Selectivity in photocatalysis by particulate semiconductors

TiO₂, Fe₂O₃, CuO, ZnO, ZnS, Nb₂O₅, MoO₃, CdO, CdS, Sb₂O₃, CeO₂, HgO, Pb₂O₃, PbO₂ and Bi₂O₃ microparticles exhibit band gap excitation with UV-A light but they are selective to photodegrade phenols. While TiO₂ anatase and ZnO photocatalyze the degradation of phenol, o-aminophenol, m-aminophenol, p-aminophenol, o-chlorophenol, m-chlorophenol, p-chlorophenol, o-nitrophenol, p-nitrophenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol and quinol, MoO₃ does not photodegrade any of the fifteen phenols. Fe₂O₃, CuO, ZnS, Nb₂O₅, CdO, CdS, Sb₂O₃, CeO₂, HgO, Pb₂O₃, PbO₂ and Bi₂O₃ are selective in photodegrading the fifteen phenols; however, the phenols get adsorbed over all sixteen particulate semiconductors.      

Enhanced photodegradation of 2,4-dinitrophenol by n–p type TiO2/BiOI nanocomposite

Photocatalysis has recently been regarded as one of the most viable technologies for water treatment. Scholars all over the world are focusing on nanocomposites for water treatment for efficient and effective sanitization of bodies of water. Because of their high surface area, high chemical reactivity, excellent mechanical strength, low cost, and nanoscale composite materials have enormous potential to purify water in a various way. In this study, n-type TiO₂ was synthesized and tailored to produce a TiO₂/BiOI n–p nanocatalyst for enhanced photodegradation of 2,4-dinitrophenol (2,4-DNP) under UV-A and solar light respectively. Because of the formation of a heterojunction between BiOI and TiO₂, the photocatalytic activity in TiO₂/BiOI absorbs strongly in both the UV and visible regions and it has a lower recombination rate of the e^-/h⁺ pairs. Furthermore, the generation of OH^?, O₂^?– radicals during the oxidation process is attributed to the photodegradation of 2,4-DNP. The results revealed that the TiO₂/BiOI manifest outperformed BiOI and TiO₂ in terms of photocatalytic function. XRD, BET, HR-SEM-EDX with ECM, HR-TEM, FT-IR, PL, and UV-DRS techniques determined the photocatalyst composition. The HR-SEM images clearly showed that the particles are less than 27 ?nm in size. Thus, nanocomposite materials have played an important role in water purification.     

V2O5·xH2O-BiVO4纳米复合材料的可控合成和可见光响应的光催化性质

以单斜相V2O5·xH2O纳米线为前驱物,在温和条件下合成出V2O5·xH2O-BiVO4复合光催化剂.为理解产物的物相含量、形貌和光催化性质随合成时间延长而变化的情况,利用X射线衍射仪、场发射扫描电子显微镜、紫外-可见漫反射光谱仪以及光催化性质测试实验对三个典型的V2O5·xH2O-BiVO4样品(分别在反应6、12和24 h获得)进行了研究.分析结果表明:V2O5·xH2O-BiVO4纳米复合材料由V2O5·xH2O纳米线和BiVO4纳米晶组成,并且随合成反应时间的延长,产物中V2O5·xH2O纳米线的含量逐渐减少而BiVO4纳米晶的含量逐渐增加.光催化性质测试结果表明:V2O5·xH2O-BiVO4复合光催化剂在可见光(λ>400 nm)辐射下降解亚甲基蓝时表现出了提高的光催化效率,其中在反应12 h获得的V2O5·xH2O-BiVO4样品体现出最好的光催化活性,这可能是由于其适当的组分含量和特殊的微结构有利于半导体激发和染料激发两种光催化机理的协同作用.     

贵金属负载的棒状ZnO复合光催化剂的制备及其提升的光催化性能

以水热制备的ZnO纳米棒为基底,通过乙二醇液相还原法负载不同贵金属颗粒(Pt、Pd、Ru)构筑贵金属负载的ZnO纳米棒复合光催化剂。实验结果表明在制备条件相同时,Pt/ZnO样品中Pt颗粒尺寸较小,分布均匀;Pd/ZnO样品中Pd颗粒尺寸较大且团聚严重;Ru/ZnO样品则几乎没有Ru颗粒负载。在紫外光照射下降解亚甲基蓝的反应中,Pt/ZnO表现出最高的光催化性能,Pd/ZnO样品次之,而Ru/ZnO则表现出与ZnO纳米棒相似的光催化活性;表明小尺寸和大小均匀的贵金属颗粒对ZnO纳米棒的催化性能有着显著的提升作用。对Pt/ZnO来说,当Pt载量为3.2%时Pt/ZnO催化剂的光催化活性最高。     

