Oxidation Potential Research Articles

Deciphering the key drivers of oxidative potential during ammonium nitrate-mediated aqueous-phase photoreaction of methoxyphenols

Methoxyphenols are released in abundance from lignin pyrolysis during biomass burning. Apart from being atmospheric brown carbon components that absorb solar radiation and warm the climate, methoxyphenols also undergo photoreaction in the atmospheric aqueous phase and form secondary organic aerosols (aqSOA). While efforts have been devoted to understanding chemical evolutions and climate-related optical properties of aqSOA, their potential health impacts also require timely investigations. Herein, we used the dithiothreitol (DTT) assay to investigate oxidative potential of the aqSOA formed during the 8-hr aqueous-phase photoreaction of two typical methoxyphenols, vanillin and vanillic acid, under pH 2 or 8, and with or without ammonia nitrate. The highest DTT consumption rates (RDTT) were observed for vanillin aqSOA formed in the presence of ammonia nitrate and at pH 8. At pH 2, although RDTT increased rapidly during early photoreaction, it reduced after prolonged illumination. High resolution mass spectrometry and linear regression analyses were performed to correlate the photoreaction products with the observed RDTT. Results showed that three products that present quinone, lactone and dimer structures, respectively, should be the key drivers of elevated RDTT for aqSOA formed during photoreaction of vanillin and vanillic acid alone, whereas it shifted to the nitrogen-containing aromatic compounds during their photoreaction with ammonia nitrate. Our results have revealed the role of nitrogen-containing aromatic compounds in the oxidative potential and health effects of aqSOA from biomass burning, which was rarely recognized before and warrants immediate assessments.

Gaseous and aerosol emissions from open burning of tree pruning and hedge trimming residues: Detailed composition and toxicity

Gaseous and PM10 samples were collected during the open burning of pruning residues (olive branches and garden waste) and characterised by distinct analytical techniques to obtain comprehensive chemical emission profiles. Oxidative potential (dithiothreoitol and ascorbic acid assays) and cell viability tests were also performed with the aim of evaluating aerosol toxicity. Emission factors (EFs) were as follows (g kg−1 biofuel, dry basis): 1537–1672 for CO2, 41.9–80 for CO, 2.74–6.6 for CH4, 0.89–3.51 for ethane, 0.79–1.78 for ethylene and 0.56–3.47 for formaldehyde. Emissions of PM10, organic carbon (OC) and elemental carbon (EC) were in the ranges 8–41, 3–18, and 0.4–1.5 g kg−1 biofuel, dry basis, respectively. OC accounted for 35–45% of the total PM10 mass, while EC contributed between around 3% and 5%. WSOC/OC ratios varied from 0.4 to 0.6, revealing that a substantial portion of the carbon emitted was hydrosoluble. Water soluble ions constituted around 8–21% of the PM10 mass, with potassium and chloride as the most abundant ions in all samples. Levoglucosan, widely used a reliable biomass burning tracer, was found in significant amounts in all samples (up to 1.2% of the PM10 mass). Retene, generally pointed out as a biomass combustion biomarker, was the predominant PAH. WSOC and some PAHs showed significant positive correlations with the intrinsic OP measured with the DTT assay, while the OPAA was significantly correlated with some trace metals, such as Fe or Ni. All samples significantly reduced the viability of alveolar epithelial cells.

The interplay of Brown carbon (BrC) surrogates and copper: Implications for the oxidative potential of ambient particles

Atmospheric particulate matter (PM) poses adverse effects on human via producing reactive oxygen species (ROS). Oxidative potential (OP, ability to generate ROS) can be induced by various chemicals in PM, while their interplay remains poorly characterized. Here, we systematically assessed influences of Cu2+ on OP of Brown carbon (BrC) (e.g., imidazoles) using dithiothreitol (DTT) assay. Results showed DTT consumption rate exhibited an initial rise and later decline (0.25 −0.56 µM/min) along with increase of BrC concentration (0.1 − 2 µM), while no general trend was observed for •OH formation. Although Cu2+ showed either antagonism or synergism with BrC against DTT consumption, Cu2+ displayed antagonism with most BrC against •OH generation. Fluorescence quenching experiments provided evidence of complexation between Cu2+ and water-soluble organic compounds (WSOCs, from ambient PM2.5), which was influenced by Cu2+ concentration. Further parallel factor analysis of spectra showed that polycarboxylate-type humic acid-like substances (complexation site number (n): 0.46, complexation equilibrium constant (k): 0.51) and fulvic acid-like compounds (n: 0.42, k: 0.62) were the main components in WSOCs that complexed with Cu2+. Our results suggest the interactions of BrC and copper play a crucial role in PM OP and highlight complexation in evaluation of PM OP.

