Formation Of Phenol Research Articles

Phenolic compounds and spare carbohydrates content dynamics in seeds of the invasive species Acer negundo and the native species Acer tataricum in connection with their competitiveness in biocenoses

Changes in the content of various phenolic carboxylic acids (FCC) – chlorogenic (HC), caffeic (CC), ferulic (FC), as well as the amounts of flavonoids and spare carbohydrates (monosaccharides, polysaccharides and starch) in the tissues of Acer tataricum and Acer negundo seed embryos (indigenous and invasive species, respectively) during their storage were studied from October to March (cold chamber, t° = +5°C, humidity 80%). There was a significant increase in the content of HC and the absence of CC in December-January in an aboriginal species with a long dormant period. In the invasive species A. negundo, which does not have a rest period, the level of HC also increased, but was ten times lower than in A. tataricum, while a high level of CC was identified. In terms of flavonoid content, the native species A. tataricum is ten times superior to the invasive A. negundo. The carbohydrate content in A. tataricum was about 40%, and in the tissues of A. negundo seed embryos about 15% and did not change during the entire storage period. The dynamics of the content of phenolic compounds and forms of spare carbohydrates, their relationship with the activation of metabolic processes and protective anti-stress mechanisms during the cold storage of seeds and competitiveness in biocenoses are discussed.

Mitochondria-Targeted NIR Ratiometric and Colorimetric Fluorescent Probe for Biothiols Based on a Thiol-Chromene Click Reaction.

In this work, a mitochondria-targeted NIR ratiometric and colorimetric fluorescent probe 1 was tactfully designed and synthesized by a novel design strategy of modifying chromene to pyridine for the first time. 1 exhibited a maximum absorption peak at 508 nm and a maximum fluorescence emission peak at 650 nm. Under the stimulus of biothiols (cysteine (Cys), homocysteine (Hcy), and glutathione (GSH)), the maximum absorption and fluorescence emission peaks of 1 blue-shifted to 448 and 541 nm, respectively, along with color changes from red to yellow under visible light and from red to green under a 365 nm ultraviolet (UV) lamp, which can be ascribed to the click reaction of biothiols with the α,β-unsaturated ketone of the chromene moiety with pyran ring-opening, phenol formation, and 1,6-elimination of the p-hydroxybenzyl moiety. 1 detected biothiols (Cys, GSH, and Hcy) with high sensitivity (LODs of 29, 23, and 16 nM for Cys, GSH, and Hcy, respectively), excellent selectivity, and fast response. Moreover, 1 can target mitochondria and image the fluctuation of intracellular biothiols by dual-emission channels.

Efficient Electrocatalytic Hydrodechlorination and Detoxification of Chlorophenols by Palladium-Palladium Oxide Heterostructure.

Electrocatalytic hydrodechlorination is a promising approach for simultaneous pollutant purification and valorization. However, the lack of electrocatalysts with high catalytic activity and selectivity limits its application. Here, we propose a palladium-palladium oxide (Pd-PdO) heterostructure for efficient electrocatalytic hydrodechlorination of recalcitrant chlorophenols and selective formation of phenol with superior Pd-mass activity (1.35 min-1 mgPd-1), which is 4.4 times of commercial Pd/C and about 10-100 times of reported Pd-based catalysts. The Pd-PdO heterostructure is stable in real water matrices and achieves selective phenol recovery (>99%) from the chlorophenol mixture and efficient detoxification along chlorophenol removal. Experimental results and computational modeling reveal that the adsorption/desorption behaviors of zerovalent Pd and PdO sites in the Pd-PdO heterostructure are optimized and a synergy is realized to promote atomic hydrogen (H*) generation, transfer, and utilization: H* is efficiently generated at zerovalent Pd sites, transferred to PdO sites, and eventually consumed in the dechlorination reaction at PdO sites. This work provides a promising strategy to realize the synergy of Pd with different valence states in the metal-metal oxide heterostructure for simultaneous decontamination, detoxification, and resource recovery from halogenated organic pollutants.

