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111.
Asif Nisar Muhammad Saeed Muhammad Usman Majid Muneer Muhammad Adeel Iltaf Khan Javaid Akhtar 《国际化学动力学杂志》2020,52(10):645-654
Photodegradation of organic pollutants strongly depends on design of metal oxide semiconductor photocatalysts. Graphene, if composited with ZnO, can effectively enhance its photocatalytic performance for the eradication of pollutants from aqueous medium. Here in, ZnO-rGO is reported as highly active catalyst for degradation of methylene blue. A 200-mg/L solution of methylene blue dye was completely degraded within 1 h in comparison to 74% and 56% degradation over ZnO and rGO, respectively. The commonly used mechanisms of heterogeneous catalytic reactions, the Langmuir-Hinshelwood mechanism, and the Eley-Rideal mechanisms, were used to describe the reaction kinetics. The Langmuir-Hinshelwood mechanism was found as more favorable in this study. Apparent activation energy, Eap, true activation energy, ET, entropy, ΔS, and enthalpy, ΔH were calculated as 36.2 kJ/mol, 13.1 kJ/mol, 197.5 J/mol, and 23.1 kJ/mol, respectively. 相似文献
112.
A facile hydrothermal method to synthesize flower-like Sn-doped ZnO (FLSn-ZnO) nanostructures is described. The obtained hierarchical architectures of FLSn-ZnO are found to be assembled with abundant regular-shaped nanosheets and nanoparticles. A possible formation mechanism is proposed on the base of a series of control experiments. The tests show that FLSn-ZnO architectures exhibit higher photocatalytic activity in the degrading Rhodamine B and tetracycline aqueous solution than pure ZnO under UV-light irradiation. And photocurrent response and photoluminescence of ZnO and FLSn-ZnO demonstrates that in photocatalytic performance, the latter is higher. 相似文献
113.
Mahboubeh Ghasemian Dazmiri Heshmatollah Alinezhad Zinatossadat Hossaini Ahmad R. Bekhradnia 《应用有机金属化学》2020,34(9):e5731
In this research, Fe3O4/ZnO magnetic core-shell nanoparticles (Fe3O4/ZnO MCNPs) were synthesized through a green method using Petasites hybridus rhizome water extract as a reducing and stabilizing agent. The morphology and size of the Fe3O4/ZnO MCNPs was identified by X-ray diffraction, scanning electron microscopy, and Energy-dispersive X-ray spectroscopy (EDX) analysis. The catalytic activity of the Fe3O4/ZnO MCNPs was evaluated in the efficient and green preparation of pyran derivatives in excellent yield using three-component reactions of dimedone, aldehydes, and malononitrile in ethanol at room temperature. The ability of some synthesized compounds to scavenge the 2,2-diphenyl-1-picrylhydrazyl radical was measured and the results proved this observation. Moreover, the antimicrobial activity of some synthesized compounds was proved by employing the disk diffusion test on Gram-positive and Gram-negative bacteria. The results for the disk diffusion test showed that compounds ( 4c, 4d, 4f and 4g ) prevented bacterial growth. 相似文献
114.
Pure and Sm-doped ZnO nanoparticles were synthesized applying a simple sonochemical method. The nanocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques which confirmed the successful synthesis of the doped sonocatalyst. The sonocatalytic degradation of Acid Blue 92 (AB92), a model azo dye, was more than that with sonolysis alone. The 6% Sm-doped ZnO nanoparticles had a band gap of 2.8 eV and demonstrated the highest activity. The degradation efficiency (DE%) of sonolysis and sonocatalysis with undoped ZnO and 6% Sm-doped ZnO was 45.73%, 63.9%, and 90.10%, after 150 min of treatment, respectively. Sonocatalytic degradation of AB92 is enhanced with increasing the dopant amount and catalyst dosage and with decreasing the initial AB29 concentration. DE% declines with the addition of radical scavengers such as chloride, carbonate, sulfate, and tert-butanol. However, the addition of enhancers including potassium periodates, peroxydisulfate, and hydrogen peroxide improves DE% by producing more free radicals. The results show adequate reusability of the doped sonocatalyst. Degradation intermediates were recognized by gas chromatography–mass spectrometry (GC–MS). Using nonlinear regression analysis, an empirical kinetic model was developed to estimate the pseudo-first-order constants (kapp) as a function of the main operational parameters, including the initial dye concentration, sonocatalyst dosage, and ultrasonic power. 相似文献
115.
Ga and In co‐doped ZnO (GIZO) thin films together with ZnO, In‐doped ZnO (IZO), Ga‐doped ZnO (GZO), and IZO/GZO multilayer for comparison, were grown on corning glass and boron doped Si substrates by PLD. The photoluminescence spectra of GIZO showed a strong white light emission and the current–voltage characteristics showed relatively lower turn‐on voltage and larger forward current. The CIE coordinates for GIZO were observed to be (0.31, 0.33) with a correlated colour temperature of 6650 K, indicating a cool white light, and establishing a possibility of white light emitting diodes. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
116.
