Reaction Mechanism Of Oxidation Research Articles

Experimental and kinetic modeling study of polycyclic aromatic hydrocarbon formation pathways in fuel-rich oxidation of 2-methylfuran using an atmospheric flow reactor

2-Methylfuran is one of promising biofuels that is expected to be an alternative fuel or fuel additive to conventional fuels for reducing greenhouse gas emissions from internal combustion engines. Although oxidation experiments under a wide range of conditions are required for a better understanding of 2-methylfuran combustion, the fuel-rich oxidation of 2-methylfuran has not been studied extensively. In this study, the fuel-rich oxidation of 2-methylfuran was investigated using an atmospheric flow reactor at temperatures of 1000–1350 K, equivalence ratios of 3.0–12.0, and residence times of 0.2–1.5 s. Chemical species such as the polycyclic aromatic hydrocarbons (PAHs) with one to six aromatic rings formed in the oxidation were sampled and quantified using gas chromatography mass spectrometry, while small intermediate products from C1 to C5 were quantified using gas chromatograph equipped with flame ionization detector. A kinetic model was developed by combining the existing reaction mechanisms for 2-methylfuran oxidation and PAH growth, which were constructed separately. The developed model was validated against the experimental results obtained in this study, showing that the simulated concentration profiles of the chemical species were in reasonable agreement with the measured data under the present experimental conditions. Kinetic analyses using the model were conducted to unravel the reaction pathways of PAHs as well as the main consumption pathways of 2-methylfuran. These results showed that 2-methylfuran underwent ring cleavage and CO/CH3CO removal, resulting in production of C2–C4 species. It was also found that the resonantly stabilized radicals, particularly the propargyl radical, were the key species responsible for PAH growth reactions, and the hydrogen-abstraction carbon-addition mechanism was important for the formation of several PAHs.

Mechanism of the Photochemical Isomerization and Oxidation of 2-Butenedial: A Theoretical Study.

Under tropospheric conditions, 2-butenedial is photochemically removed to produce secondary organic aerosol. Upon solar irradiation in the lower troposphere, the main photochemical products are ketene-enol (a key intermediate product), furanones, and maleic anhydride. The oxidative reaction mechanism was studied using the multireference method CASSCF to explore the hypersurface of the two most accessible singlet excited states, and by DFT for the ground state. Photoisomerization of 2-butenedial in the first excited state directly produces ground state ketene-enol upon nonradiative relaxation. From this intermediate, furan-2-ol and successively 3H-furan-2-one and 5H-furan-2-one are formed. The cooperative effect of two water molecules is essential to catalyze the cyclization of ketene-enol to furan-2-ol, followed by hydrogen transfers to furanones. Two water molecules are also necessary to form maleic anhydride from furan-2-ol. For this last reaction, in which one extra oxygen must be acquired, we hypothesize a mechanism with singlet oxygen as the oxidant.

Fabrication of CuTNPc/MWCNTs composites by in-situ solvothermal method for efficient selective oxidation of styrene

The tetranitro-copper phthalocyanine/multi-walled carbon nanotubes (CuTNPc/MWCNTs) composites have been successfully fabricated by a straightforward in-situ solvothermal approach. The as-prepared CuTNPc/MWCNTs composites can be used as effective catalysts for the styrene catalytic oxidation to benzaldehyde. Effects of solvent type, oxidant type, catalyst dose, and reaction temperature on catalytic performance are investigated. It can be found that the CuTNPc/MWCNTs composites showed significant catalytic oxidation of styrene activity. Under the optimal conditions of 0.3 g styrene, 20 mg CuTNPc/MWCNTs, 3 mL TBHP as oxidant, and 5 mL THF at 90 ℃ for 6 h, the styrene conversion, and benzaldehyde selectivity could reach 99.74% and 79.53%, respectively. In addition, the possible reaction mechanism of styrene selective oxidation to benzaldehyde by CuTNPc/MWCNTs is also proposed.

