Chemical Oxidation Research Articles

Design of highly stable Co3O4/RGO/CoFe2O4 hybrid nanocomposites with multiple nanointerfaces for enhanced supercapacitor performance

In this study, we developed a novel hybrid electrode nanomaterial composed of Co3O4, CoFe2O4, and reduced graphene oxide (RGO) for electrochemical supercapacitor applications. The hybrid nanocomposite of Co3O4/RGO/CoFe2O4 was prepared using a modified chemical oxidation process and the phase formation of the composites was evidenced by X-ray diffraction (XRD). The grain size for Co3O4 and CoFe2O4 was estimated as 12 nm and 22 nm. For Co3O4/CoFe2O4 the reduced grain size of 19 nm for CoFe2O4 was observed and further it was reduced with RGO up to 15 nm. The bare Co3O4 exhibited a hexagonal plate-like morphology, whereas the bare CoFe2O4 showed mostly a spherical morphology. The reduced saturation magnetization for the hybrid electrode material due to the non-magnetic fraction of Co3O4 and RGO was observed to be 21 emu/g compared to the bare CoFe2O4 (77 emu/g). The Co3O4/RGO/CoFe2O4 electrode exhibited enriched electroactive sites and enhanced diffusion pathways, achieving a high specific capacity of 235C g − 1 at 5 A g − 1 with excellent durability.. This work highlights the significant charge storage potential of the Co3O4/RGO/CoFe2O4 hybrid, making it a promising candidate for advanced energy storage systems.

Chemical reduction-induced defect-rich bismuth oxide-reduced graphene oxide anode for high-performance supercapacitors

We prepare bismuth oxide-reduced graphene oxide (Bi2O3-rGO) composite anode using a one-step chemical precipitation/reduction method. Under a reducing atmosphere, oxygen atoms on the surface of Bi2O3 are gradually removed and neighboring oxygen atoms migrate to the surface, leaving oxygen vacancies. Defective Bi2O3 enhances the number of active sites, providing additional pseudocapacitive performance. The transition metal oxide-based Bi2O3 acts as an anode, providing capacitive performance that far exceeds that of conventional carbon materials. Moreover, the introduction of rGO forms a conductive network for Bi2O3, improving capacitive contribution and ion diffusion capabilities for the electrode. The Bi2O3-rGO-100 (GO added at 100 mg) exhibits a high specific capacitance of 1053F/g at 1 A/g, significantly higher than that of Bi2O3 (866F/g). The Bi2O3-rGO-100 anode and Ni3Co2-rGO cathode are assembled into a battery-type supercapacitor. The coin-cell device achieves an energy density of 88.2 Wh kg−1 at a power density of 850 W kg−1. The Ni3Co2-rGO//Bi2O3-rGO-100 pouch-cell device demonstrates an extremely low Rct of 0.77 Ω. At a power density of 850 W kg−1, the energy density reaches 118.5 Wh kg−1, and remains 67.4 Wh kg−1 at 8500 W kg−1.

Dual Pathways in Catalytic Ammonia Oxidation by a Ruthenium Complex Bearing a Tetradentate Bipyridine-Bipyrazole Ligand: Isolation of a Diruthenium Intermediate with a μ-Hexazene Derivative.

We report herein chemical and electrochemical ammonia oxidation (AO) catalyzed by a Ru complex, [RuII(H2L)(pic)2]2+ [1, H2L = 6,6'-di(1H-pyrazol-3-yl)-2,2'-bipyridine, pic = 4-picoline], where H2L is a tetradentate ligand with a bipyridyl unit connected to two pyrazoles. 1 functions as an efficient electrocatalyst for the oxidation of NH3 to N2, with a low overpotential of 0.51 V vs Fc+/0 and a Faradaic efficiency of 96%. 1 also undergoes catalytic chemical AO using (4-BrPh)3N•+ as an oxidant, with a turnover number for N2 reaching 41. A novel binuclear complex, [RuIII(L)(pic)2(N2)RuIII(L)(pic)2]4+ (2), was isolated and structurally characterized in the catalytic chemical AO by 1. Complex 2 possesses a zigzag dianionic μ-hexazene unit where the N2 derived from ammonia oxidation is bonded to the pyrazoles, with an NN2-NN2 bond length of 1.3091(70) Å. 2 readily releases N2 upon treating with NH3. Based on experimental and DFT studies, in chemical AO the formation of an N-N bond is proposed to occur via bimolecular coupling of a ruthenium pyrazole imido intermediate to give 2; while in electrochemical AO the N-N bond is formed by nucleophilic attack of NH3 on the intermediate.

