ZnO/CdS/Ag复合光催化剂的制备及其催化和抗菌性能

先用水热反应合成六方晶相CdS多层级花状微球并在其表面生长ZnO纳米棒形成均匀的ZnO/CdS复合结构,然后用光还原法将Ag纳米颗粒负载于ZnO纳米棒制备出ZnO/CdS/Ag三元半导体光催化剂,对其进行扫描电镜和透射电镜观察、光电性能测试、活性基团捕获实验以及光催化降解和抗菌性能测试,研究其对亚甲基蓝(MB)的降解和抗菌性能。结果表明：ZnO纳米棒均匀生长在CdS微球表面,CdS晶体没有明显裸露,Ag纳米粒子负载在ZnO纳米棒的表面;ZnO/CdS/Ag三元复合光催化剂有良好的可见光响应、较低的阻抗和较高的光电流密度;ZnO/CdS/Ag复合光催化剂能同时产生羟基和超氧自由基等活性氧基团;ZnO/CdS/Ag三元复合光催化剂对亚甲基蓝(MB)的30 min降解率高于90%;0.25 mg/mL的ZnO/CdS/Ag对革兰氏阴性菌(大肠杆菌)的灭菌率高于96%,对革兰氏阳性菌(金黄色葡萄球菌)能完全灭除。     

Enhanced photocatalytic performance of Cu2O nano-photocatalyst powder modified by ball milling and ZnO

In this paper, a ball milled Cu₂O-ZnO nano-photocatalyst with good photocatalytic performance in visible light range was prepared. Effect of ZnO presence and ball milling of Cu₂O on the structure, microstructure, optical properties and photocatalytic performance were studied. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), high resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) analysis and UV–Vis spectrophotometer were used as characterization techniques. FESEM results indicated that ball milling of Cu₂O changed the morphology of Cu₂O-ZnO composite. The uniform formation of ZnO particles with average size of 30 nm over the Cu₂O surface was observed. The formation of p-n heterostructure with good contact between Cu₂O and ZnO nanoparticles was found by HRTEM image. Ball milling of Cu₂O promotes visible light absorption and reduction band gap to 1.9 eV in Cu₂O-ZnO photocatalyst. Intensity of PL spectra for the ball milled Cu₂O-ZnO photocatalyst was obviously lower. Ball milled Cu₂O-ZnO photocatalyst shows the highest photocatalytic activity and degradation efficiency of 98% was obtained for 2 mg/L methylene blue (MB) solution after 240 min. The kinetics of the photodegradation was followed the Langmuir-Hinshelwood (L-H) model and degradation rates were decreased by increase of MB concentration. In the case of ball milled Cu₂O and presence of ZnO, the MB degradation kinetics was two times faster.     

Fabrication of Ag-doped MoO3 and its nanohybrid with a two-dimensional carbonaceous material to enhance photocatalytic activity

Recently, two-dimensional (2D) carbon-based materials and their nanocomposites have gained considerable fascination as a photocatalysts due to their remarkable contribution towards photocatalytic water splitting and remediation. Herein, a novel 2D reduced graphene oxide (rGO) based silver doped molybdenum trioxide (Ag/MoO₃) photocatalyst was synthesized successfully via hydrothermal and ultra-sonication methods. The surface structure, morphology, functional group characterization, and bandgap of the synthesized photocatalysts were analyzed using advanced physicochemical techniques. The photocatalytic performance of the prepared materials was scrutinized for Methylene blue (MB) dye degradation under solar light illumination. Because of its lower charge transfer resistance (19.54 Ω) and higher electrical conductivity (12.74 × 10² Sm^?1) the rGO/Ag/MoO₃ photocatalyst demonstrated significantly higher photocatalytic activity for dye removal than pure MoO₃ and Ag/MoO₃ photocatalysts. In particular, the rGO/Ag/MoO₃ photocatalyst illustrated about 98% dye degradation at a rate constant (0.0571 min^?1) greater than MoO₃ (0.0097 min^?1) and Ag/MoO₃ (0.0184 min^?1). Ag doping and the addition of rGO sheets led to enhanced optical absorbance and effectual separation of photo-induced electron-hole pairs, causing major progress in the photocatalytic behavior of MoO₃. Transient photocurrent results revealed longstanding photo-excited charge carriers in the graphene-based material.     

