Carbon Chain Research Articles

Metal-Exchanged Phosphomolybdic Acid Salts-Catalyzed Esterification of Levulinic Acid

We examined the effectiveness of metal-exchanged phosphomolybdic acid salts in converting levulinic acid, derived from biomass, into valuable products (alkyl levulinate). We prepared salts of phosphomolybdic acid using different metals (Fe3+, Al3+, Zn2+, Cu2+, Mn2+, Ni2+, and Co2+). The influence of metal cations on the conversion and selectivity of the reactions was assessed. We found that the salts prepared with iron and aluminum phosphomolybdate were the most effective catalysts for the esterification of levulinic acid with methanol, with the conversion and selectivity tending towards 100% after 6 h of reaction at a temperature of 323 K. The effect of catalyst loading and its recovery and reuse was evaluated; the results from the reaction using aluminum phosphomolybdate remained similar for four cycles of use. The influence of temperature on conversion and selectivity was investigated between 298 and 353 K. The reactivity of different alcohols with a carbon chain size of C1-C4 was assessed and conversions above 65% were obtained for all alcohols tested under the conditions evaluated, except for tert-butyl alcohol. These catalysts are a promising alternative to the traditional soluble and corrosive Brønsted acid catalysts. The superior performance of these catalysts was ascribed to the higher pH decline triggered by the hydrolysis of these metal cations.

Quantum rotational dynamics of linear C5 at low interstellar temperatures for H2 collision.

The quantum dynamics of carbon chains through H2 and He collisions in the interstellar medium (ISM) is an important step toward accurate modeling of their abundance in non-local thermodynamic equilibrium conditions. The C5(Σg+1) molecule is the longest pure carbon chain detected in the ISM to date. While He collisions are computationally easy to perform, the collision with much more abundant H2 is both complicated and computationally demanding. Using templates for approximating p-H2 collisional rates, such as scaling He rates and using a reduced 4D → 2D potential energy surface (PES), has limited applicability. On the other hand, any such approximation does not exist for o-H2. Therefore, a full rotational dynamics of C5 with both p- and o-H2 is performed considering both molecules as rigid-rotors. The PES is calculated using CCSD(T)-F12a/AVTZ, and a neural network fitting model has been carefully chosen to strictly obey spectroscopic accuracy and augment the PES. The augmented PES is then expanded into radial terms using the bispherical harmonics function, and close coupling calculations have been done to get the cross sections and, subsequently, rate coefficients for various rotational transitions of C5.

Constructing a Multifunctional SEI Layer Enhancing Kinetics and Stabilizing Zinc Metal Anode

AbstractZn dendrite growth and parasitic reactions at the interface of zinc anode/electrolyte in aqueous zinc batteries severely hinder its lifespan in application. Herein, the zinc anode is effectively stabilized by introducing trace amounts of 4‐aminobutane‐1‐phosphate (ABPA) into the ZnSO4 electrolyte. The ABPA adsorbs onto the surface of zinc anode and then further decomposes to a high conductive organic/inorganic composite in situ SEI layer including amino, partial carbon chain, and zinc phosphate. In the SEI layer, the residual undecomposed carbon chain promotes the desolvation of Zn2+, the amino induces uniform Zn2+ plating and zinc phosphate facilitates the migration of Zn2+. Thus, this in situ SEI layer not only suppresses water‐related side reactions but also enhances the Zn2+ transport kinetics. As a result, Zn||Zn symmetric cell delivers an ultralong cycle life of over 13 000 cycles at 50 mA cm−2 and 1 mAh cm−2. A high average Coulombic efficiency of 99.72% is achieved in over 1000 cycles in Zn||Cu half‐cell. The Zn||I2 full cell delivers a high‐capacity retention of 91.42% after 40,000 cycles. Moreover, a 49 mAh Zn||I2 pouch cell maintains 80.28% capacity retention over 300 cycles and 61.22% after 1000 cycles.

