钴掺杂氧化铜/可见光协同活化PMS降解罗丹明B及其机理研究

元素掺杂是提升催化剂性能的重要方法。研究采用快速沉淀法制备了钴掺杂氧化铜(Co-doped CuO)纳米催化材料,在可见光条件下,20 min内其活化的过氧硫酸氢钾复合盐(PMS)对罗丹明B染料的降解率达到96%以上,远优于同等条件制备的CuO。本研究还考察了溶液pH、染料初始浓度、催化剂用量等对降解效率影响。钴掺杂后氧化铜纳米颗粒由三维针梭状结构转变为近二维薄带状结构。同时钴掺杂提高了CuO的平带电位进而提升了电荷转移效率。XPS及EPR结果表明钴掺杂能够提高CuO的氧空位含量进而提升催化活性。捕获剂实验结果表明反应过程中的主要活性物种为空穴(h⁺_VB),且羟基自由基(·OH)、单线态氧(¹O₂)、超氧自由基(·O₂^–)、硫酸根自由基(SO₄^–·)也参与了降解反应。最后,本文初步阐明了Co-doped CuO协同可见光活化PMS降解有机污染物的反应机理。     

Role of oxygen active species in the photocatalytic degradation of phenol using polymer sensitized TiO2 under visible light irradiation

The role of dissolved oxygen, and of active species generated by photo-induced reactions with oxygen, in the photocatalytic degradation of phenol was investigated using polymer [poly-(fluorene-co-thiophene) with thiophene content of 30%, so-called PFT30] sensitized TiO2 (PFT30/TiO2) under visible light irradiation. The photoluminescent (PL) quantum yield of PFT30/TiO2 was about 30% of that of PFT30/Al(2)O(3), proving that electron transfer took place between the polymer and TiO2. The result that photocatalytic degradation of phenol was almost stopped when the solution was saturated with N(2) proved the importance of O(2). Addition of NaN(3), an effective quencher of singlet oxygen ((1)O(2)), caused about a 40% decrease in the phenol degradation ratio. Addition of alcohols caused about a 60% decrease in the phenol photodegradation ratio, indicating that the hydroxyl radicals (OH), whose presence was confirmed by electron spin resonance (ESR) spectroscopy, was the predominant active species in aqueous solution. In anhydrous solution, singlet oxygen ((1)O(2)) was the predominant species. These results indicate that oxygen plays a very important role in the photocatalytic degradation of phenol.     

A Cascade Nanoreactor of Metal-Protein-Polyphenol Capsule for Oxygen-Mediated Synergistic Tumor Starvation and Chemodynamic Therapy

Starvation therapy kills tumor cells via consuming glucose to cut off their energy supply. However, since glucose oxidase (GOx)-mediated glycolysis is oxygen-dependent, the cascade reaction based on GOx faces the challenge of a hypoxic tumor microenvironment. By decomposition of glycolysis production of H₂O₂ into O₂, starvation therapy can be enhanced, but chemodynamic therapy is limited. Here, a close-loop strategy for on demand H₂O₂ and O₂ delivery, release, and recycling is proposed. The nanoreactor (metal-protein-polyphenol capsule) is designed by incorporating two native proteins, GOx and hemoglobin (Hb), in polyphenol networks with zeolitic imidazolate framework as sacrificial templates. Glycolysis occurs in the presence of GOx with O₂ consumption and the produced H₂O₂ reacts with Hb to produce highly cytotoxic hydroxyl radicals (•OH) and methemoglobin (MHb) (Fenton reaction). Benefiting from the different oxygen carrying capacities of Hb and MHb, oxygen on Hb is rapidly released to supplement its consumption during glycolysis. Glycolysis and Fenton reactions are mutually reinforced by oxygen supply, consuming more glucose and producing more hydroxyl radicals and ultimately enhancing both starvation therapy and chemodynamic therapy. This cascade nanoreactor exhibits high efficiency for tumor suppression and provides an effective strategy for oxygen-mediated synergistic starvation therapy and chemodynamic therapy.     

Antifungal activity of ZnO nanoparticles--the role of ROS mediated cell injury

Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml(-1) ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds.     

