海胆形氧化锌纳米结构的制备与光催化性能

以Zn(AC)2.2H2O为原料,NH3.H2O为络合剂,在NaBH4辅助下140℃水热反应2 h制备出ZnO纳米棒自组装的海胆形结构。采用X射线衍射仪、扫描电镜和透射电镜对产物进行表征。结果表明,海胆形ZnO结构的直径约为3～17μm,它是由直径约为100 nm,长度约为500 nm～3μm范围的ZnO纳米棒自组装而成。提出了ZnO纳米棒自组装海胆形结构的可能生长机理。NaBH4与溶液中的少量H+结合生成H2气泡,ZnO纳米晶吸附在H2的气液界面形成了纳米颗粒自组装的微球,随着反应时间的延长,组装成微球的ZnO纳米颗粒沿[0001]方向取向生长成ZnO纳米棒,最终形成ZnO纳米棒自组装的海胆形颗粒。室温下以海胆形ZnO纳米结构和ZnO纳米棒为光催化剂,以偶氮染料甲基橙作为光催化研究对象,紫外光照70 min,对甲基橙的降解率分别为97%和67%。     

Ni/NiO hybrid nanostructure supported on biomass carbon for visible-light photocatalytic hydrogen evolution

Well-dispersed Ni-based nanocrystals with Ni/NiO hybrid nanostructure are built on cellulose-derived carbon (Ni-C-500), which exhibits outstanding photocatalytic performance in the hydrogen evolution from water. Control experiments confirm that the optimal nickel content in Ni-C-500 is 16 wt% and the optimum calcination temperature is 500 °C. The hydrogen evolution rate on Ni-C-500 in the presence of Eosin Y and triethanolamine (TEOA) reaches 13.5 mmol/g_cat/h in the first hour, which is even higher than that on commercial Pt/C catalyst (11.4 mmol/g_cat/h). The carbon support facilitates the transfer of photogenerated electrons from photosensitizer to Ni-based nanocrystals, efficiently preventing the recombination of photogenerated electrons and holes during the photocatalytic procedure. Density functional theory (DFT) calculations further demonstrate that the NiO islands on Ni(111) surface facilitate the adsorption of water molecules because of the interaction between the oxygen atom of NiO island and the hydrogen atom of water. Furthermore, produced H_ad around NiO island of Ni(111) surface is more easily to form hydrogen on Ni/NiO hybrid nanostructure than on clean Ni(111) surface.

Graphical abstract

Ni/NiO hybrid nanostructure supported on biomass carbon for visible-light photocatalytic hydrogen evolution

     

Microwave-assisted combustion synthesis of ZnAl2O4 and ZnO nanostructure particles for photocatalytic wastewater treatment

ZnAl₂O₄ and ZnO nanostructure particles and in situ crystallization of zinc aluminate and zinc oxide coating layers on sintered α-Al₂O₃ and γ-Al₂O₃ granules by the microwave-assisted combustion method were investigated. For powders, the effects of solution pH value and for coated samples the influence of support type on the structure, microstructure, and photocatalytic activity of powders were studied. Results showed that variation of synthesis pH value caused to considerable change in agglomeration, specific surface area, obtaining up to 88 and 92% yields for zinc aluminate and zinc oxide nanoparticles, respectively. γ-alumina granules were more appropriate supports than the α-alumina ones because of the better photocatalytic activities and lower extent of the attritions for both zinc aluminate and zinc oxide coating layers.     

纳米结构TiO2/SiO2的制备、结构与光催化性能

用自组装技术合成了纳米TiO2包覆的SiO2粒子.其中TiO2胶体通过溶胶-凝胶方法得到.讨论了不同晶型负载TiO2的合成条件及光催化性.样品经IR,SEM,XRD等进行表征.实验结果表明:SiO2粒子表面的纳米TiO2具有较好的均匀性;TiO2的含量随覆盖层的增加而增多;组装两层样品具有较大的比表面;经100℃干燥可得到不同晶型的纳米TiO2,且锐钛矿型含量较高的纳米TiO2组装粒子具有较好的光催化性能,     

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.     

The effect of pH value on the synthesis and photocatalytic performance of MnWO4 nanostructure by hydrothermal method

In this study MnWO₄ nanocrystals with different morphologies were synthesised by a simple hydrothermal method with MnCl₂?·?4H₂O and Na₂WO₄?·?2H₂O as source materials. The products were characterised by X-ray powder diffraction, field-emission scanning electron microscopy, Raman spectroscopy and fluorescence spectroscopy. The results reveal that pH value plays an important role in the morphology and phase of samples. A simple reaction mechanism for the formation of MnWO₄ was presented. The photodegradation of acetone was employed as a probe reaction to test the photoactivities of the as-prepared samples.     

