Organic Precursors Research Articles

Cost-effective synthesis of stable CoxC@few-layered graphene nanostructures embedded in a carbon matrix

In this study, a two-step surfactant sol-gel strategy is developed to synthesize Co particles with confined sizes in the nanoscale using organic precursors. This approach does not require the use of vacuum techniques or strong reducing atmospheres, making it a simple approach economically attractive. The strategy involves the generation of few-layered graphene shells to provide chemical stability, prevent oxidation and aggregation tendencies. Additionally, the study investigates the use of precursors based on nitrates and acetates, exploring their structural and magnetic properties in densified samples. Remarkably, magnetic properties are competitive for both approaches, with coercivities reaching up to 300 Oe and saturation magnetization of ∼60 and ∼80 emu/g for samples based on nitrates and acetates prepared at 650 °C, respectively. However, it is observed that smaller and more uniformly sized nanoparticles (around ∼10 nm) are obtained with nitrate-based precursors due to an effective ligand decomposition process. Therefore, this chemical approach offers effective nanoscale confinement with intriguing magnetic properties through a cost-effective and reproducible synthesis.

Innovative porous organic polymer incorporating ferrocene and s-triazine: An effective method for converting nitroarenes to benzimidazoles using visible light

The study introduces a novel porous organic polymer, FeII(Cp)2-POP, synthesized from ferrocene and s-triazine, and characterized through various analytical techniques such as FT-IR, Raman, XRD, XPS, UV–visible, SEM, HR-TEM, EDX, BET surface area analysis, TGA, photocurrent measurements, EIS, and CV. This photocatalyst exhibits reusability, contributing to by-products reduction and resource efficiency. The sustainable methodology adheres to green chemistry principles, promoting eco-friendly synthetic approaches. FeII(Cp)2-POP was utilized in the photocatalytic reduction of nitroarenes to anilines, essential organic chemistry precursors, using N2H4 and visible-light activation under mild conditions. The incorporation of porous organic polymers with a ferrocene framework displayed promising outcomes in enhancing the reduction of nitroarene compounds, with a focus on reducing the nitro-functional group in benzimidazole-based compound.

Online headspace monitoring of volatile organic compounds using proton transfer reaction-mass spectrometry: Application to the multiphase atmospheric fate of 2,4-hexadienedial

Chemical processes in clouds have been suggested to contribute significantly to the mass of organic aerosol particles in the atmosphere. Experimental and theoretical evidence suggest that organic mass production in clouds can be substantial and depends on the concentration of organic precursor compounds available in the gas phase. The present study aims at studying the aqueous phase reactivity of one of these overlooked precursors, i.e. 2,4-hexadienedial, an important and toxic intermediate in the atmospheric oxidation of aromatic species. Cautious synthesis and purification of 2,4-hexadienedial was performed. Its effective Henry's law constant was measured using a new simple and fast method based on online flow-injection analysis. The reactivity of 2,4-hexadienedial in the aqueous phase relevant to atmospheric conditions was studied, including hydrate formation, photolysis, ∙OH- and SO4∙--oxidation as well as reaction with NH3. The results revealed a low hydration constant compared to other dicarbonyls (Khyd1 = 7 × 10−2) and no dihydrate formation, indicating in an intermediate solubility (KH = 1.0 × 104 M atm−1) and high absorption cross sections (σ278nm > 10−16 cm2 molecule−1). Compared to its gas phase photolysis, its aqueous phase photolysis showed low quantum yields (Φ290–380nm = 0.9 %), and a significant red shift of the absorbance maximum, leading to a fast aqueous photolysis kinetics (Jaq,atm = 8.7 × 10−5 s−1) under atmospheric solar radiation, but no triplet state formation was detected. Radical oxidation experiments revealed extremely rapid oxidation kinetics (k∙OH = 1.10 × 1010 M−1 s−1 and kSO4∙- = 1.4 × 109 M−1 s−1) driven by fast addition of the radicals to the unsaturated bonds. In contrast, the reaction with aqueous NH3 (kNH3 = 2.6 × 10−3 M−1 s−1) was found slower than glyoxal and 2-butenedial, likely due to the hyperconjugation of 2,4-hexadienedial. Using these new data complemented with assumed aqueous phase kinetics (for NO3, 3C* and 1O2 reactions) and previous gas-phase kinetic ones, the multiphase atmospheric fate of 2,4-hexadienedial was established under atmospheric conditions reported from previous field measurements and models. The results revealed a short day lifetime (∼1 h) and a long night lifetime (>12 h). It was shown that daytime atmospheric chemistry of 2,4-hexadienedial can be influenced by aqueous-phase reactivity during cloud events, up to ∼50 % under thick cloud conditions (Liquid Water Content >2000 g/m3), indicating that even a compound of intermediate solubility can be strongly affected by condensed-phase reactivity. Besides its fast aqueous phase reactivity towards ∙OH and photolysis, its daytime condensed-phase reactivity may be driven by reactions with dissolved triplet states (3C*), up to 35 %, highlighting the need to study further the kinetics, the nature and concentrations of dissolved 3C* under various atmospheric conditions. In addition, the molecular properties and atmospheric behavior of 2,4-hexadienedial were found different from those of glyoxal and 2-butenedial, highlighting the need for detailed atmospheric reactivity studies of polyfunctional compounds, in particular unsaturated compounds.