Ratiometric coumarin-neutral red (CONER) nanoprobe for detection of hydroxyl radicals

Excessive production of reactive oxygen species can lead to alteration of cellular functions responsible for many diseases including cardiovascular diseases, neurodegenerative diseases, cancer, and aging. Hydroxyl radical is a short-lived radical which is considered very aggressive due to its high reactivity toward biological molecules. In this study, a COumarin-NEutral Red (CONER) nanoprobe was developed for detection of hydroxyl radical based on the ratiometric fluorescence signal between 7-hydroxy coumarin 3-carboxylic acid and neutral red dyes. Biocompatible poly lactide-co-glycolide (PLGA) nanoparticles containing encapsulated neutral red were produced using a coumarin 3-carboxylic acid conjugated poly(sodium N-undecylenyl-Nε-lysinate) (C3C-poly-Nε-SUK) as moiety reactive to hydroxyl radicals. The response of the CONER nanoprobe was dependent on various parameters such as reaction time and nanoparticle concentration. The probe was selective for hydroxyl radicals as compared with other reactive oxygen species including O(2)(?-), H(2)O(2), (1)O(2), and OCl(-). Furthermore, the CONER nanoprobe was used to detect hydroxyl radicals in vitro using viable breast cancer cells exposed to oxidative stress. The results suggest that this nanoprobe represents a promising approach for detection of hydroxyl radicals in biological systems.     

Effect of magnetic field on the zero valent iron induced oxidation reaction

The magnetic field (MF) effect on the zero valent iron (ZVI) induced oxidative reaction was investigated for the first time. The degradation of 4-chlorophenol (4-CP) in the ZVI system was employed as the test oxidative reaction. MF markedly enhanced the degradation of 4-CP with the concurrent production of chlorides. The consumption of dissolved O₂ by ZVI reaction was also enhanced in the presence of MF whereas the competing reaction of H₂ production from proton reduction was retarded. Since the ZVI-induced oxidation is mainly driven by the in situ generated hydroxyl radicals, the production of OH radicals was monitored by the spin trap method using electron spin resonance (ESR) spectroscopy. It was confirmed that the concentration of trapped OH radicals was enhanced in the presence of MF. Since both O₂ and Fe⁰ are paramagnetic, the diffusion of O₂ onto the iron surface might be accelerated under MF. The magnetized iron can attract oxygen on itself, which makes the mass transfer process faster. As a result, the surface electrochemical reaction between Fe⁰ and O₂ can be accelerated with the enhanced production of OH radicals. MF might retard the recombination of OH radicals as well.     

A review of classic Fenton's peroxidation as an advanced oxidation technique

Hydrogen peroxide (H(2)O(2)) is a strong oxidant and its application in the treatment of various inorganic and organic pollutants is well established. Still H(2)O(2) alone is not effective for high concentrations of certain refractory contaminants because of low rates of reaction at reasonable H(2)O(2) concentrations. Improvements can be achieved by using transition metal salts (e.g. iron salts) or ozone and UV-light can activate H(2)O(2) to form hydroxyl radicals, which are strong oxidants. Oxidation processes utilising activation of H(2)O(2) by iron salts, classically referred to as Fenton's reagent is known to be very effective in the destruction of many hazardous organic pollutants in water. The first part of our paper presents a literature review of the various Fenton reagent reactions which constitute the overall kinetic scheme with all possible side reactions. It also summarises previous publications on the relationships between the dominant parameters (e.g. [H(2)O(2)], [Fe(2+)], . . .). The second part of our review discusses the possibility of improving sludge dewaterability using Fenton's reagent.     

Verification of competitive kinetics technique and oxidation kinetics of 2,6-dimethyl-aniline and o-toluidine by Fenton process

The competitive kinetics technique is shown to be a useful and reliable tool for determining rate constants. Regardless of the conditions of the reaction and the operation mode, the intrinsic second-order rate constants of 2,6-dimethyl-aniline and hydroxyl radicals were 1.65 × 10(10), 1.60 × 10(10), and 1.71 × 10(10)M(-1)s(-1) in the absence of SiO(2) under complete-mix conditions, in the presence of SiO(2) under complete-mix conditions, and in a fluidized-bed Fenton reactor with SiO(2) as the media, respectively, demonstrating that the rates are comparable under a variety of reaction conditions. The average intrinsic second-order rate constant of o-toluidine and hydroxyl radicals obtained in a homogeneous system under various conditions was 7.36 × 10(9)M(-1)s(-1), indicating that o-toluidine is less susceptible to hydroxyl radicals than 2,6-dimethyl-anilne. Hydroxyl radicals primarily attacked the amine group rather than the methyl group of the o-toluidine to form o-cresol and 2-nitrotoluene, which sequentially transformed to carboxylic acids including acetic, oxalic, lactic, and maleic acids after the collapse of the benzene ring.     

