Quantitative analysis of hydrogen peroxide by <Superscript>1</Superscript>H NMR spectroscopy

A technique utilizing ¹H NMR spectroscopy has been developed to measure the concentration of hydrogen peroxide from 10^–3 to 10 M. Hydrogen peroxide produces a peak at around 10–11 ppm, depending upon the interaction between solvent molecules and hydrogen peroxide molecules. The intensity of this peak can be monitored once every 30 s, enabling the measurement of changes in hydrogen peroxide concentration as a function of time. ¹H NMR has several advantages over other techniques: (1) applicability to a broad range of solvents, (2) ability to quantify hydrogen peroxide rapidly, and (3) ability to follow reactions forming and/or consuming hydrogen peroxide as a function of time. As an example, this analytical technique has been used to measure the concentration of hydrogen peroxide as a function of time in a study of hydrogen peroxide decomposition catalyzed by iron(III) tetrakispentafluorophenyl porphyrin.Electronic Supplementary Material Supplementary material is available for this article at     

Effect of oxidation treatment of multi-walled carbon nanotubes on the adsorption of pentachlorophenol from aqueous solution: Kinetics study

Multi-walled carbon nanotubes (MWCNTs) were oxidized using different oxidizing agents and the produced oxidized MWCNTs were characterized using different techniques. IR measurements showed the presence of carboxylic acid function groups especially for the MWCNTs oxidized with nitric acid and hydrogen peroxide. The adsorption of pentachlorophenol (PCP) to pristine and oxidized multi-walled carbon nanotubes (MWCNTs) has been studied. The results showed that the oxidation of the MWCNTs decreased their abilities to adsorb PCP compared with the pristine MWCNTs. The adsorption was studied kinetically and the results showed that the adsorption process occurs in two different steps. The first step involves the transfer of PCP to the surface of the oxidized MWCNTs, which was very fast due to the diffusion of PCP from the liquid phase to the solid phase. This step followed by a second slower step of adsorption could be due to intra-particle diffusion.     

Study of Water Adsorption on Activated Carbons with Different Degrees of Surface Oxidation

A carbon of wood origin was oxidized with different oxidizing agents (nitric acid, hydrogen peroxide, and ammonium persulfate). The microstructural properties of the starting material and the oxidized samples were characterized using sorption of nitrogen. The surface acidity was determined using Boehm titration and potentiometric titration. The changes in the surface chemistry were also studied by diffuse reflectance FTIR. Water adsorption isotherms were measured at three different temperatures close to ambient (relative pressure from 0.001 to 0.3). From the isotherms the heats of adsorption were calculated using a virial equation. The results indicated that the isosteric heats of water adsorption are affected by the surface heterogeneity only at low surface coverage. In all cases the limiting heat of adsorption was equal to the heat of water condensation (45 kJ/mol).     

Selective flow-injection determination of methanol in the presence of ethanol based on a multi-enzyme system with chemiluminescence detection

A highly selective flow-injection system was developed for the determination of methanol. The system consisted of three immobilized enzymes with luminol chemiluminescence detection. First, methanol was oxidized in the presence of alcohol oxidase to yield formaldehyde and hydrogen peroxide. The hydrogen peroxide produced was then destroyed by catalase. The formaldehyde formed in the first stage was further oxidized by NAD⁺-formaldehyde dehydrogenase. The NADH formed was oxidized by 1-methoxy-5-methylphenazinium methylsulphate (1-MPMS), and finally the reduced 1-MPMS was spontaneously oxidized and hydrogen peroxide was produced. The concentration of the hydrogen peroxide produced, which was proportional to the initial concentration of methanol, was determined by luminol chemiluminescence. The determination range was from 0.1 to 100 mg l⁻¹ and the response time was less than 2 min per sample with a relative standard deviation of less than 3%. The system showed good selectivity for methanol; the response was ca. 50 times higher than for ethanol.     

