Wyniki wyszukiwania - Biblioteka Nauki

1

Thermodynamics and kinetics of thermal deactivation of catalase Aspergillus niger

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Miłek J.

Polish Journal of Chemical Technology

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2020

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tom Vol. 22, nr 2

67--72

EN

The thermal stability of enzyme-based biosensors is crucial in economic feasibility. In this study, thermal deactivation profiles of catalase Aspergillus niger were obtained at different temperatures in the range of 35° C to 70° C. It has been shown that the thermal deactivation of catalase Aspergillus niger follows the first-order model. The half-life time t 1/2 of catalase Aspergillus niger at pH 7.0 and the temperature of 35° C and 70° C were 197 h and 1.3 h respectively. Additionally, t 1/2 of catalase Aspergillus niger at the temperature of 5° C was calculated 58 months. Thermodynamic parameters the change in enthalpy ΔH*, the change in entropy ΔS* and the change Gibbs free energy ΔG* for the deactivation of catalase at different temperatures in the range of 35° C to 70° C were estimated. Catalase Aspergillus niger is predisposed to be used in biosensors by thermodynamics parameters obtained.

2

Study and Application of HRP-like Catalyst Copper 2-Hydroxy-1-naphthaldehyde-2-aminothiazole {Cu II-(HNATS)2]

100%

Tang B.

Polish Journal of Chemistry

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2002

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tom Vol. 76 / nr 11

1527-1535

EN

2-Hydroxy-1-naphthaldehyde-2-aminothiazole (HNATS) and its copper complex [CuII-(HNATS)2] had been synthesized. The complex of [CuII-(HNATS)2] was used to mimic the active group of horseradish peroxidase (HRP). The catalytic characteristics of this HRP-like catalyst in the H2O2-phenol- 4-AAP redox coupling reaction was studied, and the catalytic activity of [CuII-(HNATS)2] was compared with those of HRP and other Schiff base metal complexes. It was found that [CuII-(HNATS)2] exhibits a good catalytic activity and could be used as a novel catalyst in the determination of hydrogen peroxide (H2O2). The reaction mechanism, optimal experimental conditions and interferences of coexisting substances were discussed. Under the experimental conditions established, the linear relationship between the absorbance at 504 nm (A504) and H2O2 concentration was in the range of 5.6×10-6~1.1×10-4 mol/L, with a correlation coefficient (r) of 0.9990. The linear regression equation was A504 = 2540×C (mol/L) - 3.0×10-3 with a detection limit of 1.7×10-6 mol/L. In this paper, the complex [CuII-(HNATS)2] was applied successfully with catalytic spectrophotometric method to the determination of (-O-O-H) in polyethylene glycol.

3

A facile and effective method for preparation of 2.5-furandicarboxylic acid via hydrogen peroxide direct oxidation of 5-hydroxymethylfurfural

100%

Zhang S. , Zhang L.

Polish Journal of Chemical Technology

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2017

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tom Vol. 19, nr 1

11--16

EN

In this paper, 2,5-furandicarboxylic acid (FDCA) was efficiently prepared by the direct oxidation of 5-hydroxymethylfurfural (5-HMF) using hydrogen peroxide (H2O2) in alkaline conditions without any catalysts. The effects of reaction parameters on the process were systematically investigated and the optimal parameters were obtained as follows: molar ratio of 5-HMF:KOH: H2O2 was 1:4:8, reaction temperature and reaction time were determined as 70°C and 15 minutes, respectively. Under these conditions, the yield of FDCA was 55.6% and the purity of FDCA could reach 99%. Moreover, we have speculated the detailed oxidation mechanism of 5-HMF assisted by hydrogen peroxide in alkaline condition to synthesize FDCA.

4

The oxidation of limonene at raised pressure and over the various titanium-silicate catalysts

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Wróblewska A. , Makuch E. , Miądlicki P.