Group 7 carbonyl complexes of a PNN-heteroscorpionate ligand.

A series of rhenium and manganese carbonyl complexes of a heteroscorpionate ligand with an atypical N2P-donor set has been prepared to better understand their electronic and CO releasing properties. Thus, the ligand, pz2TTP, with an a,a-bis(pyrazol-1-yl)tolyl group decorated with an ortho-situated di(p-tolyl)phosphanyl reacts with carbonyl group 17 reagents to give [fac-(κ2NP-pz2TTP)Re(CO)3Br], 1, and [fac-(κ3N2P-pz2TTP)M(CO)3](OTf = O3SCF3), 2-M (M = Re, Mn), if care is taken during the preparation of the manganeses derivative. When heated in CH3CN, 2-Mn slowly transforms to [fac,cis-(κ3N2P-pz2TTP)Mn(CO)2(NCCH3)](OTf), 3-Mn. In contrast, the corresponding 3-Re can only be prepared from 2-Re using Me3NO; pure 3-Mn can also be prepared by this method. Experimental and density functional calculations at the M06L/Def2-TZVP/PCM(CH3CN) level show that the replacement of a carbonyl with an acetonitrile solvent decreases the oxidation potential by around 0.8 V per carbonyl released, making decarbonylated species potent reductants. At the same time, the electronic spectrum broadens and undergoes a red-shift, making dicarbonyl complexes more susceptible to photo-initiated decarbonylation reactions than tricarbonyls. When 2-Mn or 3-Mn are irradiated in with 390 nm LED light in aerated solutions, [trans-Mn(pz2TTP = O)2](OTf)2, 4, along with insoluble manganese oxides are rapidly formed.

Tailoring rGO[sbnd]Cu-Cu2O as a three-dimensional catalytic system in boosting of methanol electro-oxidation reaction

Tailoring a reduced graphene oxide-Cu-Cu2O (rGOCu-Cu2O) as a three-dimensional (3D) integrated catalytic system via an in-situ potential-controlled electrodeposition approach is a feasible pathway to boost methanol oxidation reaction (MOR) for direct methanol fuel cell. The enhancement in catalytic functionality and performances is due to the synergistic interaction between the in-situ electroreduced graphene oxide (rGO) and copper metal ions over it. The sequential and synergistic effect of the co-deposition potential, optimized time, and probable corrosion-promotion effect (formation of a galvanic cell between rGO and copper due to entrapped dissolved oxygen) is believed to be responsible for the structural growth of as-developed 3D catalytic systems. The MOR results suggest that the composite material deposited at the higher cathodic deposition potential (-1.2 V vs SCE), i.e., rGOCu (c) featured the remarkable lowest onset oxidation potential (i.e., +0.37 V), peak potential (i.e., +0.73 V), peak current density (135.76 mAcm−2), potentiostatic durability at +0.6 V after 3.5 h (∼65.85 mAcm−2) and outstanding cyclic stability (∼97.7 % current retention after 500 cycles), which is superior to the other modified composite electrodes. The enhanced performances are due to the effective dissociative adsorption of methanol from the available active catalytic site's and the presence of hydroxyl groups which has probably improved the oxidation of adsorbed intermediates from the surface. Further, Fourier-transform infrared (FT-IR) experiments revealed that formate as an active intermediate is being generated on all three rGOCu-Cu2O modified electrodes and follows the non-CO reaction pathway for direct oxidation of methanol.

