Photoswitching of diarylethene using bisazomethine dye

The photoswitching behavior of a diarylethene/glass/bisazomethine (DE/glass/BAE) three-layered structure was investigated. Upon UV light irradiation of 300 nm, DE in the three-layered structure was isomerized by a cyclization photochromic reaction and its color changed from red to deep red. BAE is a blue–violet compound with strong absorption in the region from 400 to 600 nm and fluorescence from 550 to 700 nm. When UV radiation having a wavelength of 300 nm was irradiated on the BAE layer, DE underwent a cycloreversion photochromic reaction, and its color changed from deep red to red due to fluorescence from BAE at 604 nm. Exposure of the BAE layer to visible light did not induce the decoloration of DE because visible light induces the cycloreversion of DE was absorbed by BAE. We demonstrated that DE/glass/BAE three-layered structure has a potential application for photoswitching using a single UV light source.     

Au/ZnO nanocomposites: Facile fabrication and enhanced photocatalytic activity for degradation of benzene

Au nanoparticles supported on highly uniform one-dimensional ZnO nanowires (Au/ZnO hybrids) have been successfully fabricated through a simple wet chemical method, which were first used for photodegradation of gas-phase benzene. Compared with bare ZnO nanowires, the as-prepared Au/ZnO hybrids were found to possess higher photocatalytic activity for degradation of benzene under UV and visible light (degradation efficiencies reach about 56.0% and 33.7% after 24 h under UV and visible light irradiation, respectively). Depending on excitation happening on ZnO semiconductor or on the surface plasmon band of Au, the efficiency and operating mechanism are different. Under UV light irradiation, Au nanoparticles serve as an electron buffer and ZnO nanowires act as the reactive sites for benzene degradation. When visible light is used as the light irradiation source, Au nanoparticles act as the light harvesters and photocatalytic sites alongside of charge-transfer process, simultaneously.     

Facile synthesis of Au/ZnO nanoparticles and their enhanced photocatalytic activity for hydroxylation of benzene

Au/ZnO nanocomposites have been prepared by a simple chemical method. For the first time, the nanocomposites were directly used as photocatalysts for hydroxylation of aromatic hydrocarbons under UV and visible light irradiation. The results show that the as-prepared photocatalysts display high photocatalytic activity for UV and visible catalytic hydroxylation of benzene. Without the assistance of any solvent or additive, high selectivity and high conversion efficiency were still obtained. Different photocatalytic mechanisms were proposed depending on whether excitation happens on ZnO semiconductor or on the surface plasmon band of Au. The former is Au nanoparticles act as electron buffer due to irradiation by UV light and ZnO nanoparticles as reactive sites for hydroxylation of benzene, the latter is that Au nanoparticles act as light harvesters and inject electrons into ZnO conduction band and as photocatalytic sites under visible light irradiation.     

Photochromism of spiropyran and diarylethenedoped silica gels prepared by the sol-gel process

Spiropyran and diarylethene were doped in silica gels which were prepared from Si(OCH₃)₄ and Si(OC₂H₅)₄, respectively, and their photochromic properties were compared. In the gels, both organics are incorporated with open modifications and show the photochromism between red and colourless modifications. The closed form of spiropyran, which is converted from the open one by irradiation with light, is thermally backed into the open form after the light is blocked. The activation energy of thermochemical reaction is 0.86 eV. Diarylethene shows no thermochemical reaction below 140°C, but shows a photochemically reversible change on alternate irradiation by light of 436.5 and 578 nm.     

A Supra‐photoswitch Involving Sandwiched DNA Base Pairs and Azobenzenes for Light‐Driven Nanostructures and Nanodevices

A supra‐photoswitch is designed for complete ON/OFF switching of DNA hybridization by light irradiation for the purpose of using DNA as a material for building nanostructures. Azobenzenes, attached to D ‐threoninols that function as scaffolds, are introduced into each DNA strand after every two natural nucleotides (in the form (NNX)n where N and X represent the natural nucleotide and the azobenzene moiety, respectively). Hybridization of these two modified strands forms a supra‐photoswitch consisting of alternating natural base pairs and azobenzene moieties. In this newly designed sequence, each base pair is sandwiched between two azobenzene moieties and all the azobenzene moieties are separated by base pairs. When the duplex is irradiated by visible light, the azobenzene moieties take the trans form and this duplex is surprisingly stable compared to the corresponding native duplex composed of only natural oligonucleotides. On the other hand, when the azobenzene moieties are isomerized to the cis form by UV light irradiation, the duplex is completely dissociated. Based on this design, a DNA hairpin structure is synthesized that should be closed by visible light irradiation and opened by UV light irradiation at the level of a single molecule. Indeed, perfect ON/OFF photoregulation is attained. This is a promising strategy for the design of supra‐photoswitches such as photoresponsive sticky ends on DNA nanodevices and other nanostructures.     