Polish Journal of Chemical Technology

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2015

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tom Vol. 17, nr 4

82--87

EN

This work presents the studies on the oxidation of limonene with hydrogen peroxide and tert-butyl hydroperoxide (TBHP) in the presence of : TS-2, Ti-Beta, Ti-MCM-41 and Ti-MWW catalysts, at the autogenic pressure and atmospheric pressure. The examination were performed at the following conditions: the temperature of 140°C (studies in the autoclave) and 80°C (studies in glass reactor), the molar ratio of limonene/oxidant (H2O2 or WNTB) = 1:1, the methanol concentration 80 wt%, the catalyst content 3 wt%, the reaction time 3 h and the intensity of stirring 500 rpm. The analysis of the results showed that in process not only 1,2-epoxylimonene was formed but also: 1,2-epoxylimonene diol, carveol, carvone and perillyl alcohol but for 1,2-epoxylimonene obtaining the better method was the method at the autogenic pressure and in the presence of TBHP.

5

Mechanism and leaching kinetics of molybdenite concentrate in a hydrogen peroxide-acid system

100%

Aracena A. , Azocar A. , Ibáñez J. P. , Jerez O.

Physicochemical Problems of Mineral Processing

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2019

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tom Vol. 55, iss. 1

140--152

EN

The mechanism and leaching kinetics of a molybdenite concentrate in a H2O2-H2SO4 system were studied. The experimental work was performed in a batch reactor equipped with a condenser, a mechanical agitator and a temperature control system. The effects of the temperature, H2O2 and H2SO4 concentrations, particle size, liquid/solid ratio and agitation speed on the Mo recovery were investigated. The thermodynamic results showed that the leaching mechanism it was governed by several intermediate reactions; however, the influences of sulfuric acid and passivation were not observed in the reaction. The most predominant experimental result was the maximum Mo recovery of 81.3% by leaching 64 μm particles at 333 K (60 °C) for 5400 s (90 min). The molybdenum recovery was generally enhanced by increasing the H2O2 and H2SO4 concentrations. However, at H2SO4 concentrations higher than 1.0 mol/dm3, the Mo recovery decreased. Although the agitation speed affected the Mo recovery considerably, high recoveries could be still obtained without mixing. The experimental results and XRD analysis confirmed the reaction mechanisms. The leaching kinetics were analyzed using a shrinking core model in which the rate was controlled by diffusion through a porous layer with radius ro. The reaction rate orders were 1.0 and 0.2 for the H2O2 and H2SO4 concentrations, respectively, and the rate was inversely proportional to the square of the initial particle radius. The calculated activation energy was 75.2 kJ/mol in the temperature range of 278-333 K (5-60 °C).

6

Labile iron pool correlates with iron content in the nucleus and the formation of oxidative DNA damage in mouse lymphoma L5178Y cell lines.

100%

Kruszewski M. , Iwaneńko T.

Acta Biochimica Polonica

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2003

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tom 50

|

nr 1

211-215

EN

Labile iron pool (LIP) constitutes a crossroad of metabolic pathways of iron-containing compounds and is midway between the cellular need for iron, its uptake and storage. In this study we investigated oxidative DNA damage in relation to the labile iron pool in a pair of mouse lymphoma L5178Y (LY) sublines (LY-R and LY-S) differing in sensitivity to hydrogen peroxide. The LY-R cells, which are hydrogen peroxide-sensitive, contain 3 times more labile iron than the hydrogen peroxide-resistant LY-S cells. Using the comet assay, we compared total DNA breakage in the studied cell lines treated with hydrogen peroxide (25 μM for 30 min at 4°C). More DNA damage was found in LY-R cells than in LY-S cells. We also compared the levels of DNA lesions sensitive to specific DNA repair enzymes in both cell lines treated with H2O2. The levels of endonuclease III-sensitive sites and Fapy-DNA glycosylase-sensitive sites were found to be higher in LY-R cells than in LY-S cells. Our data suggest that the sensitivity of LY-R cells to H2O2 is partially caused by the higher yield of oxidative DNA damage, as compared to that in LY-S cells. The critical factor appears to be the availability of transition metal ions that take part in the OH radical-generating Fenton reaction (very likely in the form of LIP).

