H2O2 Aqueous Solution Research Articles

Reactivity of redox sensitive paramagnetic nitroxyl contrast agents with reactive oxygen species.

The reactivity of nitroxyl free radicals, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) and 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (CmP), with reactive oxygen species (ROS) were compared as typical 6-membered and 5-membered ring nitroxyl compounds, respectively. The reactivity of the hydroxylamine forms of both these nitroxyl radicals (TEMPOL-H and CmP-H) was also assessed. Two free radical species of ROS, hydroxyl radical (•OH) and superoxide (O2•−), were subjected to a competing reaction. •OH was generated by UV irradiation from an aqueous H2O2 solution (H2O2-UV system), and O2•− was generated by a reaction between hypoxanthine and xanthine oxidase (HX-XO system). •OH and O2•− generated by the H2O2-UV and HX-XO systems, respectively, were measured by electron paramagnetic resonance (EPR) spin-trapping, and the amount of spin adducts generated by each system was adjusted to be equal. The time courses of the one-electron oxidation of TEMPOL, CmP, TEMPOL-H, and CmP-H in each ROS generation system were compared. A greater amount of TEMPOL was oxidized in the HX-XO system compared with the H2O2-UV system, whereas the reverse was observed for CmP. Although the hydroxylamine forms of the tested nitroxyl radicals were oxidized evenly in the H2O2-UV and HX-XO systems, the amount of oxidized CmP-H was approximately 3 times greater compared with TEMPOL-H.

Sensitivity of the selective oxidation of methane over Fe/ZSM-5 zeolites in a micro fixed-bed reactor for the catalyst preparation method

Selective oxidation of methane in a micro fixed-bed reactor by using aqueous H2O2 solution as oxidant was studied. Sub-micrometer sized crystals of HZSM-5 and silicalite-1 with Fe contents below 10 ppm were synthesized. Different methods were used to introduce iron to produce Fe/ZSM-5 zeolites with similar but defined Fe contents. Commercial ZSM-5 with trace amount (175 ppm) of Fe impurity showed considerable methane conversion while over the own nearly Fe-free HZSM-5 no conversion could be measured. Fe/ZSM-5 catalysts prepared by different methods starting from the own nearly Fe-free HZSM-5 showed similar methane conversions and catalysts based on Fe(II) as the precursor exhibited a better performance with regard to retarding over-oxidation. The productivities of oxygenates were enhanced more than two orders of magnitude while at the same time obtaining high turnover frequencies (TOFs) of 303 h−1. A methane conversion as high as 23.5% together with oxygenates selectivity of 90.1% was reached. In contrast to Fe/ZSM-5, Fe/silicalite-1, prepared from Fe-free silicalite-1 by activation via the same post-synthetic preparation methods that were also used to prepare Fe/ZSM-5 and having similar Fe contents, never led to an active catalyst.

Degradation of bisphenol A by combining ozone with UV and H2O2 in aqueous solutions: mechanism and optimization

A laboratory-scale study on the abatement of bisphenol A (BPA) was performed by combining O3 with H2O2 and UV (O3/H2O2/UV), an ozone-based advanced oxidation processes technique (AOP). This work aimed to (1) evaluate the removal of BPA with O3/H2O2/UV, and to compare the degradation efficiency with other ozone-based AOPs (such as O3 alone, O3/H2O2, and O3/UV), (2) structurally optimize BPA abatement by using a central composite design (CCD) for experimental design purposes and/or a response surface methodology to find the optimum, and (3) identify the degradation pathways, and main intermediate products, formed during BPA abatement with O3/H2O2/UV. The degradation pathways of BPA degradation were revealed by O3/H2O2/UV on the basis of evidences of intermediate generation. The effect of initial pH, ozone, and H2O2 dose during BPA abatement was studied in detail. By increasing each of these three parameters, an enhancement of the BPA degradation efficiency is mostly observed. BPA can be degraded completely when a sufficiently high ozone dose is applied. However, excess H2O2, as a scavenger of HO·, has a negative effect on BPA abatement, resulting in a decrease in the BPA’s degradation efficiency. For example, the removal decreased from 64 to 58% by enhancing the H2O2 initial dose from 0.5 to 0.75 mmol/L (at an initial pH and ozone dose of, respectively, 7 and 0.1 mg/L). The results confirmed that combining ozone with H2O2 and UV was a more efficient method than the other three ozone-based AOPs on the removal of BPA. Therefore, this method could be further applied for the treatment of real wastewaters containing BPA and other micropollutants.