Fabrication and characterization of flower-like CuO-ZnO heterostructure nanowire arrays by photochemical deposition

A simple two step solution-based method was applied to fabricate CuO-ZnO heterostructured nanowire (NW) arrays. First, ZnO nanowires were grown on a Si substrate using the ammonia solution hydrothermal reaction. Afterwards, flower-like CuO crystals were photochemically deposited on the tip of the ZnO NWs, using ultraviolet (UV) light (312 nm wavelength) irradiation at room temperature. The morphology of the CuO was controlled by reaction time, density of ZnO NWs, and concentration of the solution. Because the deposited CuO is p-type and has narrow band gap properties, CuO-ZnO heterostructured NWs exhibited a stable p-n junction property and good ability to absorb visible light. Through investigation of UV light-triggered reaction phenomena, we found that the production of OH(-) from the photocatalytic process on the surface of ZnO NWs plays a critical role in the CuO deposition mechanism.     

单壁碳纳米管的光解法功能化及其对分散性能的影响(英文)

将单壁碳纳米管分散到溶有光引发剂2-羟基-2-甲基-1-苯基-1-丙醇的四氢呋喃溶液中,在紫外光辐照下,光引发剂裂解生成2-羟基异丙基自由基。通过自由基的偶合反应,2-羟基异丙基自由基偶合到碳纳米管表面。用UV-Vis光谱、FTIR、拉曼光谱、TGA-MS及HRTEM等表征方法,证实在单壁碳纳米管表面引入了羟基。UV-Vis光谱上范霍夫吸收峰的消失表明碳纳米管表面被功能化。羟基化的SWCNTs样品在FTIR光谱中出现的3420cm-1(O—H键)、2930和2859cm-1(烷基C—H键)峰进一步证实了碳纳米管的功能化。拉曼光谱显示,随着SWCNTs的功能化,其切向模式吸收带与杂碳原子吸收带的相对比值(IG/ID)下降。TGA-MS的m/z59峰(400℃)揭示了SWCNTs上存在着异丙醇基团。HRTEM和溶解数据表明,光解改性有助于碳纳米管管束间缠结的解开,进而提高了其在有机溶剂中的溶解性,并且在一定程度上保持了碳纳米管的结构。     

The synthesis and photocatalytic activity of ZnSe microspheres

This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C(4)H(4) Se) and ZnCl(2) without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (～2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed.     

Effect of the surface treatment on the room-temperature bonding of Al to Si and SiO2

Bonding of polycrystalline Al to Si(1 0 0) and SiO2 (fused silica) was carried out at room temperature by means of surface-activated bonding method. In the present work, different means of surface activation such as irradiation of an argon fast atom beam (FAB) and a hydrogen radical beam (RB) were used. Influence of the exposure to a vacuum atmosphere of the activated surfaces by fast atom irradiation on the bonding behaviour was investigated. The strength of the Al–Si joints sputter cleaned by FAB before bonding reaches as much as 32 MPa. When the activated surfaces were exposed to 30 L (where L is the abbreviation for langmuir (1.33×10-4 Pa s)) in the residual gases (mainly vapour), the strength of the Al–Si joint decreased to 20 MPa and approached that of the Al–SiO2 joint. This indicates that the fracture strength of the joint of Al and Si with an intermediate layer of OH groups and oxide is close to that of Al and Si oxide. The adhesion between Al and Si deteriorated strongly because of hydrogen termination on the Si surface which had been irradiated by the hydrogen RB. On the contrary, bonding of Si with native oxides to Al was successful with the hydrogen RB irradiation.     