7

Utlenianie wybranych barwników metalokompleksowych nadtlenkiem wodoru i chloranem(I) sodu

100%

Anielak P. , Wiktorowski S.

Przemysł Chemiczny

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2003

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tom T. 82, nr 8-9

995-998

8

Modification of the Detonation Parameters of Mining Explosives Containing Hydrogen Peroxide and Aluminium Powder

100%

Paszula J. , Maranda A. , Nikolczuk K. , Giercuszkiewicz A.

Central European Journal of Energetic Materials

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2021

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tom Vol. 18, no. 4

477--491

EN

Presently, due to rising environmental consciousness, numerous actions are being taken to prevent devastation of the natural environment. If explosive mixtures are manufactured in an insufficiently controlled manner, they contain too much ammonium nitrate and generate nitrogen oxides (NOx), which are both harmful for living organism and responsible for negative weather phenomena. However, the products from decomposition of hydrogen peroxide are only oxygen and hydrogen, which are both environmentally friendly. This paper presents the results of research on the impact of two types of aluminium powder on the detonation parameters of mining explosives containing hydrogen peroxide 60% as an oxidiser. The detonation velocities were measured by means of short circuit sensors. Direct measurement of the blast wave overpressure was performed with piezoelectric sensors and the positive phase impulse was analyzed. Measurement of the explosive strength was made by the ballistic pendulum method for 10 g samples. The results of these experiments showed that the addition of both types of aluminium, as well as their content in the explosive mixture, have a significant impact on all of the measured parameters.

9

Cytoprotective effect of methanolic extract of Nardostachys jatamansi against hydrogen peroxide induced oxidative damage in C6 glioma cells

100%

Dhuna K. , Dhuna V. , Bhatia G. , Singh J. , Kamboj S. S.

Acta Biochimica Polonica

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2013

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tom 60

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nr 1

21-31

EN

Oxidative stress has been implicated as an important factor in the process of neurodegeneration and hydrogen peroxide (H2O2) is one of the most important precursors of reactive oxygen species (ROS), responsible for many neurodegenerative diseases. This study used extracts from Nardostachys jatamansi rhizomes, known for nerve relaxing properties in Ayurvedic medicine, to ascertain their protective role in H2O2-induced oxidative stress in C6 glioma cells. The protective effect of methanolic, ethanolic and water extracts of N. jatamansi (NJ-MEx, NJ-EEx and NJ-WEx respectively) was determined by MTT assay. NJ-MEx significantly protected against H2O2 cytotoxicity when cells were pretreated for 24 h. The level of antioxidant enzymes, catalase, superoxide dismutase (Cu-ZnSOD), glutathione peroxidase (GPx), and a direct scavenger of free radicals, glutathione (GSH), significantly increased following pre-treatment with NJ-MEx. Lipid peroxidation (LPx) significantly decreased in NJ-MEx-pretreated cultures. The expression of a C6 differentiation marker, GFAP (glial fibrillary acidic protein), stress markers HSP70 (heat shock protein) and mortalin (also called glucose regulated protein 75, Grp75) significantly decreased when cells were pre-treated with NJ-MEx before being subjected to H2O2 treatment as shown by immunofluorescence, western blotting and RT-PCR results. The present study suggests that NJ-MEx could serve as a potential treatment and/or preventive measure against neurodegenerative diseases.

10

Novel mi-X Bridged Dicopper(II) Complex System : Synthesis, Structural Characterization and Catalytic Activity

100%

Gao J.