Catalytic Properties of Cadmium Sulfide Nanoparticles Obtained via Precipitation from Solutions

The catalytic properties of cadmium sulfide nanoparticles in the photochemical decomposition of hydrogen peroxide are studied. It is shown that in aqueous H2O2 solutions of any concentration, cadmium sulfide accelerates the reaction and does not change its order. The quantum yield of the reaction is 1 and does not depend on the concentration of hydrogen peroxide. The scattering of light by particles and an increase in their concentration reduces the quantum yield.

Microstructural analysis of undoped and moderately Sc-doped TiO2 anatase nanoparticles using Scherrer equation and Debye function analysis

UV light sensitive undoped and moderate (4 at.%) Sc-doped anatase nanocrystallites were prepared by an efficient and environmentally benign method based on homogeneous hydrolysis of TiOSO4 and Sc2(C2O4)3.5H2O aqueous solutions using urea as a precipitation agent, without post-synthesis calcination or annealing.X-ray diffraction study of the obtained powders revealed single phase anatase in both samples. Two different methods were applied to estimate the anatase crystallite size and shape from the X-ray diffraction data. The first one is based on the more conventional Scherrer equation (as implanted in GSAS-II program) while the second one is based on Debye function analysis (as implanted in DUBUSSY suite version 2.2), which is considered to be more adequate for nanocrystallites. Although each program has its own shape models, both methods indicated similar results of elongated nanocrystallite geometry for Sc-doped TiO2: (i) GSAS-II confirmed ellipsoid shape with equatorial size of 5.1(0) nm and axial size of 6.8(0), (ii) DEBUSSY suite 2.2 showed cylinder shape with diameter of equivalent circle in the ab-plane, Dab = 4.9(1.0) nm and crystallite length along the c-axis, Lc = 5.4(3.2) nm. For the undoped TiO2 sample, equatorial size of 5.5(0) nm and axial size of 7.3(0) nm for the ellipsoid shape was determined according to GSAS-II, while Dab = 5.5(1.3) nm and Lc = 6.0(2.2) nm for the cylinder shape was determined by DEBUSSY suite 2.2. These outcomes were found to corroborate with HRTEM analysis.Doping with 4 at.% Sc caused ~0.3% growth of lattice parameters from a = 3.7979 [4] Å, c = 9.4995 [9] Å for the undoped sample to a = 3.8110 [7] Å, c = 9.5274 [16] Å for the moderately Sc doped sample, while reduction in the Ti vacancies by half was confirmed by both methods.The introducing of Sc as electronically active secondary species into the crystal lattice of TiO2 can greatly alter its optical absorption. The incorporation of Sc into the crystal lattice of TiO2 favors the substitution of Ti, as both have approximately the same ionic size, and generates surface oxygen vacancies which can act as trapping center for the photogenerated electrons and reduce the recombination of electron–hole pairs. We can expect Sc doped TiO2 nanomaterials to have applications as effective photocatalysts for selective photocatalytic oxidation of various environmental organic pollutants.

In situ fabrication of Ni(OH)2/Cu2O nanosheets on nanoporous NiCu alloy for high performance supercapacitor

The rapid depletion of fossil fuels along with critical environmental pollution has put forward urgent demands for advanced energy storage devices such as high-performance supercapacitors (SCs). Nickel hydroxides (Ni(OH)2) have been proved to be a high capacity electrode material for SCs, however, the preparation method and stability of Ni(OH)2 structures are unsatisfactory. In this work, via a low cost and one-step hydrothermal method in H2O2 aqueous solution without other reagents, vertically arranged Ni(OH)2/Cu2O nanosheets can be facilely fabricated on three-dimensional nanoporous NiCu alloy (NPNC), which exhibits large surface area and high electrical conductivity. Being the source of Ni and Cu, NPNC acts as the matrix of active materials as well. Thus, the strong combination and electron transportation between the active materials and NPNC can be achieved. Furthermore, the uniform distribution of Cu2O in the hybrids enhances the electrochemical stability of electrode. As a result, the binder-free Ni(OH)2/Cu2O/NPNC electrode materials exhibit a high capacity (8234 mC cm−2 or 823.4 C cm−3 at 20 mA cm−2) with excellent cycling stability (112.8% capacity retention after 10,000 cycles at 200 mA cm−2) and rate capability. Such desirable properties signify that the Ni(OH)2/Cu2O/NPNC composites hold great promise for the high-performance supercapacitors.