SnO<Subscript>2</Subscript>-based thin films with excellent photocatalytic performance

SnO₂ semiconductor is a new-typed promising photocatalyst, but wide application of SnO₂-based photocatalytic technology has been restricted by low visible light utilization efficiency and rapid recombination of photogenerated electrons–holes. To overcome these drawbacks, we prepared B/Fe codoped SnO₂–ZnO thin films on glass substrates through a simple sol–gel method. The photocatalytic activities of the films were evaluated by degradation of organic pollutants including acid naphthol red (ANR) and formaldehyde. UV–Vis absorption spectroscopy and photoluminescence (PL) spectra results revealed that the B/Fe codoped SnO₂–ZnO film not only enhanced optical absorption properties but also improved lifetime of the charge carriers. X-ray diffraction (XRD) results indicated that the nanocrystalline SnO₂ was a single crystal type of rutile. Field emission scanning electron microscopy (FE-SEM) results showed that the B/Fe codoped SnO2–ZnO film without cracks was composed of smaller nanoparticles or aggregates compared to pure SnO2 film. Brunauer–Emmett–Teller (BET) surface area results showed that the specific surface area of the B/Fe codoped SnO₂–ZnO was 85.2 m² g^?1, while that of the pure SnO₂ was 20.7 m² g^?1. Experimental results exhibited that the B/Fe codoped SnO₂–ZnO film had the best photocatalytic activity compared to a pure SnO₂ or singly-modified SnO₂ film.     

Growth and characterization of flower-like Ag/ZnO heterostructure composites with enhanced photocatalytic performance

Flower-like Ag/ZnO heterostructure composites were prepared through a solvothermal method without surfactants or templates. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL) spectroscopy. Results demonstrate that flower-like Ag/ZnO heterostructure composites were composed of wurtzite ZnO flowers coated by face-center-cubic Ag nanoparticles. The growth process of flower-like ZnO crystals was investigated, and a possible growth mechanism was proposed. The photocatalytic activity of the as-prepared flower-like Ag/ZnO samples, pure ZnO samples, and commercial TiO₂ (Degussa, P-25) was tested with the photocatalytic degradation of methylene blue. Results show that the Ag/ZnO heterostructures were superior in photocatalytic activity to the pure ZnO samples and the commercial TiO₂ (Degussa, P-25), but the mixture of Ag (0.1 wt%) particles and ZnO flowers did not, which implies that the heterostructure promoted the separation of photogenerated electron–hole pairs, enhancing the photocatalytic activity. That was primarily verified by the PL results.     

Facile preparation of Ag–Ag<Subscript>2</Subscript>S hetero-dendrites with high visible light photocatalytic activity

A stable and highly efficient Ag–Ag₂S hetero-dendrites (HDs) photocatalyst has been obtained via an extremely facile electrodeposition and subsequently in situ sulfuration route. The SEM and TEM show well-defined uniform dendrites morphology with an average diameter about 30 nm. In addition, the absorption spectra of Ag–Ag₂S HDs exhibit strong absorption in both visible and NIR regions. The EIS indicates that the low charge transfer resistance of Ag–Ag₂S HDs enhances the photocatalytic activity. The prepared HDs-4 photocatalyst with moderate degree of vulcanization shows excellent activity for degradation the methylene blue (MB) under the sunlight irradiation owing to the suitable ratios of Ag–Ag₂S. The enhanced photocatalytic activity could be attributed to the favorable synergistic effects between Ag and Ag₂S materials, such as huge extended absorption of solar light, low charge transfer resistance and high electron–hole separation efficiency. Moreover, radical scavenger experiments confirmed that superoxide radicals and holes were the main reactive species for MB degradation. Meanwhile, the Ag–Ag₂S HDs displays good photocatalytic stability after being recycled five times.     