Computer prediction of acute toxicity of thioderivatives of 3,5-bis(5-mercapto-4-R-4H-1,2,4-triazol-3-yl)phenol

This study presents the computational prediction of acute toxicity for new derivatives of 3,5-bis(5-mercapto-4-R-4H-1,2,4-triazol-3-yl)phenols and their alkylated analogues. The aim of the work was to evaluate the impact of structural changes, particularly alkylation and chain length extension, on the toxicity levels of new derivatives of 3,5-bis(5-mercapto-4-R-4H-1,2,4-triazol-3-yl)phenols and their alkylated analogues. Materials and methods. QSAR methodologies were used to predict toxicity, allowing the evaluation of toxicological properties based on molecular descriptors. Toxicity modeling was performed using computer software, enabling the estimation of toxicity without the need for in vivo experimental studies. Results. The results showed, that alkylation of 3,5-bis(5-mercapto-4-R-4H-1,2,4-triazol-3-yl)phenol derivatives does not lead to a significant toxicity reduction. Moreover, an increase in toxicity was observed with the prolongation of the carbon chain in the synthesized compounds. It was also found, that acid derivatives, particularly 2,2’-(((5-hydroxy-1,3-phenylene)bis(4-R-4H-1,2,4-triazol-5,3-diyl))bis(sulfanyl))diacetate acids and 3,3’-((((5-hydroxy-1,3-phenylene)bis(4-R-4H-1,2,4-triazol-5,3-diyl))bis(sulfanyl))bis(methylene))dibenzoyl acids, exhibit toxicity ranging from 521.9 mg/kg to 2232.2 mg/kg, corresponding to toxicity class IV (low toxicity) on the OECD scale. It was found, that molecular structure and hydrophobic properties play a crucial role in determining compound toxicity. This study helps to establish a structure-toxicity relationship and to optimize compound structures for reduced toxicity. Conclusions. These results provide a foundation for further development of potential drug candidates with predicted toxicological properties.

Parameters of Collision and Adhesion Process Between a Rising Bubble and Quartz in Long-Chain Amine Solution and Their Correlation with Flotation

The successful adhesion of air bubbles to mineral particles is the crucial to flotation technology. This paper systematically investigates the parameters variation in the dynamic interaction process between a rising bubble and a quartz plate in long-chain amine solutions (dodecylamine, tedecylamine, and octadecylamine). The results show that the type and concentration of long-chain amine affected the collision and adhesion process between bubbles and quartz plates remarkably. The maximum rebound distance (rebound distance after the first collision) of bubbles and the stable-state liquid film thickness gradually decreases with the increase of reagent concentration. Additionally, the collision-rebound duration and induction time shorten accordingly, the surface tension of the solution decreases, the surface hydrophobicity of quartz increases, and the deformation degree and average movement velocity of bubbles decrease. With the increase in carbon chain length, the adsorption form of the amine collector and quartz surface becomes closer to vertical, and the density of water molecules decreases. The recovery of quartz particles is highest with octadecylamine systems, corresponding well with the changing trend in steady-state liquid film thickness. This research provides an effective method for in-depth analysis of the microscopic interaction mechanism between bubbles and mineral surfaces and the prediction of flotation results.

Electrochemical Hydrodimerization of Lignocellulose-Derived Carbonyls in Aqueous Electrolytes for Biobased Polymer and Long-chained Synfuel Production: A Review.

The transformation from fossil resources, crude oil and natural gas to biomass-derived feedstocks is an urgent and major challenge for the chemical industry. The valorization of lignocellulose as renewable resource is a promising pathway offering access to a wide range of platform chemicals, such as vanillin, furfural and 5-HMF. The subsequent conversion of such platform chemicals is one crucial step in the value-added chain. The electrochemical hydrodimerization (EHD) is a sustainable tool for C-C coupling of these chemicals to their corresponding hydrodimers hydrovanilloin, hydrofuroin and 5,5'-bis(hydroxymethyl)hydrofuroin (BHH). This review covers the current state of art concerning the mechanism of the electrochemical reduction of biobased aldehydes and studies targeting the electrochemical production of these hydrodimers in aqueous media. Moreover, the subsequent conversion of these hydrodimers to valuable additives, polymers and long carbon chain synfuels will be summarized offering a broad scope for their application in the chemical industry.