Effect of Fenton-like oxidation reagent on hydrophobicity and floatability of chalcopyrite and molybdenite

A fundamental study is provided in this work to understand the effect of Fenton-like reagent made by the addition of FeSO4 in H2O2 aqueous solution on surface hydrophobicity and floatability of chalcopyrite (CuFeS2) and molybdenite (MoS2). Contact angle measurements were performed to assess the surface hydrophobicity. The contact angle results showed that Fenton-like reagent could alter the surface hydrophobicity of chalcopyrite at lower concentration of H2O2 aqueous solution compared to that of using H2O2 aqueous solution. On the other hand, molybdenite surface remained hydrophobic after the oxidation treatments using Fenton-like reagent and H2O2 aqueous solution. Surface characterizations using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) shows that the chalcopyrite surface covered with a thicker layer of oxidation products after the oxidation treatment using Fenton-like reagent, indicating a stronger surface oxidation. Flotation results were in agreement with contact angle results, showing that Fenton-like reagent could depress the floatability of chalcopyrite at lower concentration of H2O2 aqueous solution. On the other hand, molybdenite recovery remained high under various oxidation treatments owing to low surface oxidation.

Highly selective oxidation of styrene to benzaldehyde over Fe3O4 using H2O2 aqueous solution as oxidant

Fe3O4 was prepared by an alternative method using the dropwise addition of FeCl3 and FeSO4 precursor solutions into a NaOH solution, as proved by XRD, TEM and magnetic measurements. The Fe3O4 material was confirmed to be well-crystallized magnetite with an average size of about 21.5 nm and stronger superparamagnetic with a saturation magnetization of 57.04 emu/g and it was found to be an effective catalyst for liquid-phase oxidation of styrene to benzaldehyde (BzH) with H2O2 as oxidant, getting ca. 100% selectivity to BzH with 40.4% conversion of styrene. This catalyst can be easily recovered by a simple magnetic separation and effectively reused. However, the reaction mechanism was confirmed by in situ DRIFTS spectra analysis and according to literature reports.

A facile method to increase dielectric properties of rutile TiO2

Investigations on dielectric properties of N2-sintered TiO2 ceramic samples followed by chemically oxidized in H2O2 aqueous solution with different time spans were performed in the frequency range of 102–106 Hz. The results reveal that the dielectric properties strongly depend on the lengths of oxidizing time. An optimum oxidizing time of 12–16 h gives rise to superior dielectric properties with the permittivity of 12589 and the loss factor of 0.34 at 100 Hz. The time effect is attributed to the formation of an insulating layer at grain boundaries. Chemical oxidation proves to be a facile strategy to manipulate the insulating layer and opens a new way to modify the dielectric permittivity of versatile oxides.

Facile-fabricated iron oxide nanorods as a catalyst for hydrogenation of nitrobenzene

β-FeOOH nanorods were prepared by a poly ethylene glycol (PEG) assisted precipitation of FeCl3 ∙ 6H2O aqueous solution with urea. Na2CO3 aqueous solution was introduced to maintain their shapes under annealing. The one-dimensional porous iron oxide nanorods were synthesized successfully. The as-prepared catalysts were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The hydrogenation of nitrobenzene to aniline was taken as probe reaction to evaluate their catalytic performance. FeOOH (iron oxides hydroxide) nanorods, fabricated by annealing β-FeOOH nanorods at 250°C in Ar atmosphere for 4h, exhibited high catalytic activity for the transfer hydrogenation of nitrobenzene to aniline with hydrazine hydrate as hydrogen donors.

Fabrication of Metal-Substituted Polyoxometalates for Colorimetric Detection of Dopamine and Ractopamine.