The role of ammonia hydroxide in the formation of ZnO hexagonal nanodisks using sol–gel technique and their photocatalytic study

ZnO nanomaterials with large surface area are desired particularly for the gas sensor, biosensor and photocatalyst applications. In this study, ZnO hexagonal nanodisks with thickness to diagonal aspect ratio (～1/80) were successfully synthesised via sol–gel approach. By using aluminium sulphate as a complexing agent and carefully controlling the amount of ammonia hydroxide, zinc oxide hexagonal nanodisks were produced. The ZnO nanodisks had perfect hexagonal shape with about 4 μm in diagonal and 50 nm in thickness. The growth of the nanodisks was favoured along the six symmetric directions of ±[1ī00], ±[01ī0] and ±[10ī0]. The growth mechanism of ZnO hexagonal nanodisks is proposed as follows. The formation of ZnO hexagonal nanodisks was mediated by the adsorption of aluminate ions, Al(OH)₄^?, on the polar surface of ZnO. The Al(OH)₄^? ions were produced as a result of reaction between Al₂(SO₄)₃ and NH₄OH. The Al(OH)₄^? ions were bonded to the positively charged Zn²⁺-terminated (0001) polar surface of ZnO. This suppressed the preferential growth of ZnO along [0001] direction but allowed the lateral growth of ZnO in <01ī0>. Eventually, ZnO hexagonal nanodisks with ±(0001) top/bottom surfaces and {1ī00} side surfaces were formed. The size of the ZnO hexagonal nanodisks could be adjusted via the synthesis duration and the amount of ammonia hydroxide. The photocatalytic study indicates that ZnO hexagonal nanodisks were a good photocatalyst for the degradation of Rhodamine B under ultraviolet light irradiation with a rate constant of 0.036 min^?1.     

Fabrication of novel ZnO/MnWO4 nanocomposites with p-n heterojunction: Visible-light-induced photocatalysts with substantially improved activity and durability

We report, for the first time, binary ZnO/MnWO₄ nanocomposites with p-n heterojunction fabricated by a simple ultrasonic-calcination route. The phase structure, morphology, and optical along with textural properties were comprehensively characterized. The photocatalytic performance was studied via degradations of rhodamine B, methyl blue and methyl orange (RhB, MB, MO), and fuchsine pollutants under visible-light illumination. The ZnO/MnWO₄ nanocomposites exhibited better photocatalytic performance than their single components and the nanocomposite with 30?wt% MnWO₄ showed the highest activity. Photocatalytic performance of this nanocomposite is 22.5, 17.7, 26.8, and 23.9 times higher than that of the ZnO sample in degradations of RhB, MB, MO, and fuchsine dyes, respectively. The improved photocatalytic performance was ascribed to the formation of p-n heterojunction between ZnO and MnWO₄ with high charge separation efficiency as well as strong visible-light absorption ability. The possible mechanism for the improved photocatalytic performance was proposed. This study revealed that the novel ZnO/MnWO₄p-n heterojunction can act as a promising visible-light-active photocatalyst for environmental applications.     

Synthesis of novel Cu doped anatase TiO<Subscript>2</Subscript> catalysts and assessment of the influence of Nb concentration on the photocatalytic and electrochemical properties

In the present study, Cu doped (Ti_0.8Cu_xO_2?x/2) and (Cu, Nb) co-doped (Ti_0.8Cu_x?y Nb_yO_2?(x?y/2+y)) TiO₂ photocatalysts were fabricated by sol–gel method. The catalysts were polycrystalline in nature with preferential orientation along (101) plane answering to anatase phase of TiO₂. Higher Nb concentration results in the formation of secondary phase (Nb₂O₅). A decrease in average crystallite size was noticed with the addition of Nb concentration in Cu doped TiO₂ photocatalyst. The formation of anatase phase was also fixed by Raman spectra. The TEM photograph confirmed the co-doped TiO₂ photocatalyst in nanometer range of about 15 nm and the particles were in hexagonal shape. The doping of Nb⁵⁺ ions inspired a shift in the absorption threshold towards the visible spectral range (red shift) compared to Cu doped TiO₂ catalyst. The photocatalysts have direct bandgaps of 3.253 to 2.974 eV. Semiconducting properties were investigated through electrochemical impedance spectroscopy. The results indicate that the presence of Nb⁵⁺ ions into Cu doped TiO₂ has enhanced the efficiency of electrochemical conductivity. Photocatalytic performance was assessed from the sample degradation by illuminating methylene blue dye under visible light exposure. It is found that TCN3 photocatalyst bleaches MB much faster than all others. Also it exhibits great improvement of photocatalytic activity (96.86%) within 120 min. The photocatalytic degradation process is explained using the pseudo first order kinetics and it fits well with higher correlation coefficient. All these analyses elucidate that the incorporation of Nb⁵⁺ ions might tune the structural, optical, electrochemical and phocatalytic properties of Cu doped TiO₂ photocatalysts.     

