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.     

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.     

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.     

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。     

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.     

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.     

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%。     

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).     

Investigation of the photocatalytic activity of TiO2--polyoxometalate systems

The present study reports the investigation of polyoxometalate catalyzed electron transfer from the conduction band of photoexcited TiO2 to molecular oxygen. The oxidation of 1,2-dichlorobenzene (DCB) was used as an index reaction for evaluating the photocatalyst systems TiO2-PW12O40(3-), TiO2-SiW12O40,4- and TiO2-W10O32(4-) in oxygenated aqueous solution. Addition of these polyoxometalate (POM) anions to TiO2 suspensions resulted in significant rate enhancement for DCB oxidation. Photodegradation kinetics exhibited [POM] dependence, experiencing different maximum (k = 0.0318 min(-1), 0.0108 min(-1), and 0.0066 min(-1)) for each POM at different [POM] (0.1 mM PW12O40(3-), 0.07 mM SiW12O40,4- and 1 mM W10O32,4-respectively). The probability that the difference in the adsorption affinity of POMs on TiO2 surface could account for the observed ranking of photodegradation rates was ruled out by adsorption isotherm experiments that revealed similar binding constants for each POM (467 M(-1), 459 M(-1), and 417 M(-1) for PW12O40(3-), SiW12O40(4-), and W10O32(4-), respectively). DCB degradation over TiO2 with O2 or POM+O2 systems can be modeled by the Langmuir-Hinshelwood (saturation kinetics) model. The concentration-independent rate constants (kL-H) for TiO2-O2, TiO2-W10O32(4-), TiO2-SiW12O40(4-), and TiO2-PW12O40(3-) were 0.0818, 0.152, 0.421, and 0.638 min(-1), respectively. An analysis of deltaG for electron transfer from the conduction band of TiO2 to POMs in this study shows that the electron transfer takes place even when it is endothermic.     

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.     

Effects of pH and catalyst concentration on photocatalytic oxidation of aqueous ammonia and nitrite in titanium dioxide suspensions

Batch experiments were conducted to study the effects of titanium dioxide (TiO2) concentration and pH on the initial rates of photocatalytic oxidation of aqueous ammonium/ ammonia (NH4+/NH3) and nitrite (NO2-) in UV-illuminated TiO2 suspensions. While no simple kinetic model could fit the data at lower TiO2 concentrations, at TiO2 concentrations > or = 1 g/L, the experimental data were consistent with a model assuming consecutive first-order transformation of NH4+/NH3 to NO2- and NO2- to nitrate (NO3-). For TiO2 concentrations > or = 1 g/L, the rate constants for NO2 photocatalytic oxidation to NO3 were far more dependent on TiO2 concentration than were those for NH4+/NH3 oxidation to NO2-, suggesting that, without sufficient TiO2, complete oxidation of NH4+/NH3 to NO3- will not occur. Initial NH4+/NH3 photocatalytic oxidation rates were proportional to the initial concentrations of neutral NH3 and not total NH3(i.e., [NH4+] + [NH3]). Thus, the pH-dependent equilibrium between NH4+ and NH3, and not the pH-dependent electrostatic attraction between NH4+ and the TiO2 surface, is responsible for the increase in rates of NH4+/NH3 photocatalytic oxidation with increasing pH. Electrostatic adsorption, however, can partly explain the pH dependence of the initial rates of NO2- photocatalytic oxidation. Initial rates of NO2- photocatalytic oxidation were 1 order of magnitude higher for NO2- versus NH4+/NH3, indicating thatthe rate of NH4+/NH3 photocatalytic oxidation to NO3- was limited by NH4+/NH3 oxidation to NO2- under our experimental conditions.     

