Characterization on titanium surfaces and its effect on photocatalytic bactericidal activity

Many studies have been published on the use of TiO₂ as a photocatalyst, which decomposes various organic compounds under UV illumination by generating various radicals. The purpose of the present study was to evaluate the photocatalytic bactericidal effects of variously treated titanium surfaces on Escherichia coli K-12. The specimens were fabricated from grade 4 commercially pure titanium, 12 mm in diameter and 1 mm in thickness. Five different surfaces were prepared (MA: machined surface; AO: anodized at 300 V; NO: NaOH-treated; NW: NaOH- and water-treated; and HT: heat-treated). Surface analysis was performed using scanning electron microscopy, optical interferometer, and thin-film X-ray diffractometry. Photocatalytic activity of each group was confirmed by degradation of methylene blue (MB). The antibacterial activity was assessed by calculating the survival ratio in a drop of a culture of E. coli placed on the surface under UV illumination. Significant photocatalytic activity and bactericidal effects were observed on the titanium surfaces of AO and NW, regardless of the surface roughness (P < 0.01). The group with anatase was the most susceptible to the photocatalytic effect, while the surface without anatase showed the least susceptibility. Based on this in vitro study, the crystallography of the oxide layer on its titanium surfaces is an important factor affecting the photocatalytic bactericidal activity.     

MOFs基材料在光催化CO2还原中的应用

系统总结了金属有机框架(MOFs)基材料在光催化还原CO₂中的最新研究进展, 其中包括MOFs直接作为光催化剂和作为复合光催化2个主要部分, 讨论了MOFs基光催化剂在催化还原CO₂方面展现出的独特优势, 并对MOFs基光催化剂的结构稳定性与CO₂转化效率等问题进行讨论与分析, 对未来发展趋势进行了展望.     

不同结构二元羧酸改性棉纤维铁配合物的制备和光催化性能

分别使用3种不同结构的二元羧酸[酒石酸(TA)、 苹果酸(MA)和丁二酸(SA)]对棉纤维改性引入羧基并与Fe ³⁺离子反应制备羧酸改性棉纤维铁配合物, 考察了二元羧酸结构和浓度对改性棉纤维的羧基含量(Q_COOH)及其铁配合物的铁配合量(Q_Fe)的影响. 研究了3种羧酸改性棉纤维铁配合物作为有机染料氧化降解反应和Cr(Ⅵ)还原反应光催化剂的性能. 结果表明, 改性棉纤维的Q_COOH值随羧酸浓度的增加而增加. 不含羟基的SA比2种羟基羧酸TA和MA能给棉纤维引入更多羧基, 而2种羟基羧酸改性棉纤维铁配合物则具有更高的Q_Fe值. 3种羧酸改性棉纤维铁配合物对染料氧化降解反应和Cr(Ⅵ)还原反应都表现出显著的光催化作用, 且随其Q_Fe和辐射光强度的提高而增强. TA改性棉纤维铁配合物比其它2种配合物具有更高的光催化活性. 3种配合物不但能将Cr(Ⅵ)还原为Cr(Ⅲ)离子, 而且还能将其部分吸附去除, MA改性棉纤维铁配合物具有较高的铬离子去除效率.     

Construction of a novel ZnCo2O4/Bi2O3 heterojunction photocatalyst with enhanced visible light photocatalytic activity

A novel ZnCo₂O₄/Bi₂O₃ heterojunction photocatalyst was prepared via balling method. The enhanced photocatalytic activity is mainly attributed to the broad photoabsorption and low recombination rate of photogenerated electron-hole pairs, which is driven by the photogenerated potential difference formed at the ZnCo₂O₄/Bi₂O₃ heterojunction interface.     

Tailorable carbazolyl cyanobenzene-based photocatalysts for visible light-induced reduction of aryl halides

Herein, a series of carbazolyl cyanobenzene (CCB)-based organic photocatalysts with a broad range of photoredox capabilities were designed and synthesized, allowing precise control of the photocatalytic reactivity for the controllable reduction of aryl halides via a metal-free process. The screened-out CCB (5CzBN), a metal-free, low-cost, scalable and sustainable photocatalyst with both strong oxidative and reductive ability, exhibits superior performance for both dehalogenation and CC bond-forming arylation reactions.     

Impact of surface hydroxylation in MgO-/SnO-nanocluster modified TiO2 anatase (101) composites on visible light absorption,charge separation and reducibility

Anatase TiO₂ surfaces, whether oxidised or hydroxylated, can be modified by nanoclusters of SnO and MgO to give a red shift in light absorption, enhanced charge separation and high reducibility.     

