Search

Ag3PO4/Ag4P2O7 photocatalysts were successfully synthesized by microwave-hydrothermal method. Tuning the properties of photocatalysts was achieved using different amount of acetic acid (CH3COOH) and sodium hydroxide (NaOH) to adjust pH value of precursor solution (pH = 4, 7, 10 and 12). The crystal structure, morphology and optical property of samples were characterized and explained. The photocatalytic activity of sample was determined by degradation of rhodamine B (RhB) and methyl orange (MO) under a wavelength range of 350–700 nm irradiation. The results demonstrated that the change in shape of particles was not observed whereas the average particle size was decreased with increasing pH value because of the high hydroxide ions (OH−). The sample synthesized in the solution with the pH of 10 exhibited excellent photocatalytic performance and stability because of the highest surface area and the present of Ag4P2O7 on the surface of particles. The highest photodegradation efficiency was 99.34 and 96.12% by degrading RhB and MO, respectively. The enhancement of photocatalytic performance of Ag3PO4/Ag4P2O7 was discussed. The active species trapping experiments showed that the h+ was the main active species to decompose the dye molecules.

BiOBr/BiOCl flowerlike composites were successfully synthesized in different solutions containing 0.00–1.50 g polyvinylpyrrolidone (PVP) by microwave-assisted hydrothermal method. The as-synthesized BiOBr/BiOCl composites were studied by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, UV–visible diffuse reflection spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy and photocatalysis. In this research, the morphologies of tetragonal BiOBr and tetragonal BiOCl products were transformed from BiOBr/BiOCl microplates without PVP into BiOBr/BiOCl microflowers with 1.00 g added PVP. The BiOBr/BiOCl microflowers have optimal visible light absorption and demonstrate excellent photocatalytic activity in degradation of rhodamine B and salicylic acid under xenon radiation. These composites are promising materials used for wastewater treatment.

Perovskite LaFeO3 nanoparticles were successfully synthesized by microwave plasma method combined with high temperature calcination at 700–1000 °C. The influences of calcination temperature on morphology, crystalline structure, purity and the atomic compositions of samples were studied. The photocatalytic performance of LaFeO3 was evaluated though the photodegradation of Rhodamine B (RhB) under visible light. In this research, the orthorhombic LaFeO3 nanoparticles showed band gaps in the range of 2.15–2.30 eV. The particle size increased with increasing in the calcination temperature, leading to the decreasing in the surface area. The LaFeO3 sample calcined at 900 °C showed the highest photodegradation of 77.8% and the apparent rate constant of 0.0077 min−1 within 180 min because of the narrower of band gap and the higher crystalline degree and oxygen adsorption.

Cubic Ag3PO4, monoclinic LaPO4 and Ag3PO4/LaPO4 samples were successfully synthesized by a one-step microwave-hydrothermal method with and without calcination at high temperature. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrophotometry, X-ray photoelectron spectroscopy, UV–visible spectroscopy and Brunauer-Emmett-Teller surface area analysis. Energy gaps of Ag3PO4 and LaPO4 containing in the Ag3PO4/LaPO4 composites without high temperature calcination were 2.37 eV and 4.23 eV, respectively. Their photocatalytic efficiency in degrading treatment of methyl orange was the highest of 94.0% within 20 min and 95.7% within 60 min controlled by Schottky interface, energy gap, specific surface area, pH of solution, dye concentration and catalytic content. A photocatalytic mechanism of Ag3PO4/LaPO4 composites was also proposed and discussed in detail.

The TiO2 (anatase) films were prepared by sol-gel method using titanium (IV) isopropoxide (TTIP) as a precursor and polyvinylpyrrolidone (PVP) as a polymeric precursor dissolved in different alcohol solvents (methanol, ethanol, isopropanol and 1-butanol) and were heated treatment at 450 °C for 1 h. In this research, the alcohol solvents have significant influence on the morphology, crystalline degree and energy band gap of TiO2. The number of carbon, boiling point, dielectric constant and viscosity of alcohol solvents were the main factor influencing the size of TiO2 nanoparticles. The alcohol solvent with higher boiling point and viscosity, and long length of carbon chain can lead to the smaller crystallite size. The number of carbon and viscosity of solvent and crystallite size can play the important role in the agglomeration of particles. The energy band gaps of the films determined by UV-visible spectroscopy were in the 3.00–3.30 eV range.

Anatase films were deposited on glass substrates by 180, 300, 450 and 500 W microwave for 1.5 min. Upon calcination the 450 and 500 W films at 450 °C for 1 h, additional rutile phase was detected by X-ray diffraction (XRD). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed morphologies of the films which were composed of a number of nanoparticles orientated in different directions with the lowest roughness for the film synthesized by 450 W microwave combined with the high temperature calcination. Band gaps of the films without calcination determined by UV–visible spectroscopy were 3.30–3.35 eV and were considerably decreased to 2.92–3.20 eV by the high temperature calcination.

PbMoO4 and PbWO4 were successfully synthesized by microwave radiation using different lead salts (acetate, chloride, nitrate and sulfate) and Na2MO4 (M = Mo, W) in propylene glycol. The products were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), Fourier transform infrared (FT-IR), Raman spectroscopy and photoluminescence (PL) spectroscopy. In this research, morphologies, crystallization and photoluminescence of the products were influenced by the kinetics of anions, including the detection of M–O (M = Mo, W) stretching modes in the (MO4)2− tetrahedrons. Photoluminescence of PbMoO4 synthesized from Pb(NO3)2 and of PbWO4 synthesized from PbCl2 showed the strongest blue emission due to the electronic diffusion in tetrahedrons at room temperature.