Generation Of Formaldehyde Research Articles

Ambient Air-Synthesized CsPbBr3 Nanocrystals Coupled with TiO2 Film as an Efficient Hybrid Photoanode for Photoelectrochemical Methanol-to-Formaldehyde Conversion.

Due to its exceptional optoelectronic properties in the visible spectrum, cesium lead bromide (CsPbBr3) perovskite has attracted considerable attention in solar-driven organic transformations via photoelectrochemical (PEC) cells. However, the performance of the devices is adversely affected by electron-hole recombination occurring between a transparent conductive substrate, such as fluorine-doped tin dioxide (FTO), and a perovskite layer. Herein, to mitigate this issue, a compact layer of titanium dioxide (TiO2) was employed as both an electron transport layer and a hole blocking layer to diminish charge recombination while facilitating electron transfer in such perovskite material. At the oxidation peak potential of 0.70 V vs Ag/AgNO3, a hybrid photoanode of CsPbBr3/TiO2/FTO exhibited a significant increase in photocurrent density, from 15 to 41 μA/cm2, compared to a configuration without a TiO2 layer. Furthermore, the introduction of methanol as a hole scavenger in the PEC system using the hybrid photoanode facilitated the separation of electron-hole pairs, which led to an enhanced photocurrent density of 60 μA/cm2 and promoted the production of formaldehyde. High-performance liquid chromatography (HPLC) confirmed the generation of formaldehyde at a concentration of 26.69 μM with a Faradaic efficiency of 92% under an applied potential of 0.50 V vs Ag/AgNO3 for 60 min of PEC reaction. In addition to the enhanced PEC performance achieved from this hybrid photoanode, CsPbBr3 nanocrystals (NCs) in this work were synthesized by the modified one-pot method under ambient air, where highly uniform and high-purity NCs were obtained. This work signifies the groundbreaking exploration of CsPbBr3 NCs with TiO2 as a photoelectrode material in the organic-based PEC cells, which efficiently improved the interfacial charge transfer within the photoanode for the conversion of methanol to formaldehyde, marking a significant advancement in the field.

Low Carbon Formaldehyde Generation from Chemical Looping Gasification of Heterogeneous Solid Waste

Low Carbon Formaldehyde Generation from Chemical Looping Gasification of Heterogeneous Solid Waste

Portable temperature-controlled permeation device for the generation of formaldehyde gas standard

Formaldehyde is a major indoor air pollutant. Accurate analysis of airborne formaldehyde is essential for effective monitoring and risk assessment. For many formaldehyde analysis techniques, the accuracy of the results depends on the calibration system. Existing formaldehyde calibration methods often face limitations, such as instability over time or limited concentration range. They also lack practicality for on-field calibration either because of bulkiness or because of high gas consumption. To address these challenges, a device using a paraformaldehyde permeation tube within a custom-built, temperature-controlled system was designed and evaluated.The device weighs less than 3 kg and operates using a nitrogen source. Its low gas consumption (30–100 mL min−1) enables the use of a portable gas cylinder of pure nitrogen (<2 kg) as gas supply. Formaldehyde concentrations ranging from 8.3 to 464 µg/m−3 were successfully generated, demonstrating the device’s versatility. A custom-built high-emission permeation tube could generate concentrations from 5 940 to 49 471 µg/m−3 using the same system. Additionally, the emission rate is independent of the flow rate and follows Antoine’s law with respect to temperature, enabling accurate prediction of concentration in various conditions over the evaluated range and beyond. Furthermore, the study confirms the long-term stability (1 year) of the low-emission paraformaldehyde permeation tube, with emission rates remaining mostly within ± 5 % of the average value for each temperature.The temperature-controlled permeation system approach enabled rapid stabilisation of formaldehyde generation at various concentrations and low flow rates, eliminating the need for additional dilution equipment and facilitating on-site instrument calibration at various gas concentrations. This reliable and efficient portable formaldehyde generator offers a valuable solution for field calibration, providing accurate and stable reference gas for diverse analytical needs.