Analysis of the Thermal Behavior Characteristics and Dynamics of Coal Under High Primary Temperature Conditions in Deep Mines

ABSTRACT The exposure to spontaneous combustion of coal subjected to high ground temperatures increases as the depth of mine excavation increases. To research the oxidative heat release characteristics of deep coal, a study was carried out to characterize the oxidation kinetics and thermal effects on coal in deep thermal environments; deep coals (heat-treated coals) in 30°C (T30), 45°C (T45) and 60°C (T60) environments were prepared using a simultaneous thermal analysis, and the thermal weight characteristics (TG) and thermal release characteristics (DSC) of heat-treated coals were tested by simulating coal samples in different deep thermal environments; the thermal effects of heat-treated coals were analyzed by oxidation kinetic theory. The findings indicated that the characteristic point temperature of the coal gradually reduces (T60 has the lowest oxidation characteristic temperature) as the heat treatment temperature increases, and the maximum mass loss (63.76%) during thermal treatment coal oxidation occurs in the combustion stage. The oxidation reaction mechanism function for the low-temperature oxidation phases of the deep coal conforms to the Z-L-T equation with a three-dimensional diffusion reaction mechanism. As the temperature of the thermal environment is increased, the apparent activation energy of the coal decreases and the exothermic heat increases. This increases the tendency for oxidation of the deep coal, making it more amenable to spontaneous combustion as the ambient temperature at depth rises. The results contribute to a theoretical framework for monitoring and preventing coal spontaneous combustion fires in deep mine excavations.

Rational Design and Construction of a CdS QDs/InVO4 Atomic‐Layer (110)/(110) Facet S‐Scheme Heterojunction for Highly Efficient Photocatalytic Degradation of C2H4

Exploring high efficiency S‐scheme heterojunction photocatalysts with strong redox ability for removing volatile organic compounds from the air is of great interest and importance. However, how to predict and regulate the transport of photogenerated carriers in heterojunctions is a great challenge. Here, density functional theory calculations were first used to successfully predict the formation of a CdS quantum dots/InVO4 atomic‐layer (110)/(110) facet S‐scheme heterojunction. Subsequently, a CdS quantum dots/InVO4 atomic‐layer was synthesized by in‐situ loading of CdS quantum dots with (110) facets onto the (110) facets of InVO4 atomic‐layer. As a result of the deliberately constructed built‐in electric field between the adjoining facets, we obtain a remarkably enhanced photocatalytic degradation rate for ethylene. This rate is 13.8 times that of pure CdS and 13.2 times that of pure InVO4. In‐situ irradiated X‐ray photoelectron spectroscopy, photoluminescence and time‐resolved photoluminescence measurements were carried out. These experiments validate that the built‐in electric field enhanced the dissociation of photoexcited excitons and the separation of free charge carriers, and results in the formation of S‐scheme charge transfer pathways. The reaction mechanism of the photocatalytic C2H4 oxidation is investigated by in‐situ electron paramagnetic resonance. This work provides a mechanistic insight into the construction and optimization of semiconductor heterojunction photocatalysts for application to environmental remediation.

Influence of Time Scale on the Reaction Mechanism of CO Oxidation over a Au/TiO2 Catalystt.

Knowledge of the reaction mechanism is key for rational catalyst improvement. Traditionally mechanistic studies focus on structure and the reaction conditions like temperature, pH, pressure, etc, whereas the time dimension is often overlooked. Here, we demonstrate the influence of time on the mechanism of a catalytic reaction. A dual catalytic mechanism was identified for the CO oxidation over Au/TiO2 by time-resolved infrared spectroscopy coupled with modulation excitation spectroscopy. During the first seconds CO on the gold particles is the only reactive species. As the reaction proceeds the redox properties of TiO2 dominate the catalytic activity through electronic metal-support interaction (EMSI). CO induces the reduction and reconstruction of TiO2 whereas oxygen leads to its oxidation. The activity of the catalyst follows the spectroscopic signature of the EMSI. These findings demonstrate the power of studying the short-time kinetics for mechanistic studies.

