Pore Structure Controlling the Activity of Mesoporous Crystalline CsTaWO6 for Photocatalytic Hydrogen Generation

The quaternary oxide CsTaWO₆ exhibits a very high activity for photocatalytic hydrogen generation and water splitting. To improve its properties with regard to photocatalytic applications, it is prepared with mesoporous morphology for the first time, utilizing a template‐based evaporation‐induced self‐assembly process. The resulting material exhibits a median mesopore size of 10 nm, a surface area of 60 m² g^?1, and high crystallinity after preparation at 550 °C with phase‐pure defect‐pyrochlore structure. To further improve the textural properties of mesoporous CsTaWO₆, the addition of additives to the synthesis procedure is also investigated. By using H₂SO₄/HCl and a carbonization/oxidation procedure, the surface area of the resulting mesoporous CsTaWO₆ is increased to 78 m² g^?1, which is a 20‐fold increase compared to a nonporous reference via sol‐gel preparation, also leading to improved photocatalytic activity. By investigating the ability for photocatalytic hydrogen generation, the importance of high surface area and pore diameter of the resulting materials in comparison to nonporous materials is presented. Interestingly, the photocatalytic activity does not increase linearly with surface area, due to a strong influence of the pore diameter on the photocatalytic activity.     

玻璃负载TiO2膜光催化降解垃圾渗滤液的研究

研究了以SOL=GEL法制备的TiO₂膜光催化降解垃圾渗滤液的可行性,探讨了负载TiO₂膜的影响因素及TiO₂膜的催化活性,TiO₂膜的最佳煅烧温度为450℃.测定了反应时间、进水浓度、pH值、光源强度等因素对垃圾渗滤液的COD_Cr和色度去除率的影响.光强越大,催化效果越好,光照时间越长,催化效果越好;溶液的初始浓度越大,降解率越低;反应液的在偏酸、碱的条件下有利于光催化氧化反应的进行.在最佳的实验条件下,TiO₂膜的煅烧温度为450℃,溶液的pH值为3~4,垃圾渗滤液的初始COD_Cr为537mg·L^-1,光催化降解2h,COD_Cr和UV335的去除率分别为94.4%和96.9%.     

Microplate-based assays for the evaluation of antibacterial effects of photocatalytic coatings

Three microplate-based viability assays for assessing the antibacterial effects of photocatalytic coatings were compared to the conventional colony count method. In the experimental design, cultured Escherichia coli were exposed to photocatalysis on various TiO₂ films in the presence of either UVA or visible light. The photocatalytic effects on the bacterial physiology were determined by real-time measurements of metabolic activity (XTT assay), biomass formation in the liquid medium (growth assay), and by assessing membrane integrity (with propidium iodide and SYTO 9 fluorescent nucleic acid binding dyes—BacLight assay). All three methods proved to be more sensitive and reproducible than colony count for the evaluation of the bactericidal effect of photocatalysis, XTT, and growth assay succeeded in detecting differences in both UVA and visible light-activated photocatalytic coatings. BacLight could efficiently detect the visible light-dependent photocatalytic effect on bacteria and identify membrane damage, but resulted inadequate for evaluating the UVA-dependent antibacterial effects. The described microplate-based evaluation methods proved being more effective and rapid than the colony count assay for assessing the antibacterial effect of various photocatalytic coatings.     

光催化降解敌百虫农药废水的影响因素分析

在TiO₂悬浮体系,对农用敌百虫有机磷农药进行光催化氧化降解反应。发现光催化降解过程中适当补充NaOH溶液,可以维持较高的有机磷降解率,对于处理有机磷农药废水保持一定的pH值有作用。敌百虫农药有机磷含量起始浓度处于3.1mg·L^-1和31mg·L^-1之间,在50mg的催化剂TiO₂作用下90min内无机磷浓度变化符合零级反应,而且反应速率常数和敌百虫起始浓度呈线形关系,实验中探讨了降解过程中出现的影响因素。     

Dual Roles of Capsular Extracellular Polymeric Substances in Photocatalytic Inactivation of Escherichia coli: Comparison of E. coli BW25113 and Isogenic Mutants