Synthesis of biobased poly(ether-ester) from potentially bioproduced betulin and p-coumaric acid

For a more sustainable future, innovative polymer materials synthesized from biobased molecules are currently a key trend, in the frame of the bioeconomy. In this study, new renewable macromolecular architectures poly(ether-esters) has been synthesized from betulin and para-coumaric acid, two plant-based building blocks, poorly valorized till now, and potentially bioproduced by white biotechnologies. To date, these are the first synthesized polymers with such a reported architecture. In a first step, different chemical modifications were carried out on these biomolecules to increase their reactivities. Betulin hydroxyl groups were esterified with aliphatic acids of carbon chain lengths C6, C8 and C10 terminated by a bromine, with good yields (79–85%). P-coumaric acid was dimerized by [2 + 2] cycloaddition, and then esterified with ethanol, butanol or isobutanol with excellent yields (92–96%). These modified building blocks were finally copolymerized by Williamson polyetherification reaction, leading to various analogous materials with molar masses ranging from 9700 to 15500 g mol−1. Different thermal characterizations have been then performed. TGA results show that these poly(ether-esters) displayed high thermal stabilities (up to 336 °C). Besides, DSC analyses revealed Tg ranging from 38 to 81 °C, depending on the length of the aliphatic carbon chain and the nature of the pendant ester groups for a large range of potential applications.

High-throughput synthesis and optimization of ionizable lipids through A3 coupling for efficient mRNA delivery

BackgroundThe efficacy of mRNA-based vaccines and therapies relies on lipid nanoparticles (LNPs) as carriers to deliver mRNA into cells. The chemical structure of ionizable lipids (ILs) within LNPs is crucial in determining their delivery efficiency.ResultsIn this study, we synthesized 623 alkyne-bearing ionizable lipids using the A3 coupling reaction and assessed their effectiveness in mRNA delivery. ILs with specific structural features—18-carbon alkyl chains, a cis-double bond, and ethanolamine head groups—demonstrated superior mRNA delivery capabilities. Variations in saturation, double bond placement, and chain length correlated with decreased efficacy. Alkynes positioned adjacent to nitrogen atoms in ILs reduced the acid dissociation constant (pKa) of LNPs, thereby hindering mRNA delivery efficiency. Conversion of alkynes to alkanes significantly enhanced mRNA delivery of ILs both in vitro and in vivo. Moreover, combining optimized ILs with cKK-E12 yields synergistic LNPs that showed markedly augmented mRNA expression levels in vivo.ConclusionsOverall, our study provides insights into the structure–function relationships of ILs, providing a foundation for the rational design of ILs to enhance the efficacy of LNPs in mRNA delivery.Graphical

Effect of organic acid additives on sulfite oxidation in a calcium-based slurry

The forced oxidation of sulfite ions was conducted to obtain high-quality gypsum in the flue gas desulfurization system. The effects of formic, lactic, acrylic, acetic, propionic, and hexanoic acids added to calcium-based slurry on sulfite oxidation were investigated in this study. Sulfite oxidation was inhibited when the pKa value of organic acids was small or the carbon chain was long. In the identical slurry pH 6, the SO4 2- fractions of slurries with formic and lactic acids, which have the smallest pKa values, were lower than half that of the additive-free slurry. The addition of hexanoic acid with the longest carbon chain showed a similar SO4 2- fraction to that of additive-free slurry. These results indicate that the inhibitory effect on sulfite oxidation is more expressed by the acidity of organic acids. The SO4 2- fraction in the slurry affects the growth and quality of gypsum crystals. The slurry with acetic acid presented the highest SO4 2- fraction and resulted in the formation of high-quality gypsum crystals. The findings of this study can contribute to the selection of organic acid additives with high desulfurization efficiency and the production of high-quality gypsum.

A comparative study for organophosphate triesters and diesters in mice via oral gavage exposure: Tissue distribution, excreta elimination, metabolites and toxicity

Organophosphate triesters (tri-OPEs) and diesters (di-OPEs) may threaten human health through dietary intake, whereas little information is available about their fate in mammals. Herein, mice exposure experiments were carried out through gavage with six tri-OPEs and six di-OPEs, respectively. The residual levels of di-OPEs in mice were generally higher than those of tri-OPEs. The residual di-OPEs mainly distributed in the liver and blood while the most tri-OPEs remained in stomach, indicating easier transfer and lower metabolism levels of di-OPEs. The accumulation of tri- and di-OPEs with large octanol–water partition coefficients and long carbon chain were observed in tissues and feces, implying that the elimination of these OPEs through fecal excretion is an important elimination pathway. A total of 86 OPE metabolites were found in murine urine and feces, 57 of which were identified for the first time. For tri-OPEs, carboxylated OPEs had higher peak intensities and fewer interference factors among the metabolites, which could serve as ideal biomarkers. The predicted oral median lethal doses of OPEs and corresponding metabolites showed an increased toxicity of some hydroxylated OPEs and di-OPEs, needing further attention. These results provided new insights and evidence on the fates and biomarkers of OPEs exposure for mammals.