Enhanced Charge Separation of α-Bi2O3-BiOI Hollow Nanotube for Photodegradation Antibiotic Under Visible Light

It is highly desirable to exploit semiconductor materials with high photocatalytic degradation activity, especially bismuth oxyhalide semiconductor photocatalysts with special layered structure and suitable bandgap width. The low utilization rate of visible light and high recombination rate of photogenerated electron-hole of BiOI photocatalyst severely restrict its development. Herein, a heterojunction photocatalyst of α-Bi₂O₃-BiOI hollow nanotube was prepared by electrospinning method, solvothermal method and ion-exchange method. The α-Bi₂O₃-BiOI(BB-4, the stirring time of Bi₂O₃ in KI solution was 4 h) exhibited the best photocatalytic performance towards degrading the tetracycline hydrochloride(TC) solution, which could remove 85% of TC(10 mg/L) in 2 h under visible light irradiation. The estimated k_TC of α-Bi₂O₃-BiOI(BB-4) was ca. 3.9 and 1.8 times as much as that of α-Bi₂O₃ and pure BiOI, respectively. It indicated that the formation of α-Bi₂O₃-BiOI heterojunction can significantly improve the separation efficiency of photogenerated electron-hole pairs, therefore the photocatalytic ability was enhanced. Furthermore, a corresponding photocatalytic mechanism was proposed that ^·O₂^- radical and holes are the main active components in the photodegradation through trapping experiment.     

聚己内酯-聚醚嵌段共聚物的光降解特性与机理

聚己内酯 聚醚嵌段共聚物（ＰＣＥ）是一种可生物降解的高聚物［１］ ．我们已经报道了ＰＣＥ在体内及体外的降解特性,发现ＰＣＥ的降解速度随着共聚物中聚醚含量的增加,温度升高,介质的酸碱性和酶的存在而加快．当ＰＣＥ植入于动物体内,它的降解速度大大加快,因此ＰＣＥ是一种极具应用前景的生物医用材料［２ ,３］ ．众所周知,大多数的聚合物暴露在阳光下时,由于紫外光引发的自由基反应,会发?     

中空多壳层结构材料的制备及气体传感应用研究进展

先进气体传感器技术在现代社会安全生产生活中扮演着极为重要的角色,而高效敏感材料的设计与开发是其中的关键.中空多壳层结构材料因其独特的层层嵌套的多壳层与多腔体结构而表现出特别的物理化学性质,在气体传感领域显现出巨大的应用潜力.传统的硬模板法、软模板法以及基于奥斯特瓦尔德熟化和柯肯德尔效应的无模板法在中空多壳层纳米结构材料的普适制备及壳层结构的精确调控等方面存在诸多限制.次序模板法的出现突破了上述限制,促进了该领域的迅速发展.本文简要回顾了中空多壳层结构材料制备方法的发展历程,介绍了其在甲醛、乙醇、丙酮、甲苯及二氧化氮等有害气体检测中的具体应用,分析了其在气体传感领域的独特优势,最后对该领域面临的挑战和发展前景进行了总结与展望.     

Temperature dependency of the intrinsic carrier density of hydrogenated amorphous silicon in MOS structures

The admittance versus frequency of a hydrogenated amorphous silicon metal oxide semiconductor capacitor is measured at a fixed bias in inversion and for temperatures in the range of 20–50 °C. The data are fitted to theoretical capacitance and conductance curves where the time constant of inversion is the result of the fit. In turn, the time constant can be converted to the (minority) carrier lifetime so that a lifetime value for each measurement temperature is available. The conversion from the time constant to the minority carrier lifetime requires the knowledge of the temperature-dependent intrinsic carrier density or rather its activation energy. The criterion for the correct choice is a temperature-independent carrier lifetime. Three published room temperature values of the intrinsic carrier density have been tested. The carrier lifetime activation energy is E _a = 0.70 ± 0.03 eV. Received: 17 June 1998 / Accepted: 23 October 1998     

Synthesis,characterization and photocatalytic properties of Mg1−xZnxAl2O4 spinel nanoparticles