Initial formaldehyde generation as a predictive marker for long-term stability of Ni-rich Li-ion batteries under abusive conditions

Electrolyte decomposition significantly impacts the long-term stability of Li-ion batteries, generating liquid and gaseous byproducts. This study focuses on formaldehyde formation, a critical byproduct from CO2 reduction in Ni-rich Li-ion batteries. Through experimental and computational analyses, formaldehyde emerges from carbonate-based electrolyte decomposition. Examining overcharge, over-discharge, and fast charging conditions, formaldehyde concentration sharply increases under overcharge, indicating severe electrolyte breakdown, while over-discharge shows a gradual rise. Fast charging similarly elevates formaldehyde levels, underscoring the link between electrolyte decomposition and abusive conditions. Importantly, this research proposes utilizing formaldehyde concentration from the initial cycle as a predictive marker for assessing long-term Ni-rich Li-ion battery stability trends. Elevated initial formaldehyde indicates potential capacity fade and accelerated degradation, enabling proactive mitigation strategies. The study elucidates mechanisms governing formaldehyde formation, providing a foundation for developing electrolyte formulations and electrode materials with enhanced decomposition resistance and improved stability. This investigation contributes to the fundamental understanding of electrolyte decomposition in Ni-rich Li-ion batteries and presents a novel approach to predicting long-term performance based on initial formaldehyde measurements, advancing high-performance and reliable energy storage solutions.

Reaction mechanism and light gas conversion in pyrolysis and oxidation of dimethyl ether (DME): A ReaxFF molecular dynamics study

To uncover the microscopic reaction mechanisms of dimethyl ether (DME) pyrolysis and oxidation, reactive molecular dynamics simulations were employed to investigate the reaction processes under various O2/DME ratios and impurity environments at 2200 K–3200 K. The results show that DME pyrolysis begins with a decomposition reaction of CH3OCH3 → CH3O + CH3, ultimately leading to the formation of CO, H2 and PAHs. The reaction pathways of DME oxidation contain light gas conversion and combustion. In fuel rich conditions, the oxidation produces mainly H2 and CO, while in fuel lean conditions, the oxidation products tend to be H2O and CO2. The carbon components of DME are completely converted into CO2 and CO regardless of O2 content. In the presence of impurities H2O or CO2, the oxidation reaction pathway is altered, causing consumption and transformation of these impurities into active radicals such as OH, further promoting the progress of the reaction. The top three light gases produced are hydrogen, methanol and methane, and increasing H2 production in the DME oxidation process can be achieved through both oxygen subtraction and water addition. The rate of formaldehyde generation during pyrolysis is higher than that during oxidation. However, a higher oxygen content leads to increased formaldehyde production.

The Process of Sterilizing Tattoo Inks Releases Formaldehyde

Introduction: Around 12% of Europeans and 20% of Americans have at least one tattoo. Tattoo inks, the substances used to create tattoos on the body, consist of chemicals that contain formaldehyde, which can be harmful to human health. The amount of formaldehyde present in commercially available tattoo inks and its causes are not well understood. Methods: We investigated the levels of formaldehyde in tattoo ink products sold in different countries and identified the factors contributing to its production. We also explored methods to reduce formaldehyde generation in tattoo inks. Seven tattoo inks from various brands were tested. Results: Formaldehyde release was predominantly associated with gamma radiation sterilization. Formaldehyde levels were observed to be higher in compositions containing organic components compared to those with inorganic components, irrespective of sterilization method and container type. Glycerin released over seven times more formaldehyde than other components during gamma-ray sterilization. Conclusion: The results suggest that the presence of hydroxyl groups in carbon organic compounds in tattoo ink leads to photodegradation during gamma-ray radiation sterilization, resulting in increased concentrations of formaldehyde. Further research is needed to examine the chemical reactions occurring during sterilization processes and identify alternative sterilization methods that minimize formaldehyde formation. Additionally, the development of tattoo inks with reduced formaldehyde content and the establishment of strict quality control measures can help ensure the safety of tattooing practices.