Steering sp-Carbon Content in Graphdiynes for Enhanced Two-Electron Oxygen Reduction to Hydrogen Peroxide.

Compared to sp2-hybridized graphene, graphdiynes (GDYs) composed of sp and sp2 carbon are highly promising as efficient catalysts for electrocatalytic oxygen reduction into oxygen peroxide because of the high catalytic reactivity of the electron-rich sp-carbon atoms. The desired catalytic capacity of GDY, such as catalytic selectivity and efficiency, can theoretically be achieved by strategically steering the sp-carbon contents or the topological arrangement of the acetylenic linkages and aromatic bonds. Herein, we successfully tuned the electrocatalytic activity of GDYs by regulating the sp-to-sp2 carbon ratios with different organic monomer precursors. As the active sp-carbon atoms possess electron-sufficient π orbitals, they can donate electrons to the lowest unoccupied molecular orbital (LUMO) orbitals of O2 molecules and initiate subsequent O2 reduction, GDY with the high sp-carbon content of 50 at % exhibits excellent capability of catalyzing O2 reduction into H2O2. It demonstrates exceptional H2O2 selectivity of over 95.0 % and impressive performance in practical H2O2 production, Faraday efficiency (FE) exceeding 99.0 %, and a yield of 83.3 nmol s-1 cm-2. Our work holds significant importance in effectively steering the inherent properties of GDYs by purposefully adjusting the sp-to-sp2 carbon ratio and highlights their immense potential for research and applications in catalysis and other fields.

Steering sp‐Carbon Content in Graphdiynes for Enhanced Two‐Electron Oxygen Reduction to Hydrogen Peroxide

AbstractCompared to sp2‐hybridized graphene, graphdiynes (GDYs) composed of sp and sp2 carbon are highly promising as efficient catalysts for electrocatalytic oxygen reduction into oxygen peroxide because of the high catalytic reactivity of the electron‐rich sp‐carbon atoms. The desired catalytic capacity of GDY, such as catalytic selectivity and efficiency, can theoretically be achieved by strategically steering the sp‐carbon contents or the topological arrangement of the acetylenic linkages and aromatic bonds. Herein, we successfully tuned the electrocatalytic activity of GDYs by regulating the sp‐to‐sp2 carbon ratios with different organic monomer precursors. As the active sp‐carbon atoms possess electron‐sufficient π orbitals, they can donate electrons to the lowest unoccupied molecular orbital (LUMO) orbitals of O2 molecules and initiate subsequent O2 reduction, GDY with the high sp‐carbon content of 50 at % exhibits excellent capability of catalyzing O2 reduction into H2O2. It demonstrates exceptional H2O2 selectivity of over 95.0 % and impressive performance in practical H2O2 production, Faraday efficiency (FE) exceeding 99.0 %, and a yield of 83.3 nmol s−1 cm−2. Our work holds significant importance in effectively steering the inherent properties of GDYs by purposefully adjusting the sp‐to‐sp2 carbon ratio and highlights their immense potential for research and applications in catalysis and other fields.

