Enhanced visible-light-induced photocatalytic disinfection of E. coli by carbon-sensitized nitrogen-doped titanium oxide

Nitrogen-doped titanium oxide (TiON) nanoparticle photocatalysts were synthesized by a sol-gel process, for disinfection using E. coli as target bacteria. Our work shows thatthe calcination atmosphere has strong effects on the composition, structure, optical, and antimicrobial properties of TiON nanoparticles. Powders calcinated in a flow of N2 atmosphere (C-TiON) contain free carbon residue and demonstrate different structures and properties compared to the TiON powders calcinated in air. Disinfection experiments on Escherichia coli indicate that C-TiON composite photocatalyst has a much better photocatalytic activity than pure TiON photocatalyst under visible light illumination. The enhanced photocatalytic activity is related to stronger visible light absorption of the carbon-sensitized TiON.     

Hydrothermal synthesis and photocatalytic activity of zinc oxide hollow spheres

ZnO hollow spheres with porous crystalline shells were one-pot fabricated by hydrothermal treatment of glucose/ZnCl2 mixtures at 180 degrees C for 24 h, and then calcined at different temperatures for 4 h. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of Rhodamine B aqueous solution at ambient temperature. The results indicated that the average crystallite size, shell thickness, specific surface areas, pore structures, and photocatalytic activity of ZnO hollow spheres could be controlled by varying the molar ratio of glucose to zinc ions (R). With increasing R, the photocatalytic activity increases and reaches a maximum value at R = 15, which can be attributed to the combined effects of several factors such as specific surface area, the porous structure and the crystallite size. Further results show that hollow spheres can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and reused than conventional powder photocatalyst. After many recycles for the photodegradation of RhB, the catalyst does not exhibit any great loss in activity, confirming ZnO hollow spheres is stability and not photocorroded. The prepared ZnO hollow spheres are also of great interest in solar cell, catalysis, separation technology, biomedical engineering, and nanotechnology.     

Efficient photocatalytic decomposition of perfluorooctanoic acid by indium oxide and its mechanism

Perfluorooctanoic acid (C(7)F(15)COOH, PFOA) has increasingly attracted worldwide concerns due to its global occurrence and resistance to most conventional treatment processes. Though TiO(2)-based photocatalysis is strong enough to decompose most organics, it is not effective for PFOA decomposition. We first find that indium oxide (In(2)O(3)) possesses significant activity for PFOA decomposition under UV irradiation, with the rate constant about 8.4 times higher than that by TiO(2). The major intermediates of PFOA were C(2)-C(7) shorter-chain perfluorocarboxylic acids, implying that the reaction proceeded in a stepwise manner. By using diffuse reflectance infrared Fourier transform spectroscopy, (19)F magic angle spinning nuclear magnetic resonance, and electron spin resonance, we demonstrate that the terminal carboxylate group of PFOA molecule tightly coordinates to the In(2)O(3) surface in a bidentate or bridging configuration, which is beneficial for PFOA to be directly decomposed by photogenerated holes of In(2)O(3) under UV irradiation, while PFOA coordinates to TiO(2) in a monodentate mode, and photogenerated holes of TiO(2) preferentially transform to hydroxyl radicals, which are inert to react with PFOA. PFOA decomposition in wastewater was inhibited by bicarbonate and other organic matters; however, their adverse impacts can be mostly avoided via pH adjustment and ozone addition.     

钨酸铋负载涤纶织物的制备及其光催化性能

为探讨Bi2WO6负载涤纶织物对染料的降解效果,采用丙烯酸丁酯对涤纶织物进行前处理,将十二烷基硫酸钠(SDS)和Bi2WO6 (简写为SDS-Bi2WO6)、Bi2WO6分别负载到涤纶织物上,得到负载涤纶织物。用扫描电镜、X 射线衍射与傅里叶变换红外光谱表征织物的表面形貌、晶体结构和化学结构。评价负载涤纶织物的抗紫外线性能与拒水性能,并以紫外光照射下降解亚甲基蓝研究其光催化性能。结果表明,合成的Bi2WO6颗粒为正交晶相并且均匀地负载在涤纶织物表面。与SDS-Bi2WO6负载涤纶织物相比,Bi2WO6负载涤纶织物有更好的抗紫外线性能和拒水性能。Bi2WO6负载涤纶织物具有比SDS-Bi2WO6负载涤纶织物更优异的光催化活性,紫外光照射7 h后,其对亚甲基蓝的降解率达到92%。     