Spectroscopic and Computational Study of Vanillin-Dipyrrin Ligand that Capable of Colorimetric Sensor for Zinc and Copper Ions

Phenolic-dipyrrin is a promising colorimetric chemosensor due to its tautomeric formation (phenolic-hemiquinone forms). In methanol solution, the vanillin-dipyrrin compound exists as a hemiquinone species, whereas the complexes exist in a phenolic form. This molecule showed a red-magenta color in methanol, in contrast to yellowish allyl-protected-dipyrrin. In the presence of zinc or copper ions, the vanillin-dipyrrin solution turned into a pale-yellow complex, similar to that of protected-dipyrrin. A computational study of the ligands and complexes showed a close relevance, where the energy transition between the highest molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the ligand in the hemiquinone form had a lower energy transition, and the two complexes showed slightly different transition energies. Apart from naked-eye color changes, vanillin-dipyrrin showed limits of detection of 9.2 × 10–7 M and 4.8×10−7 M for zinc and copper ions, respectively.

Synthesis and characterizations of a novel trans-Pd(O,N)2 complex with an AZO-dye ligand: Crystal structure, theoretical studies and DNA binding interactions

The transition metal-azo dye complexes have attracted attention in both fundamental and applied research due to their electronic and structural properties, particularly due to their potential to yield new compounds with diverse biological activities and anticancer agents. A novel square planar-trans-Pd(O,N)2 was synthesized with a high yield utilizing a one-pot approach employing (E)-methyl 2-((2-hydroxynaphthalen-1-yl)diazenyl)benzoate as the AZO-dye ligand. In order to analyze their structure and understand their properties. The desired complex was characterized using FT-IR, UV–Vis, NMR, and CHN-EA techniques. Subsequently, theoretical modeling of the complex was performed using MEP/MAC/NPA methodologies. Two methodologies were employed to monitor the coordination process of AZO-ligand with Pd(II): UV–Vis absorption and FT-IR spectrum analysis. The TD-DFT and DFT/IR behaviors were simultaneously assessed to compare the experimental results with theoretical predictions. Furthermore, both SC-XRD and DFT analysis demonstrated that the deprotonated phenolic diazene form of the AZO-ligand attached to the Pd(II) center by utilizing one nitrogen atom of the AZO-ligand and the ionic oxygen of the phenol. The SC-XRD analysis verified the presence of a slightly distorted square-planar geometry around the PdII center in the neutral trans-Pd(O,N)2 complex. All of the oxygen atoms in the complex participated in non-classical C-H….O hydrogen bonding, leading to the formation of novel edge-fused rings R22(24) and R22(12) synthons. These synthons create a 3D-network with a linked parallel matrix. Interestingly, Hirshfeld surface analysis (HSA) stimulation revealed many hot sites on the complex surface, confirming the formation of strong non-classical [C-H....O] interactions. From the observed docking behavior with the DNA, it can be concluded that the trans-Pd(O,N)2 showed superior binding compared to the free AZO-ligand. The results of this work are a contribution to the study of this class of metal complexes and their physicochemical properties and offer promising perspectives for the realization of new works.

Comparison of the pyrolysis behavior of PC, ABS and PC/ABS

Three types of plastics—polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), and PC/ABS blend—were studied in this work. Kinetic analyses were performed using the Flynn-Wall-Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. The evolved volatiles during the pyrolysis of each material were analyzed, and the pyrolysis behavior was proposed using in-situ tools such as thermogravimetric analyzer-Fourier transform infrared spectroscopic (TG-FTIR) and gas chromatographic separation and mass spectrometry detection (Py-GC/MS). The three samples were also pyrolysed in a fixed bed reactor to elucidate the impact of secondary reaction. For PC, the activation energy increases as the reaction progresses. PC primarily generated CO2 and oxygenated compounds. For ABS, the activation energy experienced a slight decrease once the depolymerization reaction initiates, while a reversed trend can be observed at higher conversion rates. ABS pyrolysis mainly produced nitrogen-containing compounds and mono-aromatics. In the case of PC/ABS blend, a distinctive two-stage decomposition mechanism was observed. The interaction between PC and ABS in the blend promoted the formation of N/O-containing compounds. Additionally, this interaction enhanced the production of lighter phenols at the expense of bisphenol A, while ABS was not affected markedly. Stronger re-condensation and cracking reactions in the fixed bed system, facilitated the formation of poly-aromatics and lighter phenols (p-cresol and 4-ethylphenol) at the expense of bisphenol A during the pyrolysis of PC. In contrast, styrene from ABS decomposition was weakly affected by the secondary reaction. The intensified secondary reactions occurring the sample bed of the fixed bed experiments can also enhance the interaction between volatiles from ABS and PC, forming more heterocyclic N-compounds.