Chiral-induced synthesis of chiral covalent organic frameworks core-shell microspheres for HPLC enantioseparation.

Twochiral covalent organic frameworks (CCOFs) core-shell microspheres based on achiral organic precursors by chiral-induced synthesis strategy for HPLC enantioseparationare reported for the first time. Using n-hexane/isopropanol as mobile phase, various kinds of racemates were selected as analytes and separated on the CCOF-TpPa-1@SiO2 and CCOF-TpBD@SiO2-packed columns with a low column backpressure (3 ~ 9bar). The fabricated two CCOFs@SiO2 chiral columns exhibited good separation performance towards various racemates with high column efficiency (e.g., 19,500 plates m-1 for (4-fluorophenyl)ethanol and 18,900 plates m-1 for 1-(4-chlorophenyl)ethanol) and good reproducibility. Some effects have been investigated such as the analyte mass and column temperature on the HPLC enantioseparation. Moreover, the chiral separation results of the CCOF-TpPa-1@SiO2 chiral column and the commercialized Chiralpak AD-H column show a good complementarity. This study demonstrates that the usage of chiral-induced synthesis strategy for preparing CCOFs core-shell microspheres as a novel stationary phase has a good application potential in HPLC.

Hybrid Two‐Step Inkjet‐Printed Perovskite Solar Cells

Perovskite photovoltaics are on their way to commercialization, but crucial advancements are still required to realize scalable and reliable fabrication processes Concerning solution processing of perovskite top solar cells, the hybrid two‐step process offers an auspicious combination of good thin‐film formation control, even on textures, and high power conversion efficiencies (PCEs). Herein, a scalable fabrication process that consists of a hybrid two‐step process and combines evaporated PbI2 with inkjet‐printed organic precursor materials is addressed. It is shown that optimizing the printing parameters enables high PCEs, high reproducibility, and the potential for conformal growth on textured silicon. The perovskite films are free of macroscopic drying effects and omit the use of toxic solvents. To achieve optimal conversion, the morphology of the PbI2 thin film and the selected resolution in the printing process are decisive. To facilitate intermixing and enable stoichiometry, a dimethyl sulfoxide vapor treatment is introduced to increase the PbI2 porosity. Reproducible PCEs are demonstrated with champion devices showing 18.2% which are on par with spin‐coated counterparts. In the results, it is demonstrated that the hybrid two‐step process with an inkjet‐printed second step is a promising scalable process for reliable and high‐quality perovskite deposition even on texture, thereby paving the path toward industrialization.

Embedding Perovskite in Polymer Matrix Achieved Positive Temperature Response with Inversed Temperature Crystallization

Organic perovskites are promising semiconductor materials for advanced photoelectric applications. Their fluorescence typically shows a negative temperature coefficient due to bandgap change and structural instability. In this study, a novel perovskite‐based composite with positive sensitivity to temperature was designed and obtained based on its inverse temperature crystallization, demonstrating good flexibility and solution processability. The supercritical drying method was used to address the limitations of annealing drying in preparing high‐performance perovskite. Optimizing the precursor composition proved to be an effective approach for achieving high fluorescence and structural integrity in the perovskite material. This perovskite‐based composite exhibited a positive temperature sensitivity of 28.563% °C−1 for intensity change and excellent temperature cycling reversibility in the range of 25–40 °C in an ambient environment. This made it suitable for use as a smart window with rapid response. Furthermore, the perovskite composite was found to offer temperature‐sensing photoluminescence and flexible processability due to its components of perovskite‐based compounds and polyethylene oxide. The organic precursor solvent could be a promising candidate for use as ink to print or write on various substrates for optoelectronic devices responding to temperature.

