) showed superior photocatalytic performance compared to rutile TiO2-NPs.