Introduction of peroxide groups onto carbon black surface by radical trapping and radical graft polymerization of vinyl monomers initiated by the surface peroxide groups

The introduction of peroxide groups onto carbon black surface was achieved through the trapping of the peroxide radicals formed by the decomposition of polymeric peroxide, such as poly(tetraethylene glycol peroxyadipate) (ATPPO), and bis-peroxide, such as 1,1′-bis (t-butyldioxy)cyclohexane (Perhexa-C), by the surface: the amount of peroxide groups introduced onto carbon black surface by the treatment with ATPPO and Perhexa-C were determined to be 0.07 mmol/g and 0.12 mmol/g, respectively. The polymerization of vinyl monomers with positive e-value, such as methyl methacrylate and 2-hydroxyethy methacrylate, was successfully initiated by the peroxide groups introduced onto carbon black surface. During the polymerization, the corresponding polymers were effectively grafted onto the surface as a result of the propagation of polymer from the surface radicals formed by decomposition of the peroxide groups. The polymerization of vinyl monomers with negative e-value, such as styrene and vinyl acetate, however, was scarcely initiated by the peroxide groups on carbon black. This may be due to the fact that surface active radicals, which were formed by the hydrogen abstraction from carbon black by fragment radicals, inhibit the polymerization of vinyl monomers with negative e-value. © 1996 John Wiley & Sons, Inc.     

Directed modification of carbons of varied origin and chemical nature of the surface in order to control their catalytic activity

Simple methods were suggested and conditions were found under which modified carbon materials with varied chemical nature of the surface and controllable catalytic activity in the model reaction of hydrogen peroxide decomposition can be produced from various raw materials. The pore structure parameters of the carbons synthesized were determined, the kinetics of the reaction under study on these carbons was analyzed, and the possibility of synthesis of carbon catalysts with high catalytic activity exceeding that of the known active carbons was demonstrated.     

Sorption removal of cephalexin by HNO3 and H2O2 oxidized activated carbons

Cephalexin’s traces within pharmaceutical effluents have toxic impact toward ecological and human health.Low-cost activated carbon derived from Trapa natans husk was oxidized with hydrogen peroxide and nitric acid,and tested for their ability to remove cephalexin from aqueous solutions.Oxidization with H2O2 showed negative effect on the cephalexin sorption,whereas HNO3 oxidization improved the adsorption.The cephalexin adsorption isotherms on the native and HNO3 oxidized carbons correlated well with the Freundlich equation while their kinetics followed the pseudo-second order model.The removal of cephalexin by the native and HNO3 oxidized carbons was found to be most favored at low ionic strength and strong acidic conditions.Based on the thermal and FTIR analyses,the interaction mechanisms of the interaction between cephalexin and the carbons were proposed.Electrostatic attraction,hydrophobic interaction and chemical bonding with surface functional groups were demonstrated as primary mechanisms for cephalexin removal.The nitrogen functionalities on the carbon surface were considered to be an important factor affecting the adsorption process.     

Determination of carbon monoxide in metal carbonyl complexes

Carbon monoxide is liberated from carbonyl-containing metal complexes by treatment with various reagents such as pyridinium hydrobromide perbromide in dichloromethane, hydrogen peroxide in acetone, or iodine in pyridine, and oxidized to carbon dioxide by the Schütze iodine pentoxide reagent. The carbon dioxide is determined gravimetrically following absorption on soda asbestos.     

Selective detection of vapor phase hydrogen peroxide with phthalocyanine chemiresistors

The use of hydrogen peroxide as a precursor to improvised explosives has made its detection a topic of critical importance. Chemiresistor arrays comprised of 50 nm thick films of metallophthalocyanines (MPcs) are redox selective vapor sensors of hydrogen peroxide. Hydrogen peroxide is shown to decrease currents in cobalt phthalocyanine sensors while it increases currents in nickel, copper, and metal-free phthalocyanine sensors; oxidation and reduction of hydrogen peroxide via catalysis at the phthalocyanine surface are consistent with the pattern of sensor responses. This represents the first example of MPc vapor sensors being oxidized and reduced by the same analyte by varying the metal center. Consequently, differential analysis by redox contrast with catalytic amplification using a small array of sensors may be used to uniquely identify peroxide vapors. Metallophthalocyanine chemiresistors represent an improvement over existing peroxide vapor detection technologies in durability and selectivity in a greatly decreased package size.     