Electric vehicle battery closed-loop supply chain pricing and carbon reduction decisions under the carbon cap-and-trade and reward-penalty policies

Recycling end-of-life electric vehicles (EVs) batteries to conserve resources and reduce carbon emissions has obtained a great deal of concern. This paper studied how carbon cap-and-trade and reward-penalty measures jointly impacted EV battery pricing and decarbonization strategies. Three recycling modes covering single-participator, mixed-participator, and joint recycling are established. Optimal pricing and carbon mitigation strategies, total revenue, and recycling percentage are solved and compared. The dynamic effects of target recycling percentage and rewards and punishments on total revenue and recycling percentage are analyzed by numerical examples. Results show that: (1) The factory price, selling price, collection price, and carbon emission mitigation scale of power batteries are affected by cap-and-trade and reward-penalty mechanisms; (2) Reward-penalty can improve both total revenue and recycling percentage; (3) The cap-and-trade mechanism optimizes the total revenues, showing that the total revenue increase with the increasement of carbon quota and carbon price, while the increase of carbon price leads to worse recycling percentage; (4) The supply chain performance under different recycling modes is affected by policy intervention, and the joint recycling mode is better.

Self-assembly aggregation-induced emission from Eu (III) complexes with o-hydroxy-benzophenone ligands

In this work, europium (III) complexes were synthesized by using different o-hydroxy-benzophenone ligands, namely 2-hydroxy-4-octyloxybenzophenone (HL1), 4-allyloxy-2-hydroxybenzophenone (HL2) and 2-hydroxy-4-methoxybenzophenone (HL3). The structures and optical properties of the EuIII complexes E1, E2 and E3 were characterized by elemental analysis, infrared/fluorescence spectroscopy and mass spectrometry. The aggregation-induced emission properties from E1, E2 and E3 were systematically investigated in the acetone/water binary mixtures. At the same time, the corresponding agglomeration behavior and self-assembly structures in the EuIII complex system was confirmed through scanning electron microscopy. Excellent luminescent performance was illustrated in sample of E1 (the luminescence quantum yield of 21.36% in solid state) which should be attributed to the aggregation-induced emission from better self-assembly behavior with longer carbon chain in ligand. The results of ultraviolet aging resistance from E1 reveal that the self-assembly behavior could not only improve the aggregation-induced emission performance, but also enhance the photostability of EuIII complex compared with the traditional β-diketone EuIII complex. This discovery may provide a facile strategy to design and prepare more promising rare earth complexes with good luminescence properties and strong photostability for application in solid state.

Designing dicationic organic salts and ionic liquids exhibiting high fluorescence in the solid state

Dicationic ionic liquids (DILs) are emerging as a powerful, next-generation approach to designing applied ILs because of their superior physicochemical properties as well as their diverse complexity and tunability for task specific applications. DILs are scarce in the literature compared to monocationic ILs (MILs), and one of their main issues is their expected tendency to possess higher melting temperatures. A series of 1,4-bis[2-(4-pyridyl)ethenyl]benzene and 1,4-bis[2-(2-pyridyl)ethenyl]benzene quaternary salts (Q-BPEBs) with different counterions (bromide, tosylate, and triflimide) and carbon chain lengths (C6, C9, and C12) have been synthesized for their potential as DILs with thermal properties and strong photoluminescent properties in the solid state. All Q-BPEB salts demonstrated robust thermal stabilities as determined by thermogravimetric analysis (TGA). The differential scanning calorimetry (DSC) thermograms for Q-BPEB tosylates and triflimides displayed crystalline polymorphisms before melting transitions as verified by polarizing optical microscopy (POM). The Q-BPEB bromide and tosylate salts all showed high melting points of above >170 °C because of their dicationic rigid structures and strong ionic interactions of their anions. Once the Q-BPEB tosylates were exchanged with triflimide ions, para- isomers 1aTf2N-1cTf2N still possessed very high melting points (>225 °C), however, the ortho- isomers 2aTf2N, 2bTf2N, and 2cTf2N exhibited melting points lower than 100 °C, classifying them as DILs. Their photoluminescent properties were also studied in methanol with the emission values of λem = 476-482 nm for the para- isomers and those of λem = 448-453 nm for the ortho- isomers. In the solid state, the Q-BPEB salts exhibited strong fluorescence with quantum yields of up to 50%. The relatively simple synthesis of these fluorescent dicationic organic salts and ILs are pertinent towards the scarcity of these materials in the literature and provide a deeper insight on the design of fluorescent ILs containing more than one charge center.

