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[Display omitted] • Using the USP method, Au supported ZnO particles were generated. • Au nanoparticles were dispersed inner and outer portions of the ZnO particles. • The optimal photocatalytic activity occurs with 0.1 mass% Au supported. • The optimal photolysis activity was exhibited at a dose of 10 mg of Ag/ZnO. Environmental pollution by organic dyes used in industry is a serious problem in developing countries. Environmentally friendly treatment methods are being studied because conventional methods require chemical or additional decomposition treatment. In particular, oxidation via a photocatalyst is a promising alternative due to its chemical and physical stabilities and low cost. However, electron-hole recombination limits the photocatalytic activity in semiconductor photocatalysts such as ZnO and TiO 2. This study investigates control of electron-hole recombination of the photocatalyst by loading Au on ZnO (Au/ZnO). Using the Ultrasonic Spray Pyrolysis (USP) method, Au/ZnO particle generation is easily achieved under various conditions. XRD analysis confirms the crystal peaks of ZnO and Au. The EDX mapping and STEM images of the particles show that the Au crystals are well dispersed in the inner and outer portions of ZnO. The photocatalytic decomposition rate of organic dye (Rhodamine-B) is faster than that of ZnO in all Au/ZnO particles, and the best photocatalytic activity occurs in particles with 0.1 mass% Au supported on ZnO particles. In addition, optimal photolysis activity occurs in 100 mL of 5 mg/L RhB aqueous solution and 10 mg dose of Au/ZnO particles. [ABSTRACT FROM AUTHOR]

ZnO nanoparticles were synthesized in a horizontal three zones furnace at 500 °C using different zinc nitrate hexahydrate concentrations (0.01 M, 0.1 M, and 1.0 M) as a reactive precursor solution by air assisted Ultrasonic Spray Pyrolysis (USP) method. The physico-chemical, structural and functional properties of synthesized ZnO nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), Brunauer, Emmett and Teller (BET) method, UV–vis spectroscopy and photoluminescence (PL) measurements. Also, the photocatalytic activities of ZnO synthesized from different precursor concentrations were evaluated by removal rate of methyleneblue (MB) under UV irradiation (365 nm) at room temperature. SEM revealed two types of ZnO nanoparticles: a quasi-spherical, desert-rose like shape of the secondary particles, which does not change significantly with the increasing of precursor solution concentration as well as some content of the broken spheres. Increasing the precursor solution concentration leads to the increase in the average size of ZnO secondary particles from 248 ± 73 to 920 ± 190 nm, XRD reveals the similar tendency for the crystallite size which changes from 23 ± 4 to 55 ± 12 nm in the analyzed region. HRTEM implies the secondary particles are with hierarchical structure composed of primary nanosized subunits. The PL spectra imply a typical broad peak of wavelength centered in the visible region exhibiting the corresponding red-shift with the increase of solution concentration: 560, 583 and 586 nm for the 0.01, 0.1 and 1.0 M solution, respectively. The reported results showed the photocatalytic efficiency of ZnO nanoparticles was enhanced by increased precursor concentration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag-supported ZnO particles were generated using the spray pyrolysis method. • Ag/ZnO particles with high efficiency showed twice the photolysis activity of P25. • The generated particles were recovered by gravity sedimentation and reused. • Change of Ag nanoparticles was not observed after the photolysis experiment. Environmental issues caused by the rapid industrialization and urbanization of modern society are a serious problem. For example, conventional wastewater treatment technologies such as adsorption, coagulation, and filtration are expensive and cannot completely treat the discharge of organic pollutants in industrial wastewater. A promising alternative is the decomposition treatment of organic pollutants using an eco-friendly metal oxide photocatalyst. However, the rapid recombination of excited electron-holes limits the photolytic activity of semiconductor photocatalysts. This study investigates the inhibition of electron-hole recombination by supporting Ag nanoparticles on a ZnO photocatalyst. Ag/ZnO particles are generated under various conditions using ultrasonic spray pyrolysis. XRD analysis confirms the presence of Ag and ZnO crystal peaks in the generated particles. EDX mapping and STEM images show that Ag nanoparticles are well dispersed in ZnO. The photolysis rate of organic dye (rhodamine-B) is faster than that of ZnO in all Ag/ZnO particles, and particles with a 0.2 mass% silver nitrate supported on ZnO particles exhibit twice the photolysis activity of P25. Additionally, the optimal photolysis activity in 100 mL of 5 mg/L rhodamine-B aqueous solution with 10 mg of Ag/ZnO particles are confirmed and had excellent persistence and stability even during 7 reuses. [ABSTRACT FROM AUTHOR]