Investigation on formaldehyde generation characteristics and influencing factors of PODE/methanol dual-fuel combustion mode.

Polyoxymethylene dimethyl ether (PODE) and methanol are important low-carbon substitutable fuels for reducing carbon emissions in internal combustion engines. In the research, the impacts of methanol ratio, injection timing, and intake temperature on HCHO generation and emission were investigated using both engine tests and numerical simulations. Results suggest that an increase in methanol ratio suppresses auto-ignition tendency of PODE, leading to the increase of ignition delay period, pressure peak, and heat release rate peak inside the cylinder. The decrease in in-cylinder combustion temperature contributes to an increase in HCHO emission due to partial oxidation of methanol in the cylinder and exhaust pipe. While the injection timing is gradually postponed from -10 °CA ATDC to 2 °CA ATDC, in-cylinder high-temperature area decreases, the quantity of unburned methanol increases, but part of HCHO is converted to HCO due to H radical influence, resulting in 72% increased HCHO emission. With the increment of intake temperature, the oxidation and decomposition of in-cylinder methanol accelerate, leading to an improvement in combustion stability, more uniform temperature distribution, and a decrease in unburned methanol, which results in lower HCHO emission. When the intake temperature is rose from 30 to 60 °C, HCHO emission decreases by 11.2%.

Inactivation of DNA Polymerase Theta (PolΘ) Is Synthetic Lethal in DNMT3A Mutated Myeloid Malignancies - Potential Clinical Applications

Somatic mutations in DNMT3A are associated with unfavorable outcome in patients with AML, MPN and CML. DNMT3A mutations promote resistance to anthracyclines (including daunorubicin, the component of standard “7+3” induction therapy), interferon alpha, and ABL1 kinase inhibitor imatinib. Thus, malignant clones carrying DNMT3A mutations may be difficult to eliminate using standard treatments. AML, MPN and CML cells harbor oncogenic tyrosine kinase (OTK) such as FLT3(ITD), JAK2(V617F) and BCR-ABL1, respectively. We reported before that elevated levels of formaldehyde generated by altered serine/one-carbon cycle metabolism contributed to accumulation of highly lethal DNA double-strand breaks (DSBs) in OTK-positive cells. To protect malignant cells from DSB-induced apoptosis, OTKs regulate DNA damage response (DDR) mechanisms involving DSBs sensing (ATM and ATR kinases) and repairing (RAD51-mediated homologous recombination = HR, RAD52-mediated transcription associated homologous recombination = TA-HR and single strand annealing = SSA, DNA-PK -mediated non-homologous end-joining = NHEJ, Polθ-dependent microhomology-mediated end-joining = TMEJ) as well as these activating cell cycle checkpoints (CHK1 and CHK2 kinases). Unfortunately, DNMT3A mutations caused resistance of OTK-positive cells to numerous DDR inhibitors (DDRis). DDRis sensitivity screen and synthetic lethal CRISPR/Cas9 screen revealed that OTK-positive cells with DNMT3A mutations are uniquely sensitive to the inhibition of DNA polymerase theta (Polθ encoded by POLQ gene). This effect was dependent on generation of formaldehyde by serine/one-carbon cycle metabolism. Abrogation of DNMT3A function by CRISPR/Cas9 targeting, Cre-loxP gene deletion, and heterozygous R882H mutation resulted in hypersensitivity of OTK-positive murine AML-like cells and human primary AML cells to Polθ inhibitors (Polθis) due to accumulation of toxic DSBs and activation of cGAS/STING pro-apoptotic pathway. Moreover, simultaneous loss of functional DNMT3A combined with inactivation of Polθ (by CRISPR/Cas9 targeting, insertion of neo-resistance gene, and D2230A+Y2231A polymerase inactive mutant) caused accumulation of DSBs, and reduced OTK-driven clonogenic potential and leukemogenic activity in mice. Polθ is abundantly overexpressed in OTK-positive DNMT3A-deficient cells due to enhanced POLQ mRNA stability and elevated translation of Polθ protein but not due to altered POLQ methylation and Polθ protein stability. Polθ is a key element not only in TMEJ of DSBs with limited end-resection, but also in replication fork restart and in single-strand DNA (ssDNA) gap filling. OTK-positive DNMT3A-deficient cells displayed hyperactivity of Polθ-mediated TMEJ and replication fork restart, but not ssDNA gap filling. These effects were accompanied by increased loading of Polθ on DNA damage detected by Polθ foci formation and chromatin extraction. Moreover, DNMT3A deficiency modulates chromatin architecture at DSBs to limit DNA end-resection thus favoring TMEJ over HR. Furthermore, we tested the effectiveness of Polθis combined with FDA approved drugs (quizartinib, etoposide, cytarabine, azacytidine) against FLT3(ITD)-positive DNMT3A-deficient cells (primary patient cells and cell lines) in vitro and in vivo. The combination of Polθis + quizartinib and Polθis + etoposide completely eradicated clonogenic activity of these cells while Polθis + cytarabine and Polθis + azacytidine exerted modest and weak effects, respectively, when compared to individual compound treatments. These drug combinations were only modestly toxic to normal bone marrow cells. Treatment with Polθi or etoposide reduced the percentage of GFP+ FLT3(ITD)-positive DNMT3A-deficient leukemia cells in peripheral blood of the mice by ~2-fold and prolonged survival time by ~1.5-fold. Remarkably, the combination of Polθi and etoposide eradicated leukemia cells below detectable levels in 6/12 mice with no visible toxicity. Median survival time of the mice will be recorded. Altogether, we discovered that Polθ protects OTK-positive DNMT3A-deficient myeloid malignant cells from the toxic effects of DSBs and identified Polθ as a novel therapeutic target.