Barrier height modulation in Amorphous IGZO/Metal interface using Trichlorosilane-Based Self-Assembled monolayers

Amorphous InGaZnO (a-IGZO) has become a key material for thin-film transistors (TFTs) due to its high mobility, low leakage current, and optical transparency. However, the increasing demands for ultra-high-resolution displays, such as those required for virtual and augmented reality applications, pose challenges related to contact resistance and Fermi level pinning at the a-IGZO/metal interface, as TFTs are scaled down. To address these challenges, we investigated trichlorosilane-based self-assembled monolayers (SAMs) as an interfacial layer between a-IGZO and metal contacts (Al, Ag, and Ni). By employing SAMs with varying carbon chain lengths—methyl trichlorosilane (MTS), octyl trichlorosilane (OTS), and octadecyl trichlorosilane (ODTS)—we aimed to improve interface properties and reduce contact resistance. Our study comprehensively analyzed thermionic emission characteristics, including barrier height, saturation current, ideality factor, and contact resistance, across different metal electrodes. The results show that the SAM layers effectively modulate barrier height and Fermi level pinning, depending on the combination of SAM layers (MTS, OTS, and ODTS) and metal electrodes (Al, Ag, and Ni). Additionally, the study provides insights into the influence of SAM carbon chain length on direct tunneling current and interface passivation, and contributes to a deeper understanding of conduction mechanisms at a-IGZO/metal interfaces.

Determination of 42 antimicrobials in disinfection products by dispersive solid phase extraction-high performance liquid chromatography-tandem mass spectrometry

Antimicrobials inhibit the growth and reproduction of microorganisms thereby alleviating skin and other problems caused by microorganisms. Antimicrobials are classified into different categories, including antibacterials, antifungals, and antivirals, among others, and include azoles, sulfonamides, tetracyclines, quinolones, and many other classes of synthetic and natural compound. The inappropriate or excessive use of antimicrobials can damage skin and other human organs and increase antimicrobial resistance. Relevant regulations and standards clearly state that antimicrobials are prohibited for use as ingredients in disinfection products. However, since antimicrobials enhance the disinfection or antibacterial effect of a product, with a significant short-term effect, antimicrobials are occasionally illegally added to disinfectant products, including those intended for human use. Therefore, establishing testing methods that provide technical support for enforcing regulations is an urgent objective. Herein, a method was established for the analysis of 42 antimicrobials in disinfection products, that is applicable to common types of disinfection-product matrix, including creams, gels, and aqueous solutions, using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) combined with dispersive solid phase extraction. The 42 antimicrobials comprise antibacterials, antifungals, and antivirals, and include seven sulfonamides, ten quinolones, three lincosamides, five tetracyclines, three macrolides, eight azoles, three purine nucleoside analogs, one furan, one nonpolyene antifungal, and one steroid. Briefly, 0.2 g of a sample was first dispersed in 2 mL of water and then extracted with 10 mL of 0.5% formic acid in acetonitrile, with 3 g of anhydrous Na2SO4 added to remove water. After centrifugation, 5 mL of the supernatant was cleaned using dispersive solid phase extraction with EMR-Lipid as the adsorbent. Lipids, waxes, surfactants, and moisturizing lubricants are commonly used as cream and gel matrices. Matrix substances containing long carbon chains dissolved in acetonitrile were removed using the EMR-Lipid adsorbent. Target analytes were separated on a Poroshell 120 EC-C18 analytical chromatography column (150 mm×3.0 mm, 2.7 μm), with 0.1% formic acid in acetonitrile and 0.1% formic acid aqueous solution used as mobile phases under gradient-elution conditions. The target analytes in the test solution were detected in positive ionization (ESI+) and multi-reaction-monitoring (MRM) modes. Analytes were characterized in terms of their retention times and selected ions, and quantified using the external-standard method. The main factors affecting method response, recovery, and sensitivity, such as the extraction method and solvent, purification method and adsorbent, mobile phase, and MS conditions, were examined during sample pretreatment and instrumental analysis. The 42 antimicrobials were effectively separated under the optimized experimental conditions; the target compounds exhibited linear working curves in the 0.25-5.0 mg/kg concentration range, with correlation coefficients (r) greater than 0.99. Limits of detection (LODs) for the 42 antimicrobials were determined from the signal-to-noise ratios (S/N) of their chromatographic peaks. LODs of 0.03-0.10 mg/kg were determined for the three matrices using 0.2-g samples and 10-mL test solution. Recoveries of 80.3-109.8%, with relative standard deviations (RSDs) of less than 9.8%, were obtained by determining three levels of each target analyte added to the three blank matrices; this process was repeated for six parallel samples. The developed method was used to analyze antimicrobials in commercially available disinfection products, with two sample batches testing positive. The established method is simple, accurate, precise, and suitable for the rapid screening and quantification of antimicrobials in disinfection products. This study provides powerful technical support for regulating the illegal addition of related antimicrobials to disinfection products.