The dual roles of capsular extracellular polymeric substances (EPS) in the photocatalytic inactivation of bacteria were demonstrated in a TiO₂-UVA system, by comparing wild-type Escherichia coli strain BW25113 and isogenic mutants with upregulated and downregulated production of capsular EPS. In a partition system in which direct contact between bacterial cells and TiO₂ particles was inhibited, an increase in the amount of EPS was associated with increased bacterial resistance to photocatalytic inactivation. In contrast, when bacterial cells were in direct contact with TiO₂ particles, an increase in the amount of capsular EPS decreased cell viability during photocatalytic treatment. Taken together, these results suggest that although capsular EPS can protect bacterial cells by consuming photogenerated reactive species, it also facilitates photocatalytic inactivation of bacteria by promoting the adhesion of TiO₂ particles to the cell surface. Fluorescence microscopy and scanning electron microscopy analyses further confirmed that high capsular EPS density led to more TiO₂ particles attaching to cells and forming bacterium-TiO₂ aggregates. Calculations of interaction energy, represented by extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) potential, suggested that the presence of capsular EPS enhances the attachment of TiO₂ particles to bacterial cells via acid-base interactions. Consideration of these mechanisms is critical for understanding bacterium-nanoparticle interactions and the photocatalytic inactivation of bacteria.     

Methodologies for the analysis of antimicrobial effects of immobilized photocatalytic materials

Photocatalytic coatings are considered sustainable materials as they only need sunlight for their activation and regeneration. Some photocatalytic disinfecting coatings are already commercialized, but many more are still in the developmental stage. Efficient and reliable analytical methodologies for testing the antimicrobial effects of photocatalytic coatings should therefore be used and further developed (1) to avoid inactive or unstable final products, (2) to allow fast, reproducible, and inexpensive antimicrobial activity measurements, and (3) to reflect real environmental conditions and challenges for these materials. Aiming to improve the existing methodologies of antimicrobial testing, this mini review summarizes and discusses the testing parameters and procedures in this expanding research field, including research on antimicrobial activity of photocatalytic coatings for different applications, i.e., self-cleaning/disinfecting coatings (films) and photocatalytic coatings for water and air treatment/disinfection.     

A Floating Sheet for Efficient Photocatalytic Water Splitting

Solar photocatalytic water splitting has been a promising way to provide clean hydrogen energy. There are two weaknesses in the typical photocatalytic process in which photocatalysts are generally dispersing in water under stir. One is the inadequate utilization of light energy and the other one is the cumbersome operation in the recycling procedure. This study demonstrates an efficient solar photocatalytic water splitting using a floating sheet with a novel WSe₂ cocatalyst. The sheet is fabricated by laser‐depositing WSe₂ film on a carbon foam (CF) substrate and drop‐casting of the synthesized nanodiamond‐embedded Cu₂O (NEC) photocatalysts. This is a new‐type artificial photocatalytic system that overcomes the above‐mentioned weaknesses of a powder‐dispersing system. The WSe₂ cocatalyst acts as an electron sink to promote electron–hole separation, resulting in the further improvement of photocatalytic performance. This floating NEC/WSe₂/CF structure achieves efficient water splitting upon simulated solar irradiation with an increased H₂ evolution rate, which is 13.2 times that of the powder‐dispersing system. This study offers a strategy for the design of new‐type photocatalytic system and discovery of alternative noble metal‐free cocatalysts.     

Photocatalytic inhibition of microbial adhesion by anodized titanium

Biofouling is one of the concerns in the use of titanium for seawater cooled condensers of power plants. Earlier studies have shown that anodized titanium and its alloys with a thin film of anatase (TiO(2)) on its surface can inhibit attachment of Pseudomonas sp. when illuminated with near-UV light (350 - 380 nm). In the present study, a comparison of the photocatalytic inhibition of microbial attachment on titanium surfaces anodized at different voltages was carried out. Thin films of anatase of varying thickness were produced on titanium grade-2 by anodizing in dilute orthophosphoric acid solution at 30 V, 50 V and 100 V. The photocatalytic efficiency of these anodized surfaces was measured by the methylene blue degradation method. The anodised surfaces were exposed to liquid cultures of Gram-negative Pseudomonas sp., Gram-positive Micrococcus sp. and to a mixed algal culture. Photocatalytic inhibition of microbial attachment was maximum on the titanium surface anodized at 30 V, followed by the surface anodized at 50 V and then at 100 V. The photocatalytic inhibition of microbial attachment was also found to be dependent on the cell wall characteristics of the organism. The Gram-negative Pseudomonas sp. with a lipoproteinaceous outer membrane was the most susceptible to the photocatalytic effect, while the Gram-positive Micrococcus sp. with peptidoglycan cell wall showed moderate susceptibility and the algae with siliceous cell wall showed no susceptibility at all.     