Au Single Metal Atom for Carbon Dioxide Reduction Reaction

CO2 is the gas that contributes the most to the greenhouse effect and, therefore, to global warming. One of the greatest challenges facing humanity is the reduction of the concentration of CO2 in the air. Here, we analyze the possible use of Au1@g-C3N4 electrocatalyst to transform CO2 into added-value products. We use density functional theory (DFT) to determine the reaction Gibbs energies for eight electron–proton transfer reaction paths of the electrochemical carbon dioxide reduction reaction (CO2RR) using a single Au atom supported on 2D carbon nitride support. Our simulations classify the Au1@g-C3N4 electrocatalysts as “beyond CO” since their formation is energetically favored, although their strong binding with a Au single atom does not allow the desorption process. DFT calculations revealed that the lowest energy pathway is CO2 (g) → COOH* → CO* → HCO* → HCOH* → CH2OH* → CH2* → CH3* → CH4 (g), where the first hydrogenation of CO to HCO is predicted as the rate-limiting step of the reaction with slightly lower potential than predicted for Cu electrodes, the most effective catalysts for CO2RR. Methane is predicted to be the main reaction product after eight proton–electron transfers (CO2 + 8 H+ + 8e− → CH4 + 2H2O). The generation of formaldehyde is discarded due to the large formation energy of the adsorbed moiety and the production of methanol is slightly less favorable than methane formation. Our computational study helps to identify suitable electrocatalysts for CO2RR by reducing the amount of metal and using stable and low-cost supports.

Pollution characteristics and sources of carbonyl compounds in a typical city of Fenwei Plain, Linfen, in summer

