Sharif Digital Repository

Horseradish peroxidase (HRP) was successfully immobilized on amine functionalized TiO2-coated multiwalled carbon nanotubes (NH2 – TiO2 – CNTs) by a convenient and efficient method. Electrochemical impedance spectroscopy, cyclic voltammetry and amperometry were applied to characterize the HRP/NH2 – TiO2 – CNT nano-composite. These techniques showed that the NH2 – TiO2 – CNTs greatly enhance the electron transfer between HRP and the modified electrode. Owing to the redox reaction of the electroactive centre of HRP, the HRP = NH2 – TiO2 – CNTs modified electrode exhibited a pair of quasi-reversible peaks with a peak-to-peak separation (ΔEp) of 70.6 mV and a formal potential (E 0′) of 367.65 mV... 

Horseradish peroxidase (HRP) was successfully immobilized on amine functionalized TiO 2-coated multiwalled carbon nanotubes (NH 2-TiO 2-CNTs) by a convenient and efficient method. Electrochemical impedance spectroscopy, cyclic voltammetry and amperometry were applied to characterize the HRP/NH 2-TiO 2-CNT nano-composite. These techniques showed that the NH 2-TiO 2-CNTs greatly enhance the electron transfer between HRP and the modified electrode. Owing to the redox reaction of the electroactive centre of HRP, the HRP/NH 2-TiO 2-CNTs modified electrode exhibited a pair of quasi-reversible peaks with a peak-to-peak separation (ΔE p) of 70.6mV and a formal potential (E 0′) of -367.65mV (versus... 

In this work, the combination of H2O2 and an active visible-light-driven photocatalyst (Ag-S/PEG/TiO2) was utilized under natural solar radiation for the degradation of 2-nitrophenol (2-NP), and interaction effects between the photocatalyst and hydrogen peroxide were analyzed. For this purpose, experiments were designed using the response surface methodology based on the central composite design. The resulting data was utilized to obtain a model for the prediction of response (the degradation efficiency) as a function of two independent factors (H2O2 concentration and the photocatalyst loading). The statistical analysis indicated that optimum values of each of the two independent factors... 

Palm oil (PO) and sunflower oil (SFO) blends with varying proportions were subjected to enzymatic interesterification (EIE) using a 1,3-specific immobilised lipase. The interesterified blends were evaluated for their slip melting point (SMP), solid fat content (SFC) at 10-40°C, p-anisidine value, peroxide value, free fatty acids (FFA), induction period of oxidation at 110°C (IP110) and composition of fatty acids by gas chromatography. Under EIE treatment, the blends of PO and SFO in different proportions (20:80, 40:60, 50:50, 60:40 and 80:20) had saturated and unsaturated fatty acid content in the range of 37.6-52.0% and 48.0-62.4%, respectively. The blends showed a considerable reduction in... 

Zeolite-based Ag/AgBr and Ag/AgBr/TiO 2 photocatalysts were prepared by sol-gel and deposition methods and were characterized. Their photocatalytic activities were evaluated by inactivation of Escherichia (E.) coli and the photodegradation of Acid Blue 92 and potassium permanganate. The composites containing Ag/AgBr showed the antibacterial activity in the dark by releasing Ag ions into the medium. The results for inactivation of E. coli indicated that Ag/AgBr/TiO 2 modified photocatalyst had better antibacterial activity than Ag/AgBr/zeolite, while zeolite and TiO 2/zeolite did not show any antibacterial activity under visible light and dark conditions. Photodecolarization rate was affected... 

TiO2 nanoparticles were prepared by the sol - gel process using 2-hydroxylethy- lammonium formate as an ionic liquid. Nanoparticles were crystallized at various temperatures (300-700°C). The products were characterized using X-ray diffraction (XRD), nitrogen adsorption - desorption isotherms and scanning electron microscopy (SEM) techniques. It was found that the resulting TiO2 nanoparticles had good thermal stability either to resist collapse or the anatase-to-rutile phase transformation during heat treatment. The photocatalytic activity of the nanocrystalline TiO2 was evaluated by the degradation of Acid Blue 92 (AB92) which is commonly used as a textile dye. The results showed that the... 

Platinum nanotubes (PtNTs) are fabricated by potentiostatic electrodeposition at various overpotentials (−200 up to −400 mV versus SCE) in polycarbonate templates (PCTs) with pore diameter of 200 nm in a solution containing 5 mM H2PtCl6 and 0.1 M H2SO4. The synthesized PtNTs are characterized by field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The electrochemical growth mechanism within nanoscopic pores and the relationship between morphological variations and kinetic parameters are investigated for the first time. It is shown that more porous structure of nanotubes forms at high overpotentials possibly due to preferably nucleation. The... 

This paper reports on the recovery of zinc, cobalt and manganese by two-step leaching of zinc-plants purification residue with sulfuric acid. The residue, hot filter press cake (HFC), contains 14 % ZnO, 4.8 % Co 3O4 and 22.9 % MnO. Effects of different parameters are determined and used to optimize the process. With acid to hot filter press cake (HFC) stoichiometry of 0.85, acid concentration of 30 g/L and temperature of 25°C, it took two minutes to separate zinc from zinc plant residue. Hydrogen peroxide (H2O2) was used as an oxidation agent. The most suitable acid concentration for leaching of both cobalt and manganese was 50 g/L. Recovery of cobalt and manganese increased with peroxide... 

