Ratiometric Nanoparticle Probe Based on FRET‐Amplified Phosphorescence for Oxygen Sensing with Minimal Phototoxicity

Luminescent oxygen probes enable direct imaging of hypoxic conditions in cells and tissues, which are associated with a variety of diseases, including cancer. Here, a nanoparticle probe that addresses key challenges in the field is developed, it: i) strongly amplifies room temperature phosphorescence of encapsulated oxygen‐sensitive dyes; ii) provides ratiometric response to oxygen; and iii) solves the fundamental problem of phototoxicity of phosphorescent sensors. The nanoprobe is based on 40 nm polymeric nanoparticles, encapsulating ≈2000 blue‐emitting cyanine dyes with fluorinated tetraphenylborate counterions, which are as bright as 70 quantum dots (QD525). It functions as a light‐harvesting nanoantenna that undergoes efficient Förster resonance energy transfer to ≈20 phosphorescent oxygen‐sensitive platinum octaethylporphyrin (PtOEP) acceptor dyes. The obtained nanoprobe emits stable blue fluorescence and oxygen‐sensitive red phosphorescence, providing ratiometric response to dissolved oxygen. The light harvesting leads to ≈60‐fold phosphorescence amplification and makes the single nanoprobe particle as bright as ≈1200 PtOEP dyes. This high brightness enables oxygen detection at a single‐particle level and in cells at ultra‐low nanoprobe concentration with no sign of phototoxicity, in contrast to PtOEP dye. The developed nanoprobe is successfully applied to the imaging of a microfluidics‐generated oxygen gradient in cancer cells. It constitutes a promising tool for bioimaging of hypoxia.     

普鲁士蓝基HClO荧光纳米探针及其对肿瘤细胞的特异性检测（英文）

次氯酸(HClO)是一种活性氧(ROS),在许多生理和病理过程中起着至关重要的作用。然而,过量的HClO会导致组织损伤、动脉粥样硬化、神经退行性疾病甚至癌症。因此,实时检测肿瘤细胞中HCl O对于探索HClO在肿瘤进展以及免疫治疗中的作用具有重要意义。与目前常用的工艺复杂、水溶性差的有机分子探针不同,本工作简单地将异硫氰酸荧光素(FITC)与中空介孔普鲁士蓝纳米粒子(HMPB)相结合,构建了一种新型的无机亲水荧光纳米探针。由于内滤光效应,HMPB中FITC的荧光有一定程度的猝灭,但通过Fe²⁺-ClO^–氧化还原反应可恢复荧光。体外条件下,加入HClO后, FITC在发射峰(520 nm)处荧光逐渐增强, HClO在5×10^–6～50×10^–6 mol/L范围内呈良好的线性关系,检出限为2.01×10^–6mol/L。此外,在细胞水平上,该纳米探针对癌细胞中的HClO显示出良好的特异检测能力,且灵敏度高。     

Photodegradation of glyphosate in the ferrioxalate system

The photoinduced degradation of glyphosate (GLP) in the ferrioxalate system was investigated under irradiation with a 250W metal halide lamp (lambda>/=365nm). The efficiency of orthophosphates release, representing the photodegradation efficiency of GLP, increased with decreasing the initial concentrations of GLP and Fe(III)/oxalate ratios. At acidic pH value in the range of 3.5-5.0, higher efficiency of orthophosphates release up to 60.6% was achieved, while the efficiency dropped to 42.1% at pH 6.0. The photochemical process mainly involved the predominant species of iron(III), namely Fe(C(2)O(4))(2)(-) and Fe(C(2)O(4))(3)(3-), which lead to the formation of hydroxyl radicals in the presence of dissolved oxygen under UV-vis irradiation. Also, the complexation of GLP with Fe(III) obviously increased the light absorption of GLP and facilitated its degradation by direct photolysis. The ninhydrin test for primary amines showed that the GLP was attacked by hydroxyl radicals with CN cleavage to yield aminomethylphosphonic acid (AMPA) and CP cleavage to yield sarcosine. The photodegradation may be enhanced by the decomposition of reactive radicals produced through ligand-to-metal charge transfer (LMCT) of ferric-GLP complexes.     