Impact of varying magnetite nanoparticle concentrations on the structural, electrical, and magnetic properties of polyaniline-based magnetic nanocomposites

We report the synthesis of polyaniline/magnetite nanocomposites (PMNCs) via in situ chemical oxidation polymerization of aniline with magnetite nanoparticles (MNPs) at 5, 12, and 25 wt%. The objective was to evaluate how the MNPs’ proportion affects the electrical, magnetic, and structural properties, which were investigated using XRD, EDXRF, TEM, EIS, ESR spectroscopy, Mössbauer spectroscopy, and VSM. EDXRF confirmed the formation of MNPs, while XRD revealed the crystalline nature of MNPs and the semicrystalline structure of PANI, with a decrease crystallinity index as the MNPs percentage increased. TEM showed PANI encapsulating MNPs with average diameters of 9.7 ± 2, 9.9 ± 2, and 13.1 ± 3 nm for PMNC25, PMNC12, and PMNC5, respectively. Conductivity values of PANI, PMNC25, PMNC12 and PMNC5 were 7.96 ×10⁻⁴, 1.38 ×10⁻⁴, 2.19 ×10⁻⁴ and 2.31 ×10⁻⁴ S/cm, respectively. ESR indicated cationic radicals responsible for conductivity. Saturation magnetization (Ms) for MNPs, PMNC25, PMNC12 and PMNC5 were 93.4, 24.6, 11.8 and 5.6 emu/g, respectively, with superparamagnetic behavior observed. Our findings show that incorporating MNPs into the PANI matrix modulates electrical conductivity and magnetic properties while maintaining the nanocomposite’s structure, highlighting the multifunctional potential of these composites.

Preparation of short carbon fiber reinforced photosensitive resin and composite material properties study

AbstractLight‐curing rapid prototyping (SLA) has become an emerging technology in the manufacturing industry because of its high precision, rapid prototyping, and the ability to mold complex parts. To enhance the mechanical properties and thermal stability of its raw material photosensitive resin (PR), carbon fiber (CF) was surface modified by chemical oxidation and grafting of amino silane (KH550) to obtain KH550‐modified carbon fiber (ACF). Then, ACF was composited with photosensitive resin to obtain modified carbon fiber/photosensitive resin (ACF/PR) composites. The viscosities of ACF/PR composites, including the viscosity, curing shrinkage, mechanical properties, and thermal stability of the ACF/PR composites, were characterized. The results showed that KH550 was successfully grafted onto CF. When the addition of ACF in the composites was 0.6%, the tensile strength, elongation at break, and impact strength of ACF/PR reached 39.48 MPa, 20.32%, and 13.62 kJ/m2, which were 120%, 27.15%, and 154% higher than that of the pure resin; the thermal decomposition temperatures and the maximum thermal decomposition temperatures at 50% mass loss of ACF/PR increased to 457.66°C and 442.44°C at 50% mass loss, which is 3.95% and 3.63% higher than that of the pure resin. Currently, the composites have excellent strength, toughness, and thermal stability. This paper gives a cost‐efficient method for improving the functioning of PR.Highlights Mixed acid oxidation and amino silane modification of CFs. Preparation of modified CF/photosensitive resin composites. Composites with excellent mechanical properties and thermal stability.

Evaluating rotary and static calcination processes for montmorillonite marl: Pozzolanic properties, compressive strength, and cementitious paste characteristics

Marls, widely available globally, are under research as supplementary cementitious materials. This study investigated metamontmorillonite reactivity and optimal calcination temperatures. The complex composition of marls, including minerals like montmorillonite and dolomite alongside chemical oxides such as CaO and MgO, posed challenges in determining the ideal calcination temperature. Material transformations at varying temperatures were tracked using X-ray diffraction, scanning electron microscopy, and nuclear magnetic resonance techniques. Comparative analysis of static and rotary kilns evaluated mortar compressive strength after 28 days, determining suitable replacement levels and the best calcination temperature. The study determined that calcination at 850 °C maximized pozzolanic reactivity, resulting in the formation of β-C2S. Static furnace calcination showed a slight advantage over rotary kiln. Mortar with 30% calcined marl replacement at water: binder ratio (W/B = 0.45) exhibited the highest compressive strength. Hydration analysis revealed the formation of calcium carboaluminate and hydrotalcite hydrates, with Al/Si = 0.18 composition.