A new sensor for simultaneous determination of peroxyacetic acid and hydrogen peroxide using silver nanoparticles (Ag-NPs) as a chromogenic reagent is introduced. The silver nanoparticles have the catalytic ability for the decomposition of peroxyacetic acid and hydrogen peroxide; then the decomposition of them induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface plasmon resonance absorbance strength could be observed. Spectra-kinetic approach and artificial neural network was applied for the simultaneous determination of peroxyacetic acid and hydrogen peroxide. Linear calibration graphs were obtained in the concentration range of (8.20×10-5 to... 

A molybdenum complex, [MoO2Cl2(DMSO)2], was immobilized on amino propyl and Schiff base modified magnetic Fe3O4@SiO2 nanoparticles by covalent linkage. The resulting nanoparticles were used as efficient and recyclable catalysts for the selective oxidation of sulfides to sulfoxides using urea hydrogen peroxide as the oxidant. The complete characterization of catalysts was carried out by means of thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), elemental analysis, FT-IR and Raman microprobe... 

Reactive oxygen species ROS and redox agents are two features of cancer medium, which could be used through responsive drug delivery systems for cancer treatment. Furthermore, mesoporous silica nanoparticles (MSNs) have special characteristics to use them in ROS-responsive and redox-responsive carriers. To shed light on this issue, we propose two drug delivery systems: 1) responsive to hydrogen peroxide (a ROS component) and 2) responsive to dithiothreitol (a redox agent). The proposed carriers are composed of 4 parts: MSNs, responsive agent (selenocystine for ROS-responsive and dithiodipropionic for the redox-responsive carrier), hyaluronic acid as the coating and targeting agent, and the... 

Hydrogen peroxide readily oxidizes phenols to the corresponding quinones in the presence of cobalt(II) acetate or manganese(II) acetate as catalyst  

Hydroxylated aromatic compounds (HACs) are considered to be primary pollutants in a wide variety of industrial wastewaters. Horseradish peroxidase (HRP) is suitable for the removal of these toxic substances. However, development of a mathematical model and optimization of the HRP-based treatment considering the economical issues by novel methods is a necessity. In the present study, optimization of phenol removal from wastewater by horseradish peroxidase (HRP) was carried out using response surface methodology (RSM) and central composite design (CCD). As the initial experimental design, 2 4-1 half-fraction factorial design (H-FFD) is accomplished in triplicate at two levels to select the... 

Manganeses(II) chloride supported on montmorillonite K10 was found to be an efficient catalysts for the oxidation of alcohols to carbonyl compounds with hydrogen peroxide as oxidant  

The oxidation of sulfides to sulfoxides with hydrogen peroxide in good yield and high selectivity has been catalyzed very effectively by a series of Schiff base salen-type iron complexes in a monophasic medium (CH 2Cl2/CH3OH) at ambient temperature. The results of the present study show that the reaction rate strongly depends on both catalyst steric effects and steric and electronic properties of sulfides. In the system, the electronic spectral studies are applied to explain the formation of a reactive (salen) Fe=O intermediate  

The oxidative desulfurization of a real refinery feedstock (i.e., non-hydrotreated kerosene with total sulfur mass content of 0.16%) with a mixture of hydrogen peroxide and acetic acid was studied. The influences of various operating parameters including reaction temperature (T), acid to sulfur molar ratio (nacid/nS), and oxidant to sulfur molar ratio (nO/nS) on the sulfur removal of kerosene were investigated. The results revealed that an increase in the reaction temperature (T) and nacid/nS enhances the sulfur removal. Moreover, there is an optimum nO/nS related to the reaction temperature and the best sulfur removal could be obtained at nO/nS8 and 23 for the reaction temperatures of 25... 

An experimental investigation was conducted on the oxidative desulfurization of model sulfur compounds such as dibenzothiophene and benzothiophene in toluene as a simulated light fuel oil with a mixture of hydrogen peroxide as the oxidant and various acids as the catalyst. The influences of various parameters including reaction temperature (T), acid to sulfur molar ratio (Acid/S), oxidant to sulfur molar ratio (O/S), type of acid, and the presence of sodium tungstate and commercial activated carbon as a co-catalyst on the fractional conversion of the model sulfur compounds were investigated. The experimental data obtained were used to determine the reaction rate constant of the model sulfur... 

The hard corona, the protein shell that is strongly attached to the surface of nano-objects in biological fluids, is recognized as the first layer that interacts with biological objects (e.g., cells and tissues). The decoration of the hard corona (i.e., the type, amount, and conformation of the attached proteins) can define the biological fate of the nanomaterial. Recent developments have revealed that corona decoration strongly depends on the type of disease in human patients from which the plasma is obtained as a protein source for corona formation (referred to as the 'personalized protein corona'). In this study, we demonstrate that graphene oxide (GO) sheets can trigger different... 

Application of immobilized horseradish peroxidase (HRP) in porous calcium alginate (ca-alginate) for the purpose of phenol removal is reported. The optimal conditions for immobilization of HRP in ca-alginate were identified. Gelation (encapsulation) was optimized at 1.0% (w/v) sodium alginate in the presence of 5.5% (w/v) of calcium chloride. Upon immobilization, pH profile of enzyme activity changes as it shows higher value at basic and acidic solution. Increasing initial phenol concentration results in a decrease in % conversion. The highest conversion belongs to phenol concentration of 2 mM. Investigation into time course of phenol removal for both encapsulated and free enzymes showed... 

A new heterogeneous catalytic system was prepared by immobilization of tungstate ions on a cross-linked poly(ionic liquid) nanogel. The solid nanogel was easily synthesized by a surfactant-less method. The resulting catalyst was highly active in selective oxidation of sulfides to sulfoxides by H2O2. The oxidation reactions were successfully performed under solvent-free conditions affording high yields. The catalyst was recycled and reused for several reaction cycles without any significant loss of catalytic activity