Efficient and stable hydrogen evolution and antibiotic degradation in all-pH-scale water/alkaline seawater using Fe-Co phosphide hollow nanocages fabricated from metallurgical solid waste

The utilization of seawater, a plentiful and cost-effective resource, instead of freshwater for H2 production through electrolysis has garnered significant attention. Herein, we present the synthesis of open-structured Fe-Co phosphide (FCP) nanocages for the overall seawater electrolysis, employing metallurgical solid waste (steel rolling sludge, SRS) as the precursor material. The FCP nanocages demonstrate exceptional catalytic activity for the hydrogen evolution reaction (HER) in all pH scales, achieving performance comparable to that of Pt/C catalysts at high current densities. The electrolyzer assembled with FCP||FCP requires 1.57 and 1.68 V to achieve current densities of 10 and 100 mA cm−2, respectively. Furthermore, the assembled FCP electrolyzer showcases over 100 h of cycling stability and nearly 100% Faradaic efficiency. Crucially, it can be powered by commercially available silicon solar panels, operating under an intensity of 100 mW cm−2, and by wind-driven sources, rendering it highly promising for real-world applications. The seawater hydrogen evolution system coupled with levofloxacin (LEV) degradation was constructed for the first time. The oxidation potential of LEV oxidation reaction (LEVOR) was significantly lower than that of oxygen evolution reaction (OER), indicating that the LEV degradation reaction occurred preferentially and achieved a removal efficiency of 98.57% within 60 min. This study provides effective strategies for valorizing SRS and offers insights into the fabrication of high-performance catalysts.

Machine learning predictions of onset and oxidation potentials for methanol and ethanol electrooxidation: Comprehensive analysis and experimental validation

Machine learning predictions of onset and oxidation potentials for methanol and ethanol electrooxidation: Comprehensive analysis and experimental validation

Bismuth-based nanocomposites as potential materials for indoor air treatment

Air pollution is a worldwide health hazard; thus, improving air quality is a demanding need. Photocatalysis is a robust strategy for air treatment. The boosted activity of the photocatalytic system depends on tuning their properties for the particular application. BiOX (X: Cl, I) compounds are emergent photocatalytic systems with numerous advantages for air treatment. However, their optical properties (Eg) and fast recombination of active species (e−/h+) limit their practical applications. In this study, we remark on the properties of BiOX-GO systems for indoor air purification. We use a microwave-activated solvothermal technique to synthesize the nanomaterials (NMs). BiOX NMs exhibit hierarchical 3D structures, crystallinity, and tunable optical absorption properties. BiOX-GO composites present an enhanced visible-light photocatalytic activity due to the electron acceptor capacity of GO and modification of Eg. The indoor air disinfection capacity of the NMs ranked as follows: BiOCl-GO (96.7%) > BiOI-GO (96.2%) > BiOI (89.2%) > BiOCl (79%). The higher efficiency under visible light of BiOCl-GO can be related to the presence of oxygen vacancies, strong oxidation potential, and single crystalline phase of the materials. Due to the abundance and biocompatibility of bismuth-containing compounds, together with their enhanced visible light activity, BiOX become potent candidates for environmentally sustainable remediation technologies.

Antioxidant and antimalarial properties of hot aqueous leaf extracts of Setaria megaphylla, Ageratum conyzoides and Chromolaena odorata

This study investigated the antioxidant and antimalarial properties of leaf extracts of Setaria megaphylla, Ageratum conyzoides Linn, and Chromolaena odorata Linn, plants used in folkloric treatment of malaria. The plants were assessed for phenolic profile, antioxidant capacity and radical scavenging activities using standard methods. Single, binary and ternary combinations of the processed leaves were subjected to hot aqueous extraction, and evaluated for in vivo antiplasmodial efficacy against Plasmodium berghei NK 65 using Swiss albino mice. The plants’ total phenolic profile varied as S. megaphylla (Sm; 118.06 µg/ml) > C. odorata (Co; 116.58 µg/ml) > A. conyzoides (Ac; 73.01 µg/ml), with catechin, dihydrocytisine and tannin being the most abundant phenolics. Total antioxidant capacities (TAC) and reducing power potentials (RPP) of the plants increased with increase in extract concentrations with Sm showing highest TAC (1.49 ± 0.02 mgAAE/g) and RPP (0.47 ± 0.01 mgAAE/g) values. A similar trend was observed for the hydroxyl, nitric oxide and DPPH radicals scavenging potentials, showing dose-dependent increases in scavenging potentials but with no observed significant (p<0.05) differences in activities at the highest extract dose of 400 µg/ml. The in vivo antimalarial study demonstrated that the combination of A. conyzoides and S. megaphylla was the most effective, significantly reducing parasitemia without causing mortality in the mice. This research highlights the potential of S. megaphylla, A. conyzoides, and C. odorata, especially the combination of their extracts as source of effective anti-malarial agents, and further confirms the folkloric use of hot aqueous extracts of the plants in malaria treatment.