Utilization of a ZnS(en)0.5 photocatalyst hybridized with a CdS component for solar energy conversion to hydrogen

Photocatalytic solar energy conversion to chemical energy attracts great attention due to its high potential in harvesting renewable energy for the future. A ZnS(en)_0.5 photocatalyst hybridized with a CdS component was synthesized by solvothermal and precipitation methods to compare the effect of preparation methods on photocatalytic performance. The highest hydrogen production rate (559 μmol g^?1 h^?1) was achieved from a solvothermally synthesized ZnS(en)_0.5?CdS composite at 80 wt% of CdS content under standard 1-sun-irradiation condition (1000 W/m²). Photocatalytic hydrogen production rates from ZnS(en)_0.5?CdS photocatalysts were highly associated with degrees of charge separation, crystallinity, reduction power, and light absorption. By comparing two different routes for the synthesis of ZnS(en)_0.5?CdS photocatalysts, solvothermally-fabricated material was shown to have a higher photocatalytic activity compared with material fabricated by a precipitation method. This improvement may be due to its excellent crystalline and charge-separation characteristics.     

Solvent-free synthesis of Cu-Cu2O nanocomposites via green thermal decomposition route using novel precursor and investigation of its photocatalytic activity

In the present study, Cu-Cu₂O binary nanocomposites were successfully synthesized through a one-pot, cost-effective and green thermal decomposition route using PMP-Cu(II), extracted from pomegranate marc peels (PMP) by Cu(II), as a novel starting reagent for the first time. The morphology, crystalline structure, and composition of as-prepared Cu-Cu₂O nanocomposites were extensively characterized by SEM, XRD, EDS and HRTEM. Effect of reaction parameters such as time, temperature and precursor type on product composition and morphology was evaluated. Moreover, methylene blue (MB) was used as a model of organic dye pollutant and photodegradation experiments were conducted by UV-vis spectrophotometry. The as-synthesized Cu-Cu₂O binary nanocomposites demonstrated their potential as an excellent photocatalyst for degradation of MB under visible-light irradiation and Cu-Cu₂O photocatalyst with higher content of Cu₂O (prepared in air) exhibits the highest photocatalytic efficiency (～99% degradation of MB in <150 min).     

High performance magnetically recoverable g-C3N4/Fe3O4/Ag/Ag2SO3 plasmonic photocatalyst for enhanced photocatalytic degradation of water pollutants

The g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ nanocomposites have been successfully fabricated by facile refluxing method. The as-obtained products were characterized by XRD, EDX, SEM, TEM, UV–vis DRS, FT–IR, TGA, PL, and VSM techniques. The results suggest that the Ag/Ag₂SO₃ nanoparticles have anchored on the surface of g-C₃N₄/Fe₃O₄ nanocomposite, showing strong absorption in the visible region. The evaluation of photocatalytic activity indicates that for the g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ (40%) nanocomposite, the degradation rate constant was 188 × 10^?4 min^?1 for rhodamine B, exceeding those of the g-C₃N₄ (16.0 × 10^?4 min^?1) and g-C₃N₄/Fe₃O₄ (20.2 × 10^?4 min^?1) by factors of 11.7 and 9.3, respectively. The results showed that the nanocomposite prepared by refluxing for 120 min has the superior photocatalytic activity and its activity decreased with rising the calcination temperature. The trapping experiments confirmed that superoxide ion radical was the main active species in the photocatalytic degradation process. Also, it was demonstrated that the magnetic photocatalyst has considerable activity in degradation of one more dye pollutant. Finally, the reusability of the photocatalyst was evaluated by five consecutive catalytic runs. This work may open up new insights into the utilization of magnetically separable nanocomposites and provide new opportunities for facile fabrication of g-C₃N₄-based plasmonic photocatalysts.     