Ag-Si Co-doped TiO2 photocatalyst synthesized via a nonaqueous method

Ag-Si/TiO2 photocatalysts were synthesized in a nonaqueous system at 140 degrees C, and then annealed at different temperatures. The obtained photocatalysts were characterized by XRD, TEM, BET, TG-DTA, XPS, as well as UV-vis DRS. The results showed that All Ag-Si/TiO2 held an anatase phase and high thermal stability and the phase transformation from anatase to rutile was retarded to about 900 degrees C. The Ag-Si/TiO2 particles were highly mono-dispersed and the particles size became smaller compared to TiO2. Additionally, UV-vis light absorption shifted to visible region after Ag doping. Si weaved into the matrix of TiO2, while Ag dispersed on the surface of TiO2 particles. The visible light photocatalytic activity was evaluated by Rhodamine B (RhB) degradation in an aqueous solution under visible light irradiation. It was found that the photccatalytic activities of the obtained Ag-Si/TiO2 samples were all 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 enhanced visible photocatalytic activity may be attributed to the simultaneous effects of silver and silicon co-doping.     

在线紫外辐照辅助沉积柔性ITO薄膜的研究

显示技术正朝着柔性化、超薄化方向发展,低温制备柔性ITO薄膜已经成为一大趋势.本文在射频磁控溅射过程中,引入在线紫外辐照,室温条件下在有机衬底上制备柔性ITO薄膜的工艺,其最低方块电阻为5Ω,电阻率为2.5×10 -4Ω·cm,透光率为92%,远远优于未采用紫外辐照制备的柔性ITO薄膜.我们用四探针测试仪、分光光度计、原子力显微镜、X射线衍射仪等测试仪器,对未采用和采用在线紫外辐照制备的薄膜进行测试,分析探讨了紫外线辐照对薄膜的光电性能、表面形貌和生长取向的影响.研究结果表明:在紫外线的照射下,ITO薄膜表面形貌得到改善,晶界缺陷减少,生长更均匀,致密度更好,在降低薄膜电阻率的同时,提高了薄膜在可见光区的透射率,在紫外辐照下,ITO薄膜更趋于〈222〉的择优取向,且平均晶粒尺寸变大,结晶度提高,宏观表现为薄膜的电阻率降低.     

Liquid-liquid extraction of alkali metal ions with photochromic crowned spirobenzopyrans

On the liquid-liquid extraction using 1,2-dichloroethane as an organic solvent, the crowned spirobenzopyrans exhibited textractability in the following order: Li+ > Na+ > K+ > or = tetramethylammonium ion (TMA+), Li+ > Na+ > K+ > TMA+, and Na+ > K+ > Li+ > TMA+ for spirobenzopyran derivatives bearing monoaza-12-crown-4, 1; monoaza-15-crown-5, 2; and monoaza-18-crown-6, 3; respectively, under dark conditions. The ion selectivity of 1 depends on the metal-ion complexing ability of monoaza-12-crown-4. Even 2, which carries a 15-crown-5 moiety, showed Li+ selectivity because of the much stronger interaction of Li+ with the phenolate ion of the merocyanine form of 2 than that of Na+. The Na+ selectivity of 3 is also attributed to the ionic interaction with the phenolate ion of the merocyanine form, since the ionic interaction prefers Na+ to K+ regardless of the higher affinity of the 18-crown-6 ring itself to the latter ion. The Li+ extraction into the organic phase with 1 was enhanced by UV irradiation (300-400 nm), while some depression in the extraction was found by visible irradiation (>500 nm). The effect of visible irradiation on the Li+ complexing ability of 1 was also examined with electrospray ionization mass spectrometry.     

Synthesizing tertiary silver/silica/kaolinite nanocomposite using photo-reduction method: Characterization of morphology and electromagnetic properties

Silver was loaded on silica/kaolinite by photo-reduction technique. The present study investigated the effects of the UV irradiation on different characteristics of the particles employing X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), UV–vis spectrophotometer (UVS), Brunauer–Emmett–Teller specific surface area method (BETM), zeta potential measurement (ZPM), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), electron dispersive X-ray spectrometer (EDX) and electromagnetic transition instrument (ETI). XRD, FTIR as well as UV absorption methods evidenced that synthesizing procedure was successful under UV irradiation. TGA results demonstrated that the Ag nanoparticles (AgNPs) generated on the silica/kaolinite surface can decrease thermal stability of particles due to proton delocalization of hydroxyl groups and Hofmann–Klemen effect. EDX results showed the presence of chemical elements namely Fe, Al, Si, Mg, K, Ti, Ag, Ca and Fe on the surface of tertiary nanocomposite. The synthesized silver/silica/kaolinite particles were found to have a higher electromagnetic absorption activity compared with silica/kaolinite. As a result, they can be used in polymer-based composites for preparing high performance electromagnetic interference shielding materials.     