Efficient ammonia removal promoted in a bifunctional system constructed with NiCu–S/DSA electrodes

Currently, the treatment of ammonia in wastewater, one of the main causes of eutrophication in water bodies, has received widespread attention. In this work, a novel electrocatalytic bifunctional system was constructed to achieve efficient degradation of ammonia. It consists of Ni1Cu0.25-S/DSA electrodes with both anode and cathode, which is prepared by a combination of electrodeposition and electrochemical tuning strategies. The crystalline phases and oxidation states of the nano-textured particulate metal oxides were determined by using a series of physical characterizations. The Ni1Cu0.25-S/DSA electrode with the best electrocatalytic performance was screened by electrochemical analysis, which has good stability and reliability when processing ammonia nitrogen. The efficiency of electrodes for ammonia removal was verified by running denitrification of synthetic and real wastewater. The results showed that the NH4+-N removal efficiency could approach up to 99%. Kinetically, compared with the monofunctional system, the bifunctional system obtained a higher NH4+-N degradation rate of 45.5 mg L−1 h−1, increased the rate of N2 generation by more than 10 times, and reduced the rate of NO3−-N and NO2−-N generation by one-third on average. The possible reaction mechanism of anodic ammonia oxidation and cathodic nitrate reduction in the bifunctional system was proposed.

GC-MS Studies on Nitric Oxide Autoxidation and S-Nitrosothiol Hydrolysis to Nitrite in pH-Neutral Aqueous Buffers: Definite Results Using 15N and 18O Isotopes.

Nitrite (O=N-O-, NO2-) and nitrate (O=N(O)-O-, NO3-) are ubiquitous in nature. In aerated aqueous solutions, nitrite is considered the major autoxidation product of nitric oxide (●NO). ●NO is an environmental gas but is also endogenously produced from the amino acid L-arginine by the catalytic action of ●NO synthases. It is considered that the autoxidation of ●NO in aqueous solutions and in O2-containing gas phase proceeds via different neutral (e.g., O=N-O-N=O) and radical (e.g., ONOO●) intermediates. In aqueous buffers, endogenous S-nitrosothiols (thionitrites, RSNO) from thiols (RSH) such as L-cysteine (i.e., S-nitroso-L-cysteine, CysSNO) and cysteine-containing peptides such as glutathione (GSH) (i.e., S-nitrosoglutathione, GSNO) may be formed during the autoxidation of ●NO in the presence of thiols and dioxygen (e.g., GSH + O=N-O-N=O → GSNO + O=N-O- + H+; pKaHONO, 3.24). The reaction products of thionitrites in aerated aqueous solutions may be different from those of ●NO. This work describes in vitro GC-MS studies on the reactions of unlabeled (14NO2-) and labeled nitrite (15NO2-) and RSNO (RS15NO, RS15N18O) performed in pH-neutral aqueous buffers of phosphate or tris(hydroxyethylamine) prepared in unlabeled (H216O) or labeled H2O (H218O). Unlabeled and stable-isotope-labeled nitrite and nitrate species were measured by gas chromatography-mass spectrometry (GC-MS) after derivatization with pentafluorobenzyl bromide and negative-ion chemical ionization. The study provides strong indication for the formation of O=N-O-N=O as an intermediate of ●NO autoxidation in pH-neutral aqueous buffers. In high molar excess, HgCl2 accelerates and increases RSNO hydrolysis to nitrite, thereby incorporating 18O from H218O into the SNO group. In aqueous buffers prepared in H218O, synthetic peroxynitrite (ONOO-) decomposes to nitrite without 18O incorporation, indicating water-independent decomposition of peroxynitrite to nitrite. Use of RS15NO and H218O in combination with GC-MS allows generation of definite results and elucidation of reaction mechanisms of oxidation of ●NO and hydrolysis of RSNO.