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.     

Influence of ozone on traffic-related particulate matter on the generation of hydroxyl radicals through a heterogeneous synergistic effect

Epidemiologic studies suggest that ozone (O(3)) and airborne particulate matter (PM) can interact causing acute respiratory inflammation and other respiratory diseases. Recent studies investigated the hypothesis that the effects of air pollution caused by O(3) and PM are larger than the effect of these two pollutants individually. We investigated the hypothesis that ozone and traffic-related PM (PM(10) and PM(2.5), diesel and gasoline exhaust particles) interact synergistically to produce increasing amounts of highly reactive hydroxyl radicals (HO) in a heterogeneous aqueous mixture at physiological pH. Electron paramagnetic resonance (EPR) and spin trapping were used for the measurements. Results showed that HO radicals are generated by the catalytic action of PM surface area with ozone and that EPR peak intensities are two to three times higher compared to PM samples without ozone. Incubation of the nucleoside 2'-deoxyguanosine (dG) in aqueous mixtures of ozone and PM at pH 7.4 resulted in the hydroxylation at C(8) position of dG. The formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) showed a 2-2.5-fold increase over control (PM without O(3)). These results suggest that PM and O(3) act synergistically generating a sustained production of reactive HO radicals. Partitioning of O(3) into the particle phase depends on the concentration, hygroscopicity and particle size.     

Sensitive chemiluminescent imaging for chemoselective analysis of glycan expression on living cells using a multifunctional nanoprobe

A novel sensitive chemiluminescent (CL) imaging method was developed for in situ monitoring of cell surface glycan expression through chemoselective labeling of carbohydrate motifs and then binding to a multifunctional nanoprobe. The nanoprobe was fabricated by assembling biotin-DNA and a large amount of horseradish peroxidase (HRP) on gold nanoparticles (AuNPs). The chemoselective labeling was performed by selective oxidization of the hydroxyl sites of sialyl and galactosyl groups on cell surfaces into aldehydes by periodate and galactose oxidase, respectively, and then aniline-catalyzed hydrazone ligation with biotin hydrazide for specific recognition to avidin. With the biotin-avidin system, the multifunctional nanoprobe could conveniently be bound to the glycan sites on the cell surface. The DNA chain presenting between the AuNPs and biotin assembled on the nanoprobe could obviate the steric effect, and HRP acted to trigger the CL emission of the luminal-H(2)O(2) system. Therefore the expression of both sialyl and galactosyl groups could be selectively monitored by CL imaging with high sensitivity due to the high amount of HRP. Using human liver cancer HCCC-9810 cells as a model, this CL imaging strategy could detect HCCC cells ranging from 6 × 10(2) to 1 × 10(7) cells mL(-1) with a detection limit down to 12 cells. More importantly, this method could be used for distinguishing cancer cells from normal cells and monitoring of dynamic carbohydrate expression on living cells, providing promising application in clinical diagnosis and treatment of cancer.     

The role of hydroxyl and atomic oxygen in multiwall carbon nanotube growth

Multiwall carbon nanotubes (CNTs) were grown by the plasma-enhanced chemical vapor deposition (PECVD) method in downstream on the p-Si (100) substrate. Besides precursors, methane as the carbon source and hydrogen as the ablation, oxygen or H₂O was alternatively inlet into the reactive chamber at the pressure of 0.05 MPa. Given characterizations of the tube structure and tube mass weight, the role of radical atomic O, hydroxyl and perhydroxyl in multiwall CNT growth was explored. In addition to a small amount of O₂ (∼0.67%) or H₂O (∼0.1%), it was found that a high quantity of pure nanotubes can be grown in the downstream. However, no nanotube could be formed or even the carbon matrix generated when the concentration of O₂ or H₂O exceeded a proper value in the mixture. The mechanism of multiwall CNT growth controlled by active radicals was explored in this paper.     