Development of photocatalytic biosensor for the evaluation of biochemical oxygen demand

The photocatalytic biosensor of flow system using semiconductor TiO2 was developed to evaluate biochemical oxygen demand (BOD) levels in river water. Photocatalysis of sample was carried out in a photoreactor with TiO2 and a 6W black-light blue fluorescent tube as light source. Sample from a photoreactor outlet was measured by an oxygen electrode with a biofilm. The sensor response of photocatalytic biosensor was between 5 and 10 min depending on concentration of biochemical in the samples. At BOD of 1 mgl-1, the sensor response increased 1.33-fold in comparison with that without photocatalysis. The degradation of tannic acid and humic acid with photocatalysis were 51.8 and 38.4%, respectively. Gum arabic and linear alkylbenzene sulfonate (LAS) were degraded a little, but gave the responses of more than double to the sensor. Free radicals yielded by photocatalysis in a photoreactor did not affect the sensor response because their lifetime is extremely short. Fairly good correlation (r=0.983) between the sensor method and the conventional method was obtained for test samples. This biosensor using photocatalytic pretreatment improved the sensitivity.     

A suggested standardised method for testing photocatalytic inactivation of aeroterrestrial algal growth on TiO2-coated glass

Aeroterrestrial green algae form conspicuous biofilms on man-made surfaces. The self-cleaning properties of photocatalytic coatings prevent their growth and can probably replace biocides. The aim of this study was to develop a laboratory method to investigate the efficiency of photocatalytic materials against algal growth. Two algal isolates (“Chlorella” luteoviridis, SAG 2196, and Coccomyxa sp., SAG 2040) functioned well as model organisms because they grew on almost all test specimens at 100% humidity and low UVA radiation. With these species, we examined algal growth prevention using photocatalytic glass. No effects on algal growth were detected, although the coated surfaces were photocatalytically active and degraded methylene blue. Because their cells are protected well against photocatalytically generated hydroxyl radicals, aeroterrestrial algae survive various stress factors. Nevertheless, the newly developed experimental design may be useful for assessing the biological function of other photocatalytic materials or stress factors.     

Application in photocatalytic degradation of zearalenone based on graphitic carbon nitride

A semiconductor nano-material was prepared, and its degradation efficiency of zearalenone (ZEN) was studied. The photocatalytic material graphitic carbon nitride (g-C₃N₄) was synthesized by the traditional method of hot cracking. Its structure was characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic degradation experiment showed that under the irradiation of ultraviolet (UV) lamp (254 nm, including 185 nm), g-C₃N₄ could induce photocatalytic effect, which provided a new method for the degradation of ZEN in real powder samples. The experimental conditions of photocatalytic degradation of the primary reference material of ZEN and ZEN in real powder samples were explored. And the degradation products of ZEN were analyzed after high-performance liquid chromatography–mass spectrometry (HPLC–MS). Under each optimal experimental conditions, the degradation rate on primary reference material of ZEN and ZEN in real powder samples was 96.0% and 50.0%, respectively. The results in this work provide a theoretical reference and practical basis for the photocatalytic degradation of mycotoxin in real powder samples by g-C₃N₄.     

In situ green synthesis of highly fluorescent Fe2O3@CQD/graphene oxide using hard pistachio shells via the hydrothermal‐assisted ball milling method

In this study, highly photoluminescent and photocatalytic Fe₂O₃@carbon quantum dots/graphene oxide nanostructures were synthesized using ball milling‐assisted hydrothermal synthesis with hard pistachio shells. Different analyses, such as X‐ray diffraction, energy dispersive X‐ray spectroscopy, and Fourier transform infrared spectroscopy were used to study the product structure. Scanning electron microscopy and transmission electron microscopy images were used to study product size and morphology. Optical properties of the as‐synthesized nanomaterials were investigated using ultraviolet–visible light and photoluminescence analyses. To increase photoluminescence intensity, ethylene diamine tetraacetic acid, polyethylene glycol, polyvinylpyrrolidone, and acetylacetonate anions were used to modify the product surface. Thermal stability of the product was studied using thermal gravimetric analysis. Finally, photocatalytic activity and surface adsorption of the product were investigated; the produce was found to be highly photoluminescent with high photocatalytic and surface activities.     

