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 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.     

Designing Novel Nonsymmetric Ag/AgI Nanoplates for Superior Photocatalytic Activity

Precisely engineering the decoration of metal nanoparticles on the special surface of semiconductor represents a promising strategy to design efficient metal–semiconductor heterostructured photocatalysts. This study demonstrates a versatile soft‐template method to fabricate a novel nonsymmetrical heterostructured Ag/AgI nanoplate, in which only one side surface of the nanoplate is covered with uniform 2D Ag nanoweb. Compared with symmetrical heterostructure, the nonsymmetrical heterostructure may further facilitate the separation of photogenerated electron–hole pairs and shows a greatly enhanced photocatalytic activity. This study may open up a new way to improve the photocatalytic property by synthesizing nonsymmetrical metal–semiconductor composites.     

Highly efficient visible light photocatalysis of novel CuS/ZnO heterostructure nanowire arrays

Here, a facile approach for the fabrication of CuS nanoparticle (NP)/ZnO nanowire (NW) heterostructures on a mesh substrate through a simple two-step solution method is demonstrated. Successive ionic layer adsorption and reaction (SILAR) was employed to uniformly deposit CuS NPs on the hydrothermally grown ZnO NW array. The synthesized CuS/ZnO heterostructure NWs exhibited superior photocatalytic activity under visible light compared to bare ZnO NWs. This strong photocatalytic activity under visible light is due to the interfacial charge transfer (IFCT) from the valence band of the ZnO NW to the CuS NP, which reduces CuS to Cu(2)S. After repeated cycles of photodecolorization of Acid Orange 7 (AO7), the photocatalytic behavior of CuS/ZnO heterostructure NWs exhibited no significant loss of activity. Furthermore, our CuS/ZnO NWs/mesh photocatalyst floats in solution via partial superhydrophobic modification of the NWs.     

T-ZnOw光催化降解甲基橙的动力学研究

研究了四针状氧化锌晶须在紫外光照射条件下对甲基橙的降解活性,考查了甲基橙溶液初始浓度、催化剂浓度及种类等对光催化降解的影响,并初步探讨了其反应动力学.实验结果显示,四针状氧化锌晶须光催化降解反应基本符合一级动力学规律,光催化效果随着甲基橙初始溶液浓度的增加而降低,最佳浓度为2g/L,是一种降解效果优异的光催化材料.     

热处理对Ag-ZnO异质结构光催化性能的影响

用溶胶-凝胶法制备纯ZnO和Ag修饰ZnO复合光催化剂,并分别对其进行了400℃、450℃、500℃保温2 h的热处理。使用XRD、SEM、TEM、XPS、PL、BET等手段对其进行了表征。结果表明,纯ZnO和Ag修饰ZnO均为六方纤锌矿晶型,Ag颗粒沉积在ZnO表面形成了Ag-ZnO异质结构。以罗丹明B为目标污染物研究了样品的光催化活性。结果表明,热处理温度对纯ZnO的光催化性能的影响较大,在450℃热处理后光催化效果最佳;热处理温度对Ag修饰ZnO的光催化性能没有显著的影响;Ag修饰ZnO比纯ZnO的光催化活性均有所提高,因为Ag修饰提高了ZnO表面羟基的含量并抑制了光生电子与空穴的复合。在500℃热处理后Ag修饰ZnO对罗丹明B的60 min降解率达到98%,其反应速率常数为0.063 min^-1。     

Visible-light-responsive Ag–Si codoped anatase TiO2 photocatalyst with enhanced thermal stability