Photoinduced decolorization of 2, 6-dichloroindophenol by 2-anthraquinone sulfonate treated nylon

Photoactive 2-anthraquinone sulfonate sodium (2-AQS) can produce hydroxyl radical and other reactive oxygen species under UVA irradiation. Because of its acid dye like feature, 2-AQS was immobilized onto nylon fibers through an acid dyeing process, and the dyed nylon was employed as a photoactive self-cleaning material. As a model study, decolorization of representative colorants such as 2,6-dichloroindophenol (DCIP) by the material was investigated. The results revealed that DCIP was first absorbed on the fibers and then degraded by hydroxyl radicals and other reactive oxygen species generated by 2-AQS on the surfaces upon UVA exposure. The photo degradation pathway of DCIP was further studied by directly using aqueous 2-AQS solution, and the degraded products in the solutions were analyzed by LC-MS. Different light sources and hydrogen donors were investigated in degradation of DCIP. The photoactive functions on the 2-AQS-dyed nylon fibers were quite durable and maintained similar decolorization effect of DCIP after five repeated tests.     

The role of hydroxyl and atomic oxygen in multiwall carbon nanotube growth

Multiwall carbon nanotubes (CNTs) were grown by the plasma-enhanced chemical vapor deposition (PECVD) method in downstream on the p-Si (100) substrate. Besides precursors, methane as the carbon source and hydrogen as the ablation, oxygen or H₂O was alternatively inlet into the reactive chamber at the pressure of 0.05 MPa. Given characterizations of the tube structure and tube mass weight, the role of radical atomic O, hydroxyl and perhydroxyl in multiwall CNT growth was explored. In addition to a small amount of O₂ (∼0.67%) or H₂O (∼0.1%), it was found that a high quantity of pure nanotubes can be grown in the downstream. However, no nanotube could be formed or even the carbon matrix generated when the concentration of O₂ or H₂O exceeded a proper value in the mixture. The mechanism of multiwall CNT growth controlled by active radicals was explored in this paper.     

A kinetic method for HO2*/O2*- determination in advanced oxidation processes

A new kinetic method is developed for the determination of hydroperoxyl radical (HO(2)(*))/superoxide radical (O(2)(*)(-)) in aqueous solution, and the calibration using a kinetic half-life technique is also established for determining the concentration of HO(2)(*)/O(2)(*)(-) as produced in the UV/H(2)O(2) process. This new method is based on the reduction of Fe(3+)-EDTA into Fe(2+)-EDTA by HO(2)(*)/O(2)(*)(-) and the well-known Fenton-like reaction of H(2)O(2) and Fe(2+)-EDTA to yield the hydroxyl radicals (OH(*)). Benzoic acid scavenges the OH radicals to produce hydroxybenzoic acids, which are analyzed by fluorescence detection (lambda(ex) = 320 nm; lambda(em) = 400 nm). The limit of detection for the new method depends on the pH values, and it is determined as 3.22 x 10(-)(11) M with signal-to-noise ratio of 2 at pH 5. In addition, the present technique has the advantage of using inexpensive and easily available nonenzymatic reagents that do not require the specific instrument and chemicals and of being insensitive to the moderate concentration of possible interferences often found in aqueous phase.     

Development of nitroxide radicals–containing polymer for scavenging reactive oxygen species from cigarette smoke

We developed a nitroxide radicals–containing polymer (NRP), which is composed of poly(4-methylstyrene) possessing nitroxide radicals as a side chain via amine linkage, to scavenge reactive oxygen species (ROS) from cigarette smoke. In this study, the NRP was coated onto cigarette filters and its ROS-scavenging activity from streaming cigarette smoke was evaluated. The intensity of electron spin resonance signals of the NRP in the filter decreased after exposure to cigarette smoke, indicating consumption of nitroxide radicals. To evaluate the ROS-scavenging activity of the NRP-coated filter, the amount of peroxy radicals in an extract of cigarette smoke was measured using UV–visible spectrophotometry and 1,1-diphenyl-2-picrylhydrazyl (DPPH). The absorbance of DPPH at 517 nm decreased with exposure to cigarette smoke. When NRP-coated filters were used, the decrease in the absorbance of DPPH was prevented. In contrast, both poly[4-(cyclohexylamino)methylstyrene]- and poly(acrylic acid)-coated filters, which have no nitroxide radical, did not show any effect, indicating that the nitroxide radicals in the NRP scavenge the ROS in cigarette smoke. As a result, the extract of cigarette smoke passed through the NRP-coated filter has a lower cellular toxicity than smoke passed through poly[4-(cyclohexylamino)methylstyrene]- and poly(acrylic acid)-coated filters. Accordingly, NRP is a promising material for ROS scavenging from cigarette smoke.     