Algal growth inhibition on cement mortar: Efficiency of water repellent and photocatalytic treatments under UV/VIS illumination

Building materials are regularly affected by the growth of microalgae. The consequences are mainly aesthetic but the colonization can cause biodeterioration of the material in the most extreme cases. This study investigates two building material treatments that can potentially inhibit or slow down such growth: photocatalytic coatings and water repellent treatments. The efficiency of these treatments in terms of biological growth inhibition was tested on the algae species Graesiella emersonii. Algal growth on building materials was investigated using two accelerated tests simulating different types of humidification (water capillary ascent and water run-off) under different lighting conditions. Mortars treated with photocatalytic coating or with water repellent were studied. The algal growth on the mortar surface was evaluated using image analysis (area covered and intensity of fouling). No slow down of the biological growth kinetics could be attributed to photocatalytic substrates. However, for mortars impregnated with a water-repellent preparation, algal growth slowed significantly under water run-off and even stopped under water capillary ascent.     

Different inactivation behaviors of MS-2 phage and Escherichia coli in TiO2 photocatalytic disinfection

Despite a wealth of experimental evidence concerning the efficacy of the biocidal action associated with the TiO(2) photocatalytic reaction, our understanding of the photochemical mechanism of this particular biocidal action remains largely unclear. It is generally accepted that the hydroxyl radical (.OH), which is generated on the surface of UV-illuminated TiO(2), plays the main role. However, our understanding of the exact mode of action of the hydroxyl radical in killing microorganisms is far from complete, and some studies report that other reactive oxygen species (ROS) (H(2)O(2) and O(2).(-), etc.) also play significant roles. In particular, whether hydroxyl radicals remain bound to the surface or diffuse into the solution bulk is under active debate. In order to examine the exact mode of action of ROS in inactivating the microorganism, we tested and compared the levels of photocatalytic inactivation of MS-2 phage and Escherichia coli as representative species of viruses and bacteria, respectively. To compare photocatalytic microbial inactivation with the photocatalytic chemical degradation reaction, para-chlorobenzoic acid, which rapidly reacts with a hydroxyl radical with a diffusion-limited rate, was used as a probe compound. Two different hydroxyl radical scavengers, tert-butanol and methanol, and an activator of the bulk phase hydroxyl radical generation, Fe(2+), were used to investigate their effects on the photocatalytic mode of action of the hydroxyl radical in inactivating the microorganism. The results show that the biocidal modes of action of ROS are very different depending on the specific microorganism involved, although the reason for this is not clear. It seems that MS-2 phage is inactivated mainly by the free hydroxyl radical in the solution bulk but that E. coli is inactivated by both the free and the surface-bound hydroxyl radicals. E. coli might also be inactivated by other ROS, such as O(2).(-) and H(2)O(2), according to the present results.     

光催化氧化降解制药废水中头孢曲松钠的研究

以二氧化钛(TiO₂)为光催化剂,分别采用高压汞灯和反射镝灯为紫外光和模拟日光光源,对头孢曲松钠进行光催化降解,用紫外光谱跟踪其光催化降解过程。考察了光催化体系中光源、催化剂用量、光照时间、电子受体以及其他离子的存在对光催化降解过程的影响。结果显示,当反应物初始浓度500mg·L^-1,在高压汞灯和反射镝灯条件下反应5小时后,在催化剂用量分别为2.5g·L^-1和2.0g·L^-1时对头孢曲松钠的降解效果最好,分别达到93.4%和73.8%。体系中加入电子受体能促进光催化反应速率,而一些无机离子如HCO₃^-、SO₄^2-、Cl^-等的存在显著降低了TiO₂光催化剂的活性。实验结果有助于抗生素制药工业废水的光催化处理研究。     

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600 °C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity.     