Synthesizing tertiary silver/silica/kaolinite nanocomposite using photo-reduction method: Characterization of morphology and electromagnetic properties

Silver was loaded on silica/kaolinite by photo-reduction technique. The present study investigated the effects of the UV irradiation on different characteristics of the particles employing X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), UV–vis spectrophotometer (UVS), Brunauer–Emmett–Teller specific surface area method (BETM), zeta potential measurement (ZPM), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), electron dispersive X-ray spectrometer (EDX) and electromagnetic transition instrument (ETI). XRD, FTIR as well as UV absorption methods evidenced that synthesizing procedure was successful under UV irradiation. TGA results demonstrated that the Ag nanoparticles (AgNPs) generated on the silica/kaolinite surface can decrease thermal stability of particles due to proton delocalization of hydroxyl groups and Hofmann–Klemen effect. EDX results showed the presence of chemical elements namely Fe, Al, Si, Mg, K, Ti, Ag, Ca and Fe on the surface of tertiary nanocomposite. The synthesized silver/silica/kaolinite particles were found to have a higher electromagnetic absorption activity compared with silica/kaolinite. As a result, they can be used in polymer-based composites for preparing high performance electromagnetic interference shielding materials.     

Synthesis and photo-degradation application of WO3/TiO2 hollow spheres

A WO(3)/TiO(2) composite, hollow-sphere photocatalyst with average diameter of 320 nm and shell thickness of 50 nm was successfully prepared using a template method. UV-vis diffuse reflectance spectra illustrated that the main absorption edges of the WO(3)/TiO(2) hollow spheres were red-shifted compared to the TiO(2) hollow spheres, indicating an extension of light absorption into the visible region of the composite photocatalyst. The WO(3) and TiO(2) phases were confirmed by X-ray diffraction analysis. BET isotherms revealed that the specific surface area and average pore diameter of the hollow spheres were 40.95 m(2)/g and 19 nm, respectively. Photocatalytic experiments indicate that 78% MB was degraded by WO(3)/TiO(2) hollow spheres under visible light within 80 min. Under the same conditions, only 24% MB can be photodegraded by TiO(2). The photocatalytic mineralization of MB, catalyzed by TiO(2) and WO(3)/TiO(2), proceeded at a significantly higher rate under UV irradiation than that under visible light, and more significant was the increase in the apparent rate constant with the WO(3)/TiO(2) composite semiconductor material which was 3.2- and 3.5-fold higher than with the TiO(2) material under both UV and visible light irradiation. The increased photocatalytic activity of the coupled nanocomposites was attributed to photoelectron/hole separation efficiency and the extension of the wavelength range of photoexcitation.     

Preparation of micropatterned poly(silsesquioxane) thin films using adamantylphenol molecules

Poly(methyl silsesquioxane) (PMSSQ) thin films with micropatterned surface structures have been prepared by use of adamantylphenol molecules as a photo-thermal sensitive moiety together with UV lithographic technique and mild heating process. Initially, PMSSQ films form positive patterns of micronscale due to the film densification triggered by photooxidation and photopolymerization of doped moieties within UV exposed region. With thermal treatment, negative patterns from these pre-patterned films are formed by the difference of polycondensation rates between non-exposed regions and irradiated areas without additional developing or etching steps. This structural transformation of PMSSQ thin films was investigated using Fourier-transformed infrared spectroscopy, ultraviolet visible spectroscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and field emission scanning electron microscopy.     