Mg_1−xZn_xAl₂O₄ spinel nanoparticles with x = 0, 0.05, 0.10, 0.15 and 0.20 were prepared via the chemical coprecipitation method. The obtained samples were characterised by thermal gravimetric and differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, UV–Vis diffuse reflection spectrum, transmission electron microscopy and ²⁷Al MAS-NMR spectroscopy. Mg_1−xZn_xAl₂O₄ spinel powders with the mean crystallite size of around 11 nm–14 nm were obtained. The crystallinity of the MgAl₂O₄ samples increases with the increase in the calcination temperature. At the same calcination temperature, higher amount of Zn²⁺ substitution leads to the higher level of crystallinity, but has no apparent influence on the mean crystallite size of the samples. The photocatalytic activity of the obtained Mg_1−xZn_xAl₂O₄ spinel nanoparticles was evaluated by monitoring the degradation of methylene blue under UV light. The degradation rates of methylene blue using the MgAl₂O₄ nanoparticles prepared at the calcination temperatures of 700 °C and 800 °C are much higher than those prepared at 900 °C and 1000 °C. The photocatalytic activities of the spinel powders with lower level of Zn²⁺ substitution such as Mg_0.95Zn_0.05Al₂O₄ are inferior to that of MgAl₂O₄. Results of ²⁷Al MAS-NMR spectroscopy analysis and the first principle total density of state calculations reveal that this is probably due to the substitutions of Zn²⁺ decreasing the degree of Al³⁺ ions inversion over the sites of tetrahedral and octahedral coordination. With the increase in the amounts of Zn²⁺ substitution, the effects of Zn²⁺ additions on the photocatalytic activities become gradually predominant, leading to the increases in the degradation rates. The methylene blue degraded by 99% within 4 h using the Mg_0.8Zn_0.2Al₂O₄ spinel powders.     

A novel nonaqueous route to V2O3 and Nb2O5 nanocrystals

The reaction between transition metal alkoxides and benzyl alcohol provides a novel soft chemistry route to metal oxide nanoparticles. The method allows the preparation of nanocrystals of two important transition metal oxides, namely V₂O₃ and Nb₂O₅. Although the reaction temperatures of 200–220 °C are comparably low, the obtained particles are highly crystalline. According to TEM investigations, the V₂O₃ crystals exhibit particle sizes between 20 and 50 nm, and the Nb₂O₅ crystals display platelet-like particle shapes with sizes of 50–80 nm, without any indications of amorphous character.     

Design of molecular precursors for nanomaterials

This work is focused on the synthesis of bimetallic oxide prepared by non-hydrolytic sol–gel method using the chemie douce approach. The bimetallic oxide was characterized by using various analytical techniques. Elemental analysis showed consistency with the formulation. From XRD, SEM and TEM studies, it is concluded that precursor chemistry has a significant effects on the surface chemistry of metal oxide on calcinations and as well as synthetic routes. XRD patterns show that an enhanced homogeneity on calcinations. Use of these metal oxides has commercial importance in future for sensor devices.     

Detection of mutant p53 using field-effect transistor biosensor

We assessed the abilities of wild p53 and mutant p53 proteins to interact with the consensus DNA-binding sequence using a MOSFET biosensor. This is the first report in which mutant p53 has been detected on the basis of DNA-protein interaction using a FET-type biosensor. In an effort to evaluate the performance of this protocol, we constructed the core domain of wild p53 and mutant p53 (R248W), which is DNA-binding-defective. After the immobilization of the cognate DNA to the sensing layer, wild p53 and mutant p53 were applied to the DNA-coated gate surface, and subsequently analyzed using a semiconductor analyzer. As a consequence, a significant up-shift in drain current was noted in response to wild p53, but not mutant p53, thereby indicating that sequence-specific DNA-protein interactions could be successfully monitored using a field-effect-based biosensor. These data also corresponded to the results obtained using surface plasmon resonance (SPR) measurements. Taken together, our results show that a FET-type biosensor might be promising for the monitoring of mutant p53 on the basis of its DNA-binding activity, providing us with very valuable insights into the monitoring for diseases, particularly those associated with DNA-protein binding events.     

Template synthesis of tin-doped indium oxide (ITO)/polymer and the corresponding carbon composite hollow colloids

SnO₂, In₂O₃, and Sn-doped In₂O₃ (ITO)/polymer and the corresponding carbon composite hollow colloids are template synthesized. It is essential that the sulfonated gel shell of the cross-linked polystyrene hollow colloid can favorably induce adsorption of target precursors. After being calcined in air to remove the template, SnO₂, In₂O₃, and ITO hollow colloids are obtained. Because the cross-linked polymer gel can be transformed into carbon in nitrogen at higher temperature such as 800 °C, metal oxide/carbon hollow colloids are consequently derived, whose shells are mesoporous. The SnO₂-, In₂O₃-, and ITO-containing polymer or carbon composite hollow colloids will be promising in sensors, catalysts, and fuel cells as electrode materials. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

离子液体在制备金属氧化物纳米材料中的应用

总结了近年来在离子液体中制备金属氧化物纳米材料的新方法以及离子液体在金属氧化物纳米材料制备方面的应用及发展趋势.目前,对于制备纳米金属氧化物,离子液体主要是作为电解液、表面活性剂;其未来的发展趋势是离子热合成和集模板-溶剂-反应物于一身的离子液体反应.