A Prospective Analysis of Per- and Polyfluoroalkyl Substances from Early Pregnancy to Delivery in the Atlanta African American Maternal-Child Cohort.

Longitudinal trends in per- and polyfluoroalkyl substances (PFAS) serum concentrations across pregnancy have not been thoroughly examined, despite evidence linking prenatal PFAS exposures with adverse birth outcomes. We sought to characterize longitudinal PFAS concentrations across pregnancy and to examine the maternal-fetal transfer ratio among participants in a study of risk and protective factors for adverse birth outcomes among African Americans. In the Atlanta African American Maternal-Child cohort (2014-2020), we quantified serum concentrations of four PFAS in 376 participants and an additional eight PFAS in a subset of 301 participants during early (8-14 weeks gestation) and late pregnancy (24-30 weeks gestation). Among these, PFAS concentrations were also measured among 199 newborns with available dried blood spot (DBS) samples. We characterized the patterns, variability, and associations in PFAS concentrations at different time points across pregnancy using intraclass correlation coefficients (ICCs), maternal-newborn pairs transfer ratios, linear mixed effect models, and multivariable linear regression, adjusting for socioeconomic and prenatal predictors. Perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) were detected in of maternal samples, with PFHxS and PFOS having the highest median concentrations. We observed high variability in PFAS concentrations across pregnancy time points (). All median PFAS concentrations increased from early to late pregnancy, except for PFOA and N-methyl perfluorooctane sulfonamido acetic acid (NMFOSAA), which decreased [paired -test for all PFAS except for PFOA and perfluorobutane sulfonic acid (PFBS)]. Prenatal serum PFAS were weakly to moderately correlated with newborn DBS PFAS ( ). The median maternal-fetal PFAS transfer ratio was lower for PFAS with longer carbon chains. After adjusting for socioeconomic and prenatal predictors, in linear mixed effect models, the adjusted mean PFAS concentrations significantly increased during pregnancy, except for PFOA. In multivariable linear regression, PFAS concentrations in early pregnancy significantly predicted the PFAS concentrations in late pregnancy and in newborns. We found that the concentrations of most PFAS increased during pregnancy, and the magnitude of variability differed by individual PFAS. Future studies are needed to understand the influence of within-person PFAS variability during and after pregnancy on birth outcomes. https://doi.org/10.1289/EHP14334.