Catalytic pyrolysis mechanism of lignin moieties driven by aldehyde, hydroxyl, methoxy, and allyl functionalization: the role of reactive quinone methide and ketene intermediates.

The catalytic pyrolysis of guaiacol-based lignin monomers, vanillin, syringol, and eugenol over commercial HZSM-5 has been investigated using operando Photoelectron Photoion Coincidence (PEPICO) spectroscopy to unveil the reaction mechanism by detecting reactive intermediates, such as quinone methides and ketenes, and products. Vanillin shares the decomposition mechanism with guaiacol due to prompt and efficient decarbonylation, which allows us to control this reaction leading to a phenol selectivity increase by switching to a faujasite catalyst and decreasing the Si/Al ratio. Syringol first demethylates to 3-methoxycatechol, which mainly dehydroxylates to o- and m-guaiacol. Ketene formation channels over HZSM-5 are less important here than for guaiacol or vanillin, but product distributionremains similar. C3 addition to guaiacol yields eugenol, which shows a more complex product distribution upon catalytic pyrolysis. By analogies to monomers with simplified functionalization, namely allylbenzene, 4-allylcatechol, and 4-methylcatechol, the eugenol chemistry could be fully resolved. Previously postulated reactive semi-quinone intermediates are detected spectroscopically, and their involvement opens alternative pathways to condensation and phenol formation. Allyl groups, produced by dehydroxylation of the β-O-4 bond, may not only decompose via C1/C2/C3 loss, but also cyclize to indene and its derivatives over HZSM-5. This comparably high reactivity leads to an unselective branching of the chemistry and to a complex product distribution, which is difficult to control. Indenes and naphthalenes are also prototypical coke precursors efficiently deactivating the catalyst. We rely on these mechanistic insights to discuss strategies to fine-tune process conditions to increase the selectivities of desired products by enhancing either vanillin and guaiacol or supressing eugenol yields from native lignin.

Catalytic conversion of biomass pyrolysis volatiles over composite catalysts of activated carbon and HY zeolite

Bio-oil has complex compositions and high oxygen content, which restricts its high-value utilization. Commercial activated carbon (AC) and HY zeolite were used as composite catalysts to study their effect on pyrolysis volatiles from rice straw and poplar sawdust by changing the mixing modes of two catalysts. The results showed that the loading modes of AC and HY zeolite obviously affected the products distribution and bio-oil components. The lowest yield of bio-oil was obtained when HY zeolite and AC were mechanically mixed at a mass ratio of 1:1 (YACM). But the loading mode of YACM was beneficial to the deoxidation and aromatic hydrocarbon generation. Under the mode of YACM, the aromatics content in rice straw and poplar sawdust bio-oil can be increased from 13.8% and 8.0% without catalyst to 56.4% and 53.1%, respectively. However, the layered loading with upper HY zeolite and lower AC (YTACL) was favorable for formation of phenolic compounds. The selectivity to monocyclic and bicyclic aromatic hydrocarbons followed the order of YTACL > ACTYL > YACM, and YACM > ACTYL > YTACL, respectively. Compared with HY zeolite, AC catalyst possessed smaller pore size and fewer acidity, and the active sites of AC were conducive to rearrangement of furan compounds to generate cyclopentanone, 2-cyclopentenone and methyl-cyclopentenone, and further rearrangement to form phenol. Therefore, the loading mode of YTACL exhibited a promotion effect on the formation of phenol, cresol, toluene, ethylbenzene and p-xylene. The strong acidic sites of HY zeolite were favorable for the aromatization, so the loading mode of ACTYL had good selectivity to the formation of naphthalene, methylnaphthalene, anthracene and pyrene. This work will provide a guide for products regulation from biomass pyrolysis and enrich aromatics and phenols in bio-oil.