Adjustable Intermolecular Interactions Allowing 2D Transition Metal Dichalcogenides with Prolonged Scavenging Activity for Reactive Oxygen Species

There is an increasing demand for control over the dimensions and functions of transition metal dichalcogenides (TMDs) in aqueous solution toward biological and medical applications. Herein, an approach for the exfoliation and functionalization of TMDs in water via modulation of the hydrophobic interaction between poly(ε‐caprolactone)‐b‐poly(ethylene glycol) (PCL‐b‐PEG) and the basal planes of TMDs is reported. Decreasing the hydrophobic PCL length of PCL‐b‐PEG from 5000 g mol^?1 (PCL₅₀₀₀) to 460 g mol^?1 (PCL₄₆₀) significantly increases the exfoliation efficiency of TMD nanosheets because the polymer–TMD hydrophobic interaction becomes dominant over the polymer–polymer interaction. The TMD nanosheets exfoliated by PCL₄₆₀‐b‐PEG₅₀₀₀ (460‐WS₂, 460‐WSe₂, 460‐MoS₂, and 460‐MoSe₂) show excellent and prolonged scavenging activity for reactive oxygen species (ROS), but each type of TMD displays a different scavenging tendency against hydroxyl, superoxide, and 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radicals. A mechanistic study based on electron paramagnetic resonance spectroscopy and density functional theory simulations suggests that radical‐mediated oxidation of TMDs and hydrogen transfer from the oxidized TMDs to radicals are crucial steps for ROS scavenging by TMD nanosheets. As‐prepared 460‐TMDs are able to effectively scavenge ROS in HaCaT human keratinocytes, and also exhibit excellent biocompatibility.     

聚(ε-己内酯)-b-聚丙烯酸嵌段聚合物的合成

结合配位-插入开环聚合(CROP)及原子转移自由基聚合(ATRP)成功制备出一种两亲性新型四臂星型聚合物聚(ε-己内酯)-b-聚丙烯酸(PCL4-b-PAA4)。首先以季戊四醇为四官能团引发剂,辛酸亚锡Sn(Oct)2为催化剂,由ε-己内酯制备出分子量为8000、分子量分布为1.13的四臂星型聚(ε-己内酯)(PCL4),其末端羟基与小分子2-溴异丁酰溴进行酯化反应,得到用于ATRP聚合的星型大分子引发剂(PCL-Br)4,然后引发丙烯酸叔丁酯(tBA)聚合,把得到的PCL4-b-Pt-BA4水解,得到目标产物PCL4-b-PAA4。水解3 h和6 h的样品通过凝胶渗透色谱(GPC)测试可知,分子量分布很窄,分别为1.31和1.40。用核磁共振(1H-NMR)和红外光谱(FT-IR)等手段,对中间及最终产物进行了详细表征。     

Photo degradation of methyl orange an azo dye by advanced Fenton process using zero valent metallic iron: influence of various reaction parameters and its degradation mechanism