Metabolomics reveals how ethylene‐auxin interaction delays tomato ripening maintaining fruit nutritional and sensorial quality

SummaryThe antagonistic roles of ethylene and auxin are well established, although the exact role of auxin in ripening regulation remains unclear. A metabolomic approach can be a strategy to understand the role of this phytohormone in improving tomato quality. This study used metabolomic approaches to investigate how the interaction between ethylene and auxin affects tomato fruit nutritional and sensorial quality, with a particular emphasis on aroma metabolites. Tomato (Solanum lycopersicum cv. Micro‐Tom) fruits were randomly grouped according to treatment with ethylene (ETHY), auxin (IAA), or both (ETHY + IAA) phytohormones. Fruits without treatment were grouped in CTRL. Ethylene and auxin treatments affected carbohydrates (fructose, sucrose, and glucose), organic acids (citric and malic acids), and amino acids (valine, asparagine, and GABA), with the main volatile organic compounds precursors positively impacting ETHY + IAA aroma compounds. In conclusion, the comparison of metabolome profiles suggests that auxin regulation may overlap the ethylene regulatory system. Furthermore, tomato fruits treated with both phytohormones maintained metabolic profiles similar to those of untreated fruits in delayed ripening conditions, besides the improved tomato aroma.

Graphene Oxide‐Assisted Molecular Crystal Co‐Assembly for Large‐Scale Freestanding 2D Photoresponse Heterostructures with Synaptic Plasticity

Abstract2D van der Waals heterostructures (2D vdWHs) have been gaining significant attention in neuromorphic electronics. However, the facile synthesis of large‐scale, high‐quality freestanding 2D vdWHs remains challenge, particularly for organic counterparts due to susceptible nucleation behaviors and weak intermolecular interactions. Here, the study reports a graphene oxide (GO)‐assisted molecular crystal co‐assembly method for one‐step growth of centimeter‐scale freestanding heterostructures. This co‐assembly involves the simultaneous assembling of organic and GO precursors at the liquid–liquid interface, where the amphiphilic nature of GO nanosheets facilitates the diffusion of organic molecules and 2D nucleation of organic crystals, and the nanosheets also become enriched to grow a quasi‐solid film for the bilayer formation. Owing to integrated photosensitive and charge‐trapping properties as well as type II band structure, this heterostructure exhibits exceptional photonic synaptic behaviors, with a paired‐pulse facilitation index of 141% and image recognition of 91%.

Incremental Feeding of Perovskite Powders: Angstrom‐Precision Growth for Single‐Source Solar Cell Fabrication

Vacuum‐based deposition of halide perovskites receives a lot of attention for its proven scalability and conformal depositions. Co‐evaporation has remarkable success, but efficiencies continue to lag behind their solution‐based counterparts. This is in part attributed to the complex sublimation behavior of some organic ammonium precursor salts and the increased complexity of the absorber materials, requiring the use of four or more sources in a conventional co‐evaporation setup. The latter has driven work into single‐source methods with flash evaporation presented as one such method. However, flash evaporation processes typically evaporate all material in a single batch, leading to short deposition times at high temperatures. Particle sputtering effects seen at these high temperatures drive processes toward low temperatures where prolonged exposure causes degradation. Here, a pulse‐driven incremental powder feeding system is presented. This method is capable of stable flash evaporation rates for >1 h, with controlled rates as low as 1.5 Å per pulse (±0.89). The feasibility of this method is demonstrated for three different perovskite compositions: FAPbBr3, MAPbI3, and FA1−xMAxPbSnI3:SnF2. Furthermore, FAPbBr3 and MAPbI3 are integrated into all vacuum‐processed thin‐film solar cells leading to power conversion efficiencies (PCE) of ~4% and 10%, respectively.