C and N doped nano-sized TiO2 for visible light photocatalytic degradation of aqueous pollutants

A facile large scale synthesis of high surface area anatase TiO₂ nano material has been carried out by using the solution combustion synthesis with very widely available urea as fuel. The as-obtained puffy powder of anatase TiO₂ was characterised by X-ray diffraction (XRD), Brunauer–Emmett–Teller surface area analysis, ultraviolet–visible (UV–vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques in order to analyse the structural, optical and surface properties of the synthesised material. Diffuse UV–vis spectroscopic data show a red shift in absorption spectra which may be attributed to the possible energy levels added in between the band edges of TiO₂ due to the C and N doping as confirmed by XPS. Photocatalytic activity of the catalyst was assessed by the photocatalytic degradation of methyl orange under visible light irradiation. The effect of an electron acceptor in order to maximise the electron trapping for further inhibiting exciton recombination and thereby enhancing the oxidation of dyes has also been studied by using peroxomono sulphate(PMS) as the electron acceptor.     

Application of surfactant enhanced permanganate oxidation and bidegradation of trichloroethylene in groundwater

Fe-C-TiO(2) photocatalysts were prepared by mechanical mixing of commercial anatase TiO(2) precursor with FeC(2)O(4) and heating at 500-800 degrees C under argon flow. These photocatalysts were tested for dyes decomposition: Methylene Blue (MB), Reactive Black (RB) and Acid Red (AR). The preliminary adsorption of dyes on the photocatalysts surface was performed. Modification of anatase by FeC(2)O(4) caused reducing of zeta potential of the photocatalyst surface from +12 to -7mV and decreasing of their adsorption ability towards RB and AR, which were negatively charged, -46.8 and -39.7, respectively. Therefore, unmodified TiO(2) showed the highest degree of RB and AR decompositions in the combination of dyes adsorption and UV irradiation. Methylene Blue, which had zeta potential of +4.3 in the aqueous solution was poorly adsorbed on all the tested photocatalysts and also slowly decomposed under UV irradiation. The high rate of dyes decomposition was noted on Fe-C-TiO(2) photocatalysts under UV irradiation with addition of H(2)O(2). It was observed, that at lower temperatures of heat treatment such as 500 degrees C higher content of carbon is remained in the sample, blocking the built in of iron into the TiO(2) lattice. This iron is reactive in the photo-Fenton process resulting in high production of OH radicals and also high activity of the photocatalyst. At higher temperatures of heat treatment, less active FeTiO(3) phase is formed, therefore Fe-C-TiO(2) sample prepared at 800 degrees C showed low photocatalytic activity for dyes decomposition. Fe-C-TiO(2) photocatalysts are active under visible light irradiation, however, the efficiency of a dye decomposition is lower than under UV light. In a dark Fenton process there is observed an insignificant generation of OH radicals and very little decomposition of a dye, what suggests the powerful of photo-Fenton process in the dyes decomposition.     

微波加热法制备Ag/TiO_2及光催化降解气相甲苯

以钛酸四丁酯为钛源,分别使用微波加热法和水热法制备Ag改性的TiO2,采用X射线衍射(XRD)、X射线荧光探针(XRF)、紫外-可见漫反射(UV-Vis)和扫描电镜(SEM)对其进行表征.以气相甲苯为降解对象,分别在紫外和可见光辐照下,对样品进行光催化活性试验.结果表明:与水热法比较,微波加热法更有利于Ag对TiO2微观结构的改性,所制备的Ag改性TiO2包含了锐钛矿、金红石和板钛矿三种晶相,其粒径更小(16.4nm)、孔道结构更丰富、团聚体更小(80~200nm)、带隙能更低(2.87eV),表现出对气相甲苯更有效的紫外光和可见光降解能力.     

Effect of Laser Irradiation on Oxygen Defect Concentration on Disperse Si02 Surface

The analysis of spectral luminescence characteristics of disperse Si0₂ indicates the presence of two types of surface oxygen vacancies (O-VI and O-VII). Their concentrations can be decreased by means of near UV and IR laser irradiation. It is established that the O-V concentration decreasing under IR irradiation (λ_irr = 1064 nm) in air is caused by their laser annealing under seven-photon ionization of surface O-V with the participation of atomic oxygen formed near the surface under dissociation of atmospheric 0₂ molecules in the laser field. The irradiation by near UV laser light (λ_irr ~250-360 nm) leads to a lower effective O-V concentration with decreasing IR irradiation. The analysis of the dose dependence shows that in this case the observed effect is due to the interaction of surface O-V with bulk reagents (water, OH^- groups, 0₂ centers) or their photolysis products, not with atmospheric oxygen. The choice of laser irradiation wavelength is important for selective effect on O-VI and O-VII concentrations.