Rate Constant Increases Research Articles

Hierarchical Zeolites Prepared Using a Surfactant-Mediated Strategy: ZSM-5 vs. Y as Catalysts for Friedel-Crafts Acylation Reaction.

Hierarchical ZSM5 and Y zeolites were prepared through a surfactant-mediated strategy with NH4OH changing the duration of the treatment and the amount of CTAB surfactant and taking as reference multiples of the critical micellar concentration (CMC). The materials were characterized using powder X-ray diffraction, N2 adsorption isotherms at -196 °C, and SEM and TEM microscopy. The catalytic performance was evaluated in Friedel-Crafts acylation of furan with acetic anhydride at 80 °C. The alkaline surfactant-mediated treatment had different effects on the two zeolites. For ZSM5, the CTAB molecular aggregates can hardly diffuse inside the medium-size pores, leading mainly to intercrystalline mesoporosity and increased external surface area, with no positive catalytic impact. On the other hand, for large-pore Y zeolite, the CTAB molecular aggregates can easily diffuse and promote the rearrangement of crystal units around micelles, causing the enlargement of the pores, i.e., intracrystalline porosity. The optimized Y-based sample, treated for 12 h with a CTAB amount 32 times the CMC, shows an increase in product yield and rate constant that was not observed when a higher amount of surfactant was added. The reuse of spent catalysts upon thermal treatment at 400 °C shows a regeneration efficiency around 90%, showing good potentialities for the modified catalysts.

Photocatalytic Degradation of Sulfamethoxazole and Enrofloxacin in Water Using Electrospun Composite Photocatalytic Membrane

Photocatalysis has emerged as a promising technology for the removal of emerging contaminants such as antibiotics from water. Fixing photocatalytic materials on polymers to prepare applicable membranes is a feasible method for applying photocatalysis. This study explored the preparation of composite PAN-TiO2 and PAN-TiO2-rGO (PAN-rGTi) photocatalytic membranes by combining TiO2, TiO2-reduced graphene oxide (rGO) and polyacrylonitrile (PAN) using electrospinning. Characterization through SEM and EDS analysis confirms the composite membrane’s microstructure and elemental composition. The electrospun PAN-TiO2 and PAN-rGTi composite membranes exhibit a stable and efficient photocatalytic performance in degrading sulfamethoxazole (SMX) and enrofloxacin (ENR), two typical antibiotics commonly found in water bodies. Photocatalytic degradation experiments under simulated solar light reveal the superior performance of the composite photocatalytic membranes compared to PAN alone, with a notable increase in the reaction rate constants of PAN-TiO2 (1.8 to 2.2 times for SMX and 3.2 to 4.0 times for ENR) and even higher enhancements for PAN-rGTi (2.8 to 3.0 times for SMX and 5.4 to 6.5 times for ENR) compared to PAN alone. Despite minor decreases (from 97.6% to 90.4%) in activity over five cycles, the photocatalytic composite membranes remain effective, showcasing their stability and recyclability. This study highlights the potential application of PAN-TiO2 and PAN-rGTi composite membranes as sustainable and effective materials for removing emerging contaminants from water. Further exploration should focus on optimizing materials for specific emerging contaminants and improving their application feasibility for wastewater and water treatment and water purification in water bodies.

Thermally activated delayed fluorescence tetradentate ligand-containing gold(III) complexes with preferential molecular orientation and their application in organic light-emitting devices.

A new class of thermally activated delayed fluorescence (TADF) pyridine-/pyrazine-containing tetradentate C^C^N^N gold(III) complexes have been designed and synthesized. Displaying photoluminescence quantum yields (PLQYs) of up to 0.77 in solid-state thin films, these complexes showed at-least a six-fold increase in the radiative decay rate constant (kr) in toluene upon increasing temperature from 210 to 360 K. Using variable-temperature (VT) ultrafast transient absorption (TA) spectroscopy, the reverse intersystem crossing (RISC) processes were directly observed and the activation parameters were determined, in line with the results of the Boltzmann two-level model fittings, in which the energy separation values between the lowest-lying singlet excited state (S1) and the lowest-lying triplet excited state (T1), ΔE(S1-T1), of these complexes were estimated to be in the range of 0.16-0.18 eV. Through strategic modification of the position of the electron-donating -tBu substituent in the cyclometalating ligand, the permanent dipole moments (PDMs) of these tetradentate gold(III) emitters could be manipulated to enhance their horizontal alignment in the emitting layer of organic light-emitting devices (OLEDs). Consequently, the resulting vacuum-deposited OLEDs demonstrated a 30% increase in the theoretical out-coupling efficiency (ηout), as well as promising electroluminescence (EL) performance with maximum external quantum efficiencies (EQEs) of up to 15.7%.