A novel colorimetric detection method based on the peroxidase-like activity of metal-substituted polyoxometalates (POMs) of SiW9M3 (M = Co2+, Fe3+, Cu2+, Mn2+) has been established. POMs can catalyze oxidation of dopamine (DA) and ractopamine (RAC) by H2O2 in aqueous solutions. SiW9Co3-based POMs detect DA at concentrations as low as 5.38 × 10−6 mol·L−1 simply by observation of the color change from colorless to orange using the naked eye. RAC is detected by observing the change from colorless to slight red by SiW9Cu3 with a detection limit of 7.94 × 10−5 mol·L−1. This study shows that colorimetric DA and RAC detection using SiW9Co3 and SiW9Cu3 is highly selective and sensitive as well as visually observable.

Selective flotation of chalcopyrite and molybdenite using H2O2 oxidation method with the addition of ferrous sulfate

Hydrogen peroxide (H2O2) has been used as an oxidizing agent in the selective flotation of chalcopyrite and molybdenite. However, this method required relatively high concentration of H2O2 to deliver flotation results (i.e., mineral grades and recoveries) comparable to those obtained by the conventional copper-molybdenum (Cu-Mo) ores flotation using sodium hydrosulfide (NaHS). Therefore, further improvements are needed to reduce the consumption of H2O2 reagent. In this study, ferrous sulfate (FeSO4) was used to enhance the oxidation performance of H2O2 through Fenton-like reactions. Flotation results showed that the consumption of H2O2 reagent could be reduced by the addition of FeSO4 without losing the flotation selectivity. The reason might be caused by increasing of oxidation performance as indicated by the increasing concentration of dissolved oxygen after the addition of FeSO4 into the H2O2 aqueous solution. Surface analysis using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) images showed that the surface of chalcopyrite was covered by more hydrophilic precipitates after the oxidation treatment using H2O2 aqueous solution with the addition of FeSO4, thus more hydrophilic surface and lower floatability. On the other hand, the surface of molybdenite was slightly oxidized and its surface remained hydrophobic as confirmed from contact angle results. Flotation tests using Cu-Mo bulk concentrate demonstrated that selective flotation might be possible using a mixture of FeSO4 and H2O2 aqueous solution. Moreover, this new method could be used as an alternative to copper depressant in Cu-Mo selective flotation, replacing the NaHS reagent.

Mesoporous SiO2-TiO2 epoxidation catalysts: Tuning surface polarity to improve performance in the presence of water

Herein, we present the preparation by the non-hydrolytic sol-gel (NHSG) route of a mesoporous SiO2-TiO2 epoxidation catalyst with high specific surface area and large pores, and we discuss its modification by methylation. The pristine NHSG catalyst is tested for the catalytic conversion of cyclohexene with H2O2 in acetonitrile, showing performance comparable to a reference TS-1 catalyst. To expand the scope of the catalysts, we study their performance in the presence of water – present in aqueous solutions of H2O2, formed as a by-product of the epoxidation reaction, or used as a co-solvent. While TS-1 maintains high epoxidation activity, the pristine amorphous and mesoporous SiO2-TiO2 catalysts strongly deactivates when water is used as co-solvent. In order to circumvent this deactivation in the presence of water, we investigate the effect of surface hydrophobization with methyl groups on the catalytic activity and selectivity. Two functionalization methods are investigated: one-pot synthesis with methyltrichlorosilane and post-synthesis silanization with methyltrimethoxysilane. On the one hand, the one-pot methylation does not increase water resistance, in spite of an increased surface hydrophobicity. We interpret this result in the light of a poorer Ti dispersion and lower Ti4+ surface content in these catalysts. On the other hand, post-synthesis grafting was successful, allowing to maintain good epoxidation activity even in the presence of water. This result is explained by a combination of a hydrophobic surface with a high active site content in this catalyst.

High density liquid structure enhancement in glass forming aqueous solution of LiCl.