Polish Journal of Chemistry

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2001

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tom Vol. 75, nr 3

379-385

EN

Three NAPH (1,8-naphthalate dianion) bridged dicopper(II) complexes have been synthesized, namely [NAPHCu2(_-X)2_2H2O]_nH2O, X = OH- (1), OAc- (2) and Cl- (3). NAPH was found to have the ability to form a dinuclear core with _-X as additional ligand. Based on IR, elemental analysis and electronic spectra, these complexes were found to have heterocyclic structure with both NAPH and _-X as bridging ligands. The temperature dependence of magnetic susceptibilities of 1 has been studied, giving the exchange integral of J = -216 cm-1, g = 2.09. This result is in agreement with proposed dihydroxo-bridged structure of 1, since Cu2O2 unit normally undergoes a strong antiferromagnetic interaction. Significantly, these complexes were found to exhibit catalase- like activity.

11

Measurements of the VOD of Selected Mining Explosives and Novel “Green Explosives” Using the Continuous Method

100%

Nikolczuk K. , Maranda A. , Mertuszka P. , Fuławka K. , Wilk Z. , Koślik P.

Central European Journal of Energetic Materials

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2019

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tom Vol. 16, no. 3

468--481

EN

Explosive velocity, also known as detonation velocity or velocity of detonation (VOD), is one of the most important and basic parameters describing the properties of explosives. This work presents the VOD results of three different explosives. Two of the explosives were ammonium nitrate-based (straight emulsion and Heavy ANFO). The third explosive was based on hydrogen peroxide (HP). The aim of the experiments was to compare the VOD of the HP-based against the VOD of the ammonium nitrate-based explosives. The final conclusions and results of this preliminary work and the analysis of available literature show that HP-based explosives, so called “green explosives”, have the potential to successfully replace ammonium nitrate-based explosives in some applications. The results of this work will be used to develop production technology for new HP-based explosives and to find their possible applications, considering their environmentally friendly character (this novel formulation of explosive eliminates post-blast nitrogen oxide fumes (NOx), as a direct product of the detonation process). During the burning reaction, nitrogen oxides (NO, NO2) are produced as a result of the use of bulk ammonium nitrate-based commercial explosives. Exposure to these toxic gases can have negative effects on the health and safety of personnel and the surrounding environment. The results obtained for the new emulsion explosives allow them to be used extensively in the industry as a competitive product on the market.

12

Hydrogen peroxide as a biodegradation stimulator in remediation processes of soils heavily contaminated with petrochemicals

100%

Rosik-Dulewska C. , Krzyśko-Łupicka T. , Ciesielczuk T. , Kręcidło Ł.

Polish Journal of Chemical Technology

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2015

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tom Vol. 17, nr 2

17--22

EN

The soil contaminated with petroleum products must be excluded from the crops and treated to reclamation processes. Natural processes of decomposition of hydrocarbon compounds go very slow, so it is necessary to use bioaugumentation or stimulation in order to accelerate the return of the soil to high culture. In this study the effect of hydrogen peroxide on the process of cleaning soil strongly contaminated with pertochemicals was investigated. For this purpose, a pot experiment lasting 60 days was carried. The dynamics of changes in the population of filamentous fungi, yeasts and bacteria were examined and also content of aliphatic hydrocarbons (n-alkanes), monoaromatic and polycyclic aromatic hydrocarbons (PAHs). Experimental use of hydrogen peroxide in the process of biodegradation of petroleum compounds assisted in the analyzed soil led to an increase of the number of grampositive bacteria during the test. Stimulation of oil products biodegradation by hydrogen peroxide also increased by 35% decomposition efficiency of aliphatic hydrocarbons (C8-C40) and about 50% PAH’s in comparison to control samples without hydrogen peroxide. There was no influence of hydrogen peroxide on the content of monoaromatic hydrocarbons (BTEX) with respect to controls, although in the end of experiment, the total concentration decreased by about 50% compared to the initial content.

13

Technological parameters of epoxidation of sesame oil with performic acid

100%

Musik M. , Milchert E. , Malarczyk-Matusiak K.