TiO2涂层织物的隔热性能及其影响因素

以TiO2为功能粒子,采用涂层方法制得了隔热性能较好的TiO2涂层织物.通过扫描电镜分析对比了涂层前后织物及其纤维的形貌,讨论了基布材料、基布白度和涂层剂种类对涂层织物隔热性能的影响.结果表明:涂层后,TiO2粒子可牢固附着在织物纤维上,织物的隔热性能明显提高;基布材料对其隔热性能的影响较明显,基布白度和涂层剂对其隔热性能的影响甚微.     

溶胶-凝胶法制备的钛溶胶形态及其光催化性能

采用高分辨透射电镜(HRTEM)、X射线衍射分析(XRD)、粒度分析(DLS)等表征手段对溶胶-凝胶法所制钛溶胶和典型商品粉体TiO2的粒径、晶型和分散状态进行比较和分析,采用紫光-可见分光光度计评估上述TiO2对紫外－可见光的吸收特性,以及对酸性品红6B染料的光催化降解作用。发现,溶胶-凝胶法所制钛溶胶颗粒具有典型的锐钛晶型,且相对于粉体TiO2,其在水分散液中的表观粒径更小、分散程度更高、分散稳定性更好。因而对紫外－可见光具有高的选择性吸引特性(紫外屏蔽/可见光透过),对染料分子具有更强的光催化降解作用。     

Application of reduced graphene oxide and carbon nanotube modified electrodes for measuring the enzymatic activity of alcohol dehydrogenase

An electrochemical method was developed to measure the enzymatic activity of alcohol dehydrogenase (ADH) by monitoring the amount of reduced nicotinamide adenine dinucleotide (NADH) generated in the catalysed oxidation of ethanol by ADH. The concentration of NADH was determined by amperometric measurements, which recorded the oxidation current of NADH versus time on reduced graphene oxide and functionalised multi-walled carbon nanotube modified electrodes. The initial reaction rates and the apparent Michaelis constants of the enzymatic reaction were obtained in the absence and presence of Al³⁺ and nanometre-sized tridecameric aluminium polycationic (nano-Al₁₃) species. The results showed that Al³⁺ and nano-Al₁₃ exhibited inhibitory effect on the enzymatic activity of ADH. Fluorescence and circular dichroism spectra indicated the inhibitory effect was likely caused by the conformational changes of ADH and/or NADH induced by Al³⁺ and nano-Al₁₃.     

Fe3+/TiO2负载型活性炭的制备及其光催化活性的研究

以TiCl4为原料，采用沉淀法制备了Fe^3＋掺杂的TiO2溶胶。研究了溶胶浓度与负载方式对活性炭负载Fe^3＋／TiO2溶胶光催化降解亚甲基蓝的影响。对Fe^3＋／TiO2溶胶进行XRD、UV-Vis的表征显示，该溶胶为纯锐钛矿型TiO2，粒径约为12．6nm。紫外光照射300min，活性炭负载型Fe^3＋／TiO2可降解溶液中80％的亚甲基蓝，且该溶胶可多次回收利用，具有较高的重复利用率和催化降解效率。     

甘蓝过氧化物酶活性及其影响因素的研究

甘蓝POD的最适pH为5～6之间;在100℃的热烫温度下随着热烫时间的延长,POD酶活降低,而贮藏2d后酶活的再生量先增大后降低,在热处理时间为1min-1．5min时达到最大值;Na^＋和Ca^2＋显著抑制POD酶活力。因此,当热处理温度为100℃、加热2min,热处理液pH为8,ZnCl2质量浓度为100mg／L,CaCl2质量浓度为300mg／L时,可基本破坏甘蓝中的POD酶活,且甘蓝的质构和色泽较好。     