The influences of N2 introduction to a sputtering gas on structural and optical properties of vanadium-doped ZnO (VZO) films, grown by using reactive RF magnetron sputtering on a quartz substrate at room temperature, were investigated. In the VZO films, V doping caused to form a large number of O vacancies (VO) and degraded both the c-axis orientation and optical transmittance. While, on the contrary, the ZnO(002) diffraction intensity of 3.5-at.% VZO films increased adding N2 with a partial pressure ratio (αN2) >2% reaching a maximum at αN2 =5%. The average optical transmittance (wavelengths: 450−800 nm) of the 3.5-at.% VZO films was also improved by the N2 introduction and reached 74% at αN2 =5%. As a result of the analyses of the chemical binding states of the incorporated N atoms via the Raman spectroscopy and XPS, it was confirmed that the O sites were substituted by the N atoms and the amount of incorporated N increased by the high V doping. From the above, the N2 introduction was effective to suppress the VO formation even in room-temperature-grown VZO films, so it enables to improve both the c-axis orientation and optical transmittance. 相似文献
117.
Slow-rise and fast-drop current feature of ultraviolet response spectra for ZnO-nanowire film modulated by water molecules
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This study describes the fabrication of ZnO-nanowire films by electro-chemical anodization of Zn foil.The ZnO films are characterized by field emission scanning electron microscopy,X-ray diffraction patterns,and transmission electron microscopy,respectively.The ultraviolet(UV) photo-response properties of the surface-contacted ZnO film are studied through the current evolution processes under different relative humidities.Unlike the usually observed current spectra of the ZnO films,the drop time is shorter than the rise time.The photo-conductivity gain G and the response time τ are both increased with the increase of the applied bias.The photo-conductivity gain G is lowered with the increase of the environmental humidity,while the response time τ is increased.These results can be explained by considering three different surface processes:1) the electron-hole(e-p) pair generation by the UV light illumination,2) the following surface O2-species desorption,and 3) the photo-catalytic hydrolysis of water molecules adsorbed on the ZnO surface.The slow-rise and fast-drop current feature is suggested to originate from the sponge-like structure of the ZnO nanowires. 相似文献
118.
Structural and optical properties of 1 at % Al-doped Zn1−xMgxO (x=0–8%) powders prepared by sol–gel method were systematically investigated by means of X-ray diffraction, scanning electron microscopy, ultraviolet–visible absorbance measurement, photoluminescence and Raman scattering spectra. All the powders retained the hexagonal wurtzite structure of ZnO. The band gap and near band emission energies determined from absorbance and photoluminescence spectra increased linearly with increasing Mg content, respectively, which implied that the Mg worked effectively on ZnO band gap engineering, irrespective of Al codoping. However, according to the PL and Raman scattering studies, for the sample of x=8%, the Al doping efficiency was decreased by higher Mg codoping. On the other hand, the effect of Mg codoping on photocatalytic degradation of methylene orange was explored experimentally. The substitution of Mg ions at Zn sites shifted the conduction band toward higher energies and then enhanced the photocatalytic activity, while the incorporation of interstitial Mg ions and decreased Al doping efficiency for higher Mg doping sample (x=8%) reduced the photocatalytic activity. 相似文献
119.
讨论了Zn O对Ba Sm2Ti4O12介质陶瓷烧结机制和微波介电性能的影响。结果表明:Zn O添加能推动Ba Sm2Ti4O12微波介质陶瓷的烧结,可至少将其烧结温度降低至1 280℃。当添加过多的Zn O时,Zn2+会进入晶格,可能导致晶格畸变,由此造成颗粒间产生微小孔隙及晶格内形成许多缺陷,降低了材料的εr和Q×f值。含0.5 wt%Zn O的Ba Sm2Ti4O12试样在1 280℃烧结时,综合介电性能最好:εr=76.46,Q×f=6 334 GHz。 相似文献
120.
M. Benhalili A. Tiburcio-Silver A. Avila-Garci A. Tavir Y. S. Ocak M. S. Ai C. E. Benouis 《半导体学报》2015,36(8):083001-7
We synthesized the pure and indium-doped (IZO) ZnO films with a facile composition control spray pyrolysis route. The substrate temperature (Ts) and In-doping effects on the properties of as-grown films are investigated. The X-ray pattern confirms that the as-synthesized ZnO phase is grown along a (002) preferential plane. It is revealed that the crystalline structure is improved with a substrate temperature of 350 ℃. Moreover, the morphology of as-grown films, analyzed by AFM, shows nanostructures that have grown along the c-axis. The (3 × 3μm2) area scanned AFM surface studies give the smooth film surface RMS < 40 nm. The UV-VIS-IR measurements reveal that the sprayed films are highly transparent in the visible and IR bands. The photoluminescence analysis shows that the strong blue and yellow luminescences of 2.11 and 2.81 eV are emitted from ZnO and IZO films with a slight shift in photon energy caused by In-doping. The band gap is a bit widened by In-doping, 3.21 eV (ZnO) and 3.31 eV (IZO) and the resistivity is reduced from 385 to 8 Ω ·m. An interesting result is the resistivity linear dependence on the substrate temperature of pure ZnO films. 相似文献