Insights into catalytic oxidation mechanism of CO over Cu catalyst: Experimental and modeling study

Cu thin films have been synthesized using a chemical vapor deposition technique for catalytic kinetic study of CO oxidation. The obtained samples are morphologically uniform and homogeneous with porous textures. Structure analysis by X-ray diffraction indicated the formation of pure Cu metal. X-ray photoelectron spectroscopy exhibited the existence of Cu in a metallic state at the surface, in addition to a minor quantity of Cu1+ that could be formed during the deposition process. The catalytic performance was evaluated through CO oxidation at gas hourly space velocity (GHSV) of ∼300,000 mL·g−1·h−1. The results showed that the Cu catalyst is very active in CO oxidation. The CO2 effect on the CO conversion during the catalytic reaction was investigated by using different amounts of CO2 in the inlet gas mixtures. Moreover, density functional theory (DFT) calculations were performed to determine the adsorption and reaction energies, revealing the best results on Cu hollow active sites. The surface reaction mechanism of the catalytic oxidation of CO over Cu catalyst was developed with reasonable prediction against the measured results. The simulated results revealed a good correlation with the experimental data when Langmuir-Hinshelwood (LH) mechanism is followed. CO2 exhibits an inhibiting effect on the catalytic oxidation of CO. Accordingly, the findings revealed that combining experimental data and theoretical calculations could allow a better understanding of the catalytic reaction mechanism, which can pave the way to investigate other catalytic reactions.

Kinetic modeling of NH3-selective catalytic reduction (SCR) over a mildly hydrothermally aged commercial Cu-SSZ-13 catalyst

Cu-SSZ-13 is often studied as a selective catalytic reduction (SCR) of NOx catalyst for diesel after-treatment systems. Mild hydrothermal aging (HTA) is commonly known to cause changes in catalyst performance. In this study, a kinetic model of SCR over a Cu-SSZ-13 catalyst that includes mild HTA and its impact on the SCR reaction was developed. The migration of Cu species during HTA, and how this change in Cu distribution affects low-temperature and high-temperature NH3 oxidation and SCR reaction mechanisms, were considered. Flow reactor test results were used for parameter estimation and verification. Different characterization techniques, including H2 temperature-programmed reduction (H2-TPR), NO + NH3-TPR, NH3 temperature-programmed desorption (NH3-TPD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), were used to characterize and quantify catalyst site densities. The model can simulate the migration of Cu species and the NOx reduction performance changes during mild hydrothermal aging as a function of aging temperature and time.

Demonstrating an altered metal oxidation reaction mechanism correlated with variations in surface energy

Thermal processing of powder media such as annealing and quenching alters particle surface properties and can influence the powder's reactivity. In this study, thermogravimetric analysis (TGA) was performed with micro-sized (4 µm characteristic particle diameter) aluminum (Al) powder. Two powders were examined, namely, untreated Al (UN Al), i.e., procured from the manufacturer, compared with thermally processed Al by annealing and quenching (i.e., called super-quenched aluminum, SQ Al). TGA experiments were designed to compare the rate of oxidation of both materials. A new data processing technique was introduced that allows for a direct demonstration of altered reactivity by comparing the sample behavior during heating and cooling. The approach analyzes a normalized derivate drop of mass gain data throughout a programmed heating and cooling cycle depending on particle exposure time to oxygen at select temperatures. Results clearly confirm a difference between SQ Al and UN Al at temperatures around 600 °C, i.e., just below the Al melting temperature. The powders were also characterized using inverse gas chromatography (iGC) that showed a substantially higher surface energy of UN Al. Based on the experimental results, there is a correlation between Al reactivity and particle surface energy that substantiates recent observations of two different modes of Al particle combustion. Particle surface energy can be controlled to affect the mechanism for metal oxidation thereby affecting the rate of metal combustion.