Polish Journal of Chemical Technology

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2018

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tom Vol. 20, nr 3

53--59

EN

The course of epoxidation of sesame oil (SO) with performic acid formed „in situ” by the reaction of 30 wt% hydrogen peroxide and formic acid in the presence of sulfuric acid(VI) as a catalyst was studied. The most advantageous of the technological independent parameters of epoxidation are as follows: temperature 80°C, H2O2 C=C 3.5:1, HCOOH/C=C 0.8:1, amount of catalyst as H2SO4 /(H2O2 +HCOOH) 1 wt%, stirring speed at least 700 rpm, reaction time 6 h. The iodine number (IN), epoxy number (EN), a relative conversion to oxirane (RCO) and oxirane oxygen content (EOe) were determined every hour during the reaction. Under optimal conditions the sesame oil conversion amounted to 90.7%, the selectivity of transformation to epoxidized sesame oil was equal to 93.2%, EN = 0.34 mol/100 g, IN = 0.04 mol/100 g oil (10.2 g/100 g oil), a relative conversion to oxirane RCO = 84.6%, and oxirane oxygen content of EOe = 5.5%.

14

Hydrogen peroxide as a biodegradation stimulator in remediation processes of soils heavily contaminated with petrochemicals

100%

Rosik-Dulewska C. , Krzyśko-Łupicka T. , Ciesielczuk T. , Kręcidło Ł.

Polish Journal of Chemical Technology

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2015

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tom 17

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nr 2

17-22

EN

The soil contaminated with petroleum products must be excluded from the crops and treated to reclamation processes. Natural processes of decomposition of hydrocarbon compounds go very slow, so it is necessary to use bioaugumentation or stimulation in order to accelerate the return of the soil to high culture. In this study the effect of hydrogen peroxide on the process of cleaning soil strongly contaminated with pertochemicals was investigated. For this purpose, a pot experiment lasting 60 days was carried. The dynamics of changes in the population of filamentous fungi, yeasts and bacteria were examined and also content of aliphatic hydrocarbons (n-alkanes), monoaromatic and polycyclic aromatic hydrocarbons (PAHs). Experimental use of hydrogen peroxide in the process of biodegradation of petroleum compounds assisted in the analyzed soil led to an increase of the number of grampositive bacteria during the test. Stimulation of oil products biodegradation by hydrogen peroxide also increased by 35% decomposition efficiency of aliphatic hydrocarbons (C8-C40) and about 50% PAH’s in comparison to control samples without hydrogen peroxide. There was no influence of hydrogen peroxide on the content of monoaromatic hydrocarbons (BTEX) with respect to controls, although in the end of experiment, the total concentration decreased by about 50% compared to the initial content.

15

Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

100%

Zun M. , Dwornicka D. , Wojciechowska K. , Swiader K. , Kasperek R. , Rzadkowska M. , Poleszak E.

Current Issues in Pharmacy and Medical Sciences

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2014

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tom 27

|

nr 4

213-216

EN

In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w) of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w) of urea had the best constancy.

16

mi-phth-mi-X Bridged Dicobalt(II) Complexes : Synthesis, properties and Catalase-Like Activity

100%

Gao J.

Polish Journal of Chemistry

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2001

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tom Vol. 75, nr 9

1203-1208

EN

ž-phth (phthalic acid dianion), having two isolated metal-binding groups, together with X ligand (X = CH3CO2 _, CF3 CO2 _ and Ph-CO2 _ ) formed dicobalt(II) complexes [Co2(II)(ž-phth)(ž-CH3CO2 _ )(bipy)2]ClO4 (1), [Co2(II)(ž-phth)(ž-CF3CO2 _ )(bipy)2]ClO4 (2) and [Co2(II)(ž-phth)(ž-Ph-CO2 _ )(bipy)2]ClO4 (3). Their structure was characterized spectroscopically and magnetically, presenting a ž-phth-ž-X-bridged dinuclear structure. The pair of cobalt ions bridged by CH3COO undergoes antiferromagnetic coupling. Catalytic properties for H2O2 dismutation are reported for complex 1-3.