The significant role of Z-scheme band alignment at the heterojunction for the enhanced photocatalytic H2 production in TiO2/BiNbO4/rGO nanocomposite

An efficient ternary TiO2/BiNbO4/rGO nanocomposite was prepared by a simple wet impregnation process. PXRD confirmed the tetragonal and orthorhombic crystalline natures of titanium dioxide (TiO2) and bismuth niobate (BiNbO4) respectively. The loading of BiNbO4 and reduced graphene oxide (rGO) shifted the light absorption of TiO2 to a longer wavelength from 400 to 430 nm. The suitable conduction band position of BiNbO4 facilitated a favourable band alignment to suppress the electron/hole (e−/h+) recombination in TiO2 via the Z scheme mechanism at the heterojunction. The excited electrons at the CB of TiO2 were easily transported via the fast electron accepting and conducting rGO matrix for the surface redox reactions with the improved charge transfer efficiency, which was confirmed by EIS and PL studies respectively. BiNbO4 and rGO synergistically improved the specific surface area and solar light absorption. EPR analysis confirmed the presence of increased oxygen vacancies at the heterojunction. Hence, the ternary TiO2/BiNbO4/rGO nanocomposite demonstrated an enhanced hydrogen evolution (8910 μ mol h−1 gcat−1) than bare TiO2 (4820 μ mol h−1 gcat−1), bare BiNbO4 (950 μ mol h−1 gcat−1) and TiO2/BiNbO4 (6730 μ mol h−1 gcat−1) under direct solar light. The optimum of 1 wt % BiNbO4 and rGO loaded TiO2 nanocomposite produced twice the H2 production than the bare TiO2. This also further confirms that rGO played a major role during the photocatalytic process by highlighting the potential of metal oxides combined with carbon material as an efficient photocatalyst which prominently enhances the H2 evolution.

Catalytic pyrolysis of cashew de-oiled shell and spent lemongrass

Residual/ spent biomasses are rising each day due to the increased processing of crops to extract essential oils. An efficient method is required for its management and value-addition. Therefore, this study aims to explore the catalytic pyrolysis of two residual biomasses, i.e., cashew de-oiled shell and spent lemongrass biomass. Different metal oxide(s) catalysts prepared using Al2O3 support, i.e., Fe2O3/Al2O3, Co3O4/Al2O3, Mn2O3/Al2O3, and NiO/Al2O3, are considered for this study. From the product distribution, it was analysed that the incorporation of catalyst led to a decrease in the bio-oil yield as compared to non-catalytic pyrolysis, which showed that Al2O3-supported catalysts promote the cracking reactions of pyrolysis vapours and produce lighter molecules. It was found that the incorporation of catalysts significantly affected the content of the functionalities present in the pyrolysis bio-oil. Fe2O3/Al2O3 was observed to greatly increase the area % of phenolics up to 52.35 and 75.57 area % in spent lemongrass and cashew de-oiled shell bio-oil, respectively. Metal oxide catalysts were also observed to reduce the oxygenates and produce high-quality bio-oil. Overall, this study demonstrates the effective utilization of cashew de-oiled shell and lemongrass biomass for cleaner energy/chemicals production through catalytic pyrolysis, highlighting the potential of metal oxide supported on Al2O3 catalysts in biomass valorization.

Understanding oxidation potential and degradation mechanism of acid-treated TiO2 coupled g-C3N4 S-scheme heterojunction photocatalyst for the removal of gaseous formaldehyde