Urea Electrooxidation in Alkaline Environment: Fundamentals and Applications

AbstractUrea is an important chemical in agricultural, biosystem and chemical engineering. It can not only be a fertilizer and feed supplement, but also converted into electricity and hydrogen based on the counterpart half‐reactions. In this concept, we demonstrated the fundamental mechanism of electrochemical urea oxidation reaction (UOR) and its various applications on environmental, energy and healthcare devices with typical examples. UOR providing potential directions for the electrochemical treatment of urea‐contained wastewater were also introduced in this concept. This work is not focused on electrocatalyst design, but rather offers instructive guidance for the UOR developments in environmental, energy, and healthcare devices.

Voltammetric oxidation behavior of single-stranded DNA on carbon screen printed electrodes: From short oligonucleotides to ultralong amplification products

To deeper understand the electrochemical behavior of nucleic acids, the synthetic DNA oligonucleotides of general formula (ACTG)n, where n = 1–12, as well as 16-mer DNA oligonucleotides varying in the number of guanine (dG; G-n, n = 0–7) or adenine (dA; A-n, n = 0–8) residues, and single-stranded DNA (ssDNA) amplification products were employed to systematically investigate their oxidation in the ‘dissolved’ and ‘adsorbed’ forms on carbon screen printed electrodes by square wave and cycling voltammetry in the potential range of 0.5–1.5 V (vs. Ag/AgCl). Two signals at 0.9–1.0 V and 1.1–1.2 V, attributed to the oxidation of dG and dA, respectively, were registered for the most of oligonucleotides. The oxidation process of ‘dissolved’ (ACTG)n with n = 1–2 via dG was found diffusion-controlled, while (ACTG)3 has demonstrated a mixed mechanism of oxidation reaction. At the same time, ‘adsorbed’ oligonucleotides demonstrated adsorption-limited responses, except for (ACTG)1 showing a mixed reaction mechanism. At a constant nucleotide or oligonucleotide molar concentration, the registered signals for (ACTG)n exponentially decreased with the molecule length. The signals of all studied oligonucleotides after pre-adsorption on electrode surface were up to 10-fold higher than those in the soluble form, except for (ACTG)1. The dG oxidation signal for G-n oligonucleotides, registered at about 0.9 V, was practically insensitive to the position of a single dG (at the end or in the middle of polynucleotide chain), while demonstrating a bell-shaped dependence on the dG amount with a maximum at n = 3–4. The dG oxidation signal for A-n oligonucleotides with a constant portion of dG also increased with the number of dA residues in the bell-shaped fashion with a maximum at n = 5. The folding of oligonucleotides into hairpins with a stem formed via dG/dC pairing resulted in a shift of the peak potential for dG oxidation to higher values. Finally, ultralong ssDNA products generated by rolling circle amplification (RCA) were found to produce strong non-Faradaic current masking the dG and dA oxidation signals. The electrochemical detection of RCA products via dG and dA oxidation was found possible if ultralong ssDNA is fragmented by carrying out RCA in the presence of an appropriate restrictase.

Theoretical investigation on CO oxidation by single nickel atom within two-dimensional porphyrin sheet

Catalysts for CO oxidation are usually precious metals, whose high cost restricts their widespread use. In order to reduce costs and improve catalytic activity, a two-dimensional porphyrin sheet with single nickel atoms (Ni−TDPS) was used as a catalyst for CO oxidation, and the detailed reaction path was studied by DFT. The stability of Ni−TDPS was determined by AIMD simulations. Three typical reaction mechanisms of CO oxidation on Ni−TDPS were discussed, including LH, ER, and TER mechanisms. The results showed that the TER mechanism is feasible due to the minimum reaction energy barrier in the rate-determining step. Therefore, Ni−TDPS is a potential candidate catalyst for CO oxidation in theory.