Graphene oxide modified ZnO nanorods hybrid with high reusable photocatalytic activity under UV-LED irradiation

In this work, graphene oxide/zinc oxide (GO/ZnO) hybrid was prepared through a facile hydrothermal process. Transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectra and N₂ adsorption and desorption isotherms were used to investigate the morphology, crystal structure, optical properties and specific surface area of GO/ZnO hybrid. It was shown that the well-dispersed ZnO nanorods were deposited on GO homogeneously. Photocatalytic properties of GO/ZnO nanorods hybrid were evaluated under 375 nm light-emitting diode light irradiation for photodegradation of methylene blue (MB). The synergic effect between GO and ZnO was found to lead to an improved photo-generated carrier separation. An optimal GO content has been determined to be 3 wt%, and corresponding the apparent pseudo-first-order rate constant kapp$k_{\text{app}}$ is 0.0248 min⁻¹, 4.3 times and 2.5 times more than that of pure ZnO nanorods and commercial P25 photocatalyst, respectively. Moreover, the cyclic photocatalytic test indicated that GO/ZnO hybrid can be reused for degradation of MB, suggesting the possible application of GO/ZnO hybrid as excellent candidate for water treatment.     

Shifting mechanisms in the initial stage of dye photodegradation by hollow TiO2 nanospheres

Hollow TiO₂ (HT) sphere aggregates were prepared using carbon spheres as templates. The photocatalytic activity of HT was determined by degradation of two nitrogen-containing dyes, methylene blue (MB) and methyl orange (MO). The adsorption isotherms and the photocatalytic degradation kinetics of the two dyes were studied and compared using different concentrations of dyes for the pure, isopropanol-added, and KI-added systems. Isopropanol was used as a OH^? radical scavenger, while KI was added as a valance band hole scavenger. The results showed that the reaction mechanism of the photocatalytic process of MB was first governed by OH^? radicals, and then by valence band holes, whereas holes played a major role in the whole photodegradation process of MO. The photocatalytic adsorption constant K _V has a positive correlation with the reaction constant k _ov in all systems. The photodegradation efficiencies of the dyes were discussed considering the surface characteristics of HT and the structure of the dyes with different catalyst loads (0.25–2 g L^?1) and under different pH (3–10) conditions. Compared with solid TiO₂, HT exhibited enhanced performance in photocatalytic degradation of both MB and MO.     

Influence of Thermal Treatment and Fe-Loading on Morphology,Crystal Structure,and Photocatalytic Activity of Sodium Titanate Nanotubes

An understanding of collective influence of Fe-loading and calcination on changes in the crystal structure, morphology, phase composition, and photocatalytic activity of titanate-nanostructures is investigated here. Bare sodium-titanate nanotubes (TNT) having a BET-surface-area (S_BET) of 176 m² g^?1 were transformed to sodium-titanate nanorods (TNT(S)) of S_BET = 21 m² g^?1 when calcined at 800°C. Whereas, calcination of Fe-loaded-TNT at 800°C led to a variety of fragmented particles having different crystal structures, S_BET (21–39 m² g^?1), shape, and sizes (50–70 nm) attributed to the strain induced thermal-decomposition of TNT after Fe-loading. The comparative photocatalytic activity of as-prepared catalysts under UV-light irradiation was evaluated by photooxidation of naphthalene to CO₂, with the identification of its photoproduced intermediates by GC-MS analysis. These results are well explained in correlation with the surface area, size, and shape of as-prepared catalysts.     

Enhanced photocatalytic degradation for thiophene by Ag/α-MoO<Subscript>3</Subscript> heterojunction under visible-light irradiation

Ag/α-MoO₃ heterojunctions were prepared by a photoreduction process and characterized using XRD, TEM, UV–Vis-DRS, EDS, XPS, PL, EIS and PT. Ag/α-MoO₃ heterojunctions exhibited excellent photocatalytic oxidative desulfurization activity for thiophene under visible-light irradiation. The removal efficiency of 5% Ag/α-MoO₃ composites could get to 98.3% with 1.5 g L^?1 amount of catalyst used under visible-light irradiation for 270 min, which is 2.5 times as high as that of pure α-MoO₃ nanobelts. The stability of as-prepared Ag/α-MoO₃ heterojunctions were investigated through recycling run experiment, which the desulfurization rate of 5 wt% Ag/α-MoO₃ for thiophen still remained 92.8% after five consecutive cycles. Furthermore, the active species trapping experiment confirmed that h⁺ and ^·O₂ ^? were the main active in photocatalytic degradation process for thiophene. Additionally, the mechanism of the enhanced photocatalytic activity for Ag/α-MoO₃ was proposed. These features demonstrate that the Ag/α-MoO₃ heterojunctions have great application potential for refractory pollutants’ removal from fuel oil.     