Lactiplantibacillus plantarum inoculation enhanced the color stabilization and aroma quality of blueberry wine

Inoculation of Lactiplantibacillus plantarum before yeast has the potential to affect the blueberry wine quality. The effects of four L. plantarum strains on the anthocyanins and volatile profile of blueberry wine were studied. Different L. plantarum inoculated wines presented a great color variation, and B3 strain was able to retain more bluish hue of blueberry wine. Compared with RF wine fermented by only Saccharomyces cerevisiae yeast, L. plantarum inoculated wines exhibited a better preservation of monomeric and acylated anthocyanins. More importantly, inoculation of L. plantarum, especially for B3 and B4 strains, enhanced the accumulation of pyranoanthocyanins, which may improve the color stability of blueberry wine. In addition, inoculation with L. plantarum favored the formation of lactate-related esters, acetoin, C6 alcohols, terpenes, aldehydes, and volatile phenols. Flash-Profile analysis indicated that B3, B4 and SS6 strains conferred wines more sour and astringent tastes, along with more ‘fruity’ and ‘chemical’ aromas.

Thiol-chromene click reaction-triggered mitochondria-targeted ratiometric fluorescent probe for intracellular biothiol imaging.

Chromene as the efficient biothiol recognition site was widely used to develop fluorescent probes based on thiol-chromene click reaction. However, chromene-based fluorescent probes with the both properties of ratiometric measurement and mitochondria-targeted function have not been reported and remain challenging. In this paper, we skillfully designed and synthesized the first mitochondria-targeted ratiometric fluorescent probe (Probe 1) for biothiols based on chromene. Upon addition of biothiols (Cys, Hcy, and GSH), the absorption and fluorescence spectra of Probe 1 changed from 490 to 426nm and from 567 to 498nm respectively, accompanied by color changes from orange to pale yellow under natural light and from orange to blue under a 365-nm UV lamp, which can be attributed to the click reaction of biothiols with α,β-unsaturated ketone of chromene moiety, subsequent pyran ring-opening, and phenol formation as well as 1,6-elimination of p-hydroxybenzyl moiety. Probe 1 not only exhibited high sensitivity (LODs of 149nM, 133nM, and 116nM for Cys, GSH, and Hcy respectively), rapid response, and excellent selectivity for biothiols (Cys, Hcy, and GSH), but also could target in mitochondria and ratiometrically image the fluctuation of intracellular biothiols. Moreover, the novel design strategy of modifying chromene to the N atom of pyridine was proposed for the first time.

Maturation-induced changes in phenolic forms and their antioxidant activities of walnuts: A dual view from kernel and pellicle

The phenolic profiles and antioxidant activities during walnut maturation are not well understood. This study used UPLC-MS/MS to evaluate phenolic content in walnuts, including free, esterified, and bound forms, at different maturation stages. Findings showed that free phenolics were predominant, comprising 44.57 % in kernels and 56.54 % in pellicles. In vitro assays showed antioxidant capacity decreased with maturation, with IC50 values of 0.87–84.43 μg/mL in pellicles and 48.51–712.30 μg/mL in kernels. Most monomeric phenols decreased in concentration as the fruit ripened. OPLS-DA identified 5 and 8 maturity-sensitive phenolics (MSPs) in kernels and pellicles, respectively, with fold changes from 2.32 to 1664.72. Pearson correlation analysis showed a significant correlation between MSPs and antioxidant activity (r > 0.75, p < 0.05). Bioinformatics analysis elucidated three key metabolic pathways involved in these changes. This research provides insights into walnut phenolic composition, important for optimizing harvest practices and enhancing nutritional value.