Visible light-driven photocatalytic degradation and mineralization of the malachite green dye in a slurry photoreactor

The as-synthesized BiOCl nanoparticles were characterized by x-ray diffraction (XRD) and ultraviolet–visible (UV–Vis) techniques. The XRD pattern showed that a highly pure and crystalline phase has been obtained. The UV–vis diffuse reflectance spectroscopy (DRS) studies revealed the indirect band gap value of about 3.32 eV for the fabricated semiconductor. The disappearance of the dye, monitored spectrophotometrically, follows approximately pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Besides, the effect of some parameters such as the influence of the initial pH, catalyst weight, initial dye concentration, oxidant concentration, and salt concentration on the degradation of malachite green dye solution under visible light irradiation were investigated. The optimum conditions for the degradation of dye were 25 mg L^?1 dye concentration, pH of 8, and a catalyst amount of 0.7 g mL^?1. The addition of an optimal amount of hydrogen peroxide and potassium persulfate increases the degradation rate while NaCl and Na₂CO₃ decrease the rate. Complete mineralization has been confirmed by UV–Vis spectroscopy     

Construction of a Z-scheme Cu2O/SrBi4Ti4O15 p–n heterojunction for enhanced visible light photocatalytic performance for doxycycline degradation

p–n heterojunction composites with high-charge-transfer efficiency have attracted considerable attention owing to their unique structure and interface interactions. Herein, a novel Z-scheme Cu₂O/SrBi₄Ti₄O₁₅ p–n heterojunction was successfully constructed using the microwave hydrothermal method for DOC removal under visible light irradiation. The structure, composition, and photoelectric chemical properties of Cu₂O/SrBi₄Ti₄O₁₅ nanocomposites were studied. The composites exhibited high photocatalytic activity for DOC, and 92.2% of DOC was decomposed within 60 min, which is 9.2 and 5.2 times higher than those of original Cu₂O and SrBi₄Ti₄O₁₅, respectively. The extraordinary degradation performance can be attributed to the formation of Z-scheme heterostructure. On the one hand, a unique interface structure can significantly enhance the number of active sites on the catalyst surface. On the other hand, Z-scheme heterostructure can accelerate generation and migration of the photoinduced carriers. Furthermore, the effects of operational parameters such as catalyst dosage, initial concentration, inorganic salts, and water sources, were investigated. Finally, a photodegradation mechanism of Z-scheme Cu₂O/SrBi₄Ti₄O₁₅ p–n heterojunction for DOC was proposed.     

New generation photocatalysts: how tungsten influences the nanostructure and photocatalytic activity of TiO2 in the UV and visible regions

Tungsten-doped anatase was prepared by a thermal hydrolysis of aqueous solutions of peroxo complexes of titanium and tungsten. The synthesized samples included X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, Raman spectroscopy, specific surface area, and porosity determination. W doping resulted in a decrease of the unit-cell volume of anatase at lower W contents and an increase at higher W contents. The position of the most intense Raman band of the E(g) mode (near 147 cm(-1)) also has a local minimum at medium-doped titania (1.1-3.6% W in titania). W doping increases the temperature of anatase-to-rutile transformation by about 100 °C compared with nondoped anatase. The photocatalytic activity of doped titania samples was determined by decomposition of Orange II dye during irradiation at 365 and 400 nm. Specimens with moderate W doping (1.0-3.3% W) perform best: they enhance the corresponding reaction rates 10 times at 365 nm and 5 times at 400 nm, respectively, compared with pure titania obtained under the same set of synthesis conditions.     

Fabrication of nanostructure and formation of nanocrystal for non-volatile memory

In this work, we have demonstrated that the nanocrystal created by combining the self-assembled block copolymer thin film with regular semiconductor processing can be applicable to non-volatile memory device with increased charge storage capacity over planar structures. Self-assembled block copolymer thin film for nanostructures with critical dimensions below photolithographic resolution limits has been used during all experiments. Nanoporous thin film from PS-b-PMMA diblock copolymer thin film with selective removal of PMMA domains was used to fabricate nanostructure and nanocrystal. We have also reported about surface morphologies and electrical properties of the nano-needle structure formed by RIE technique. The details of nanoscale pattern of the very uniform arrays using RIE are presented. We fabricated different surface structure of nanoscale using block copolymer. We also deposited Si-rich SiNx layer using ICP-CVD on the silicon surface of nanostructure. The deposited films were studied after annealing. PL studies demonstrated nanocrystal in Si-rich SiNx film on nanostructure of silicon.     

A DNA nanostructure platform for directed assembly of synthetic vaccines

Safe and effective vaccines offer the best intervention for disease control. One strategy to maximize vaccine immunogenicity without compromising safety is to rationally design molecular complexes that mimic the natural structure of immunogenic microbes but without the disease-causing components. Here we use highly programmable DNA nanostructures as platforms to assemble a model antigen and CpG adjuvants together into nanoscale complexes with precise control of the valency and spatial arrangement of each element. Our results from immunized mice show that compared to a mixture of antigen and CpG molecules, the assembled antigen-adjuvant-DNA complexes induce strong and long-lasting antibody responses against the antigen without stimulating a reaction to the DNA nanostructure itself. This result demonstrates the potential of DNA nanostructures to serve as general platforms for the rational design and construction of a variety of vaccines.     