基于叶酸修饰的S-TiO2的PDT体外灭活HL60细胞实验研究

文章主要研究叶酸修饰硫掺杂二氧化钛(FA-S-TiO_2)纳米颗粒光催化灭活作用并初步探讨FA-S-TiO_2增强了TiO_2光催化灭活效率的作用机理。利用固相反应的方法制备了S-TiO_2,并利用表面修饰的方法制备了FA-S-TiO_2。通过紫外-可见光吸收光谱(UV-Vis),荧光光谱,傅里叶红外光谱(FTIR),透射电镜(TEM)等手段对样品进行了表征。利用Cell Counting Kit-8(CCK-8)法分别检测TiO_2、S-TiO_2、FA-S-TiO_2对HL60细胞的灭活效应,并采用活性氧检测等方法进行了分析研究。细胞实验结果表明,在暗室条件下,随着叶酸修饰S-TiO_2的比例增加,细胞的存活率随之减少;在光照条件下,细胞的存活率明显下降。其中FA-S-TiO_2样品1对HL60细胞的灭活效率最高,达到72%。其相应的活性氧含量也是最高。同时,通过荧光光谱推测FA-S-TiO_2提高HL60细胞对该纳米颗粒摄取效率,进而增强PDT灭活效果。     

Nitrogen‐Doped Carbon‐Coated CuO‐In2O3 p–n Heterojunction for Remarkable Photocatalytic Hydrogen Evolution

CuO as a catalyst has shown promising application prospects in photocatalytic splitting of water into hydrogen (H₂). However, the instability of CuO in amine aqueous solution limits the applications of CuO‐based photocatalysts in the photocatalytic H₂ evolution. In this work, a novel dodecahedral nitrogen (N)‐doped carbon (C) coated CuO‐In₂O₃ p–n heterojunction (DNCPH) is designed and synthesized by directly pyrolyzing benzimidazole‐modified dodecahedral Cu/In‐based metal‐organic frameworks, showing long‐term stability in triethanolamine (TEOA) aqueous solution and excellent photocatalytic H₂ production efficiency. The improved stability of DNCPH in TEOA solution is ascribed to the alleviation of electron deficiency in CuO by forming the p–n heterojunction and the protection with coated N‐doped C layer. Based on detailed theoretical calculations and experimental studies, it is found that the improved separation efficiency of photogenerated electron/hole pairs and the mediated adsorption behavior (|?G_H*|→0) by coupling N‐doped C layer with CuO‐In₂O₃ p–n heterojunction lead to the excellent photocatalytic H₂ production efficiency of DNCPH. This work provides a feasible strategy for effectively applying CuO‐based photocatalysts in photocatalytic H₂ production.     

Understanding selective enhancement by silver during photocatalytic oxidation.

The superiority of silver deposited titania particles over bare titania particles for the photocatalytic oxidation of selected organic compounds is explained: the presence of silver mainly enhances the photocatalytic oxidation of organic compounds that are predominantly oxidised by holes, while it has only an insignificant effect on those organic compounds that require hydroxyl radicals for their mineralisation.     

Sterilization effects of a TiO<Subscript>2</Subscript> photocatalytic film against a<Emphasis Type="Italic">Streptococcus mutans</Emphasis> culture

Streptococcus mutans is one of the more significant pathogens involved in the development of dental caries in humans. The purpose of this research was to design a TiO₂-coated dental instrument and to determine the bactericidal effects of the instrument onS. mutants. TiO₂ photocatalytic films were prepared by the low-pressure metal-organic chemical vapor deposition (LPMOCVD) method using titanium tetraisopropoxide (TTIP) as precursor. The photocatalytic reaction was carried out on a TiO₂-coated pyrex petri dish with an ultraviolet (UV) light emitting diode (LED) illuminator or a fluorescent lamp light source. Our data indicates that the relative survival ratio ofS. mutans when plated onto TiO₂ photocatalytic films and under exposure to UV-A light for 15 min was 0.01%. In addition, a fluorescent lamp light source also had bactericidal effects on theS. mutans plated TiO₂ photocatalytic films. These results indicate that TiO₂-coated dental materials or devices may be useful in dental treatments for the prevention of carious or enamel demineralization.