Controlled Orientation in a Bio-Inspired Assembly of Ag/AgCl/ZnO Nanostructures Enables Enhancement in Visible-Light-Induced Photocatalytic Performance (original) (raw)
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Journal of Alloys and Compounds, 2014
In this study, AgCl-ZnO nanocomposites were successfully prepared in water by a simple one-pot refluxing method at about 90°C. The X-ray diffraction (XRD) patterns reveal that ZnO has wurtzite hexagonal crystalline phase and its structure does not change by increasing mole fraction of silver chloride. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies represent that with loading silver chloride, remarkable changes in morphology of the nanocomposites take place. Purity and chemical state of the elements were confirmed by energy dispersive analysis of X-rays (EDX) and X-ray photoelectron spectroscopy (XPS), respectively. UV-vis diffuse reflectance spectra (DRS) demonstrate that absorption ability of the nanocomposites in the visible range increases by increasing the mole fraction of AgCl. Photocatalytic activities of the nanocomposites were investigated by degradation of methylene blue indicating an enhanced activity relative to ZnO and AgCl nanostructures. The degradation rate constant on the nanocomposite with 0.383 mol fraction of AgCl is about 3.3 and 3.5-fold greater than for ZnO and AgCl nanostructures, respectively. Moreover, influence of various operational parameters on the degradation reaction was studied and the results were discussed.
Chinese Journal of Catalysis, 2014
AgX (X = I, Br) nanoparticles-surface modified ZnO nanorod arrays (AgX/ZnO) were prepared using an impregnation method. The influence of impregnating solution concentration, immersion time, and UV light illumination pretreatment on the visible light-driven photocatalytic activity of AgX/ZnO was evaluated. The morphology, phase composition, band gap, and surface characteristics of the AgX/ZnO nanorod arrays were assessed by field-emission scanning electron microscopy, X-ray diffraction, diffuse reflectance UV-Vis absorption spectroscopy, and X-ray photoelectron spectroscopy. The AgBr nanoparticles were homogeneously distributed on the top and side surfaces of the ZnO nanorods, and connected to form a porous network structure. Following UV light illumination pretreatment, Ag nanoparticles were formed on the surface of the AgBr nanoparticles producing a Ag/AgBr/ZnO nanostructure. Methyl orange photodegradation study showed that the photocatalytic activity of AgBr/ZnO was higher than that of AgI/ZnO, synthesized under similar conditions, and was highly related to the impregnating solution concentration and immersion time. Owing to the high surface area of the ZnO nanorod arrays, the visible light sensitivity of AgBr, and surface plasmon resonance of Ag/AgBr, Ag/AgBr/ZnO exhibited the highest visible light-driven photocatalytic activity.
Results in Physics, 2019
Zinc oxide (ZnO) is one of the potential semiconductors for photocatalytic applications. However, ZnO has a high recombination rate between electrons and holes, which reduces the efficiency of its photocatalytic activity. Thus, a nanohybrid structure between ZnO and a noble metal, such as Ag, has been proposed because it is cost effective, is chemically stable, and has enhanced photocatalytic activity. In general, ZnO/Ag nanohybrids are not easily synthesized due to the self-nucleation of Ag NPs during the deposition on ZnO. In this study, the Ag nanoparticles were deposited on the ZnO nanorods (NRs) prepared on glass substrate by using the facile and rapid hydrothermal method at low temperature 80°C for 90 min. The result analysis shows that the Ag nanoparticles deposition process did not change the morphological and microstructural properties of the ZnO NRs. The Ag NPs with the diameter range of 10-20 nm spread uniformly on the surface of the ZnO NRs. The photodegradation efficiency of methyl blue using the ZnO/Ag nanohybrids was higher than pure ZnO NRs. The ease of electron transfer between the ZnO and the Ag NPs was a major cause of the increased photocatalytic activity in both UV and visible-light irradiation.