Solvothermal synthesis of Ag/ZnO micro/nanostructures with different precursors for advanced photocatalytic applications

Micro/nanostructured systems based on metallic oxide (ZnO) with noble metal (Ag) on the surface (Ag/ZnO) are synthesized by solvothermal method from zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O), zinc acetate dehydrate (Zn(CH₃COO)₂·2H₂O), zinc acetylacetonate hydrate (Zn(C₅H₇O₂)₂·xH₂O) and silver nitrate (Ag(NO₃)) as precursors. In these systems, polyvinylpyrrolidone (PVP) is used as surfactant for controlling particle morphology, size and dispersion. The obtained materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), UV–vis diffuse reflectance spectroscopy (DRS), N₂ gas adsorption–desorption (BET) and Raman spectroscopy (RS). By XRD results, all major peaks are indexed to the hexagonal wurtzite-type structure of the ZnO and samples with noble metal, extra diffraction peaks are detected which correspond to the face-centered-cubic (fcc) structure of the metallic Ag. Depending on used precursor, different morphologies have been obtained. Mainly, ZnO prims-like rods – NRs (with 0.8 ? aspect ratio ? 3.4) – have been observed. Quasi-spherical particles of metallic Ag (with diameters between 558 ± 111 μm and 22 ± 1 nm) have been detected on the ZnO surface. Photocatalytic results (all samples studied >30% MB degradation) verify the important effect of surfactant and the viability of synthesized Ag/ZnO micro/nanocomposites for environmental applications.     

Preparation of Ag nanoparticles coated tetrapod-like ZnO whisker photocatalysts using photoreduction

Ag/tetrapod-like ZnO whisker (T-ZnOw) photocatalysts with different Ag loadings were synthesized by photoreduction of Ag⁺ on the surface of T-ZnOw. The chemical composition, morphology and photocatalytic properties of Ag/T-ZnOw photocatalysts were characterized and studied in detail. It is found that metal Ag can exist either as nanoparticles or as agglomerates through varying the Ag/ZnO molar ratio (MR). In photodegradation of methyl orange, enhanced degradation rates are achieved by all Ag/T-ZnOw photocatalysts due to increased separation efficiency of photogenerated electron and hole pairs. Specifically, the photocatalytic activities of Ag/T-ZnOw photocatalysts increase with increasing Ag/ZnO MR from 2.4 to 12%. However, further increasing the Ag/ZnO MR to 14.4% induces the formation of more agglomerates, which can act as recombination centers of photogenerated electron and hole pairs, leading to decreased photocatalytic activity of the photocatalyst.     

Preparation of novel CdS-graphene/TiO2 composites with high photocatalytic activity for methylene blue dye under visible light

In this study, CdS combined graphene/TiO₂ (CdS-graphene/TiO₂) composites were prepared by a sol–gel method to improve on the photocatalytic performance of TiO₂. These composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). The photocatalytic activities were examined by the degradation of methylene blue (MB) under visible light irradiation. The photodegradation rate of MB under visible light irradiation reached 90·1% during 150 min. The kinetics of MB degradation were plotted alongside the values calculated from the Langmuir–Hinshelwood equation. 0·1 CGT sample showed the best photocatalytic activity, which was attributed to a cooperative reaction between the increase of photo-absorption effect by graphene and photocatalytic effect by CdS.     

Facile synthesis of Ag/ZnO heterostructures assisted by UV irradiation: Highly photocatalytic property and enhanced photostability

We report a new method to synthesize Ag/ZnO heterostructures assisted by UV irradiation. The formation of Ag/ZnO heterostructures depends on photogenerated electrons produced by ZnO under UV light to reduce high valence silver. Functional property of the Ag/ZnO heterostructures is evaluated by photodegradation of methylene blue (MB) under UV illumination. Results of photodegradation tests reveal that the optimal photocatalytic activity of as-syntheszied samples is about 1.5 times higher than the pure ZnO synthesized in the same condition or commercial TiO₂ (P-25), showing the advantage of the unique structure in the Ag/ZnO heterostructure. Besides, due to the reduced activation of surface oxygen atom, photocatalytic activity of the photocatalysts has no evident decrease even after three recycles.