Enhanced photocatalytic activity of nafion-coated TiO2

Photocatalytic degradation (PCD) of aqueous paraquat was accelerated by the addition of either phosphate or sulfate salt. Attachment of these anions to the TiO2 surface possibly results in increased adsorption of the cationic paraquat species and in turn its photocatalysis rate. The same effect was obtained more consistently using the Nafion (an anionic polymer)-coated TiO2. Enhanced PCD of paraquat and some amine compounds was noted. However the anionic and neutral compounds were not affected significantly. Nafion proved to be stable against photocatalysis. It has been suggested that the degradation rate is larger for the cationic compounds with higher pK(B). For a phenol-paraquat-TiO2 system, paraquat degradation did not begin till near-complete phenol removal. Using the Nafion-coated TiO2, both phenol and paraquat degradations started simultaneously. Nevertheless, complete paraquat removal still took longer than phenol.     

二氧化钛改性对光催化降解甲基橙的研究

以钛酸四丁酯为钛源,采用溶胶-凝胶法制备TiO2粉体;并以硝酸铜为铜源,氨水为氮源制成Cu掺杂、Cu-N共掺杂的改性TiO2粉体.采用球磨法对掺杂TiO2粉体进行粉磨;采用XRF、XRD、SEM、粒度分析对不同TiO2粉体进行了表征;以甲基橙为降解对象,考察了TiO2粉体作为光催化剂的光催化降解能力.结果表明:Cu-N共掺杂所起到的协同作用使改性后的TiO2粉体在紫外与可见光下的光催化能力得到了较大提高,Cu掺杂量最佳值为0.50%;通过2 h、230 r/min的高能球磨,有效地提高了光催化速率.     

N掺杂改性P_(25)抑菌材料的制备及其可见光催化抑菌活性的研究

为提高纳米Ti O2(P25)对光照的吸收能力并增强其可见光催化抑菌活性,采用研磨-煅烧法将脲掺入Ti O2(P25)中对其进行改性,以可见光条件下N-P25改性抑菌材料对大肠杆菌抑菌效果为考察指标,对N-P25改性抑菌材料的制备条件进行优化。结果表明:脲掺杂量8.70 g/g P25,煅烧温度548℃,煅烧时间为1.9 h时,改性P25-N材料在可见光条件下对大肠杆菌的抑菌率为90%,较未改性的P25材料抑菌率(79%)提高了11%,有效地提高P25材料的抑菌率。研究结果为Ti O2光催化技术应用于制备抑菌性水果包装膜提供了参考。     

Ni掺杂ZnO催化剂的制备及其光催化活性

采用沉淀法制备不同Ni掺杂比的ZnO催化剂(Ni-ZnO),用X射线衍射仪、扫描电子显微镜、紫外-可见漫反射光谱仪和荧光分光光谱仪进行表征。以亚甲基蓝溶液为模拟染料废水,考察Ni掺杂比对ZnO光催化活性的影响。结果表明,Ni掺杂到ZnO中能显著提高ZnO的光催化活性,6%Ni-ZnO的光催化活性最高,120 min时对亚甲基蓝的降解率达到94.4%。     

Colloidal structure of honey and its influence on antibacterial activity

Honey colloidal structure emerges as a new trend in research on honey functions since it became recognized as a major factor altering bioactivity of honey compounds. In honey complex matrix, macromolecules self-associate to colloidal particles at the critical concentration, driven by honey viscosity. Sequestration of macromolecules into colloids changes their activities and affects honey antibacterial function. This review fills the 80-year-old gap in research on honey colloidal structure. It summarizes past and current status of the research on honey colloids and describes physicochemical properties and the mechanisms of colloid formation and their dissociation upon honey dilution. The experimental observations are explained in the context of theoretical background of colloidal science. The functional changes and bioactivity of honey macromolecules bound to colloidal particles are illustrated here by the production of H₂O₂ by glucose oxidase and the effect they have on antibacterial activity of honey. The changes in the production of H₂O₂ and antibacterial activity of honey were coordinated with the changes in the aggregation–dissociation states of honey colloidal particles upon dilution. In all cases, these changes were nonlinear, assuming an inverted U-shaped dose–response curve. At the curve maximum, the production of H₂O₂ and antibacterial activity reached the peak. The curve maximum signaled the minimum honey concentration required for the phase separation. With phase transition from two-phase colloidal condense state to dilute state dispersion, the change to opposite effects of dilution on these honey's activities occurred. Thus, the colloidal structure strongly influences bioactivity of honey compounds and affects its antibacterial activity.     