Enhanced photocatalytic activity of Ag nanostructures
2018
Noble metal/semiconductor oxide nanocomposites have considerable interest on degradation of pollutants from textile wastewaters. Ag-ZnO, as one of the noble metal/semiconductor oxide nanocomposite, is highly efficient catalyst in textile pollutant degradation that allows irradiation wavelength towards visible light region. Application of Ag on the surface of ZnO nanoparticles has caused e its greater degradation efficiency. Oxidation of the methylene blue consumes photo efficiently, blocking the electron-hole recombination and thus, increasi scavenger of the photogenerated electrons.
Facile synthesis of Ag-ZnO core-shell nanostructures with enhanced photocatalytic activity
Journal of Industrial and Engineering Chemistry, 2017
Ag-ZnO core-shell nanostructure (CSNS) was prepared via a facile wet chemical approach. Formation was certified by various characterization techniques. The surface plasmon band of Ag-ZnO CSNS was red-shifted. Photoluminescence quenching for Ag-ZnO CSNS was attributed to improved charge separation. Ag-ZnO CSNS exhibited 6timeshigherphotocatalyticactivitythanpristineZnOand6 times higher photocatalytic activity than pristine ZnO and 6timeshigherphotocatalyticactivitythanpristineZnOand4 times higher than TiO 2 (P25). Such enhanced photocatalytic activity was attributed to synergistic effect, more charge separation, and higher surface area. Ag-ZnO CSNS also showed excellent photostability and reusability. Photocatalytic mechanism was discussed based on major reactive oxidative species such as OH and O 2 À .
Ag/Ag2S-ZnO nanocomposites were prepared via a simple hydrothermal process followed by a plasmonic Ag+ reduction through a photo-deposition method. Ag2S was introduced to narrow the overall composite bandgap and activate the surface plasmon resonance (SPR) effect of the Ag+ cation present. The physicochemical properties of the as-synthesised catalysts were characterised by X-ray diffraction (XRD) to determine the crystallinity, while scanning and transmission electron microscopies (SEM and TEM) revealed the particle size and morphology. The surface area and pore sizes were measured using a Brunauer-Emmett-Teller (BET) analysis. Fouriertransform infrared spectroscopy (FTIR), Ultraviolet diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence emission spectra (PL) was conducted to investigate the photo-absorption and emission spectra of the nanocomposites. X-ray photoelectron spectroscopy (XPS), confirmed the surface electrochemical states and electron transfer between Ag/Ag2S and ZnO. Ternary Ag/Ag2S-ZnO catalyst demonstrated an excellent photo-generated charge separation efficiency by achieving 98% phenol degradation higher than ZnO, Ag/ZnO and Ag2S-ZnO composites due to its enhanced photosensitivity and SPR effect combined. The degradation for all the synthesized catalysts followed the Langmuir-Hinshelwood model, which typically describes heterogeneous photocatalytic surface reactions. All the fits had R2 values higher than 0.97, which confirms the degree of accuracy or statistical fitness to the kinetic model. Total organic carbon analysis using the ternary Ag/Ag2S-ZnO catalyst only achieved a 74% phenol mineralization after 24 hours of photocatalysis. Recyclability tests showed good degradation stability of Ag/Ag2S-ZnO after five recycle runs. Hence, a synergistic degradation mechanism responsible for the efficient photodegradation performance was proposed.
Synthesis of mesoporous Ag/ZnO nanocrystals with enhanced photocatalytic activity
Catalysis Today, 2015
Mesoporous Ag/ZnO nanocrystals have been successfully synthesized at different Ag contents (0-10 wt%) through a single-step sol-gel method in presence of triblock copolymer as a structure directing agent. The as-prepared hybrid materials were calcined at 450 • C in air for 4 h, subsequently, Ag nanoparticles have been photo-reduced from AgNO 3 onto mesopores ZnO nanocyrstals. The XRD and Raman analysis revealed that well crystalline ZnO hexagonal wurtzite phase and face-centered cubic metallic Ag nanoparticles were formed. TEM images of mesoporous ZnO nanocrystals showed that synthesized materials composed of discrete ZnO nanoparticles agglomerated with worm-like mesoporous structure. The lattice fringes exhibit the typical distances, i.e., Ag(1 1 1) and ZnO(1 0 0) and the average Ag and ZnO nanoparticle diameters are ∼5 and 10 nm, respectively. The photocatalytic performance of different prepared photocatalysts was evaluated by degradation of methylene blue (MB) under visible light irradiation. The results indicate that the photocatalytic efficiencies of mesoporous ZnO photocatalysts were remarkably enhanced by adding 1% Ag nanoparticles which completely degrade the target MB dye within 150 min. The photodegradation rate was found to increase linearly with increasing the Ag contents from 0 to 1% and it is faster 2.2 times than undoped ZnO. From economic point of view, 1% Ag/ZnO photocatalyst contains optimum Ag content as there is no significant increase in the photocalatytic performance at higher Ag content.