Mathematical modeling and machine learning-based optimization for enhancing biofiltration efficiency of volatile organic compounds

Biofiltration is a method of pollution management that utilizes a bioreactor containing live material to absorb and destroy pollutants biologically. In this paper, we investigate mathematical models of biofiltration for mixing volatile organic compounds (VOCs) for instance hydrophilic (methanol) and hydrophobic (α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}-pinene). The system of nonlinear diffusion equations describes the Michaelis-Menten kinetics of the enzymic chemical reaction. These models represent the chemical oxidation in the gas phase and mass transmission within the air-biofilm junction. Furthermore, for the numerical study of the saturation of α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}-pinene and methanol in the biofilm and gas state, we have developed an efficient supervised machine learning algorithm based on the architecture of Elman neural networks (ENN). Moreover, the Levenberg-Marquardt (LM) optimization paradigm is used to find the parameters/ neurons involved in the ENN architecture. The approximation to a solutions found by the ENN-LM technique for methanol saturation and α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}-pinene under variations in different physical parameters are allegorized with the numerical results computed by state-of-the-art techniques. The graphical and statistical illustration of indications of performance relative to the terms of absolute errors, mean absolute deviations, computational complexity, and mean square error validates that our results perfectly describe the real-life situation and can further be used for problems arising in chemical engineering.

Structural study of an electroactive allyl ester thiophenoazomethine for PDMS blending

A conjugated thiophene azomethine was prepared having pendant allyl esters. X-ray crystallography confirmed its structure and hydrogen bonding. The compound switched its absorption between 495 and 645 nm with electrochemical oxidation/neutralization and between 495 and 710 nm with chemical oxidation. The azomethine could be blended with PDMS for homogeneous elastomeric film preparation while maintaining its intrinsic color.

Electrochemical Cyclization of o-Aminyl Azobenzenes: Roles of Aldehydes in N-N Bond Cleavage.

Direct functionalization of azobenzenes provides an approach to obtaining valuable molecules in synthetic chemistry. However, an efficient method for the cleavage of the N═N bond of azobenzenes, which is a key process for this transformation, is still lacking. We herein disclose an electrochemical reduction-induced cyclization of azobenzenes with aldehydes via N═N bond cleavage. This electrochemical cyclization of azobenzenes proceeds well in the absence of any transition metals or external chemical oxidants, leading to the formation of N-protected benzimidazoles in moderate to good yields.

Pulsed light treatment helps reduce sulfur dioxide required to preserve Malbec wines

Sulfur dioxide (SO2) has a long history of use as a preservative in wine production to prevent oxidation and microbial spoilage. However, sulfite sensitivities exist in some consumers that range from mild breathing irregularities to more severe allergic symptoms that can include anaphylactic reactions. These adverse effects have inspired the wine industry to develop alternative approaches to either lower or replace the use of sulfites. This study focused on assessing the efficacy of employing continuous Pulsed Light (PL) in conjunction with reducing SO2 applications to inactivate spoilage microorganisms and ensure optimal red wine preservation. Applying PL at an intensity of 4 J/cm2 to wine in combination with a 25 mg/L SO2 treatment generated a 12% and 22% reduction, respectively, in both the number of viable yeast and LAB cells, respectively, while having no substantial effects on color, changes in acidity, total phenolic, and anthocyanin contents after four months of aging. We conclude that PL processing of wine can help reduce the amount of SO2 needed to inactivate wine spoilage microorganisms and prevent loss of wine quality due to chemical oxidation. This combination of markedly reducing SO2 concentration use along with introducing non-thermal PL processing can be done effectively and simply to ensure a safer and stable final wine product for sulfite-sensitive consumers.

Copper-Catalyzed Tunable Oxygenative Rearrangement of Tetrahydrocarbazoles.

Herein, we report a general copper-catalyzed method for the tunable oxygenative rearrangement of tetrahydrocarbazoles to cyclopentyl-bearing spiroindolin-2-ones and spiroindolin-3-ones. The method demonstrates excellent chemoselectivity, regioselectivity, and product control simply by using the H2O and O2 as oxygen source, respectively. This open-flask method is safe and simple to operate, and no other chemical oxidants are required. Besides, inspired from the unique pathway of 1, 2-migration rearrangement, a highly controllable hydroxylation of indoles for the construction of C3a-hydroxyl iminium indolines was also developed. Mechanistic experiments suggest that a single-electron transfer-induced oxidation process is responsible for the tunable selectivity control.