光催化剥色对棉纤维结构的影响

采用傅里叶变换红外光谱（FT-IR）、X-射线粉末衍射、热重（TG）-微商热重（DTG）-差示扫描量热（DSC）联用热分析法和扫描电子显微镜（SEM）技术,研究直接染料染色棉织物经不同酸碱条件下光催化体系（UV/K₂S₂O₈）剥色处理对棉纤维结构的影响。结果表明,棉纤维经不同酸碱条件下光催化剥色处理不同时间后,其大分子链段及其官能团、聚集态结构、纤维热分解性能及表面形态都有不同程度变化,尤其是碱性条件下,影响作用更为明显。     

氧化锌/凹凸棒石复合光催化材料的制备及其光催化性能研究

以凹凸棒石(ATP)为载体,氢氧化钠、醋酸锌为原料,采用多元醇法制备了氧化锌/凹凸棒石(ZnO/ATP)复合光催化材料,并用XRD、SEM、UV-Vis等测试手段对样品进行了表征,以亚甲基蓝(MB)为目标降解物,对ZnO/ATP复合光催化剂的催化性能进行评价.结果表明:ZnO/ATP复合光催化剂对MB的光催化性明显好于纯ZnO,光照120 min后的降解率可达到95.6%.     

负载纳米ZnO非织造布的制备及其光催化性能

采用自制的纳米ZnO整理剂制备了负载纳米ZnO非织造布,利用Zeta电位及粒径分析仪研究了整理剂的Zeta电位、纳米ZnO的粒径大小和分布;运用原子力显微镜(AFM)研究了负载于非织造布上纳米ZnO颗粒分布情况。研究结果表明:整理剂中ZnO颗粒的平均粒径小于100 nm,整理后非织造布上颗粒粒径大都小于100 nm。负载纳米ZnO非织造布具有良好的光催化性能和一定的耐洗性,经洗涤8次后,其光催化性能依然保持在50%以上;在相同的条件下,采用含有丙烯酸酯黏合剂的纳米ZnO整理剂处理后的非织造布耐洗牢度较好。     

Effect of cationic flaxseed protein hydrolysate fractions on the in vitro structure and activity of calmodulin-dependent endothelial nitric oxide synthase

The objective of this study was to determine the in vitro effects of cationic flaxseed protein hydrolysate fractions on calmodulin (CaM) structure as well as the activity of CaM-dependent endothelial nitric oxide synthase (eNOS). Flaxseed protein isolate was hydrolyzed with alcalase, and two peptide fractions were isolated by cation-exchange chromatography. Fraction I, eluted first from the column, and fraction II contained 42% and 51% contents of basic amino acids, respectively. Fractions I and II reduced the activity of CaM-dependent eNOS through a mostly mixed-type inhibition mode. Fraction II was at least ten times more effective as an eNOS inhibitor when compared to fraction I, as evident from the IC(50) (concentration of protein hydrolysate that reduced eNOS activity by 50%) values. Fluorescence spectroscopy showed that the tyrosine residues in CaM were increasingly exposed upon addition of fraction I, while the opposite was the case when fraction II was added. Circular dichroism studies showed that fractions I and II reduced the alpha-helix content but increased the rigidity of the active calcium/CaM complex. We concluded that ability of the protein hydrolysate fractions to change the secondary and tertiary structures of CaM may explain their ability to reduce activity of CaM-dependent eNOS.     

Photostabilization of organic UV-absorbing and anti-oxidant cosmetic components in formulations containing micronized manganese-doped titanium oxide

Micronized titanium oxide (TiO2) and manganese-doped titanium oxide (TiO2:Mn) particles have been incorporated into a variety of oil-in-water (O/W) and water-in-oil-in-water (W/O/W) emulsions in conjunction with the UV-absorbing organic compounds butyl methoxydibenzoylmethane (BMDM) and octyl methoxycinnamate (OMC) and with the anti-oxidants vitamin E and vitamin C. The retention of the organics under solar exposure has been shown to be significantly enhanced by the addition of TiO2:Mn to the formulation. In the case of BMDM and OMC, the retention is increased from 20% and 24% to 63% and 83%, respectively, after 2 h of solar exposure. In this system, TiO2 particles are shown to provide only limited protection relative to BMDM and OMC. Vitamin E and vitamin C are actively degraded by the presence of TiO2 in the emulsion during solar exposure. This effect is reversed with TiO2:Mn, the use of which can protect >90% of anti-oxidants in both the oil and water phases of the formulation. The absence of reactive oxygen species (ROS) generation and surface scavenging of ROS by TiO2:Mn is responsible for a significantly reduced ROS load on the organic components and consequent photostabilization of the emulsion.