Advanced Fenton process (AFP) using zero valent metallic iron (ZVMI) is studied as a potential technique to degrade the azo dye in the aqueous medium. The influence of various reaction parameters like effect of iron dosage, concentration of H(2)O(2)/ammonium per sulfate (APS), initial dye concentration, effect of pH and the influence of radical scavenger are studied and optimum conditions are reported. The degradation rate decreased at higher iron dosages and also at higher oxidant concentrations due to the surface precipitation which deactivates the iron surface. The rate constant for the processes Fe(0)/UV and Fe(0)/APS/UV is twice compared to their respective Fe(0)/dark and Fe(0)/APS/dark processes. The rate constant for Fe(0)/H(2)O(2)/UV process is four times higher than Fe(0)/H(2)O(2)/dark process. The increase in the efficiency of Fe(0)/UV process is attributed to the cleavage of stable iron complexes which produces Fe(2+) ions that participates in cyclic Fenton mechanism for the generation of hydroxyl radicals. The increase in the efficiency of Fe(0)/APS/UV or H(2)O(2) compared to dark process is due to continuous generation of hydroxyl radicals and also due to the frequent photo reduction of Fe(3+) ions to Fe(2+) ions. Though H(2)O(2) is a better oxidant than APS in all respects, but it is more susceptible to deactivation by hydroxyl radical scavengers. The decrease in the rate constant in the presence of hydroxyl radical scavenger is more for H(2)O(2) than APS. Iron powder retains its recycling efficiency better in the presence of H(2)O(2) than APS. The decrease in the degradation rate in the presence of APS as an oxidant is due to the fact that generation of free radicals on iron surface is slower compared to H(2)O(2). Also, the excess acidity provided by APS retards the degradation rate as excess H(+) ions acts as hydroxyl radical scavenger. The degradation of Methyl Orange (MO) using Fe(0) is an acid driven process shows higher efficiency at pH 3. The efficiency of various processes for the de colorization of MO dye is of the following order: Fe(0)/H(2)O(2)/UV>Fe(0)/H(2)O(2)/dark>Fe(0)/APS/UV>Fe(0)/UV>Fe(0)/APS/dark>H(2)O(2)/UV approximately Fe(0)/dark>APS/UV. Dye resisted to degradation in the presence of oxidizing agent in dark. The degradation process was followed by UV-vis and GC-MS spectroscopic techniques. Based on the intermediates obtained probable degradation mechanism has been proposed. The result suggests that complete degradation of the dye was achieved in the presence of oxidizing agent when the system was amended with iron powder under UV light illumination. The concentration of Fe(2+) ions leached at the end of the optimized degradation experiment is found to be 2.78 x 10(-3)M. With optimization, the degradation using Fe(0) can be effective way to treat azo dyes in aqueous solution.     

Spin-trapping reactions of a novel gauchetype radical trapper G-CYPMPO

Chemical reactions of a novel gauchetype spin trap, G-CYPMPO (sc-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-5-methy-1-pyrroline N-oxide, O1-P1-C6-N1 torsion angle = 52.8°), with reactive oxygen species were examined by pulse radiolysis technique with 35 MeV electron beam and by electron spin resonance spectroscopy after (60)Co γ-ray irradiation. The spin-trapping reaction rate constants of G-CYPMPO toward the hydroxyl radical and the hydrated electron were estimated to be (4.2 ± 0.1) × 10(9) and (11.8 ± 0.2) × 10(9) M(-1)s(-1), respectively. Half-lives of the spin adducts, hydroxyl radical, and perhydroxyl radical adducted G-CYPMPO were estimated to be ～35 and ～90 min, respectively. A comparison of the results with earlier reports using different radical sources suggests that the purity of the solution and/or the radical generation technique may influence the stability of the spin adducts.     

Post-Trapping Derivatization of Radical-Derived EPR-Silent Adducts: Application to Free Radical Detection by HPLC/UV in Chemical, Biochemical, and Biological Systems and Comparison with EPR Spectroscopy