Field measurements of atmospheric carbonyl compounds (carbonyls) and essential precursors of O3 were carried out in the urban area of Linfen City (Linfen) where serious O3 pollution has occurred in recent years due to its unique terrain. Carbonyls were sampled using an automatic carbonyl sampler in August 2019 to determine their pollution characteristics and sources. An average concentration of ten carbonyls was 27 ± 5.7 μg m−3 detected using an HPLC-UV system. The concentrations of most detected carbonyls in August were significantly higher than those in the winter months in China. Acetone, formaldehyde and acetaldehyde were the most abundant species, accounting for 73% of all detected carbonyls. Formaldehyde, acetaldehyde, and methacrolein (MACR) were the most significant contributors to OH• reactivity and ozone generation, indicating that these three carbonyls were the key species influencing the production of O3. The concentrations of formaldehyde, acetaldehyde, and MACR showed similar diurnal variations on most days, with high values during the daytime reaching a peak at 10:00. However, the concentrations of the latter two species varied less than that of formaldehyde during the day. The acetone concentration generally increased continuously from morning to night, with the maximum value around 22:00. The C1/C2 ratio in summer was higher than that in winter. These results indicated that the carbonyls in Linfen were not only affected by anthropogenic sources such as vehicle exhaust but also by secondary photochemical production. The results of formaldehyde source apportionment showed that the contributions of background, primary, and secondary sources to the observed formaldehyde concentration were 27.6%, 36.6%, and 35.8%, respectively. Additionally, this study revealed for the first time that the vertical transport of air masses containing high concentrations of O3 and NO3 radicals above the boundary layer could increase the secondary generation of formaldehyde at night in summer.

Kinetic, products distribution, and mechanism analysis for the pyrolysis of polyglycolic acid toward carbon cycle

Present investigation was aimed at exploring the pyrolysis kinetics, product distribution, and mechanisms of polyglycolic acid (PGA) via experiments and reactive force field molecular dynamic (ReaxFF-MD) simulations to establish a foundation for the recycling of raw materials in the future. The kinetic analysis presented that the PGA pyrolysis belonged to the contracting cylinder model with the apparent activation energy ranged from 138.1 to 141.7 kJ/mol. The gaseous product was determined to contain carbon dioxide, carbon monoxide, and formaldehyde through TG-IR and TG-MS, and Py-GC/MS results showed that the yield of glycolide reached the maximum at 450 °C. The ReaxFF-MD simulation revealed that the initial pyrolysis pathway for PGA was the cleavage of alkoxy bond, followed by CC bond and acyloxy bond with the generation of carbon dioxide, carbon monoxide, formaldehyde, and ethenone. This study would provide comprehensive experiment data and meaningful guidance for recycling PGA to achieve a closed-loop economy.

Catalytic aqueous CO2 reduction to formaldehyde at Ru surface on hydroxyl-groups-rich LDH under mild conditions

Various value-added chemicals such as formic acid, carbon monoxide, methane, methanol, have been obtained using CO2 as a feedstock. However, formaldehyde generation from CO2 is less reported. Here, we performed CO2 hydrogenation with H2 in additive-free water and used layered double hydroxide supported Ru as the heterogeneous catalyst. It was found that gaseous CO2 and H2 could be efficiently and selectively converted to formaldehyde dissolved in water even at room temperature with ambient pressure. The highest gaseous CO2 conversion of 89.7% and a formaldehyde yield of 58.7% were achieved using a Ru/LDH-red catalyst in water at 30 °C with 10 bar CO2 and 10 bar H2. Combined with experimental and theoretical studies, HCOOH was found as the important reaction intermediate. The rich surface –OH of LDH and hybrid electronic state of Ru over Ru/LDH-red catalyst resulted in highly efficient HCHO formation. Our findings offer opportunities to one energy-efficient formaldehyde synthesis method.