Radikalidentifizierung auf Polymeren nach Plasmabehandlung. Radical Identification on Polymers after Plasma Treatment

Radicals form the initial germ for reactions of chemically inert polymers. The incorporation of functional chemical groups can proceed via trapping‐ or quenching reactions of polymer radicals with functionalized reaction partners. The density of surfaces radicals governs the efficiency of the surface functionalization process. Subsequent to its termination, the surviving radicals become of special importance since they can react with oxygen from air. This may introduce an unintended secondary functionalization of the polymer surface with various oxygen groups. Therefore, the identification and quantification of radicals on polymer surfaces is becoming increasingly important for the on‐going development of highly efficient and highly selective functionalization of polymer surface. Here, we present currently most relevant methods for surface radical quantification. In addition, a new approach to the generation of radicals on polymer surface is presented.     

Understanding Defect‐Stabilized Noncovalent Functionalization of Graphene

The noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high‐resolution interfacial X‐ray scattering, and ab initio density functional theory calculations. The findings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. The structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogen bonding with terminal hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton‐coupled‐electron‐transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. These results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.     

Unusual catalytic effects of iron salts on phenol degradation by glow discharge plasma in aqueous solution

Catalytic effects of iron salts on phenol degradation induced by glow discharge plasma (GDP) were examined. It was found that ferric ions showed much better catalytic effect than that of ferrous ions. The reason was that GDP could produce hydroxyl radicals and hydrogen peroxide simultaneously; the hydroxyl radicals reacted with phenol to produce dihydroxycyclohexadienyl radicals which reduced the ferric ions to ferrous ions and the newly formed ferrous ions catalyzed the hydrogen peroxide to produce more hydroxyl radicals. Without iron salts, TOC of the solution gradually decreased with treatment time while COD of the solution increased due to the accumulation of the hydrogen peroxide. Without iron salts, catechol, hydroquinone, and hydroxylhydroquinone were major by-products. However, large amounts of catechol, hydroquinone and benzoquinone yielded in the presence of iron salts. The present study presents some new information related to Fenton's reaction.     

Removal of phenol and chlorophenols from water with reusable dye-affinity hollow fibers

Reactive Green HE 4BD carrying polyamide hollow fibers were investigated as dye-affinity adsorbents for removal of chlorophenols (i.e., phenol, o-chlorophenol, p-chlorophenol and 2,4,6-trichlorophenol). Adsorption rates of chlorophenols were very high. Equilibrium was achieved in about 30 min. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption process could be the rate-limiting step in the adsorption process. The maximum adsorption values of chlorophenols onto the Reactive Green HE 4BD carrying hollow fibers were 145.9 micromol/g for phenol, 179.2 micromol/g for 2,4,6-trichlorophenol, 194.5 micromol/g for p-chlorophenol and 202.8 micromol/g for o-chlorophenol. The affinity order was as follows: o-chlorophenol>p-chlorophenol>2,4,6-trichlorophenol>phenol. The adsorption capacity of chlorophenols decreased with increasing pH. Desorption of chlorophenols was achieved using methanol solution (30%, v/v). The Reactive Green HE 4BD-carrying hollow fibers are suitable for repeated use for more than 10 cycles without noticeable loss of adsorption capacity.     

Degradation of carbofuran by using ozone, UV radiation and advanced oxidation processes.

The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a frequently used carbamate derivative pesticide that is considered a priority pollutant, is carried out in batch reactors by means of single oxidants: ozone, UV radiation and Fenton's reagent; and by the advanced oxidation processes (AOPs) constituted by combinations of ozone plus UV radiation, UV radiation plus H(2)O(2), and UV radiation plus Fenton's reagent (photo-Fenton system). For all these reactions, the apparent pseudo-first-order rate constants are evaluated in order to compare the efficiency of each process. In addition and by means of a competition kinetic model, the rate constants for the reaction of carbofuran with ozone and with hydroxyl radicals are also determined. The improvement in the decomposition levels of carbofuran reached by the combined processes in relation to the single oxidants, due to the generation of the very reactive hydroxyl radicals, is also established in every process. For the oxidant concentrations applied, the most effective process in removing carbofuran was the photo-Fenton system.     