Selective production of phenol from the end-of-life wind turbine blade through catalytic pyrolysis

This study employed catalytic pyrolysis to enhance the selectivity and yield of phenol in the pyrolysis oil derived from the end-of-life wind turbine blade (WTB). It was confirmed that the NiO(10)/Al2O3 catalyst exhibited the best activity, reaching a phenol selectivity of 28.57 % at 500 °C with a heating rate of 10 °C/min. Furthermore, a competitive phenomenon between the catalytic formation of phenol and that of gaseous products was observed. Characterization results indicated that at lower loading content of NiO on the Al2O3 carrier, NiAl2O4 crystals tended to form preferentially, which reduced catalyst activity by covering surface strong acid sites. With increasing the loading content of NiO, saturation of NiAl2O4 formation occurred, and free NiO crystals became dominant. This resulted in the creation of abundant Lewis acid sites, enhancing the catalytic formation of phenol. Whilst, excessive accumulation of free NiO crystals increased strong acid sites and significantly generated lattice oxygen, promoting the cracking of pyrolysis oil to gaseous products, which was detrimental to phenol enrichment but facilitated the production of H2-rich syngas. The conclusions offered valuable insights for upgrading pyrolysis products derived from epoxy resin polymers during the recovery of end-of-life WTB.

Hydroxylamine-driven advanced oxidation process: Impact of key environmental factors on active species, reaction pathways, and kinetics

This study investigates the Hydroxylamine (HAm)-driven Cu(II)/peroxymonosulfate (PMS) system, known for promoting toxic nitro(so)phenols formation during phenol degradation. It focuses on the intricate factors affecting nitro(so)phenols formation, aiming to unravel the complex mechanisms in the transformation of phenol to nitro(so)phenols within the HAm-Cu(II)/PMS system. Findings reveal that reaction conditions significantly impact the formation of nitro(so)phenols by affecting the phenol degradation intermediate (PhO•) and HAm oxidation reactive nitrogen species (•NO, •NO2). Additionally, the levels of specific reactants and coexisting compounds also affect the pathway of nitro(so)phenols formation. At high concentrations of HAm and halogen, the •NO and halogen radicals generated may directly oxidize phenol to produce PhO•, which in turn reacts with •NO and •NO2, and thus establishing a different nitro(so)phenols formation path from that dominated by SO4∙-. The oxidation products and driving factors of HAm vary at different stages, affecting the production of nitro(so)phenols. Moreover, the presence of halogen and natural organic matter (NOM) alters the formation of nitro(so)phenols under real water conditions compared to pure water. Overall, the investigation into various influencing factors indicates that advanced oxidation process enhanced by hydroxylamine, not just limited to persulfate-related reactions, has the potential to produce nitro(so)phenols when treating phenol-containing water.

Comparative Analysis of a Secondary Metabolite Profile from Leaves, Peel and Bulbs of Allium sativum L. by GC-MS

Garlic is a herbal plant that is widely used as a medicinal ingredient, because it contains secondary metabolite compounds such as alkaloids, flavonoids, tannins, phenols, terpenoids and saponins. The secondary metabolite content of plants is influenced by genetic, ontogenic, morphogenetic and environmental factors that can influence the biosynthesis and accumulation of secondary metabolites. Garlic is generally only used for the bulbs, while other parts such as the leaves and skin are still not widely used. This study aims to identify the secondary metabolite profile of ethanol extract of garlic leaves, bulbs and peels using the gas chromatography mass spectrometry (GC-MS) method. Identification of secondary metabolite compounds contained in each 70% ethanol extract was analyzed using the tube test, thin layer chromatography (TLC) and GC-MS methods. The results of analysis of secondary metabolite content using the tube test and TLC method showed that the ethanol extract of garlic leaves, skin and bulbs positively contained flavonoids, tannins, phenols and saponins. The results of secondary metabolite profile analysis using the GC-MS method from the ethanol extract of garlic skin and bulbs showed that 5 compounds were obtained with the main compound being 3,4-Dihydroxyphenylacetic acid and 23 compounds with the main compound being 1,2-Benzenedicaboxylic acid and palmitic acid, while the leek extract white only detected 1 compound. The conclusion is that the ethanol extract of garlic leaves, skin and bulbs has secondary metabolites in the form of flavonoids, tannins, phenols and saponins. There are differences in the profile of secondary metabolite compounds in the ethanol extract of garlic leaves, skin and bulbs in terms of the results of GC-MS analysis.

Tyrosine phenol-lyase inhibitor quercetin reduces fecal phenol levels in mice.