Free radicals are conventionally detected by electron paramagnetic resonance (EPR) spectroscopy after being trapped as spin adducts. Albeit this technique has demonstrated utmost efficacy in studying free radicals, its application to biological settings is intrinsically hampered by the inevitable bioreduction of radical-derived paramagnetic adducts. Herein, we describe a reliable technique to detect and quantify free radical metabolites, wherein reduced alkyl- and phenyl-5,5-dimethyl-1-pyrroline N-oxide (DMPO) adducts are converted into ultrastable N-naphthoate esters. To mimic the ubiquitous in vivo microenvironment, bioreductants, exogenous thiols, and sodium borohydride were studied. Nitroxyl reduction was confirmed using EPR and triphenyltetrazolium chloride. The formation of the N-naphthoyloxy derivatives was established by liquid chromatography/mass spectrometry (LC/MS). The derivatives were chromatographed using a binary eluent. HPLC and internal standards were synthesized using Grignard addition. The labeled DMPO adduct is (1) fluorescent, (2) stable as opposed to nitroxyl radical adducts, (3) biologically relevant, and (4) excellently chromatographed. Applications encompassed chemical, biochemical, and biological model systems generating C-centered radicals. Different levels of phenyl radicals produced in situ from whole blood were successfully determined. The method is readily applicable to the detection of hydroxyl radical. Analogously, DMPO, the spin trap, could be detected with extreme sensitivity suitable for in vivo applications. The developed method proved to be a viable alternative to EPR, where for the first time the reductive loss of paramagnetic signals of DMPO-trapped free radicals is transformed into fluorescence emission. We believe the proposed methodology could represent a valuable tool to probe free radical metabolites in vivo using DMPO, the least toxic spin trap.     

Photodegradation of clopyralid in TiO2 suspensions: Identification of intermediates and reaction pathways

The work is concerned with the kinetics, identification of intermediates and reaction pathways of the photocatalytic degradation of the herbicide clopyralid (3,6-dichloropyridine-2-carboxylic acid) in UV illuminated aqueous suspensions of TiO₂ (Degussa P25). In the investigated concentration range (0.5–3.0 mM) the photocatalytic degradation kinetics of clopyralid in the first stage of the reaction follows approximately a pseudo-first kinetic order. The highest reaction rate was observed at 4 mg mL⁻¹of catalyst concentration, the apparent activation energy of the reaction being 7.74 kJ mol⁻¹. The effect of the presence of hydrogen peroxide, potassium bromate, and ammonium persulfate, acting as electron acceptors along with molecular oxygen, were also studied. By studying the effect of ethanol as a hydroxyl radical scavenger it was shown that the heterogeneous catalysis takes place mainly via hydroxyl radicals. The reaction intermediates (3,6-dichloropyridin-2-ol, 3,6-dichloro hydroxypyridine-2-carboxylic acid, and 3,3′,6,6′-tetrachloro-2,4′-bipyridine-2′-carboxylic acid) were identified and the kinetics of their appearance/disappearance was followed by LC–MS/MS (ESI+). Tentative photodegradation pathways were proposed and discussed.     

Photocatalytic Activity of Protein‐Conjugated CdS Nanoparticles

Colloidal CdS nanoparticles are conjugated with a variety of proteins, including enhanced yellow fluorescent protein, tobacco etch virus protease (TEV), lysozyme, and bacterial cytochrome P450 CYP152A1, and the photochemical properties of the resulting conjugates are analyzed by EPR spectroscopy and hydroxyl radical‐specific fluorimetric assay. While irradiation of bare CdS colloids leads to photogeneration of hydroxyl and superoxide radicals, it is surprisingly observed that coating of the CdS particles with proteins effectively suppresses the production of these radical species and instead leads to increased formation of a long‐lived reactive oxygen species, most likely H₂O₂. A mechanism for the observed results is suggested. The empirical results are capitalized on for the assembly of a CdS–TEV nanohybrid, which shows significantly higher performance as a photocatalytic mediator for fatty acid hydroxylation by CYP152A1 than bare CdS nanoparticles.     

Olive mill wastewater degradation by Fenton oxidation with zero-valent iron and hydrogen peroxide

The degradation of olive mill wastewater (OMW) with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of chemical oxygen demand (COD) and phenolic compounds analyses. The effects of the H2O2 dose, the pH and the organic matter concentration have been studied. The optimal experimental conditions were found to have continuous presence of iron metal, acid pH (2.0-4.0), and relatively concentrated hydrogen peroxide (9.5M). Coloration of OMW disappeared and phenolic compound decreased to 50% of initial concentration after 3h reaction time. The application of zero-valent Fe/H2O2 procedure permitted high removal efficiencies of pollutants from olive mill wastewater. The results show that zero-valent Fe/H2O2 could be considered as an effective alternative solution for the treatment of OMW or may be combined with a classical biological process to achieve high quality of effluent water.     

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.