In this work, a step (S)-scheme heterojunction catalyst is synthesized by coupling acid-treated TiO2 (ATT) with graphitic carbon nitride nanosheet (g-C3N4: GCN) and used for adsorption-photocatalytic removal of gaseous formaldehyde (FA: 100 - 500 ppm). The acid treatment of TiO2 proves to be an effective approach for improving the surface porosity of ATT with more abundant active sites for efficient catalytic reactions. Similarly, the S-scheme heterojunction displays superior redox potential (i.e., availability of free e- at conduction band of GCN (reduction potential of −0.485 eV/NHE) and free h+ at valance band of ATT (oxidation potential 2.79 eV/NHE)). As such, in a dynamic packed-bed flow reactor, the improved textural and optical properties of ATT-GCN (bed mass = 10 mg) offer outstanding adsorption and photocatalytic oxidation potential, effectively removing 86% of 200 ppm FA vapor at a reaction rate of 70.2 nmole mg−1 min−1 under slightly humidified conditions (e.g., 20% relative humidity (RH) and 21% O2) when exposed to 32-W UV-A light source. Under these operational conditions, the ATT-GCN achieves the superior performance metrics (e.g., quantum yield of 5.1E-02 molec. photon-1, space–time yield of 5.1E-03 molec. photon-1 mg−1, and specific clean air delivery rate of 515.4 L g-1 h−1). In-situ Kelvin probe microscope analysis of ATT-GCN postulates the formation of a strong built-in electric field to improve the separation of charge carriers. Considerations on the degradation pathway and intermediate dynamics with the aid of in-situ DRIFTS analysis suggest that the presence of water molecules (e.g., 20% RH) is beneficial for accelerating the oxidation and mineralization of FA molecules relative to a dry gas stream. The overall outcomes of this work are expected to help deliver new paths for the construction of advanced photocatalytic systems for upscaled applications toward air quality management.

Supporting the investigation of health outcomes due to airborne emission by different approaches: current evidence for the waste incineration sector

Life cycle assessment (LCA) along with a survey on epidemiologic and oxidative potential studies was used for analysing the current evidence of the impact of airborne emissions from municipal solid waste incineration (MSWI) on human health. The correspondence among investigated health outcomes and pollutants was discussed based on the Chemical Service (CAS) and the International Agency for Research on Cancer (IARC). LCA indicated the ability of MSWI in avoiding human health impact, about − 2 × 10−4 DALY/tonne together with avoided emissions of particulate matter (PM) and resource depletion, about − 2.5 × 10−3 kg Sbeq/tonne and about − 0.11 kg PM2.5 eq/tonne, respectively. Positive emissions were detected for greenhouses (about 900 kg CO2eq/tonne) and ecotoxicity (about 15,000 CTUe/tonne). Epidemiologic studies performed on population exposed to MSWI reported quite contrasting results. In some of these, hazard ratio (HR) ranging from about 0.7 to 2.2 was reported concerning the incidence of stomach, liver, breast and bladder cancer. Larger agreement was detected concerning the incidence of larynx and lung cancer with HR ranging from about 1 to about 2.6. Direct causal nexuses were not definitively identified. Oxidative potential of PM was characterized by a high Pearson correlation > 0.8 to the presence of CrVI, Cu and Zn. These heavy metals were also identified by both CAS and IARC as toxic (i.e. Cu and Zn) and cancerous (i.e. CrVI) substances affecting the organs of both respiratory and digestive apparatus. In general, even if more research is necessary, LCA, oxidative potential and the epidemiologic survey results showed a high level of accordance. This suggests their integrated exploitation for supporting the investigation of both direct and indirect consequences on environment and health related to waste incineration for both retrospective and predictive studies.

Effects of fluorine atom numbers on electrochromic properties of the benzothiadiazole-based D-A polymers

In this work, two fluorinated D-π-A-π-D type monomers, F-EDOT and FF-EDOT, were facilely synthesized by donor-acceptor-donor method via Stille coupling reaction, with monofluorinated benzothiadiazole and difluorinated benzothiadiazole as the acceptor units and 3,4-ethylenedioxythiophene (EDOT) as the donor units. The electrochemical polymerization behavior of the fluorinated monomers, electrochemical and electrochromic properties of the corresponding fluorinated D-A polymers were compared to study the effects of different fluorine atom numbers on the optoelectronic properties of the monomers and their resultant D-A polymers. The results show that the introduction of more F atoms into the conjugated backbone increases the oxidation potential of monomers, both of them have low initial oxidation potential (0.65 V/0.70 V). As in the case of monomers, the substitution of more F atoms also leads to the decreased HOMO energy level of the polymers, thus leading to the increased band gap energy of P(FF-EDOT) (1.39 eV). This result can be attributed to the deviation of planarity and the reduced effective conjugate length. As prepared fluorinated D-A polymers also have good adhesion on the electrode surface, favorable redox activity, and outstanding redox stability (the redox activity of P(F-EDOT) remains 99 % after 1000 cycles). At the same time, the fluorinated D-A polymers also show distinguish electrochromic properties under various external potentials; both the optical contrast and coloration efficiency decreased with the increase of F atom numbers, and the corresponding response time increased. As a result, both the fluorinated D-A polymers show light green in the neutral state, P(F-EDOT) shows more obvious electrochromic performance in the near infrared region (optical contrast: 35.02 %, coloration efficiency: 159.94 cm2 C−1, and quick response time: 0.2 s), accompanied with excellent discoloration stability and optical memory effect. The study of novel fluorinated-based electrochromic materials further expands the selection of acceptor units and the application prospect of electrochromic materials.