To utilize visible light more efficiently and enhance the photocatalytic performance of TiO₂, Ag–Si/TiO₂ photocatalyst was synthesized via a two-step method. The obtained materials were characterized by XRD, Raman, TEM, HRTEM, BET, TG–DTA, XPS, ICP as well as UV–vis DRS. All photocatalyst materials held an anatase phase confirmed by XRD, Raman and HRTEM. The Ag–Si/TiO₂ photocatalysts possessed high thermal stability and the phase transformation was retarded to about 900 °C revealed by XRD and TG–DTA. The Ag–Si/TiO₂ particles synthesized via the nonaqueous method were highly monodispersed and the particles size became smaller compared to the un-doped TiO₂, resulting in the enlargement of surface area. In addition, UV–vis light absorption shifted to visible region after Ag doping. XPS results demonstrated that Si weaved into the matrix of TiO₂ and enriched in the surface layer, while Ag dispersed on the surface of TiO₂ particles. The Ag dopant suppressed the recombination of photogenerated electrons and holes, Si enlarged the surface of photocatalysts. Silver and silicon co-doping improved the visible photocatalytic activity, which was evaluated by Rhodamine B (RhB) degradation. The photocatalytic activity of the obtained Ag–Si/TiO₂ sample was much more higher than those of pure TiO₂ and Ag/TiO₂, reaching the maximum at the Ag and Si content of 0.5 mol% and 20.0 mol%, respectively. The improved visible photocatalytic activity may be attributed to the synergetic effects of codoping by silver and silicon.     

Construction of one dimensional ZnWO4@SnWO4 core-shell heterostructure for boosted photocatalytic performance

The one-dimensional ZnWO₄@SnWO₄ photocatalyst with a core-shell heterostructure was successfully constructed by a simple two-step method. It is interesting to note that ZnWO₄@SnWO₄ composite photocatalyst owns a higher photocatalytic activity for RhB degradation under visible light irradiation. The introduction of SnWO₄ shell layer, which forms a clear heterogenous interface between ZnWO₄ and SnWO₄, increases the photo-absorption efficiency of ZnWO₄ nanorods. In addition, its band-edge absorption evidently shifts toward the visible region. Based on the photoelectrochemical (PEC) and electron spin resonance (ESR) measurements, it is found that the photocatalytic activity was attributed to the efficient separation and transfer of photo-generated charge carriers. Hence, they can produced more hydroxyl radical (OH) as the main active species in the photocatalytic reaction process.     

银掺杂三氧化钨复合上转换材料的制备与表征

WO₃本身在紫外光下具有很强的光催化性能,在可见光下能力较弱。为了改善其光催化性能,通过热解法和水热法分别制备出WO₃颗粒和WO₃纳米管基体,采用水热还原法制备出不同质量比的WO₃与Ag复合的光催化剂。以罗丹明B为目标降解物,对其光催化性能进行了测试。结果表明:热解法制备的WO₃与Ag的复合并未改善其光催化性能,水热法制备的WO₃纳米管在与银复合后一定程度上提高了WO₃的光催化效果。为了进一步提高其催化效率,把Ag/WO₃与上转换材料NaYF₄∶Yb,Er进行了复合,并对其进行了光催化实验。实验证明Ag/WO₃与上转换材料NaYF₄∶Yb,Er质量比为0.25时,在暗反应过程中罗丹明B浓度有明显的下降。通过实验表明与上转换材料NaYF₄∶Yb,Er的复合使其具有了良好的吸附性能,在对处理环境污染起到了一定作用。     

新型异质结LaCO3OH/In(OH)3/In2S3的制备及其可见光下催化降解罗丹明B的性能

采用原位湿化学方法合成了LaCO3OH/In(OH)3/In2S3异质结光催化剂。采用XRD、 SEM、 XPS、 BET、 TG等表征技术对所制备LaCO3OH/In(OH)3/In2S3异质结光催化剂的组成、结构和形貌等进行分析。以可见光下(λ≥420 nm)降解罗丹明B(RhB)为探针反应,研究了LaCO3OH含量不同时LaCO3OH/In(OH)3/In2S3异质结光催化剂的光催化活性。结果表明,当La/In的摩尔比为15mol%时, LaCO3OH/In(OH)3/In2S3异质结光催化剂具有最高的降解活性,与In(OH)3/In2S3相比,活性提高约一倍。这可能是由于LaCO3OH/In(OH)3/In2S3异质结光催化剂具有较高的比表面积、合适的能带结构和较好的吸附性能。以对苯二甲酸为探针分子,光催化实验证明羟基自由基(·OH)是重要的活性物种。并提出了可能的降解机制。     

One-step microwave synthesis of Ag/ZnO nanocomposites with enhanced photocatalytic performance