Synthesis of r-GO-incorporated CoWO4 nanostructure for high-performance supercapattery applications

The avant-garde supercapatteries have received substantial curiosity for their noteworthy electrochemical performance. Devising battery-type substances with appreciable electrocapacitive accomplishment and high electrical transmittance is imperative to boost the energy stowing knack of supercapattery devices. A pure CoWO₄ nanostructure and a composite of CoWO₄ incorporating r-GO were prepared by hydrothermal method. The XRD and FTIR results validated the effective development of high-quality CoWO₄ and r-GO. FESEM images reveal a nanosphere-like architecture of CoWO₄ over r-GO sheets. The pure and composite nanomaterials show good battery-like traits in electrochemical studies. The CoWO₄/r-GO electrode exhibits better electrochemical activity compared to pure sample. The specific capacitance (and specific charge capacity) calculated at a current density of 2 A g^?1 for CWO/r-GO and CWO is 382.7 A g^?1 (158.1 C g^?1) and 262.7 A g^?1 (105.1 C g^?1), respectively. The results obtained herein evince that the developed nanocomposite is a propitious electrode candidate for supercapattery.

     

An approach for synthesizing various types of tungsten oxide nanostructure

Various types of tungsten oxide nanostructures, including nanowires, nanobundles, and three-dimensional nanowire networks, have been synthesized on large-area silicon substrates by simply heating an array of tungsten filaments in a vacuum chamber. The fine structure and components of as-prepared products can been controlled by changing the tungsten filament temperature. This approach is free of catalysts and templates, and provides an economical method for large-scale preparation of various types of tungsten oxide nanostructures for applications.     

Application of carbon-coated TiO2 for decomposition of methylene blue in a photocatalytic membrane reactor

An application of carbon-coated TiO(2) for decomposition of methylene blue (MB) in a photocatalytic membrane reactor (PMR), coupling photocatalysis and direct contact membrane distillation (DCMD) was investigated. Moreover, photodegradation of a model pollutant in a batch reactor without membrane distillation (MD) was also examined. Carbon-modified TiO(2) catalysts containing different amount of carbon and commercially available TiO(2) (ST-01) were used in this study. The carbon-coated catalyst prepared from a mixture of ST-01 and polyvinyl alcohol in the mass ratio of 70/30 was the most effective in degradation of MB from all of the photocatalysts applied. Photodecomposition of MB on the recovered photocatalysts was lower than on the fresh ones. The photodegradation of MB in the PMR was slower than in the batch reactor, what probably resulted from shorter time of exposure of the catalyst particles to UV irradiation. The MD process could be successfully applied for separation of photocatalyst and by-products from the feed solution.     

Novel flower-like (Bi(Bi2S3)9I3)2/3 nanostructure as efficient photocatalyst for photocatalytic desulfurization of benzothiophene under visible light irradiation

Here, we report the preparation of hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures that acts as a strong photocatalyst in the desulfurization of benzothiophene. We optimized the reaction time, type of capping agent and reflux temperature to tune the shape of porous flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures to achieve the highest desulfurization performance. We investigated the characteristic shape, size, purity, and optical response of the flower-shape nanostructures using XRD, EDS, FESEM, UV–Vis-DRS analysis. The flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures showed a significant photocatalytic property in desulfurization of benzothiophene as a model fuel. The hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 photocatalyst with an energy gap of 1.15 eV, exhibits a 92% photocatalytic desulfurization performance after 2 h of visible light irradiation. The (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures show a high photocatalytic reproducibility after 4 rounds of exposure. We proposed a photo-oxidation mechanism based on the active species scavenging, which revealed the role of photo-produced h⁺ and O₂^? species as essential in the photocatalytic desulfurization process. These findings provide a new prospect and design strategy for the development of efficient photocatalysts in desulfurization process.     

Temperature dependence of silver nanostructure for surface enhanced Raman scattering application

We study the fabrication and application of the fractal silver nanostructure using an electrochemical process. Scanning electron microscope and high resolution transmission electron microscope images show the morphology of silver nanostructure can be well controlled via the various reaction times. The surface enhanced Raman scattering of 10 microM aqueous Rhodamine 6G (R6G) solutions conducted in as-fabricated silver nanostructure achieved an enhancement factor approximately 10(5) at room temperature. Meanwhile, an approximately 10(4) enhancement factor of SERS signal can be kept under 200 degrees C in present study. This study can help us to integrate the nano-metals and nano-particles for advanced nano devices.