Zeolitic imidazolate framework-8 encapsulated with Mo-based polyoxometalates as surfaces with antibacterial activity against Escherichia coli.

Bacterial infections represent a major global health concern, causing millions of deaths and a significant economic burden. The development of antibacterial nanoporous surfaces with potential mechano-bactericidal effects can revolutionize infection control practices. In this study, a hybrid material of zeolitic imidazolate framework-8 (ZIF-8) doped with phosphomolybdic acid (PMA) was synthesized and characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and N2 sorption isotherms. PMA@ZIF-8 performance as an antibacterial agent against E. coli was superior to that of its individual constituents, suggesting a synergistic effect of PMA and ZIF-8. The incorporation of PMA into ZIF-8 significantly enhanced its antibacterial efficacy, as evidenced by a twofold reduction in MIC (375 μg mL-1 vs. 750 μg mL-1) and a 4.35 times increase in the bactericidal kinetics rate constant. The time-kill curve experiment revealed that PMA@ZIF-8 achieved a 3-log reduction within 7 hours, whereas ZIF-8 required 24 hours to reach the same level of reduction. The density functional theory (DFT) calculated bandgap of PMA@ZIF-8 was significantly less than that of ZIF-8. Also, PMA@ZIF-8 has caused the elimination of 56.72% of the thiol group as detected by Ellman's assay. Accordingly, PMA@ZIF-8 can be both computationally and experimentally demonstrated as an oxidative nanozyme. PMA@ZIF-8's surface topology revealed nanorod protrusions, suggesting a potential mechano-bactericidal effect, which was confirmed by live/dead assay on PMA@ZIF-8-coated glass. This study highlights the potential of the PMA@ZIF-8 hybrid as a highly effective antibacterial agent, holding promise for creating multifunctional antibacterial surfaces.

Reaction acceleration at the surface of a levitated droplet by vapor dosing from a partner droplet.

Chemical reactions in micrometer-sized droplets can be accelerated by up to six orders of magnitude. However, this acceleration factor (ratio of rate constants relative to bulk) drops to less than 10 for millimeter-sized droplets due to the reduction in surface/volume ratio. To enhance the acceleration in millimeter-sized droplets, we use a new synthesis platform that directly doses reagent vapor onto the reaction droplet surface from a second levitated droplet. Using Katritzky transamination as a model reaction, we made quantitative measurements on size-controlled vapor-dosed droplets, revealing a 31-fold increase in reaction rate constants when examining the entire droplet contents. This enhancement is attributed to a greater reaction rate constant in the droplet surface region (estimated as 105 times greater than that for the bulk). The capability for substantial reaction acceleration in large droplets highlights the potential for rapid synthesis of important chemicals at useful scales. For example, we successfully prepared 23 pyridinium salts within minutes. This efficiency positions droplets as an exceptional platform for rapid, in situ catalyst synthesis. This is illustrated by the preparation of pyridinium salts as photocatalysts and their subsequent use in mediation of amine oxidation both within the same droplet.

Pressure effects on both fluorescent emission and charge transport properties of organic semiconductors: a computational study.

External pressure can regulate the photophysical property and charge transport performance of organic semiconductors, however, the underlying mechanism at the microscopic level is still elusive. Using thermal vibrational correlation function coupled quantum mechanics/molecular mechanics and full quantum charge transfer rate theory, we systematically explore the influence of pressure on fluorescence emission and charge transport behaviours of representative cyclooctatetrathiophene (COTh). It is found that, upon pressurization, the intramolecular configurations of COTh became more twisted, leading to the blue-shifted emission. The fluorescence quantum efficiency (FQE) of COTh crystals decreases monotonically in a wide pressure range of 0-4.38 GPa, because the increase of intermolecular electronic energy transfer rate constant (keet) is larger than the decrease of internal conversion rate constant (kic), and the variation of keet is dominant. The decrease in kic is attributed to the decreasing reorganization energy, reflecting the suppression of the low-frequency flipping vibrations of four thiophene rings and the high-frequency stretching vibrations of central cyclooctatetraene, while the keet increase is due to the simultaneous increase in exciton coupling and spectra overlap. Moreover, we predicted that the hole mobility of COTh increases monotonically by nearly an order of magnitude from 0.39 to 3.00 cm2 V-1 s-1 upon compression, because of the increase in transfer integral and the decrease of charged reorganization energy. Furthermore, its hole mobility exhibits obvious anisotropy. Our work systematically builds the external pressure, molecular packing, luminescence and transport properties relationships of organic semiconductors and provides theoretical guidance for the rational design of pressure responsive organic semiconductors with excellent photoelectric performance.