A Double Twisted Nanographene with a Contorted Pyrene Core

AbstractThe mature synthetic methodologies enable us to rationally design and produce chiral nanographenes (NGs), most of which consist of multiple helical motifs. However, inherent chirality originating from twisted geometry has just emerged to be employed in chiral NGs. Herein, we report a red‐emissive chiral NG constituted of orthogonally arranged two‐fold twisted π‐skeletons at a contorted pyrene core which contributes to optical transitions of S0→S1 and vice versa. The thus‐obtained NG exhibited a robustness on its redox properties through 2e− uptake/release. The chemical oxidation generated stable radical cation whose absorption covers near‐infrared I and II regions. Overall, the contorted pyrene core governs electronic nature of the chiral NG. The twist operation on NGs would be, therefore, a design strategy to alter conventional chirality induction on NGs.

A Double Twisted Nanographene with a Contorted Pyrene Core.

The mature synthetic methodologies enable us to rationally design and produce chiral nanographenes (NGs), most of which consist of multiple helical motifs. However, inherent chirality originating from twisted geometry has just emerged to be employed in chiral NGs. Herein, we report a red-emissive chiral NG constituted of orthogonally arranged two-fold twisted π-skeletons at a contorted pyrene core which contributes to optical transitions of S0→S1 and vice versa. The thus-obtained NG exhibited a robustness on its redox properties through 2e- uptake/release. The chemical oxidation generated stable radical cation whose absorption covers near-infrared I and II regions. Overall, the contorted pyrene core governs electronic nature of the chiral NG. The twist operation on NGs would be, therefore, a design strategy to alter conventional chirality induction on NGs.

Controlling Redox and Wirelike Charge-Delocalization Properties of Dinuclear Mixed-Valence Complexes with MCp*(dppe) (M = Fe, Ru) Termini Bridged by Metalloporphyrin Linkers.

Four dinuclear organometallic molecular wire complexes with diethynylmetalloporphyrin linkers 1 MM' , [5,15-bis{MCp*(dppe)ethynyl}-10,20-diarylporphinato]M' (Cp* = η5-C5Me5; dppe = 1,2-bis(diphenylphosphino)ethane; M/M' = Fe/Zn (1 FeZn ), Ru/Zn (1 RuZn ), Fe/Ni (1 FeNi ), Ru/Ni (1 RuNi ); aryl = 3,5-di-tert-butylphenyl), are synthesized and characterized by NMR, CV, UV-vis-NIR, and ESI-TOF mass spectrometry techniques. Electrochemical investigations combined with electronic absorption spectroscopic studies reveal strong interactions among the electron-donating, redox-active MCp*(dppe) termini and the metalloporphyrin moieties. The monocationic species of the four complexes obtained by chemical oxidation have been characterized as mixed-valence Class II/III or Class III compounds according to the Robin-Day classification despite the long molecular dimension (>1.5 nm), as demonstrated by their intense intervalence charge transfer bands (IVCT) in the near IR region. DFT calculations indicate large spin densities on the metalloporphyrin moieties. Furthermore, the wirelike performance can be finely tuned by coordination of appropriate nitrogen donors to the axial sites of the metalloporphyrin.

Programmed alternating current optimization of Cu-catalyzed C-H bond transformations.

Direct current (DC) electrosynthesis, which has undergone optimization over the past century, plays a pivotal role in a variety of industrial processes. Alternating current (AC) electrosynthesis, characterized by polarity reversal and periodic fluctuations, may be advantageous for multiple chemical reactions, but apparatus, principles, and application scenarios remain underdeveloped. In this work, we introduce a protocol for programmed AC (pAC) electrosynthesis that systematically adjusts currents, frequencies, and duty ratios. The application of representative pAC waveforms facilitates copper-catalyzed carbon-hydrogen bond cleavage in cross-coupling and difunctionalization reactions that exhibit suboptimal performance under DC and chemical oxidation conditions. Moreover, observing catalyst dynamic variation under diverse waveform applications provides mechanistic insight.

From Nanoscale to Macroscale Characterization of Sulfur-Modified Oxidized Carbon Nanotubes in Styrene Butadiene Rubber Compounds.