Electrochemical DNA hybridization signal amplification system using methylene blue and ascorbic acid

This study presents a method for real-time monitoring of heterogeneous DNA hybridization using chronoamperometry (CA). The electrochemical assay is based on methylene blue (MB)-labeled ssDNA target (tMB) hybridization with a complementary ssDNA capture probe (p) chemisorbed to a gold electrode through the Au-S linkage. Real-time monitoring of nucleic acid binding is enabled by introducing ascorbic acid (AA) during CA measurements at oxidative potential. After hybridization, the newly formed MB-labeled double stranded DNA (ptMB) oxidized AA and, as a result, shuttled the electrons directly to the electrode. AA-ptMB electrocatalytic cycle allows amplifying the signal from hybridized MB-labeled DNA through oxidation of AA. The process consists three particular processes: hybridization of tMB to the surface probe, reaction between AA and ptMB, and (c) the electron transfer from ptMB to the electrode. We have demonstrated that system is limited by the AA-ptMB redox reaction (bimolecular constant, k = 8 ± 0.1 M–1 s–1). AA-ptMB cycle is sequence-specific, thus fully developed current saturation curves can be used to calculate hybridization parameters and evaluate binding kinetics under various conditions. In addition, evaluating the initial hybridization rate allows quantifying the concentration of labeled ssDNA (tMB) in several minutes. This study provides the first report of a simple electrocatalytic cycle between MB-labeled DNA and a reducer AA for monitoring DNA hybridization in real time.

Elucidating the potential of bimetallic mixed metal oxide (FeO/NiO) in fusion with pristine and N- and S-doped graphene oxide for biomedical applications

Antimicrobial resistance is attributed to acquiring new mechanisms by microbes to combat antimicrobial agents, highlighting the necessity to discover new antimicrobial agents to protect human health. Graphene and its derivatives have shown antimicrobial potential due to their physical and chemical distinctive features. Potent antibacterial properties were observed by decorating the surface of graphene and its derivatives with inorganic nanoparticles, such as metal and metal oxide. In an attempt to reliably overcome antimicrobial resistance, the multifunctional nanocomposites, including FeO/NiO, FeO/NiO/GO, FeO/NiO/N-GO, and FeO/NiO/S-GO, were synthesized using a wet chemical method. Accordingly, the structural analysis was performed using X-ray diffraction (XRD), infrared spectroscopy (IR), energy dispersive X-ray (EDX), ultraviolet-visible spectroscopy (UV–vis), and scanning electron microscopy (SEM). For antibacterial potential, the synthesized nanocomposites were tested against non-resistant and resistant strains of bacteria. Notably, moderate antibacterial potential was found for FeO/NiO/N-GO nanocomposite with a MIC value of 12.5 μg/mL, compared to the MIC of pure Ciprofloxacin, a positive control, with a value of 1.25 μg/mL. Toward antifungal potential, the synthesized nanocomposites were assessed against various spores of fungal strains. In this regard, the synthesized nanocomposites were demonstrated as potent antifungal agents. Among the synthesized nanocomposites, FeO/NiO and FeO/NiO/S-GO exhibited the highest ZOI against Aspergillus flavus. Additionally, the activity of these nanocomposites was evaluated by means of total reducing power (TRP), total antioxidant capacity (TAC), and free radical scavenging. Further, the antioxidant, brine shrimp lethality, and hemolytic potential of the synthesized nanocomposites were evaluated to compare their effectiveness. According to brine shrimp lethality, all synthesized nanocomposites were sufficiently active, with a calculated median lethal concentration (LC50) showing ≥ 50 % mortality. The obtained results provide a promising base for the incorporation of nanocomposites in pharmaceutical and biomedical products.