聚多巴胺包埋G-四联体/血红素DNA酶制备过氧化氢生物传感器

利用多巴胺的氧化自聚实现对G-四联体/血红素DNA酶的包埋,成功构建了H2O2电化学生物传感器。DNA和血红素混合得到G-四联体/血红素复合物;DNA酶物理吸附在玻碳电极上后,将10μL 5 g/L多巴胺的磷酸盐缓冲液(pH 8.0)滴在表面,空气中的氧气氧化多巴胺形成聚多巴胺膜,实现DNA酶的固定。考察了不同DNA序列对传感器性能的影响,表明电化学与光学传感过程具有不同序列响应。此传感器对H2O2的检出限为2.2μmol/L;线性范围为0.01～1.5 mmol/L。本研究证实了利用聚多巴胺固定酶和用DNA酶代替天然酶构筑传感器的可行性。     

The monooxidation of ethylene with hydrogen peroxide on the per-FTPhPFe<Superscript>3+</Superscript>OH/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> biomimetic

The gas-phase monooxidation of ethylene by hydrogen peroxide on a biomimetic heterogeneous catalyst (per-FTPhPFe³⁺OH/Al₂O₃) was studied under comparatively mild conditions. The biomimetic oxidation of ethylene with hydrogen peroxide was shown to be coherently synchronized with the decomposition of H₂O₂. Depending on reaction medium conditions, one of two desired products was formed, either ethanol or acetaldehyde. The kinetics and probable mechanism of ethylene transformation were studied.     

过氧化氢水溶液催化氧化环戊烯制备戊二醛机理研究

在钨酸-叔丁醇体系中,用H~2O~2水溶液氧化环戊烯制备戊而2醛的机理是:环戊烯首先氧化成环戊烯氧化物,然后生成过氧化物中间物,经分离检定,确证为β-羟基过氧化氢,中间物再进行重排,形成戊醛产物,在H~2O~2等量的情况下,重排只能部分进行,加大H~2O~2用量,可以使中间物埃常温下重排接近完全.     

脂质体@Ag/Au中空纳米壳层材料的制备及与H2O2的作用

以脂质体作为模板, 通过化学还原法制备了脂质体@Ag/Au 中空纳米材料, 并研究了其与过氧化氢(H₂O₂)的作用. 利用透射电子显微镜(TEM)、 紫外-可见(UV-Vis)吸收光谱和表面增强拉曼光谱(SERS)对纳米材料进行了表征. 在过氧化氢和纳米材料存在的情况下, 加入3,3 ',5,5'-四甲基联苯胺(TMB)作为显色液, 无色的TMB被氧化成蓝色的氧化TMB(oxTMB), 可以检测到反应后oxTMB在652 nm处的特征吸收强度及其拉曼光谱的变化. 实验结果表明, 当过氧化氢浓度在15100 μmol/L 范围内, oxTMB的特征吸收强度与其浓度呈线性关系, 可实现对过氧化氢的微量检测, 检测限为0.5 μmol/L.     

Electrochemical catalysis of styrene epoxidation with films of MnO(2) nanoparticles and H(2)O(2)

Films of polyions and octahedral layered manganese oxide (OL-1) nanoparticles on carbon electrodes made by layer-by-layer alternate electrostatic adsorption were active for electrochemical catalysis of styrene epoxidation in solution in the presence of hydrogen peroxide and oxygen. The highest catalytic turnover was obtained by using applied voltage -0.6 V vs SCE, O(2), and 100 mM H(2)O(2). (18)O isotope labeling experiments suggested oxygen incorporation from three different sources: molecular oxygen, hydrogen peroxide, and/or lattice oxygen from OL-1 depending on the potential applied and the oxygen and hydrogen peroxide concentrations. Oxygen and hydrogen peroxide activate the OL-1 catalyst for the epoxidation. The pathway for styrene epoxidation in the highest yields required oxygen, hydrogen peroxide, and a reducing voltage and may involve an activated oxygen species in the OL-1 matrix.     

Electrocatalytic oxidation of hydrogen peroxide and cysteine at a glassy carbon electrode modified with platinum nanoparticle-deposited carbon nanotubes.