17

Detonation Characteristics of a NOx-Free Mining Explosive Based on Sensitised Mixtures of Low Concentration Hydrogen Peroxide and Fuel

100%

Araos M. , Onederra I.

Central European Journal of Energetic Materials

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2017

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tom Vol. 14, no. 4

759--774

EN

Mining explosives based on ammonium nitrate(V) are safe and effective, however, the risk of NOx fume production during blasting is still present. In 2013, a project to eliminate NOx fumes from blasting began and hydrogen peroxide was chosen to replace ammonium nitrate(V) as the oxidiser. Previous work in this area demonstrated that hydrogen peroxide/fuel-based mixtures were able to detonate, provided that they are initiated under a situation of high confinement and also using hydrogen peroxide at relatively high concentrations. In contrast, a comprehensive study was conducted to determine the detonation properties of hydrogen peroxide/fuel-based mixtures that used hydrogen peroxide at lower concentrations (below 50 wt.%), detonated in unconfined conditions and used void sensitisation to achieve an efficient detonation reaction. This article presents the results of the influence of the density, water content, critical diameter and type of void sensitisation on the velocity of detonation (VOD) of hydrogen peroxide/ fuel-based explosive mixtures. The results indicate that the mixtures can achieve a different VOD which depends on the size of the sensitising voids and more importantly, the mixtures behave as non-ideal explosive, similarly to ammonium nitrate-based explosives, but with the advantage of being a NOx-free explosive.

18

The Effect of Phosphates and Fluorides, Included in TiO2 Nanotube Layers on the Performance of Hydrogen Peroxide Detection

100%

Arkusz K. , Krasicka-Cydzik E.

Archives of Metallurgy and Materials

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2018

|

tom Vol. 63, iss. 2

765--772

EN

Titania nanotube (TNT) arrays fabricated by anodizing of titanium foil in organic (ethylene glycol) and inorganic (phosphoric acid) electrolytes and thermally modified in argon revealed much improved properties to detect hydrogen peroxide. Horseradish peroxidase and acetate thionine co-absorbed by a dip coating on the TNT electrode were used to detect hydrogen peroxide in phosphate buffered saline. The morphology and electrochemical properties of TNT arrays were studied by scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. Well defined oxidation and reduction peaks for potassium ferricyanide have been observed for TNT formed in ethylene glycol and annealed in argon. TNT arrays formed in organic electrolyte and annealed in argon indicated more favorable adsorption and electrochemical properties what was confirmed by detection of hydrogen peroxide towards analyte in phosphorate buffered saline solution.

19

Vanadium(V) Catalusis of Perborate Oxidation of Iodide Ion

100%

Karunakaran C. , Muthukumaran B.

Polish Journal of Chemistry

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1999

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tom Vol. 73, nr 11

1827-1836

EN

Vanadium(V) cataluzes perborate oxidation of iodide ion in acidic solution, being 1.6 order with respect to the oxidant, first order in the catalyst, inhibited by H+ and displays Michaelis-menten kinetics on the reductant. in aqueous solution perborate generates hydrogen peroxide and the kinetic results reveal formation of oxodiperoxovanadium(V)-iodide ion complex.

20

Hydroxylation of Alkanes Using H2O2 or tert-BuOOH Catalyzed by Silica-based Fe(III) Interphase Catalysts

100%

Luo Y. , Zhang L. , Zong M. , Ménage S. , Fontecave M.

Polish Journal of Chemistry

|

2006

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tom Vol. 80, nr 8

1407-1414

EN

Two novel silica-based organic-inorganic hybrid (interphase) Fe(III) catalysts have been successfully prepared by the flexible ligandmethod, characterized and applied to the efficient catalytic oxidation of various types of substrates using 30% H2O2 or tert-BuOOH under mild conditions. The catalysts can be recovered and reused for four reaction cycles with total turnover numbers being about 29 using cyclohexene as the substrate. The mechanism for the O-O bond cleavage was proposed based on the results in combination with previous experimental results.