Ag/ZnO nanocomposites have been successfully prepared via a facile microwave method without any post-synthesis treatment. This is a facile and rapid process requiring only low power of microwave irradiation (120 W). The formation mechanism of Ag/ZnO nanocomposites was clearly discussed. The photocatalytic performance of the Ag/ZnO nanocomposites with different Ag contents for degradation of methylene blue was systematically evaluated. The Ag/ZnO nanocomposites showed enhanced photocatalytic activities compared with pure ZnO. Specifically, the photocatalytic activities of Ag/ZnO nanocomposites increased with increasing Ag content from 0.5 to 1.5 %. However, further increasing Ag content to 2.0 % induced the formation of more agglomerates, which could act as recombination centers of photoexcited electron–hole pairs, leading to decreased photocatalytic activity. It is believed that this facile, rapid microwave-assisted strategy is scalable and can be applied to synthesize other noble metal/semiconductor oxide nanocomposites for different applications.     

A facile method for fabrication of highly ordered hollow Ag/TiO2 nanostructure and its photocatalytic activity

This letter reports a facile and efficient strategy for the designed preparation of highly ordered hollow Ag/TiO₂ nanostructure. Different from previous reports, the presently proposed method conveniently combines the long-range ordering porosity and the property of Ag nanoparticles by a general colloidal crystal-templating technique. The sample was characterized by SEM and XRD. The results show that such hollow nanostructured material is composed of anatase TiO₂ and metal Ag. The as-prepared sample shows a good photocatalytic activity for photodegradation of methyl orange compared with the reference samples, which was attributed to its long-range ordering porosity and the addition of Ag nanoparticles.     

Environmentally benign chitosan as reductant and supporter for synthesis of Ag/AgCl/chitosan composites by one-step and their photocatalytic degradation performance under visible-light irradiation

A novel Ag/AgCl/chitosan composite photocatalyst was successfully prepared by a simple one-step method. During this progress, environmentally benign chitosan not only served as reductant to reduce Ag⁺ to Ag⁰ species, but also acted as supporter for Ag/AgCl nanoparticles. XRD, SEM, EDX, UV-vis DRS and XPS were employed to characterize the as-prepared simples. SEM images of Ag/AgCl/chitosan composites revealed that Ag/AgCl nanoparticles were successfully loaded onto chitosan without obvious aggregation. All Ag/AgCl/chitosan composites exhibited efficient photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation. The result of photocatalytic degradation experiment indicated that 20% of the mass ratio of AgCl to chitosan was the optimum, and after 40 min photocatalytic reaction, the degradation rate reached about 96%.     

射频磁控共溅射制备光催化Ag-TiO2薄膜

采用射频磁控共溅射法制备Ag-TiO2复合薄膜,通过控制Ag靶的溅射时间可调节Ag与TiO2的比例.所制备的Ag-TiO2薄膜为锐钛矿结构.通过紫外光照降解亚甲基蓝溶液和循环伏安法研究Ag-TiO2薄膜光催化及光电化学特性.实验结果表明:掺1.5% Ag的Ag-TiO2薄膜在紫外光照射下能增强亚甲基蓝溶液的降解并得到更大的光生电流.这种光催化的增强主要是由于光生电子-空穴对的复合被抑制的结果.     

不同合成过程对溶胶-凝胶法制备的ZnO/Ag纳米复合材料光催化性能的影响

以乙酸锌、硝酸银为前驱体,二乙醇胺作为稳定剂,利用溶胶-凝胶法分别采用一步法和两步法制备得到ZnO以及ZnO/Ag纳米复合粉体。所有ZnO/Ag复合物中Ag的含量均为3%(摩尔分数)。对所制备样品的结构和光学性质通过XRD、SEM、TEM、XPS、PL、UV-vis进行了表征,进而以甲基橙为模拟污染物进行了光催化测试。结果表明,不同方法制备得到的ZnO/Ag纳米粉体晶粒均匀,无明显团聚现象,面心立方结构的金属Ag吸附在纤锌矿结构的ZnO表面形成异质结。与纯ZnO相比,掺Ag极大地改善了样品在紫外光下的光催化活性。对不同合成工艺的比较表明,用溶胶-凝胶一步法制备的ZnO/Ag复合物的光催化活性最高,经紫外光照射70min可完全降解甲基橙。     