Reaction mechanisms of α,ω-bifunctional molecules toward atomic layer deposition versus molecular layer deposition

Atomic layer deposition (ALD) and molecular layer deposition (MLD) are key techniques used to fabricate high-quality thin films. Organic α,ω-bifunctional precursors often exhibit different growth behaviors depending on the functional groups as well as the chain length of the molecular backbone, so that some organic precursors produce thin films of organic-inorganic hybrid materials, while others may deposit purely inorganic thin films without incorporation of the hydrocarbon moiety. In this study, we investigated the surface reaction mechanisms of α,ω-bifunctional molecules (X(CH2)nX, n = 2, 3, 4, 5, 6, and X = OH, SH, NH2) with diethylzinc toward MLD and ALD using density functional theory (DFT) calculations. It was found that the length of the aliphatic alkyl chain and the terminal functional groups of bifunctional organic precursors significantly influences their reactivity, resulting in the possibility toward removal or incorporation of the organic moiety in the product. Bifunctional reactants with longer alkyl backbones (n > 4) showed higher reactivity for removal of the hydrocarbon chain, facilitated by a ω-2 hydrogen transfer reaction. Furthermore, a reactivity trend of SH > OH > NH2 for removal of the hydrocarbon chains was observed. Our study provides in-depth theoretical insights into the adsorption reaction mechanisms occurring when bifunctional molecules are employed as organic reactants in ALD and MLD processes.

Diversity in Atomic Structures of Zeolite-Templated Carbons and the Consequences for Macroscopic Properties.

Zeolite-templated carbons (ZTCs) are a family of ordered microporous carbons with extralarge surface areas and micropore volumes, which are synthesized by carbon deposition within the confined spaces of zeolite micropores. There has been great controversy regarding the atomic structures of ZTCs, which encompass two extremes: (1) three-dimensionally connected curved open-blade-type carbon moieties and (2) ideal tubular structures (commonly referred to as "Schwarzites"). In this study, through a combination of experimental analyses and theoretical calculations, we demonstrate that the atomic structure of ZTCs is difficult to define as a single entity, and it widely varies depending on their synthesis conditions. Carbon deposition using a large organic precursor and low-temperature framework densification generates ZTCs predominantly composed of open-blade-type moieties, characterized by low surface curvature and abundant H-terminated edge sites. Meanwhile, synthesis using a small precursor with high-temperature densification produces ZTCs with an increased portion of closed-strut carbon moieties (or closed-fullerene-like nodes), exhibiting large surface curvature and diminished edge sites. The variations in the atomic structure of ZTCs result in significant differences in their macroscopic properties, such as N2/CO2 adsorption, oxidative stability, work function, and electrocatalytic properties, despite the presence of comparable pore structures. Therefore, ZTCs demonstrate the potential to synthesize ordered nanoporous carbons with tunable physicochemical properties.

FACILE SYNTHESIS OF ORGANOSILOXANE-MODIFIED HYDROPHOBIC GEOPOLYMER THROUGH PEPTIZATION OF POLYDIMETHYLSILOXANE

We report a scalable, facile synthetic process for hydrophobic geopolymer containing organosilane. Using polydimethylsiloxane (PDMS) as an organic precursor, the surface of sodium and potassium geopolymers of varying precursor composition was functionalized with degraded PDMS oligomers by first partially hydrolyzing PDMS in a hot, concentrated NaOH or KOH solution and subsequently by undergoing geopolymer synthesis with metakaolin. Both types of geopolymer yielded nonporous hydrophobic materials with external surface areas of 0.6475 and 4.342 m2/g for sodium and potassium geopolymer, respectively. The materials showed an oil capacity of 75 and 134 wt%, respectively. X-ray diffraction patterns of the samples indicate that the PDMS functionalized sodium geopolymers contain zeolite A and sodalite, while the potassium geopolymers were amorphous with two overlapping broad humps in contrast to the typical geopolymers.

Tuning Germanane Band Gaps via Cyanoethyl Functionalization for Cutting-Edge Photoactive Cathodes: Photoenhanced Hybrid Zinc-Ion Capacitor Evaluation.