Unlocking the potential of mixed-valence silver oxide for electrochemical valorization of 5-hydroxymethylfurfural into valuable products

The burgeoning interest in the electrocatalytic conversion of biomass-derived compounds, exemplified by 5-hydroxymethylfurfural (HMF), into economically valuable products underscores the significance of such studies. Within this context, the electrocatalytic oxidation of HMF into 2,5-diformylfuran (DFF) using the mixed-valence silver (I, III) oxide (AgO) as the catalyst is presented for the first time. A thorough investigation has been carried out to explore the complex factors influencing the electrochemical transformation of the HMF to DFF, involving applied potentials, reactant concentrations, and the significant implications of mass transfer phenomena. Under optimized conditions, DFF, one of the highest value-added intermediates, can be produced with selectivity as high as 54%. Additionally, a yield of 10.8 μmol cm−2 h−1 was obtained under mild basic condition. Another pivotal aspect of this work involves meticulously examining the reaction process, bolstered by a comprehensive analytical approach that integrates high-performance liquid chromatography (HPLC), and operando Raman spectroscopy. The amalgamation of operando Raman spectroscopy with advanced simulation techniques represents a novel endeavor, offering a groundbreaking pathway to unravel the complexities inherent in these compounds and contribute substantially to the understanding of HMF oxidation and its intermediates. By looking closely at the catalyst surface during the reaction, a valuable insight into the steps involved was developed, helping in proposing an in-depth reaction pathway.

The effects of photochemical aging and interactions with secondary organic aerosols on cellular toxicity of combustion particles

Fine particulate matter (PM2.5) is associated with numerous adverse health effects, including pulmonary and cardiovascular diseases and premature death. Significant contributors to ambient PM2.5 include combustion particles and secondary organic aerosols (SOA). Combustion particles enter the atmosphere and undergo an aging process that changes their shape and composition, but there is limited study on the health effects of combustion particle aging and interactions with SOA. This study aimed to understand how biological responses to combustion particles would be affected by atmospheric aging and interaction with anthropogenic SOA. Fresh combustion particles underwent photochemical aging in a potential aerosol mass (PAM) oxidation flow reactor and interacted with SOA produced by the oxidation of toluene vapor in the PAM reactor. Photochemical aging and SOA interactions lead to significant changes in the PAH content and oxidative potential of the particle. Photochemical aging and SOA interactions also affected the biological responses, such as the inflammatory response and CYP1A1 induction of the particles in monoculture and coculture cells. These findings highlight the significance of photochemical aging and SOA interactions on the composition and cellular responses of combustion particles.

Between and within-city variations of PM2.5 oxidative potential in five cities in Colombia

AbstractFine particulate matter (PM2.5) has been shown to cause oxidative stress, which has negative health consequences. The oxidative potential (OP) of PM2.5, a promising health exposure metric, was assessed in five Colombian cities using the synthetic respiratory tract lining fluid assay that tracks the depletions of glutathione and ascorbate. For this, a set of 91 integrated 2-week ambient PM2.5 samples were collected using Ultrasonic Personal Aerosol Samplers (UPAS) at background (5), traffic (37), industrial (12) and residential (37) sites. Across all site types, mean PM2.5 mass concentration was 20.20 ± 9.36 µg m− 3. The oxidative potential (OPAA for ascorbate and OPGSH for glutathione) varied widely across cities with an average of 2.67 ± 1.27 for AA and 2.93 ± 1.22 % depletion m− 3 for GSH. OP metrics among cities were not correlated with PM2.5 mass concentrations. Overall, industrial sites showed higher PM2.5 mass concentrations and OPAA. In contrast, OPGSH was not found to differ among industrial, traffic, or residential sites, but was lower for background sites. Our findings provide substantial evidence of variations in PM2.5 OP between cities and within the cities. Further research is needed to assess the association between OP and adverse health effects, as well as to attribute the sources that cause such variations.

Ene‐Reductase‐Catalysed Oxidation Reactions

Ene‐reductases from the Old Yellow Enzyme (OYE) family have been traditionally employed in the reduction of conjugated C=C double bonds. This study explores the underutilised oxidative potential of OYEs, demonstrating their capability to catalyse the enantioselective desaturation of carbonyl compounds. Utilising a deprotonated tyrosine residue as a catalytic base, we developed a method to enable OYE‐catalysed desaturation at ambient temperature and alkaline pH, without the need for high‐temperature conditions. Through screening of various OYE enzymes, we identified several candidates from different genera with enhanced desaturase activity across different substrates. This work broadens the scope of biocatalytic applications for OYEs, introducing a novel approach to the synthesis of chiral α,β‐unsaturated carbonyl compounds.