The homogeneous dispersion of carbon nanotubes (CNTs) in a rubber matrix is a key factor limiting their amazing potential. CNTs tend to agglomerate into bundles due to van der Waals interactions. To overcome this limitation, CNTs have been surface-modified with oxygen-bearing groups and sulfur. Using atomic force microscopy (AFM) techniques, a deep nanoscale characterization of the morphology, the degree of dispersion of the CNTs in the styrene butadiene rubber (SBR) matrix, and the thickness of the interfacial layer was carried out in this study. In this context, the results from nanoscale characterization showed that the thermal oxidation-sulfur treatment leads to a composite with better dispersion in the matrix, as well as a thicker interfacial layer, indicating a stronger filler-rubber interaction. The second part of this work focused on the macroscale results, such as the Payne effect, vulcanization curves, and mechanical properties. The Payne effect, vulcanization curves, and mechanical properties confirmed the lower reinforcing effect observed in the case of the chemical oxidation treatment because, on the one hand, this composite showed the highest agglomeration of CNTs after the acid treatment. On the other hand, the presence of acid residues provoked the absorption of basic accelerators on the surface of the CNTs.

Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis.

Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon-neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth-abundant transition metal complex, trans-[LFeII(MeCN)2][PF6]2, where L is a macrocyclic ligand bearing four N-heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator (p-MeOC6H4)3N exhibited a catalytic half-wave potential (Ecat/2) of 0.18 V vs [Cp2Fe]+/0 in MeCN, and achieved 9.3 turnovers of N2 at an applied potential of 0.20 V vs [Cp2Fe]+/0 at -20 °C in controlled-potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFeIV(NH2)2]2+, and thereafter bimetallic coupling to form an N-N bond.

Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis

Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon‐neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth‐abundant transition metal complex, trans‐[LFeII(MeCN)2][PF6]2, where L is a macrocyclic ligand bearing four N‐heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator (p‐MeOC6H4)3N exhibited a catalytic half‐wave potential (Ecat/2) of 0.18 V vs [Cp2Fe]+/0 in MeCN, and achieved 9.3 turnovers of N2 at an applied potential of 0.20 V vs [Cp2Fe]+/0 at −20 °C in controlled‐potential electrolysis, with a Faradaic efficiency of 75%. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFeIV(NH2)2]2+, and thereafter bimetallic coupling to form an N−N bond.

FATTY ACID PROFILE OF COMMON CARP (CYPRINUS CARPIO) AFTER ADDITION OF ASTAXANTHIN TO THE FEED MIXTURE

Astaxanthin is a very strong antioxidant typically fed to rainbow trout mainly to alter the color of its’ meat to red. In our study, we incorporate a relatively low concentration of astaxanthin into the diet of common carp to enhance the chemical parameters and oxidation stability of carp meat without altering the typical coloration of meat. Also, we observed the fatty acid profile of reared fish. We observed an increase in protein content in animals with astaxanthin dietary addition. It was not statistically significant, but we observed a lowering of fat content in experimental groups. Regarding lipid oxidation, we did not observe any significant effect of astaxanthin on malondialdehyde production in samples. Fatty acid profiles were determined by gas chromatography and then compared. Only significant differences were observed in stearic and arachidonic acid and in the experimental group with lower astaxanthin addition. Our results conclude that dietary astaxanthin has no adverse effect on fatty acid profile or oxidation stability during storage (at -18 °C). On the other hand, astaxanthin has the potential to enhance the protein and lower the fat content, even in low concentrations.

An enzyme cascade biosensor based on multiwalled carbon nanotube-RuO2 nanocomposite for selective amperometric determination of lactose in milk samples

An enzyme-based electrochemical biosensor was fabricated for the sensitive determination of lactose. The utilized enzyme cascade system is composed of β-galactosidase (β-Gal) and glucose oxidase (GOx). The ruthenium(IV) oxide (RuO2) presents in MWCNT-RuO2 nanocomposite immobilized on the glassy carbon electrode acts as an electrochemical mediator, resembling a second-generation enzyme biosensor. The functional mechanism of the biosensor was discussed, explaining the chemical oxidation of H2O2, the final product of the enzymatic reaction, by RuO2 and subsequent reoxidation of generated Ru to RuO2 at the electrode surface. This shifts the oxidation of H2O2 to a lower potential magnitude of +0.40 V, enhancing the biosensor’s selectivity. The analytical figures of merit were verified for the developed lactose biosensor through repetitive measurements. The precision of the lactose biosensor was ensured with good reproducibility (RSD % = 2.68) and repeatability (RSD % = 4.12). The selectivity of the biosensor towards various saccharides and ionic species potentially present in milk samples was investigated, and no notable interference effect was detected. Moreover, the accuracy of the lactose biosensor was tested by analyzing spiked samples and a semi-skimmed milk (SS-milk) sample with certified lactose values. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be (0.036 mM) and (0.121 mM), respectively. Thanks to the short response time of the fabricated lactose biosensor, it was transferred to a screen-printed carbon electrode (SPCE) and successfully employed in flow injection analysis (FIA).