Long-term storage of onion and the factors that affect its quality: A critical review

Storage of onions is a multifaceted issue, which involves many preharvest and postharvest factors. One of the major factors that affect onion storage is the selection of the proper cultivar, since there are significant differences in storability between the cultivars and not all of them are suitable for storage. Proper preharvest and postharvest conditions are essential for storability of onion bulbs, whereas they also affect marketability (weight losses, texture and color depth of bulbs) and quality (chemical composition, nutritional value, antioxidant activity). Irrigation and fertilization are essential preharvest factors that substantially affect storability, whereas curing methods and storage conditions (temperature, relative humidity, controlled atmospheres) and processing treatments are postharvest factors. This review article examines the effect of long-term storage on the main quality features of onions, such as the incidence of sprouting and root growth, water losses, and changes in chemical composition (mineral composition, sugar content, nutritional value) and antioxidant activity (phenolic and flavonoid contents, DPPH [2,2-diphenyl-1-picrylhydrazyl] scavenging activity).     

Peroxidase-like activity of aminopropyltriethoxysilane-modified iron oxide magnetic nanoparticles and its application to clenbuterol detection

A magnetic nanoparticle-linked immunosorbent assay for clenbuterol (CL) was developed using aminopropyltriethoxysilane (APTES)-modified Fe₃O₄ magnetic nanoparticles (MNPs) as a replacement for horseradish peroxidase (HRP) in conventional ELISA configurations. The catalytic activity of the as-synthesized APTES-MNPs is, like HRP, dependent on pH, temperature, and H₂O₂ concentration. The optimal reaction conditions for APTES-MNPs require a pH of 4 and a temperature of 40 °C. However, APTES-MNPs need a higher H₂O₂ concentration than HRP to reach maximal activity. Catalysis follows Michaelis–Menten kinetics. The calculated kinetic parameters exhibit a strong affinity to substrates and high catalytic activity. Comparative studies for CL demonstrate that the IC₅₀ values of CL for APTES-MNPs are 34% lower than that for HRP. The differences in limit of detection and cross-reactivity are not significant between APTES-MNPs and HRP. The proposed approach confirms that the APTES-modified Fe₃O₄ MNPs not only possess peroxidase activity but also show potential application in a variety of simple, robust, and cost-effective ELISAs in the future.     

氧化石墨烯掺杂TiO2改性活性炭纤维

为更好地解决废水污染的问题,针对活性炭纤维(ACF)改性进行了研究。以活性炭纤维为基体,采用溶胶凝胶法制备氧化石墨烯(GO)掺杂二氧化钛(TiO₂)的溶液,通过浸渍提拉法实现负载,制备了GO掺杂TiO₂的活性炭纤维。借助红外光谱、拉曼光谱、扫描电子显微镜、X射线衍射对其微观结构和表面形态进行表征和分析,并探讨了改性ACF的吸附动力学,以及GO对其可见光光催化降解性能的影响。结果表明:制备的GO-TiO₂/ACFs中TiO₂主要由锐钛矿相组成,GO的掺杂可抑制TiO₂晶体的生长和团聚,TiO₂的晶粒尺寸从15.7 nm降为8.1 nm。与TiO₂/ACFs相比,少量添加GO的GO-TiO₂/ACFs具有更优异的可见光吸附性能,对亚甲基蓝的去除率从65%增至85%,其吸附相比准一级动力学模型更符合准二级动力学模型,属单分子吸附。