Tyrosine phenol-lyase (TPL), which is expressed in intestinal bacteria, catalyzes the formation of phenol from the substrate L-Tyr. Bacterial metabolite phenol and the sulfate conjugate (phenyl sulfate) are known as a type of uremic toxins, some of which exert cytotoxicity. Therefore, pathologically elevated phenol and phenyl sulfate levels are strongly implicated in the etiology and outcome of uremia. In this study, we explored the inhibitory effects of dietary polyphenols on TPL-catalyzed phenol production using a TPL activity assay. Quercetin, one of the most popular polyphenols, exhibited the strongest inhibitory activity (Ki = 19.9 µM). Quercetin competitively inhibited TPL, and its activity was stronger than that of a known TPL inhibitor (Tyr analog; 2-aza-Tyr, Ki = 42.0 µM). Additionally, quercetin significantly inhibited phenol production in TPL-expressing bacterial cultures (Morganella morganii and Citrobacter koseri) and Tyr-rich (5%) diet-fed C57BL/6J mouse feces. Our findings suggest that quercetin is the most promising polyphenol for reducing phenol levels. Because quercetin has a low gastrointestinal absorption rate, TPL inhibition in the intestinal tract by quercetin may be an effective strategy for treating uremia.

In Ukrainian

The contact wetting is one of the effective methods of studying the adsorption capacity of sorbents. The purpose of the work was to compare the experimentally obtained data on the adsorption capacity of shungite, obtained by the sessile drop method, and the results of modeling the behavior of liquid droplets on heterogeneous surfaces using the Boltzmann lattice method, and to show the suitability of the simplified version of the LBM method that we applied within the framework of a two-dimensional model for modeling complex cases of contact interaction between liquids and sorbent, when it cannot be carried out by the method of contact wetting. The adsorption properties of shungite with regard to the extraction of various impurities from water-alcohol solutions and the capability of the sorbent to recover were investigated by the method of contact wetting and analyzed by involving the data obtained by the methods of nitrogen adsorption, thermogravimetry and IR spectroscopy. It is shown that the adsorption properties of shungite are due to the presence on its surface of hydroxyl functional groups attached to carbon atoms in phenol or enol form, which give the surface hydrophilic characteristics. These groups play a key role in the adsorption of components from the liquid (aqueous) phase due to the formation of a hydrogen bond during the sorption of components from the liquid phase, and are restored after heating in the temperature range of 80–180 °C with the formation of carbon-containing gases and water. It has been found that silanol groups present in shungite do not participate in sorption. Compared to the original shungite sample, the sample after five cycles of adsorption is characterized by a noticeable effect of mass loss (1.8 %) in the temperature range of 80–180 °С. At the same time, the loss of mass is not significant at temperatures below 100 °С. This suggests that the sorbed substances are in the pores and not on the surface of shungite, and they begin to be removed only after heating above 100 °C. The LBM method was used to study fast-moving processes at the meso-level. A comparative analysis of the experimental data obtained by the method of contact wetting with the results of simulation by the Boltzmann lattice method within the framework of the two-dimensional model was carried out. 2D modeling by the LBM method turned out to be an effective means of studying capillary condensation in mesopores, anticipatory wetting of the solid phase, liquid penetration into a porous medium with different topologies, and the formation of anisotropic droplets and anisotropic bridges. The role of mesopores in the sorption process was analyzed by modeling the behavior of liquid droplets on heterogeneous surfaces and using data on the course of adsorption and capillary processes on the surface of a solid phase with different levels of porosity, roughness, and functional composition.

Dual roles of the inorganic aqueous phase on secondary organic aerosol growth from benzene and phenol