Surface properties of doped and undoped TiO2 thin films deposited by magnetron sputtering

In this work, transparent titanium dioxide (TiO₂) thin films were deposited onto microscope glass slides by means of the d.c. reactive magnetron sputtering method. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectroscopy (UV) and contact angle analysis using the Owens-Wendt method for the surface energy calculation. The photocatalytic activity of the films was tested by measuring the photodegradation of Rhodamine-B (RhB) dye under radiation of UV light. Iron-doped TiO₂ films were also prepared in order to study the Fe-doping effect on TiO₂ photocatalytic activity. The influences of different iron concentrations on the contact angle of the series of Fe-doped TiO₂ thin films, were investigated. The influences of total sputtering pressures on TiO₂ photocatalytic activity were also investigated. It was observed that the photocatalytic activity of the TiO₂ thin films was slightly improved by increasing the total sputtering pressure. Moreover, it was also observed that in general, iron-doping was detrimental for photocatalytic activity, nevertheless the films with low iron concentrations showed better photocatalytic activity than those with high iron concentrations. It was found that iron-doping has changed the wettability appetency of TiO₂ coated surfaces.     

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.     

Ag/ZnO-C nanocomposite-preparation and photocatalytic properties

In this present study, Ag-hybridized ZnO was prepared through a powder-sol method first, then Ag/ZnO-AC (activated carbon) composite was synthesized by a adsorption method using Ag/ZnO and AC as precursors. The structure and morphology of as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), Raman spectra, and diffuse reflectance absorption spectra, respectively. The photocatalytic performances of the prepared catalysts were investigated by photocatalystic degradation of methyl orange. The influences of initial pH value, initial dye concentration and the calcination temperature on the photocatalytic activity of the catalysts were investigated and the results were discussed. Comparing with pure ZnO and ZnO-AC, Ag/ZnO-AC composite showed greatly enhanced photocatalytic activity. The results demonstrate that the hybridization of silver, activated carbon and ZnO can significantly improve the photocatalytic activity of ZnO. This work could provide new insights into the fabrication of noble metal/ZnO-carbon based composites and facilitate their application in environmental protection issues.     

Ag/TiO2薄膜结构和光催化性能研究

采用溶胶-凝胶技术制备了Ag掺杂的TiO₂薄膜.用XRD、氮吸附法、UV-VIS-NIR分光光度计以及XPS对Ag掺杂后TiO₂薄膜结构的变化进行了分析;用分光光学法通过在紫外光照下分解亚甲基蓝的实验比较了TiO₂薄膜与Ag/TiO₂薄膜的光催化性能.结果发现,掺杂适量的Ag有助于TiO₂薄膜光催化氧化性能的提高,原因在于:（1）Ag通过引入耗尽层提高了TiO₂的电荷分离能力,并吸引空穴向薄膜表面移动,结果使薄膜表面空穴的浓度提高,薄膜光催化效率提高;（2）Ag减小了TiO₂粒子的粒径,使TiO₂禁带宽度增大,薄膜光催化氧化的能力提高;（3）Ag掺杂后,TiO₂薄膜表面对-OH基和水的吸附增加,使光照后TiO₂薄膜表面活性自由基·OH的浓度增加,空穴向薄膜所吸附物质的转移能力提高.     

掺银二氧化钛纳米带的制备及其光催化性能研究

TiO2纳米带作为一种纳米光催化剂用于污水处理中时,能克服TiO2纳米颗粒不易分离同收等困难,对其进行贵金属掺杂,可提高其光催化活性.本研究以价格低廉的钛白粉为原料,采用水热法制备了掺银的TiO2纳米带,并运用XRD,SEM和EDS等对所制备的样品进行表征,进行了光催化降解甲基橙反应,考察了纳米带中的掺银量,煅烧温度等条件对降解甲基橙反应的影响.结果表明,当TiO2纳米带掺银量为0.1%(质量分数,下同),焙烧温度为700℃,催化剂用量为0.05g,室温下用15W紫外灯光照180min时,掺银的TiO2纳米带对甲基橙的降解率可达98.51%,较掺杂前提高了22%左右.