UV-irradiation reduces the mechanical performance of wood-adhesive interphase

ABSTRACT UV irradiation leads to various usage issues of engineered wood products (EWPs), including discoloration and declined mechanical performance. The radical generation and physico-chemical changes of the wood-phenol formaldehyde (PF) adhesive interphase during alternating UV irradiation were investigated in this paper, aiming to understand the oxidation and degradation of EWPs in daily applications. Electron spin resonance spectroscopy demonstrated that UV irradiation activates the phenol ring in lignin and PF adhesive, generating the reactive oxygen species (ROSs) composed of phenoxyl radicals, singlet oxygen, superoxide anion, and hydroxyl radicals. Experiments also showed that ROSs cleavage the weak covalent bonds in the cell wall and PF adhesive, triggering photon-oxidation and degradation. The cavities in the UV irradiated cell wall were observed after UV irradiation by scanning electron microscopy. Nanoindentation analysis also demonstrated the reduced mechanical performance of cell walls in the wood-adhesive interphase and bulk wood, leading to the significant reduction in the shearing and compression strength of wood-PF adhesive bonds. In contrast, the chemical structure and mechanical performance of PF adhesive remained after UV irradiation, suggesting better stability to UV exposure. It has been demonstrated that the degradation of wood has priority during the alternating UV irradiation.

Balancing CO chemisorption with hydrogen electrochemical adsorption on Pt alloy catalyst for improving direct CO reduction to formaldehyde

Direct CO reduction to formaldehyde (CORTF) provides an alternative, energy-efficient route for production of formaldehyde, a critical chemical commodity as well as promising hydrogen carrier. However, the conventional thermal catalysis approach is challenged with slow reaction kinetics, which can be attributed to imbalanced CO and hydrogen competitive chemisorption to catalyst, with stronger CO adsorption significantly inhibiting hydrogen adsorption that suppresses their reaction towards formaldehyde generation. We report a new, innovative CORTF mechanism to promote the reaction by utilizing hydrogen underpotential deposition to balance the species coverage on catalyst surface. Our study shows that, by separately tuning Pt alloy nanoparticle catalyst composition to control CO chemical adsorption favorability and tuning hydrogen underpotential deposition potential to control hydrogen electrochemical adsorption favorability, the formaldehyde production rate with Pt alloys (866 mg/gcat/h) is 300 times higher compared to conventional thermal catalysis method (2.6 mg/gcat/h) and 50 time higher than previously reported molybdenum phosphide (MoP, 16.3 mg/gcat/h) electrocatalyst. DFT simulations show reduced energy barriers for the rate-limiting steps by means of balancing hydrogen and CO adsorption, thus supporting this new mechanism to achieve more dramatically improved CORTF kinetics. This CORTF mechanism provides a new strategy towards efficient formaldehyde production.

Intricate behaviors of gas phase CO2 photoreduction in high vacuum using Cu2O-loaded TiO2 nanotube arrays

Photoreduction of carbon dioxide (CO2) in gas phase was investigated over composites of Cu2O nanoparticles (CNPs) and anodized TiO2 nanotube arrays (TNAs). CNPs with an average size of 90 nm were pulse-electrodeposited on vertically aligned hollow TiO2 nanotubes having average pore size of 90 nm. Radical trapping experiments with electron spin resonance spectroscopy suggest that photoinduced charge separation occurs via direct Z-scheme mechanism in Cu2O-loaded TNA (CNP/TNA) sample. Successively, CO2 photoreduction for CNP/TNA from water/CO2 mixture was monitored using a quadrupole mass analyzer in high vacuum, where the partial pressures of intermediate and final reaction species were measured in real time under ultraviolet-visible (UV–VIS) light irradiation (300–600 nm). The photoreduction of CO2 on CNP/TNA happens through preferred generation of formaldehyde (HCHO) and methanol (CH3OH), while platinum-loaded TNA (Pt/TNA) produced methane (CH4) and hydrogen (H2) instead of HCHO and CH3OH. Carbon monoxide (CO) formation was commonly observed for both CNP/TNA and Pt/TNA specimens. These results reveal that CO2 photoreduction occurs through hydrogenation in gas phase over CNP/TNA even in high vacuum, although CO2 deoxygenation to CH4 is conventionally dominant for gas phase reactions.

Generation of formaldehyde and formaldehyde-d2 for hydroxymethylations and hydroxydeuteromethylations of difluoroenolates and difluorobenzyl carbanions.