Energy harvesting and storing by dual-functional photoenhanced (photo-E) energy storage devices are being developed to battle the current energy hassles. In this research work, our investigations on the photoinduced efficiency of germanane (Ge-H) and its functionalized analogue cyanoethyl (Ge-C2-CN) are assessed as photocathodes in photo-E hybrid zinc-ion capacitors (ZICs). The evaluated self-powered photodetector devices made by these germanene-based samples revealed effective performances in photogenerated electrons and holes. The photo-E ZICs findings provided a photoinduced capacitance enhancement of ∼52% (for Ge-H) and ∼26% (for Ge-C2-CN) at a scan rate of 10 mV s-1 under 100 mW cm-2 illumination with 435 nm wavelength. Further characterizations demonstrated that the photo-E ZIC with Ge-C2-CN supply higher specific capacitance (∼6000 mF g-1), energy density (∼550 mWh kg-1), and power density (∼31,000 mW kg-1), compared to the Ge-H. In addition, capacitance retention of photo-E ZIC with Ge-C2-CN is ∼91% after 3000 cycles which is almost 6% greater than Ge-H. Interestingly, the photocharging voltage response in photo-E ZIC made by Ge-C2-CN is 1000 mV, while the photocharging voltage response with Ge-H is approximately 970 mV. The observed performances in Ge-H-based photoactive cathodes highlight the pivotal role of such two-dimensional materials to be applied as single architecture in new unconventional energy storage systems. They are particularly noteworthy when compared to the other advanced photo-E supercapacitors and could even be enhanced greatly with other suitable inorganic and organic functional precursors.

Vertical heterogeneity of Gulong shale oil governed by the OM precursors and oil accumulation: Implications for shale oil exploration in the Songliao Basin, Northeastern China

Shale oil has been discovered and produced in the Cretaceous Qingshankou Formation (K2qn) of the Gulong sag in the Songliao Basin (the Gulong shale oil). However, the selection of favorable layers for shale oil development remains uncertain due to significant variations in oil production of different intervals in the Formation (Q1–Q9). In this study, the geochemical features of shale, the content and chemical features of extracted oils in different shale intervals are analyzed in detail, and the favorable intervals and mechanism for shale oil accumulation are also addressed. It is shown that the Gulong shale has total oil contents of 200–400 mg/g TOC with considerable contents of light hydrocarbons in extracted oils. In the shale, there is a “W” trend for the evolution of chemical and carbon isotopic compositions (δ13C) of shale oil with depth. It is deduced that this evolution trend of shale oil is governed by the variation of organic matter precursor associated with the deposition environment. The distributions of δ13C of mud gas and individual n-alkanes with depth reveal that the Gulong shale oil can be separated as two independent petroleum systems at the Middle–Lower Q7. Mass balance calculations imply Q2–Q3 and Q8–Q9 are two intervals with lower oil expulsion efficiency. Combined with the morphology of calcite cements and veins as well as the homogenization temperature of inclusions, an intralayer accumulation model of the Gulong shale oil was established. In addition, the statistical analysis of the oil content, lithological properties, and oil production capacity of different layers from 95 wells, demonstrates that Q2–Q3 and Q8–Q9 can be selected as the preferential target layers for future development of the Gulong shale oil. More importantly, this study may provide new insights into the enrichment of shale oil with tight shale type in China and around the world.

Probing the Reactivity of ZnO with Perovskite Precursors.

To achieve more stable and efficient metal halide perovskite devices, optimization of charge transport materials and their interfaces with perovskites is crucial. ZnO on paper would make an ideal electron transport layer in perovskite devices. This metal oxide has a large bandgap, making it transparent to visible light; it can be easily n-type doped, has a decent electron mobility, and is thought to be chemically relatively inert. However, in combination with perovskites, ZnO has turned out to be a source of instability, rapidly degrading the performance of devices. In this work, we provide a comprehensive experimental and computational study of the interaction between the most common organic perovskite precursors and the surface of ZnO, with the aim of understanding the observed instability. Using X-ray photoelectron spectroscopy, we find a complete degradation of the precursors in contact with ZnO and the formation of volatile species as well as new surface bonds. Our computational work reveals that different pristine and defected surface terminations of ZnO facilitate the decomposition of the perovskite precursor molecules, mainly through deprotonation, making the deposition of the latter on those surfaces impossible without the use of passivation.