A glassy carbon electrode modified with platinum nanoparticle-decorated carbon nanotubes (Pt-CNT/GCE) was prepared. The electrochemical behaviors for the catalysis oxidations of hydrogen peroxide and cysteine were studied. The Pt-CNT/GCE showed catalytic activity for electro-oxidation of hydrogen peroxide at 0.6 V in PBS (pH = 7.0) and for that of cysteine at 0.55 V in sulfuric acid medium (pH 相似文献   

季铵盐功能化的钛硅分子筛催化丙烯氧化酯化合成碳酸丙烯酯

将有机卤素季铵盐以硅烷化键合方式嫁接到钛硅分子筛上,制备了兼备催化氧化烯烃合成环氧化物和环氧化物碳酸酯化反应的新型双功能催化剂,考察了其在丙烯、过氧化氢和二氧化碳一步合成碳酸丙烯酯的催化性能.研究表明,具有大外表面积的层剥离的钛硅分子筛是一种嫁接季铵盐合适的载体,丙基三丁基卤化铵是酯化催化性能优良的功能化基团,两者的偶合使一步法催化丙烯环氧化酯化合成碳酸丙烯酯的收率达48%.该催化剂具有较好的稳定性和重复使用性能.     

Effect of the initial state of carbon nanotubes on their ability to be dispersed in polar solvents upon liquid-phase oxidative treatments

Effect of the structural defectiveness of carbon nanotubes on the influence exerted on these nanotubes by their liquid-phase treatments with oxidizing agents (hydrogen peroxide, concentrated nitric acid, and its mixture with sulfuric acid) was studied. It was found that this factor affects changes in the structure of oxidized carbon nanotubes, their hydrophilicity, high-quality arrays of these tubes, and their ability to form stable dispersions in water, ethanol, isopropanol, and acetone.     

Hydrogen peroxide biosensor based on the direct electrochemistry of myoglobin immobilized on ceria nanoparticles coated with multiwalled carbon nanotubesby a hydrothermal synthetic method

A novel myoglobin-based electrochemical biosensor was developed. It is based on a nanocomposite prepared from multiwalled carbon nanotubes that were coated with ceria nanoparticles. UV-vis and electrochemical measurements displayed that the nanocomposite provides a biocompatible matrix for the immobilization of myoglobin (Mb) and also facilitates direct electron transfer between its active center and the surface of the electrode. Immobilized Mb exhibits excellent electrocatalytic activity toward the reduction of hydrogen peroxide (HP). The low apparent Michaelis-Menten constant of 63.3 μM indicates high bioactivity and enhanced affinity to HP. This study also shows that the nanocomposite is a promising support for immobilization of proteins and for the preparation of third-generation biosensors.     

Catalytic Activity of Anisotropic Gold Nanoplates towards Oxygen Reduction

Glassy carbon electrode (GCE) coated with anisotropic gold nanoplates (aAuNPs) was used for the study of oxygen reduction reaction (ORR) in 0.5 M sulfuric acid instead of bulk gold electrodes. The electrode cleaning/activation procedure lead to the removal of any charged and uncharged residues on the gold nanoplates, leaving the nanostructured surface highly active towards oxygen reduction. The advantages: much lower overpotential and larger current densities of oxygen reduction are ascribed to the unique nanostructures present on the carbon electrode surface‐the gold nanoplates. They are rich in edges providing a large population of Au (100) sites with unsaturated coordination exposed to the solution, and catalytically active. Measurements performed using a rotating disc electrode, modified with the gold nanoplates, confirmed that ORR proceeds via two separate steps: oxygen is reduced to hydrogen peroxide, and the peroxide is further reduced in a two‐electron reduction to water.     

活性炭的表面处理对二苯并噻吩催化氧化脱除的影响

将一种木质活性炭经过三种表面处理,即高锰酸钾稀硫酸溶液液相氧化、浓硝酸液相氧化和350℃低温气相氧化处理。实验所选活性炭及相应的表面改性炭使用氮气吸附和Boehm滴定分别进行了结构性质和表面化学表征。研究了所选活性炭和相应的表面改性炭催化过氧化氢氧化脱除二苯并噻吩（DBT）。实验结果表明,活性炭表面化学对二苯并噻吩的氧化脱除影响很大;炭表面化学对DBT吸附脱除的影响不同于对DBT氧化脱除的影响,表面酸性越强越有利于DBT的吸附;表面羰基能加速过氧化氢产生自由基,表面羰基量的增加明显有利于DBT的氧化脱除。活性炭经过热处理后,在二苯并噻吩的氧化脱除中催化活性明显增加,正辛烷溶液中硫的体积质量从0.556g·L-1降到0.009g·L-1。