A method for the in situ production of formaldehyde from dimethylsulfoxide, bromine, and cesium carbonate is reported for reactions with difluoroenolates and difluorobenzyl carbanions. This process also generates formaldehyde-d2 for the production of 2,2-difluoro-1,1-deuteroethanols. Mechanistic and computational studies further characterize the production of hydroxymethylated and hydroxydeuteromethylated difluorinated organic molecules.

Opposite Roles of Co-enzyme Q10 and Formaldehyde in Neurodegenerative Diseases.

Most of neurodegenerative diseases (NDD) have no cure. The common etiology of neurodegenerations is unclear. Air pollutant-gaseous formaldehyde is notoriously known to induce demyelination and cognitive impairments. Unexpectedly, an amount of formaldehyde has been detected in the brains. Multiple factors can induce the generation and accumulation of endogenous formaldehyde. Excessive formaldehyde can induce oxidative stress to generate H2O2; in turn, H2O2 promote formaldehyde production. Clinical investigations have shown that an abnormal high level of formaldehyde but low level of coenzyme Q10 (coQ10) was observed in patients with NDD. Further studies have proven that excessive formaldehyde directly inactivates coQ10, reduces the ATP generation, enhances oxidative stress, initiates inflammation storm, induces demyelination; subsequently, it results in neurodegeneration. Although the low water solubility of coQ10 limits its clinical application, nanomicellar water-soluble coQ10 exhibits positive therapeutical effects. Hence, nanopackage of coQ10 may be a promising strategy for treating NDD.

Formaldehyde emission from wood promoted by lignin in the presence of iron residues

A Lignin-Mediated Fenton (LMF) mechanism for low temperature generation of formaldehyde from wood is described where low levels of iron (ubiquitous in the environment) participate in oxygen radical generation which then initiates attack on lignin.

Changes in the physicochemical composition of Auricularia auricula during growth stages and control of endogenous formaldehyde

To maintain quality and reduce endogenous formaldehyde content in the edible fungus, Auricularia auricula, the critical period of formaldehyde generation was identified and controlled. In this study, different growth stages of A. auricula were used to assess the nutritional composition (polyphenol monomers, 5′-nucleotides, organic acids and water-soluble vitamins) and related enzyme activities; the correlation between quality and endogenous formaldehyde content was also analysed. The results showed that formaldehyde was positively correlated with soluble protein and melanin levels; it was negatively correlated with the total sugar and flavonoid contents. Among the four growth stages, ripe A. auricula (RAA) had the highest endogenous formaldehyde content. The activities of γ-glutamyl transpeptidase (GGT) and l-cysteine sulphoxide lyase (C-S lyase) were highest in RAA; they promoted endogenous formaldehyde production. RAA is a critical period for interventions to reduce endogenous formaldehyde contents. Experiments to distinguish the effects of 10 exogenous substances on GGT and C-S lyase indicated that cysteine (Cys) and glutamic acid (Glu) inhibited the production of endogenous formaldehyde by 17.13% and 14.89%, respectively. This study provides a new perspective for controlling safety during the growth of edible fungi and maintaining the quality of processed products.

Electrochemical reduction of CO2 on fluorine-modified boron-doped diamond electrode

Fluorine-containing diamond was deposited onto boron-doped diamond (BDD) substrate in the hot-filament chemical vapor deposition (HFCVD) process. The carbon source composed of acetone and trimethyl borate was mixed with hexafluoropropylene and then used to prepare a fluorine-modified BDD (F-BDD) film. X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurement were employed to characterize the film surface. Electrochemical reduction of CO2 was performed on the F-BDD electrode in a three-electrode cell in NaCl electrolyte. The Faradaic efficiency of formaldehyde (HCHO) generation on the electrode surface in CO2 reduction was measured and analyzed. The fluorinated surface decreased the adsorption of foreign species, stabilizing the F-BDD electrode. Scanning electron microscope (SEM) was used to observe the chemical contamination on the electrode surface in the reductive circumstance. In comparison with the substrate BDD electrode, the F-BDD electrode was found to be highly durable after a long reduction process because of its improved chemical stability and anti-contamination properties.