We investigate using molecular dynamics simulations the dynamical and structural properties of LiCl:6H2O aqueous solution upon supercooling. This ionic solution is a glass forming liquid of relevant interest in connection with the study of the anomalies of supercooled water. The LiCl:6H2O solution is easily supercooled and the liquid state can be maintained over a large decreasing temperature range. We performed simulations from ambient to 200 K in order to investigate how the presence of the salt modifies the behavior of supercooled water. The study of the relaxation time of the self-density correlation function shows that the system follows the prediction of the mode coupling theory and behaves like a fragile liquid in all the range explored. The analysis of the changes in the water structure induced by the salt shows that while the salt preserves the water hydrogen bonds in the system, it strongly affects the tetrahedral hydrogen bond network. Following the interpretation of the anomalies of water in terms of a two-state model, the modifications of the oxygen radial distribution function and the angular distribution function of the hydrogen bonds in water indicate that LiCl has the role of enhancing the high density liquid component of water with respect to the low density component. This is in agreement with recent experiments on aqueous ionic solutions.

Transformation of carbon-encapsulated metallic Co into ultrafine Co/CoO nanoparticles exposed on N-doped graphitic carbon for high-performance rechargeable zinc-air battery

In this work, Co-MOFs microrod structures were firstly fabricated using Co2+ source and trimesic acid (H3BTC) as reaction precursors by a simple solvothermal method, followed by pyrolysis treatment at 900 °C in N2 atmosphere to obtain metallic Co encapsulated into graphitic carbon structure (Co@C) with an average Co particle size of 7.7 ± 0.2 nm excluding large-sized Co particles (>20 nm) and a surface area of 184 g cm−2. Interestingly, ultrafine Co/CoO nanoparticles with an average size of 1.8 ± 0.2 nm anchored on graphitic carbon surface (Co/CoO-C) can be obtained through further acid/alkali rinsing treatment of the as-prepared Co@C using HNO3 and NH3·H2O aqueous solutions respectively, followed by thermal treatment at 900 °C in N2 atmosphere. The formation of Co/CoO-C with a surface area of 247 g cm−2 can be ascribed to the dissolution and reorganization process of carbon-encapsulated metallic Co under acid/alkali rinsing and post-thermal-treatment conditions. As the electrocatalyst, Co/CoO-C exhibits superior bifunctional electrocatalytic activities of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media, notably better than ORR and OER activities of Co@C. The characterization results show that Co-Nx and N doping can be found in both Co@C and Co/CoO-C due to triethylamine (TEA) as solvent providing N source during Co-MOFs synthesis, which are catalytic active species toward electrocatalytic oxygen reactions. Furthermore, the highly exposed ultrafine Co/CoO on graphitic carbon surface can provide more catalytic active sites for high-performance ORR and OER, while carbon-encapsulated metallic Co in Co@C is incapable of directly contacting the electrolyte (only influencing shell-layer carbon function work) with limitedly improved electrocatalytic performance. The fabricated Co/CoO-C with superior bifunctional ORR and OER activities as air cathode material was assembled into a rechargeable zinc-air battery, exhibiting high power density and long-term stability. Our work provides an approach to transform low catalytic active electrocatalyst to high catalytic active one for renewable energy applications.

Effect of Surface Preparation on the Residual Oxide Thickness and Material Loss of In-Ga-As Epi Layer