Effective cracking of heavy crude oil by using shock-induced nanobubble collapse: A molecular dynamics study

We investigate molecular mechanisms of hydrocarbon cracking in heavy crude oil promoted by nanobubble collapse due to ultrasound-originated shock wave. Our millions-atom molecular dynamics simulations reveal rapid flow of molecules, causing nanobubble collapse and formation of energetic nanojet with a mushroom-like shape. The nanojet apex exhibits extremely high temperature before and just after the bubble collapse, which makes a favorable condition for effective cracking of paraffin molecules. The cracking rate and portion of nanobubble-containing systems are larger than those of perfect system before the bubble collapse, and larger size of nanobubble is preferable for the cracking. The cracking efficiency is improved for the paraffin molecules with longer carbon chain.

Soot formation and laminar combustion characteristics of anisole: ReaxFF MD simulation and kinetic analysis

The application of biomass energy is one of the important ways to achieve carbon neutrality and deal with global warming. The study on the combustion mechanism of anisole, an oxygen-containing fuel, is helpful for biofuel large-scale application. In this study, the soot formation and laminar combustion characteristics of anisole were analyzed by reactive force field molecular dynamics (ReaxFF MD) and kinetic simulation, respectively. ReaxFF MD simulation studies had shown that soot formation of anisole combustion occurred in three stages, stage 1 (0–1 ns), stage 2 (1–2.5 ns), stage 3 (2.5–6 ns). The three stages represented the pyrolysis of the fuel, the developmental stage of the soot, and the graphitization stage of the soot, respectively. During the combustion of anisole, primary mechanisms for the soot formation were as follows: H-abstraction-C2H2-addition, carbon-addition-hydrogen-addition, internal ring formation and long carbon chain link. The formation of soot graphitization exhibited different morphologically behaviors: from flakes to onions to spheres with fewer branched chains. From the study of the laminar combustion characteristics of anisole, it can be found that the laminar burning velocities increased along with the increase of temperature, while the opposite trend was shown along with the increase of pressure. The sensitivity coefficient of naphthalene, the main soot precursor, revealed that the main promotional reactions for soot formation were R5 (O2 + H < = > O + OH), R36 (CO + OH < = > CO2 + H).

Regulatory mechanism of grafted alkyl chain length of carbon quantum dots as additives on the tribological properties of lithium greases

Carbon quantum dots (CQDs) exhibit exceptional structural properties and minimal environmental impact, garnering significant interest in the field of lubrication. In this study, four types of modified CQDs with varying alkyl chain lengths were synthesized through hydrothermal methods and subsequently mixed with lithium grease (LG) to formulate mixed greases. The influence of the alkyl chain length on the CQDs used as additives in the mixed greases was investigated with a four-ball friction and wear tester, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Specifically, compared to pure LG, the modified CQDs with the shortest alkyl chain length reduced the coefficient of friction (COF), the diameter of abrasive spots, and the depth of abrasive scars by 33.65%, 42.11%, and 51.87%, respectively. This improvement can be attributed to the ease of these shorter-chain CQDs entering the contact area and forming a stable film containing carbon, nitrogen, and oxygen elements through friction. The tribological properties of modified CQDs can be effectively controlled by adjusting the length of the carbon chain, providing a theoretical basis for the design of environmentally friendly and sustainable grease additives in engineering applications.

Effects of Crystallinity and Branched Chain on Thermal Degradation of Polyethylene: A SCC-DFTB Molecular Dynamics Study.

As a widely used plastic, the aging and degradation of polyethylene (PE) are inevitable problems, whether the goal is to prolong the life of PE products or address the issue of white pollution. Molecular simulation is a vital scientific tool in elucidating the mechanisms and processes of chemical reactions. To obtain the distribution and evolution process of PE's thermal oxidation products, this work employs the self-consistent charge-density functional tight binding (SCC-DFTB) method to perform molecular simulations of the thermal oxidation of PE with different crystallinity and branched structures. We discovered that crystallinity does not affect the thermal oxidation mechanism of PE, but higher crystallinity makes PE more susceptible to cross-linking and carbon chain growth, reducing the degree of PE carbon chain breakage. The branched structure of PE results in differences in free volumes between the carbon chains, with larger pores leading to a concentrated distribution of O2 and chemical defects subsequently formed. The breakdown of PE is slowed down when chemical defects are localized in low-density regions of the carbon chain. The specifics and mechanism of PE's thermal oxidation are clearly revealed in this paper, which is essential for understanding the process in depth and for the development of anti-aging PE products.