Hydroxyl Radical Scavenging and Producing Activities of Water-Soluble Malonic Acid C60

The effects of several water-soluble malonic acid derivatives of C₆₀ with different addition number (M1∼M4) on hydroxyl radical were studied by ESR method. It was shown that the OH signal produced by the Fenton system could be remarkably reduced by M1 and M2, but could not by M3 and M4. The action of M1 and M2 was dose-dependent, and M1 was found to be more effective than M2. In addition, under irradiation and in the presence of oxygen, M2 could produce hydroxyl radicals. These data indicate that the quenching activity of the malonic acid derivative of C₆₀ was closely related to the integrity of conjugated double bonds, and some C₆₀ derivatives with specific structures might act as the eliminator or producer of hydroxyl radicals under different conditions.     

Mechanisms of Radical Formation on Chemically Modified Graphene Oxide under Near Infrared Irradiation

In this work, the mechanisms of radical generation on different functionalized graphene oxide (GO) conjugates under near-infrared (NIR) light irradiation are investigated. The GO conjugates are designed to understand how chemical functionalization can influence the generation of radicals. Both pristine and functionalized GO are irradiated by a NIR laser, and the production of different reactive oxygen species (ROS) is investigated using fluorimetry and electron paramagnetic resonance to describe the type of radicals present on the surface of GO. The mechanism of ROS formation involves a charge transfer from the material to the oxygen present in the media, via the production of superoxide and singlet oxygen. Cytotoxicity and effects of ROS generation are then evaluated using breast cancer cells, evidencing a concentration dependent cell death associated to the heat and ROS. The study provides new hints to understand the photogeneration of radicals on the surface of GO upon near infrared irradiation, as well as, to assess the impact on these radicals in the context of a combined drug delivery system and phototherapeutic approach. These discoveries open the way for a better control of phototherapy-based treatments employing graphene-based materials.     

Diatomite supported nano zero valent iron with 3D network for peroxymonosulfate activation in efficient degradation of bisphenol A

Diatomite supported nano zero valent iron (nZVI) catalyst (NDA) with complex network structure was prepared via a mild reduction precipitation method in this work.The pore structure and pore distribu-tion of NDA can be regulated and controlled through adjusting the loading amount of nZVI.In general,the nano three-dimensional network formed by nZVI and diatomite channels greatly increase the specific surface area and pore volume of NDA,and further formed more active sites,which made NDA have better performance in activating PMS to degrade BPA than pure nZVI.The pseudo-first-order reaction rate con-stant of 50-NDA (50％-nZVI/diatomite) is almost 3 times higher than that of pure nZVI.Besides,the elec-tron paramagnetic resonance (EPR) and radical quenching experiments showed that the activation process was dominated by the sulfate radical (SO4·-) and hydroxyl radical (OH) produced by Fe0 oxidation.The generated electrons promote the self-decomposition of PMS to produce singlet oxygen (1O2),and then the valence state of iron changes to produce free radicals.In addition,the possible degradation pathway of BPA was inferred from the intermediate products identified by liquid chromatograph-mass spectrom-eter (LC-MS).This study provides a novel strategy for the design and preparation of three-dimensional composite catalysts derived from natural mineral.     

Rate constants for the reactions of ozone with chlorophenols in aqueous solutions

The oxidation by ozone of several chlorophenols (CPs): 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4, 6-tetrachlorophenol, tetracholorocatechol (3,4,5, 6-tetrachloro-2-hydroxy phenol) and 4-chloroguaiacol (4-chloro-2-methoxy phenol), is studied in order to provide values of the overall rate constant for the reaction between ozone and these chlorophenols. Single ozonation experiments of 4-chlorophenol were conducted in an homogeneous system, and ozonation reactions of CP mixtures were performed in a heterogeneous system, leading to the evaluation of the overall ozonation rate constants in acidic aqueous solutions. These second order rate constants increase several order of magnitude with the pH as does the degree of deprotonation of the dissolved compounds (i.e. from 10(3) to 10(9)l/(mols) for different CPs). The specific rate constants for the ozonation of the non-dissociated and dissociated forms of the studied CPs are also determined and reported. The values obtained allow calculation of the overall rate constants and prediction of the reactivities of the several CPs at different operating conditions in the whole range of pH.     