Si-based complementary metal-oxide-semiconductor (CMOS) is facing physical limitation resulting from the scaling down of devices. In addition, several issues such as short channel effect and increase in the leakage current become critical. In order to solve those problems in the Si-based CMOS, introduction of a new channel material for the transistor such as III-V compound semiconductors and Ge can be one of the solutions due to their high electron mobilities [1, 2]. Among the III-V compound semiconductors, InGaAs is receiving an attention for improving device performance because it has electron mobility as high as 11400 cm2/Vs [3]. However, it is known that III-V semiconductors are not as robust as Si against the wet chemistries. Therefore, in order to introduce InGaAs as a new channel material, surface preparation of InGaAs in wet chemical processes should be controlled. In the current study, we investigated the effect of various wet chemical treatments on the InGaAs surface. In order to study surface reaction of InGaAs such as oxidation and etching, undoped epitaxial InGaAs (100) on InP:Fe wafers were used. InGaAs samples were dipped in the solutions such as HCl, HCl/H2O2 mixture (HPM), NH4OH, and NH4OH/H2O2 (APM). The chemical state of InGaAs surface was observed by X-ray photoelectron spectroscopy (XPS) and the oxide thickness and etching rate of InGaAs were measured by transmission electron microscopy (TEM) and spectroscopic ellipsometry. The chemical states (Ind35/2, Ga3d and As3d) of InGaAs surface after HCl, HPM, deionized water, NH4OH and APM are shown in Fig. 1. It is first observed that the oxidation states in In3d, Ga3d and As3d (In2O3, Ga2O3 and As2O3) decreased after HCl treatment as compared to as-received InGaAs surface, while they increased after NH4OH treatment. On the other hand, significant increases in oxidation states of InGaAs were observed after the treatment of HPM or APM, which suggests that oxidation of InGaAs surface is accelerated by H2O2 in aqueous solutions. It is also noted that InGaAs surface was also oxidized after deionized water treatment. Although E-pH diagram is based on the theoretical calculations of thermodynamical equilibrium in a single metal-water system, based on each E-pH diagram of In, Ga and As, it is expected that InGaAs surface can be dissolved in both acidic and basic solution [4]. Therefore, from the fact that the XPS oxidation states of the InGaAs surface after basic treatment were larger than in acidic solution as shown in Fig. 1, it is suggested that dissolution of the oxidized InGaAs layer is dominant in acidic solution, while it is a rate limiting step in the basic solution. Those findings imply that further increase in the oxidant concentration in acidic solution (HCl or HPM) will accelerate overall etching kinetics of InGaAs, while its impact in the basic solution is smaller. The effect of process sequence on the residual oxide thickness on InGaAs surface was investigated and the results are shown in Fig. 2. The oxide thickness was obtained by ellipsometry and TEM measurements, and the results are relatively well matched each other as shown in Figs. 2(a) and (b). It is here noted that a significant increase in the oxide thickness was observed with 1/1/100 HPM (1HPM) as compared to 1/0.1/100 HPM (0.1HPM) in either HF-last or HPM-last process, which suggests a higher concentration of H2O2 in HPM solution produced an increased oxide thickness on InGaAs surface. The amount of material loss of InGaAs epi layer during each sequence is also given in Fig. 2(a). As expected from the observation of XPS spectra, once 1/1/100 HPM (1HPM) is introduced in the wet processes, the loss of InGaAs was much larger due to active and balanced surface oxidation and etching, as compared to 1/0.1/100 HPM (0.1HPM) process. Based on those results, it is concluded that the concentration of H2O2 in HPM solution is one of key factors to determine the residual oxidation and overall etching rate of InGaAs layer, which strongly suggests that the concentration of H2O2 especially in HPM process should be optimized at the surface preparation of InGaAs semiconductor.

Oxidative desulfurization of dibenzothiophene and diesel by hydrogen peroxide: Catalysis of H3PMo12O40 immobilized on the ionic liquid modified SiO2

Here we reported an oxidative desulfurization system for oxidation of sulfur-containing compounds in model oil and diesel by catalysis using SiO2-supported phosphomolybdate hybrid material with 30% H2O2 aqueous solution as the oxidant. Firstly, The SiO2 was modified with 1-propyl-3-triethoxysilyl 3-methylimidazolium chlorid by grafting method. We used the 29Si MAS NMR to demonstrate that the organic silane group was attached to the SiO2 surface by one or two SiOSi bonds. Secondly, the phosphomolybdate was immobilized onto the modified SiO2 to prepare the hybrid material catalyst. The FT-IR, UV–vis, and TG characterization results indicate that the Keggin structure of the [PMo12O40]3− and imidazole ring were remained. The catalyst was used to oxidative desulfurization of dibenzothiophene by H2O2 as the oxidant. Maximum oxidation activity was observed at a loading of 30 wt.% H3PMo12O40 which can complete oxidation 0.2 wt.% of dibenzothiophene at 50 °C and an O/S molar ratio of 3.0 in 30 min. The catalyst could be easily separated by centrifugation and reused for seven times without any deactivation. The high performance of this oxidative desulfurization system was verified in the sulfur removal from a real diesel oil by oxidation followed by dimethylformamide extraction.