Energy transfer or electron transfer?—DFT study on the mechanism of [2+2] cycloadditions induced by visible light photocatalysts

The intramolecular [2+2] cycloaddition of 1,3-dienes under visible light irradiation investigated by Yoon and his co-workers shows remarkably high yield and stereoselective differences under different photocatalysts. The reaction was speculated to be induced by energy transfer. However, the origin for these phenomena is still unclear. In this scene, the detailed mechanism for the [2+2] cycloaddition of 1,3-dienes under visible light has been investigated using density functional theory B3LYP and TPSSTPSS methods. The result shows that the reaction not only can be induced by energy transfer between photocatalysts and reactants, but also can be induced by electron transfer between them. The [2+2] cycloaddition induced by energy transfer is carried out along the potential energy surface (PES) of triplet excited states (T₁) firstly, and then goes back to the singlet ground state (S₀) via MECPs (minimum energy crossing points) between the PESs of the S₀ and T₁ states, forming the product in the S₀ state. The [2+2] reaction induced by electron transfer proceeds along the doublet state PES of the cation radical reactant and the neutral four-membered ring product could be obtained by electron transfer from the corresponding reactant or reduced photocatalyst. The origin of stereoselectivity of the [2+2] reaction is attributed to the reaction mechanism difference under different photocatalysts.     

Low-temperature fabrication and photocatalytic activity of clustered TiO2 particles formed on glass fibers

Clustered anatase phase TiO₂ particles were uniformly formed on the surface of glass fibers by a liquid phase deposition (LPD) method at 60 °C using TiF₄ and H₃BO₃ as the precursors. The clustered TiO₂ particles deposited on the glass fibers and as a photocatalyst these particles not only have a larger surface area than TiO₂ thin films, but also can avoid the disadvantages of using TiO₂ powders encountered in air purification or water treatment. The photocatalytic activity of the sample was evaluated by the photocatalytic oxidation of nitrogen monoxide (NO) in the gaseous phase. The deposition conditions and chemical composition of the clustered TiO₂ particles were discussed. It was found that the clustered TiO₂ particles that formed on the glass fibers obviously showed photocatalytic activity without high-temperature calcination. A formation mechanism was proposed to account for the formation of TiO₂ clustered morphology on the glass fibers.     

Overview on multicomponent ceramic composite materials used for efficient photocatalysis – An update

Water is an important item for the survival of humans, animals and plants in the planet earth. In the industrialized world, water pollution is raising every day, mainly in the textile, paper, medicine, and plastic production industries. Pollution from coloured compounds is primarily identified as being the major threat to wastewater. In the absence of any pre-treatment, substituted phenols, dyes and agricultural wastes seriously contaminate groundwater systems. For the removal of dyes from the industrial waste water, the following three traditional methods are used: chemical, physical and biological but, the cost of the methods little high. For alternation of these methods, now a days photocatalytic degradation method was used. Metal and metal oxide nanoparticles are excellent catalysts for reducing and degrading aqueous phase nitro compounds and aromatic dyes. Nanoparticles are commonly assembled into two types, i.e., organic (carbon nanoparticles) and inorganic (metal, semiconductor and magnetic nanoparticles) nanoparticles. In this review article we are mainly focused on the behaviour of different types of pure metal oxides and metal oxide@metal/metal oxide/carbon/polymer nanocomposites for the removal of various organic pollutants from water and their efficiency has been reported. As a result of their review the cerium-based metal oxides such as CdS/CeO₂, CeO₂/Y₂O₃, GQDs/CeO₂ and Ag/cellulose@CeO₂/QDs shows more degradation efficiency (above~95%) towards the organic pollutants when compared to other metal oxides.     

Generation of low-molecular-weight organic compounds in water by titania photocatalyst under UV-Vis light radiation

We attempted to develop a new type titania photocatalyst that, when activated, responded in not only the ultraviolet rays region but also visible light radiation region by the new titania photocatalyst with the zirconia and nitrogen simultaneously introduced in the titania lattice. The decomposition performance of the standard organic compound in water by this new type titania photocatalyst nanoparticle was compared with the conventional type under both the ultraviolet ray and visible light radiation conditions. It was suggested that the low-molecular-weight organic compounds were also generated from the organic compound in water by the new type titania photocatalyst activities under the visible light radiation.