Hydroxyl Radical Scavenging and Producing Activities of Water-Soluble Malonic Acid C60

Abstract

The effects of several water-soluble malonic acid derivatives of C₆₀ with different addition number (M1～M4) on hydroxyl radical were studied by ESR method. It was shown that the OH signal produced by the Fenton system could be remarkably reduced by M1 and M2, but could not by M3 and M4. The action of M1 and M2 was dose-dependent, and M1 was found to be more effective than M2. In addition, under irradiation and in the presence of oxygen, M2 could produce hydroxyl radicals. These data indicate that the quenching activity of the malonic acid derivative of C₆₀ was closely related to the integrity of conjugated double bonds, and some C₆₀ derivatives with specific structures might act as the eliminator or producer of hydroxyl radicals under different conditions.     

Singlet oxygen generation properties of Fe-OCAP and its influence on the antibacterial and mechanical properties of Fe-OCAP/PU blends

In this paper, the singlet oxygen generation properties of Fe-octacarboxyl acid phthalocyanine (Fe-OCAP)/polyurethane (PU) blends were investigated by ultraviolet–visible spectra. 1,3-diphenylisobenzofuran was used as the reaction substrate to detect the yields of the singlet oxygen of the samples. It was found that Fe-OCAP showed a high efficiency in generating singlet oxygen when it was dissolved in dimethylacetamide (DMAc), while no singlet oxygen was generated when it was in ethanol. The singlet oxygen generation properties of Fe-OCAP/PU blends were also investigated. It was found that with increasing Fe-OCAP content, Fe-OCAP/PU blends showed increased efficiency in generating singlet oxygen. The influence of wavelength of light on the singlet oxygen generation of Fe-OCAP/PU was studied. Compared with orange light, Fe-OCAP/PU had a higher efficiency in generating singlet oxygen under the illumination of red light. The generated singlet oxygen by Fe-OCAP/PU blends had a high efficiency in cell inactivation. As a result, the percentage bacterial reduction of the samples increased with increasing Fe-OCAP content. The influence of the generated singlet oxygen on the mechanical properties of PU was also investigated. The generated singlet oxygen could initiate the oxidation of PU chain and cause the degradation of PU. Therefore, after illuminated by white light, the tensile strength of the samples containing Fe-OCAP decreased, but still was higher than that of pure PU.     

Oxidation Reaction between Periodate and Polyhydroxyl Compounds and Its Application to Chemiluminescence

The oxidation reaction between periodate and polyhydroxyl compounds was studied. A strong chemiluminescent (CL) emission was observed when the reaction took place in a strong alkaline solution without any special CL reagent. However, in acidic or neutral solution, it was hard to record the CL with our instrument. It was interesting to find that in the presence of carbonate the CL signal was enhanced significantly. When O(2) gas and N(2) gas were blown into the reagent solutions, both background and CL signals of the sample were enhanced by O(2) and decreased by N(2). The spectral distribution of the CL emission showed two main bands (λ = 436-446 and 471-478 nm). Based on the studies of the spectra of CL, fluorescence and UV-visible, a possible CL mechanism was proposed. In strongly alkaline solution, periodate reacts with the dissolved oxygen to produce superoxide radical ions. A microamount of singlet oxygen ((1)O(2)*) could be produced from the superoxide radicals. A part of the superoxide radicals acts on carbonates and/or bicarbonates leading to the generation of carbonate radicals. Recombination of carbonate radicals may generate excited triplet dimers of two CO(2) molecules ((CO(2))(2)*). Mixing of periodate with carbonate generated were very few (1)O(2)* and (CO(2))(2)*. These two emitters contribute to the CL background. The addition of polyhydroxyl compounds or H(2)O(2) caused enhancement of the CL signal. It may be due to the production of (1)O(2)* during the oxidized decomposition of the analytes in periodate solution. This reaction system has been established as a flow injection analysis for H(2)O(2), pyrogallol, and α-thioglycerol and their detection limits were 5 × 10(-)(9), 5 × 10(-)(9), and 1 × 10(-)(8) M, respectively. Considering the effective reaction ions, IO(4)(-), CO(3)(2)(-), and OH(-) could be immobilized on a strongly basic anion-exchange resin. A highly sensitive flow CL sensor for H(2)O(2), pyrogallol, and α-thioglycerol was also prepared.