Ag Grafted ZnO Nanoplates for Photocatalytic Applications
Herein, ZnO nanoplates were synthesized by chemical method and Ag nanoparticles were grafted on ZnO nanoplates surface by sonochemical method. The formation of the nanocomposites was investigated using X-ray diffractometer (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). Optical properties of the nanocomposite were investigated using Photoluminescence spectroscopy (PL) and UV-Visible spectroscopy (UV-Vis). FESEM investigation confirms that the nanoplates were uniformly distributed and Ag nanoparticles were grafted on the surface on ZnO nanoplates. The photocatalytic activity of Ag/ZnO nanocomposites was evaluated in terms of their efficiency of the photo excitation of methyl orange dye (MeO) under UV illuminator. A photo excitation of Ag/ZnO showed enhanced photocatalytic activity compared to pure ZnO Nanoplates. This enhanced UV activity of Ag/ZnO nanocomposite makes it a potential candidate for optoelectronic devices for Solar Energy conservation, water splitting and Light Emitting devices etc.
Ag-ZnO nanoreactor grown on FTO substrate exhibiting high heterogeneous photocatalytic efficiency
ACS Combinatorial science
This Research Article reports an unusually high efficiency heterogeneous photodegradation of methyl orange (MO) in the presence of Ag nanoparticle-loaded ZnO quasinanotube or nanoreactor (A-ZNRs) nanocatalyst grown on FTO substrate. In typical process, photodegradation efficiency of as high as 21.6% per μg per Watts of used catalyst and UV power can be normally obtained within only a 60-min reaction time from this system, which is 10 3 order higher than the reported results. This is equivalent to the turnover frequency of 360 mol mol −1 h −1 . High-density hexagonal A-ZNRs catalysts were grown directly on FTO substrate via a seed-mediated microwave-assisted hydrolysis growth process utilizing Ag nanoparticle of approximately 3 nm in size as nanoseed and mixture aqueous solution of Zn(NO 3 )·6H 2 O, hexamethylenetetramine (HMT), and AgNO 3 as the growth solution. A-ZNRs adopts hexagonal cross-section morphology with the inner surface of the reactor characterized by a rough and rugged structure. Transmission electron microscopy imaging shows the Ag nanoparticle grows interstitially in the ZnO nanoreactor structure. The high photocatalytic property of the A-ZNRs is associated with the highly active of inner side's surface of A-ZNRs and the oxidizing effect of Ag nanoparticle. The growth mechanism as well as the mechanism of the enhanced-photocatalytic performance of the A-ZNRs will be discussed.
Synthesis and characterization of plasmonic visible active Ag/ZnO photocatalyst
Ag deposited ZnO nanoparticles (NPs) have been synthesized by simple sol-gel method for visible light active photocatalytic application. X-ray diffraction (XRD), TEM, UV-DRS and PL studies have been used to characterize the photocatalyst. The results show that Ag/ ZnO NPs are wurtzite phase (WZ) of ZnO with Ag NPs in the surface region forming a hetero-interface of Ag-WZ (ZnO). Visible light activity of the material has been studied using photocatalytic degradation kinetics of methylene blue as a probe pollutant. Ag/ZnO NPs exhibit five times higher visible-light driven photocatalytic activity than pristine ZnO and four times than the reference Degussa P-25, under identical conditions. The high visible activity of Ag/ZnO may be attributed to the surface plasmon effect complemented sensitization in the presence of metallic Ag and effective charge separation through Ag-WZ hetero-interfaces.