Experimental and Theoretical Study on Crown Ether-Appended-Fe(III) Porphyrin Complexes and Catalytic Oxidation Cyclohexene with O2.

Modifying non-precious metal porphyrins at the meso-position is sufficient to further improve the ability to activate O2 and the selectivity of the corresponding redox products. In this study, a crown ether-appended Fe(III) porphyrin complex (FeTC4PCl) was formed by replacing Fe(III) porphyrin (FeTPPCl) at the meso-position. The reactions of FeTPPCl and FeTC4PCl catalysed by O2 oxidation of cyclohexene under different conditions were studied, and three main products, 2-cyclohexen-1-ol (1), 2-cyclohexen-1-one (2), and 7-oxabicyclo[4.1.0]heptane (3), were obtained. The effects of reaction temperature, reaction time, and the addition of axial coordination compounds on the reactions were investigated. The conversion of cyclohexene reached 94% at 70 °C after 12 h, and the selectivity toward product 1 was 73%. The geometrical structure optimization, molecular orbital energy level analysis, atomic charge, spin density, and density of orbital states analysis of FeTPPCl, FeTC4PCl, as well as the oxygenated complexes (Fe-O2)TCPPCl and (Fe-O2)TC4PCl formed after adsorption of O2, were carried out using the DFT method. The results of thermodynamic quantity variation with reaction temperature and Gibbs free energy variation were also analysed. Finally, based on experimental and theoretical analysis, the mechanism of the cyclohexene oxidation reaction with FeTC4PCl as a catalyst and O2 as an oxidant was deduced, and the reaction mechanism was obtained as a free radical chain reaction process.

Microscopic oxidation reaction mechanism of methanol in H2O/CO2 impurities: A ReaxFF molecular dynamics study

In this study, the ReaxFF molecular dynamics (MD) simulations were performed to investigate the dynamic evolution of reactants and intermediates in the oxidation reaction of methanol, the oxidation reaction path was determined, and the effects of O2/methanol ratio and H2O/CO2 impurity on the oxidation were explored. The results indicate the consumption rate of methanol is significantly higher than that of O2, and the preferred product of the reaction are H2O, H2, CO and CO2. With the increase of reaction temperature, the consumption rate of reactants increases, which promotes the formation of intermediate products in advance, resulting in the increase of products. The amount of final products of H2O, H2, CO and CO2 at 3000 K under fuel rich condition is 1.59, 4.07, 4.36 and 3.20 times that at 2400 K, respectively. The presence of H2O/CO2 impurities promote the initial dissociation of methanol, and inhibits the consumption of O2 and the generation of H2O. The presence of CO2 impurities can promote the generation of CO. The activation energy is lowest in the CO2 impurity environment. This study provides a microscopic insight into the oxidation mechanism of methanol in various environment.

Zero-valent tungsten boosted Fenton-like oxidation (Fe(III)/peroxydisulfate) towards long-lasting oxidation of carbamazepine: Performance and mechanism

The slow conversion of the Fe(III)/Fe(II) redox couple arising from Fe(III) accumulation strongly restricts the ongoing generation for reactive oxygen species (ROS) in Fenton/Fenton-like systems. Hereby, micron zero-valent tungsten (μZVW) was applied as a co-catalyst to boost Fe(III) reduction for promoting the Fenton-like activation of peroxydisulfate (PDS), and the oxidation capacity and reaction mechanism of μZVW/Fe(III)/PDS system are investigated with carbamazepine (CBZ) as the target pollutant. The results show that CBZ can be completely degraded by the μZVW/Fe(III)/PDS system within 30 min, μZVW exhibits exceptionally high stability for long-lasting CBZ oxidation during 10 cycling tests. According to a mechanistic analysis, the main ROS responsible for CBZ oxidation include high-valent iron (Fe(IV)), hydroxyl radicals, and sulfate radicals, meanwhile, μZVW can rapidly reduce Fe(III) into Fe(II) and further boost Fenton-like activation of PDS. Fe(III) and PDS can speed up the stepwise oxidation of μZVW to steadily release low-valence tungsten species, which can induce reduction of dissolved oxygen to produce H2O2 and donate electrons to cleave peroxide O-O bonds of H2O2 and PDS to produce ROS. In addition, the self-cleaning function of μZVW makes it efficient to remove CBZ was discovered. Therefore, the finding of this study proposes a novel co-catalyst to boost Fenton-like activation of PDS, which can promote the scientific advances in enhanced Fenton-like oxidation towards realistic use in water remediation.