Abstract. Benzene, emitted from automobile exhaust and biomass burning, is ubiquitous in ambient air. Benzene is a precursor hydrocarbon (HC) that forms secondary organic aerosol (SOA), but its SOA formation mechanism is not well studied. To accurately predict the formation of benzene SOA, it is important to understand the gas mechanisms of phenol, which is one of the major products formed from the atmospheric oxidation of benzene. Laboratory data presented herein highlight the impact of the aqueous phase on SOA generated through benzene and phenol oxidation. The roles of the aqueous phase consist of (1) suppression of the aging of hydrocarbon and (2) conventional acid-catalyzed reactions in the inorganic phase. To explain this unusual effect, it is hypothesized that a persistent phenoxy radical (PPR) effectively forms via a heterogeneous reaction of phenol and phenol-related products in the presence of wet inorganic aerosol. These PPR species are capable of catalytically consuming ozone during an NOx cycle and negatively influencing SOA growth. In this study, explicit gas mechanisms were derived to produce the oxygenated products from the atmospheric oxidation of phenol or benzene. Gas mechanisms include the existing Master Chemical Mechanism (MCM v3.3.1), the reaction path for peroxy radical adducts originating from the addition of an OH radical to phenols forming low-volatility products (e.g., multi-hydroxy aromatics), and the mechanisms to form heterogeneous production of PPR. The simulated gas products were classified into volatility- and reactivity-based lumped species and incorporated into the Unified Partitioning Aerosol Reaction (UNIPAR) model that predicts SOA formation via multiphase reactions of phenol or benzene. The predictability of the UNIPAR model was examined using chamber data, which were generated for the photooxidation of phenol or benzene under controlled experimental conditions (NOx levels, humidity, and inorganic seed types). The SOA formation from both phenol and benzene still increased in the presence of wet inorganic seed because of the oligomerization of reactive organic species in the aqueous phase. However, model simulations show a significant suppression of ozone, the oxidation of phenol or benzene, and SOA growth compared with those without PPR mechanisms. The production of PPR is accelerated in the presence of acidic aerosol and this weakens SOA growth. In benzene oxidation, up to 53 % of the oxidation pathway is connected to phenol formation in the reported gas mechanism. Thus, the contribution of PPR to gas mechanisms is less than that of phenol. Overall, SOA growth in phenol or benzene is negatively related to NOx levels in the high-NOx region (HC ppbC / NOx ppb &lt; 5). However, the simulation indicates that the significance of PPR rises with decreasing NOx levels. Hence, the influence of NOx levels on SOA formation from phenol or benzene is complex under varying temperature and seed type conditions. Adding the comprehensive reaction of phenolic compounds will improve the prediction of SOA formation from aromatic HCs due to the missing mechanisms in the current air quality model.

Crystal violet degradation by visible light-driven AgNP/TiO2 hybrid photocatalyst tracked by SERRS spectroscopy

Dyes are important concerns regarding aquatic environmental contamination given their extensive industrial use and the occurrence of highly toxic and carcinogenic effects on the biota. In this work, photodegradation processes of the organic dye crystal violet (CV) by a hybrid plasmonic photocatalyst involving titanium dioxide (TiO2) and silver nanoparticles (AgNP), through irradiation with low-power visible light were studied, and the experiments were tracked by ultraviolet-visible absorption (UV–VIS) and surface-enhanced resonance Raman scattering (SERRS) spectroscopies. Enhanced photocatalytic activity was observed, reaching about 71, 80 and 87 % of CV removal with only 100 minutes of irradiation, depending on the Ag loading used. The high photocatalytic efficiency is further highlighted by the low energy consumption in the process, requiring only ca. 1.46 kW h L-1 in the best reaction condition. Quantum-mechanical calculations were used to the assignment of electronic spectra, as well as to the prediction of frontier molecular orbitals and atomic charges, aiming to propose mechanisms for radical attacks. Such results allow suggesting degradation processes involved mainly N-demethylation and bond breaking of central carbon. The presence of CV protonated species was also supported through Density Functional Theory (DFT) investigation. The integration of theoretical and experimental results allows proposing the formation of pararosaniline, phenol and benzophenone derivatives, which may have highest ecotoxicity than the original contaminant, outstanding the remarkable relevance of SERRS spectroscopy in monitoring such recalcitrant substances.

Supramolecular hydrogen-bonded networks formed from copper(II) carboxylate dimers.