Copper oxides supported sulfur-doped porous carbon material as a remarkable catalyst for reduction of aromatic nitro compounds

Synthesis and manufacturing of metal–organic framework derived carbon/metal oxide nanomaterials with an advisable porous structure and composition are essential as catalysts in various organic transformation processes for the preparation of environmentally friendly catalysts. In this work, we report a scalable synthesis of sulfur-doped porous carbon-containing copper oxide nanoparticles (marked CuxO@CS-400) via direct pyrolysis of a mixture of metal–organic framework precursor called HKUST-1 and diphenyl disulfide for aromatic nitro compounds reduction. X-ray diffraction, surface area analysis (BET), X-ray energy diffraction (EDX) spectroscopy, thermal gravimetric analysis, elemental mapping, infrared spectroscopy (FT-IR), transmission electron microscope, and scanning electron microscope (FE-SEM) analysis were accomplished to acknowledge and investigate the effect of S and CuxO as active sites in heterogeneous catalyst to perform the reduction-nitro aromatic compounds reaction in the presence of CuxO@CS-400 as an effective heterogeneous catalyst. The studies showed that doping sulfur in the resulting carbon/metal oxide substrate increased the catalytic activity compared to the material without sulfur doping.

Nitrite Attenuates the In Vitro Inflammatory Response of Immune Cells to the SARS-CoV-2 S Protein without Interfering in the Antioxidant Enzyme Activation.

SARS-CoV-2 induces a hyperinflammatory reaction due to the excessive release of cytokines during the immune response. The bacterial endotoxin lipopolysaccharide (LPS) contributes to the low-grade inflammation associated with the metabolic syndrome, enhancing the hyperinflammatory reaction induced by the SARS-CoV-2 infection. The intake of sodium nitrate, a precursor of nitrite and nitric oxide, influences the antioxidant and pro-inflammatory gene expression profile after immune stimulation with LPS in peripheral blood mononuclear cells from metabolic syndrome patients. We aimed to assess the inflammatory and antioxidant responses of immune cells from metabolic syndrome patients to exposure to the SARS-CoV-2 spike protein (S protein) together with LPS and the effect of nitrite in these responses. Whole blood samples obtained from six metabolic syndrome patients were cultured for 16 h at 37 °C with four different media: control medium, control medium plus LPS (100 ng/mL), control medium plus LPS (100 ng/mL) plus S protein (10 ng/mL), and control medium plus LPS (100 ng/mL) plus S protein (10 ng/mL) plus nitrite (5 µM). Immune stimulation with the LPS/S protein enhanced nitrate biosynthesis from nitrite oxidation and probably from additional organic precursors. In vitro incubations with the LPS/S protein enhanced the expression and/or release of pro-inflammatory TNFα, IL-6, IL-1β, and TLR4, as well as the expression of the anti-inflammatory IL-1ra and IL-10 and antioxidant enzymes. Nitrite attenuated the pro- and anti-inflammatory response induced by the S protein without interfering with the activation of TLR4 and antioxidant enzyme expression, raising the possibility that nitrite could have potential as a coadjutant in the treatment of COVID-19.

Application of EEM fluorescence spectroscopy for characterizing organic DBP precursors in different water sources: a review

Abstract Disinfection by-products (DBPs), generated from the reaction of disinfectants with DBP precursors, have been found to pose unintentional risks to human health. Considering that the concentration and speciation of DBPs formed during disinfection will be affected by the content and composition of dissolved organic matter (DOM), widespread concern about the characteristics of DBP precursors in water sources have been prompted. Three-dimensional excitation–emission matrix (EEM) can quickly and efficiently determine the properties and composition of DOM in water, and thus is generally used to investigate the origin of DBP precursors in water sources. This study overviews the fluorescent properties of different DBP precursors, summarizes the application of different EEM interpretation methods in DBP precursors and analyses the key factors affecting the correlation between the fluorescent components and DBP precursors (e.g., natural organic matter, algal organic matter, effluent organic matter and organic matter derived from other sources). A series of factors, including composition of fluorophores, bromide concentration, spatio-temporal characteristics and disinfectant types, could impact the correlation between DBP formation potential and fluorescent components. As for future research needs, it is of significance to select suitable fluorescence analysis methods and investigate the combination of EEM with other characterization technologies based on different situations.