CO oxidation mechanism on surfaces of B-site doped SrFeO3-δ-based perovskite materials for thermochemical water splitting

Density functional theory (DFT) calculations were performed to explore the reaction mechanism of CO oxidation on both the perfect and O pre-adsorbed surfaces of B-site (B = Al, Zr, Nb and W) doped SrFeO3-δ-based perovskite materials. Our calculations showed that metal doping benefited the adsorption of molecular CO over the perfect surface, while it inhibited the adsorption of molecular CO over the O pre-adsorbed surface. The reaction of CO with lattice oxygen of SrFeO3 was inhibited with the doping of Zr, Nb and W, but promoted by the doping of Al. The reaction of CO with surface pre-adsorbed O of SrFeO3 was found to be thermodynamically inhibited by the doping of Al, Zr, Nb and W. This study provided significant insights into the interaction of CO with the surfaces of doped SrFeO3-δ perovskite materials for thermochemical water splitting applications.

Understanding Trends in Electrochemical Methanol Oxidation Reaction Activity on a Single Transition-Metal Atom Embedded in N-Coordinated Graphene Catalysts

The lack of efficient catalysts and research on the mechanism for the methanol oxidation reaction (MOR) impedes the development of direct methanol fuel cells. In this work, based on density functional theory calculations, we systematically investigated the activity trends of electrochemical MOR on a single transition-metal atom embedded in N-coordinated graphene (M@N4C). By calculating the free energy diagrams of MOR on M@N4C, Co@N4C was screened out to be the most effective MOR catalyst with a low limiting potential of 0.41 V due to the unique charge transfers and electronic structures. Importantly, one- and two-dimensional volcano relationships in MOR on M@N4C catalysts are established based on the d-band center and the Gibbs free energy of and ΔG*CO, respectively. In one word, this work provides theoretical guides toward the improved activity of MOR on M@N4C and hints for the design of active and efficient MOR electrocatalysts.

Guideline for screening antioxidant against lipid‐peroxidation by spectrophotometer

AbstractLipid peroxidation (LPO), an oxidative chain reaction often occurring in the human body and food, is harmful to human health. Due to its convenience and low cost, this guideline highlights the benefits and drawbacks of LPO models by spectrophotometer in vitro and in vivo. The preparation process and reaction mechanism of lipid substrates, oxidation triggers and detection methods are discussed in this paper to better screen antioxidants. The lipid substrates mostly consist of rat liver/brain homogenate, microsomal, low‐density lipoprotein (LDL), and linoleic acid (LA), are appropriate for modeling oxidative damage in a variety of situations. Transition metals, ascorbic acid, 2,2′‐azobis (2‐amidinopropane) hydrochloride (AAPH), sodium Nitroprusside (SNP), 3‐morpholinosydnonimine (SIN‐1) and nicotinamide adenine dinucleotide phosphate (NADPH) make up the majority of the oxidizing triggers. The following LPO quantification techniques have been reviewed: (a) thiobarbituric acid reactive substances (TBARS) assay, (b) measurement of conjugated‐diene (CV), (c) β‐carrot bleaching assay, (d) thiocyanate method, (e) ferrous oxidation‐xylenol orange (FOX‐2) assay. It can be concluded that more than one test system should be applied to obtain comprehensive results. In a word, this guideline provides a scientific basis for future research on antioxidants screening in food and body systems.