Role of defects on the enhancement of the photocatalytic response of ZnO nanostructures

Zinc oxide (ZnO) nanostructures have been synthesized by a simple controlled precipitation method to study the effects of the type solvent – including water, acetic acid and ethylene glycol – on the formation of ZnO and on its photocatalytic activity for the decomposition of H2O2 in aqueous solution. Scanning electron microscopy (SEM) and synchrotron-based X-ray diffraction (XRD) were used to determine the morphology, crystallinity, and chemical composition of the ZnO structures. Raman spectroscopy and photoluminescence measurements were carried out to determine the nature of the defects present in the different ZnO nanostructures and how they affect the photocatalytic activity. Based on the results, we propose plausible growth mechanisms underlying the formation of ZnO with different morphology, according to the solvent used during the synthesis. A direct relation between the photocatalytic activity and the defects type was established, suggesting that defects play a vital role in modulating the photocatalytic response.

A Simple Additive Potential Model for Simulating Hydrogen Peroxide in Chemical and Biological Systems.

Hydrogen peroxide (H2O2) has numerous industrial, environmental, medical, cosmetic, and biological applications. Given its importance, we provide a simple model as an alternative to experiment for studying the properties of pure liquid H2O2 and its concentrated aqueous solutions, which are hazardous, and for understanding the biological roles of H2O2 at the molecular level. A four-site additive model is calibrated for H2O2 based on the ab initio and experimental properties of the gaseous monomer and the density and heat of vaporization of liquid H2O2 at 0 °C. Our model together with the TIP3P water model reproduce the ab initio binding energies of (H2O2) m, H2O2· nH2O, and nH2O2·H2O clusters ( m = 2, 3 and n = 1, 2) calculated at the MP2 level using the 6-311++G(d,p) or the 6-311++G(3df,3pd) basis set. It yields structure, the self-diffusion coefficient, heat capacity, and densities at temperatures up to 200 °C of the pure liquid in good agreement with experiment. The model correctly predicts the hydration free energy of H2O2 and reproduces the experimental density of aqueous H2O2 solutions at 0-96 °C. Investigation of the solvation of H2O2 and H2O in aqueous H2O2 solutions reveals that, as in the gas phase, H2O2 is a better H-bond donor but poorer acceptor than H2O and the bonding stability follows the order Op-Hp···Ow > Ow-Hw···Ow ≥ Op-Hp···Op > Ow-Hw···Op. Stronger H-bonding in H2O/H2O2 mixtures than in the pure liquids is consistent with exothermic heats of mixing and explains why the observed density and vapor pressure of the aqueous solutions are higher and lower, respectively, than expected from ideal mixing. Results also show that H2O2 adopts a skewed equilibrium geometry in gas and liquid phases but more polar cis and nonpolar trans conformations also are accessible and will stabilize H2O2 in environments of different polarity. In sum, our simple model presents a reliable tool for simulating H2O2 in chemistry and biology.

Photocatalytic degradation properties of α-Fe 2 O 3 nanoparticles for dibutyl phthalate in aqueous solution system

The phthalate ester compounds in industrial wastewater, as kinds of environmental toxic organic pollutants, may interfere with the body's endocrine system, resulting in great harm to humans. In this work, the photocatalytic degradation properties of dibutyl phthalate (DBP) were investigated using α-Fe2O3 nanoparticles and H2O2 in aqueous solution system. The optimal parameters and mechanism of degradation were discussed by changing the morphology and usage amount of catalysts, the dosage of H2O2, pH value and the initial concentration of DBP. Hollow α-Fe2O3 nanoparticles showed the highest degradation efficiency when 30 mg of catalyst and 50 µl of H2O2 were used in the DBP solution with the initial concentration of 13 mg l−1 at pH = 6.5. When the reaction time was 90 min, DBP was degraded 93% for the above optimal parameters. The photocatalytic degradation mechanism of DBP was studied by the gas chromatography–mass spectrometry technique. The result showed that the main degradation intermediates of DBP were ortho-phthalate monobutyl ester, methyl benzoic acid, benzoic acid, benzaldehyde, and heptyl aldehyde when the reaction time was 2 h. DBP and its intermediates were almost completely degraded to CO2 and H2O in 12 h in the α-Fe2O3/ H2O2/UV system.