The well-known copper carboxylate dimer, with four carboxylate ligands extending outwards towards the corners of a square, has been employed to generate a series of crystalline compounds. In particular, this work centres on the use of the 4-hydroxybenzoate anion (Hhba-) and its deprotonated phenolate form 4-oxidobenzoate (hba2-) to obtain complexes with the general formula [Cu2(Hhba)4-x(hba)xL2-y]x-, where L is an axial coligand (including solvent molecules), x = 0, 1 or 2, and y = 0 or 1. In some cases, short hydrogen bonds result in complexes which may be represented as [Cu2(Hhba)2(H0.5hba)2L2]-. The main focus of the investigation is on the formation of a variety of extended networks through hydrogen bonding and, in some crystals, coordinate bonds when bridging coligands (L) are employed. Crystals of [Cu2(Hhba)4(dioxane)2]·4(dioxane) consist of the expected Cu dimer with the Hhba- anions forming hydrogen bonds to 1,4-dioxane molecules which block network formation. In the case of crystals of composition [Et4N][Cu2(Hhba)2(H0.5hba)2(CH3OH)(H2O)]·2(dioxane), Li[Cu2(Hhba)2(H0.5hba)2(H2O)2]·3(dioxane)·4H2O and [Cu2(Hhba)2(H0.5hba)2(H0.5DABCO)2]·3CH3OH (DABCO is 1,4-diazabicyclo[2.2.2]octane), square-grid hydrogen-bonded networks are generated in which the complex serves as one type of 4-connecting node, whilst a second 4-connecting node is a hydrogen-bonding motif assembled from four phenol/phenolate groups. Another two-dimensional (2D) network based upon a related square-grid structure is formed in the case of [Et4N]2[Cu2(Hhba)2(hba)2(dioxane)2][Cu2(Hhba)4(dioxane)(H2O)]·CH3OH. In [Cu2(Hhba)4(H2O)2]·2(Et4NNO3), a square-grid structure is again apparent, but, in this case, a pair of nitrate anions, along with four phenolic groups and a pair of water molecules, combine to form a second type of 4-connecting node. When 1,8-bis(dimethylamino)naphthalene (bdn, `proton sponge') is used as a base, another square-grid network is generated, i.e. [Hbdn]2[Cu2(Hhba)2(hba)2(H2O)2]·3(dioxane)·H2O, but with only the copper dimer complex serving as a 4-connecting node. Complex three-dimensional networks are formed in [Cu2(Hhba)4(O-bipy)]·H2O and [Cu2(Hhba)4(O-bipy)2]·2(dioxane), where the potentially bridging 4,4'-bipyridine N,N'-dioxide (O-bipy) ligand is employed. Rare cases of mixed carboxylate copper dimer complexes were obtained in the cases of [Cu2(Hhba)3(OAc)(dioxane)]·3.5(dioxane) and [Cu2(Hhba)2(OAc)2(DABCO)2]·10(dioxane), with each structure possessing a 2D network structure. The final compound reported is a simple hydrogen-bonded chain of composition (H0.5DABCO)(H1.5hba), formed from the reaction of H2hba and DABCO.

Influencing factors and identifying precursors in phenolic compounds formation from tobacco extracts pyrolysis

Tobacco extracts is one of the important flavors used in tobacco products, however, some toxic phenolic compounds (phenol, o-Cresol, p-Cresol, catechol, and hydroquinone) are formed during pyrolysis. In this study, the effects of temperature, heating rate, carrier gas atmosphere, and potassium salts on the formation of phenolic compounds by the pyrolysis of tobacco extracts were investigated quantitatively. The characteristics of phenols formation by five phenol-producing precursors (chlorogenic acid, protein, rutin, glucose, and fructose) were further studied. The results showed that with increasing temperature (300–500 ℃), the phenols yields first increased and then decreased, reaching the maximum at about 450 ℃. The yields of phenol and catechol can be significantly decreased by air atmosphere, lower heating rate, and addition of potassium acetate. It was further proved that chlorogenic acid, protein, and rutin are important precursors of phenolic compounds, and chlorogenic acid had the highest phenol yield of 18178.52 μg/g. Moreover, combined with the content of each precursor in the extracts, it was calculated that 83.6 % of the phenol formed at 350 ℃ came from protein and chlorogenic acid, with chlorogenic acid contributing 41.52 %. Potassium acetate decreased the formation of phenol and catechol mainly by acting on chlorogenic acid, inhibiting them by 54.17 % and 57.26 %, respectively; however, it promoted the cresols formation from these precursors to varying degrees during pyrolysis.