The effect of heavy atoms on the deactivation of electronic excited states of dye molecules near the surface of metal nanoparticles.

The influence of a heavy atom and the plasmon field on the efficiency of populating the lowest triplet state (T1) and on the phosphorescence intensity has been studied for fluorescein, 2Br-fluorescein, eosin and erythrosine, which have an increasing number of substituted heavy atoms. We show that the heavy atoms affect not only the rate constant of intersystem crossing (kISC) but also the rate constant of internal conversion (kIC). The calculations show that the C-H bonds in the meso position are the primary acceptors of the excitation energy of the lowest excited electronic singlet state (S1). Substitution of the meso hydrogen atoms with I or Br leads to a smaller kIC rate constant of 1 × 108 s-1 for fluorescein to 8 × 106 s-1 for eosin. Substitution with heavy atoms also leads to a larger ISC rate constant (kISC) between the T2 and S1 states because the spin-orbit coupling matrix element 〈S1|HSO|T2〉 increases by two orders of magnitude from 0.36 cm-1 for fluorescein to 35.0 cm-1 for erythrosine. The phosphorescence rate constant increases by three orders of magnitude from 4.8 × 10 s-1 for fluorescein to 3.3 × 104 s-1 for erythrosine, which is supported by experimental data. The plasmon effect increases the intensity of the xanthene dye emissions. The intensity and the quantum yield of fluorescence increase in the series fluorescein < 2Br-fluorescein < eosin < erythrosine. The intensity of the delayed fluorescence and phosphorescence grows in the same way. The enhancement factor of the phosphorescence intensity increases from 1.8 to 5.6 in the series from fluorescein to erythrosine. The differences in the plasmon effect originate from intensity borrowing to the radiative triplet-singlet transition (T1 → S0) from the singlet-singlet transitions (Sn → S0), which is more efficient when molecules have heavy atoms in the meso position.

Semi-analytical models for two-dimensional multispecies transport of sequentially degradation products influenced by rate-limited sorption subject to arbitrary time-dependent inlet boundary conditions

Most of the semi-analytical and analytical models employed to depict multidimensional, multispecies transport of sequentially degrading reaction products are built upon solving a set of coupled advection-dispersion equations (ADEs). Within these equations, sorption is considered as being equilibrium-controlled. However, it has been demonstrated that more realistic predictions of the transport of contaminants in the groundwater could be obtained by the use of a rate-limited sorption process instead of an equilibrium sorption assumption. This study is thus designed to devise semi-analytical models for the two-dimensional multispecies transport of a chemical mixture comprised of a parent compound and its degradation-daughter products which is influenced by rate-limited sorption subject to arbitrary time-dependent inlet boundary conditions. Three integral transforms are applied to generate a set of linear algebraic equations (AEs) resulting from the reductions of the ADEs. The contaminant concentration of each species is calculated by solving these AEs and then retransforming the solutions back to the original time-space domain. The simulation results obtained with our newly developed semi-analytical model are nearly identical to those generated using a numerical model based on the Laplace transform finite difference (LTFD) method. This confirms the validity of the new semi-analytical model. An investigation of the effect of rate-limited sorption on the migration of the contaminant plume is carried out using various time-dependent inlet boundary conditions. The sorption rate values vary from low to high, specifically, 0.05, 0.5, 5, and 50 years−1. The results show that the predicted concentrations of all contaminants within in the decay chain decrease as the sorption rate constant increases, for both constant and exponentially time-dependent boundary sources. However, under pulse loading boundary conditions, the concentrations of the later degradation products tend to increase with the sorption rate constant. The semi-analytical models created in this study, allow for different inlet boundary conditions, so can be utilized to simulate the transport of sequentially degrading reaction products. This greater accuracy makes them useful for many applications.

Linear, Y- and Ψ-shaped poly(2-(dimethylamino)ethyl methacrylate) and poly(methyl methacrylate) brushes prepared by surface-initiated polymerization from a homologous series of ATRP initiators

A series of 3 homologous surface-anchored initiators for atom transfer radical polymerization has been used to graft linear, Y- and Ψ-shaped poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(methyl methacrylate) (PMMA) brushes from silicon surfaces. The film thicknesses of these architecturally different polymer brushes could be tuned both by controlling the polymerization time, as well as (as was shown for the polymerization of 2-(dimethylamino)ethyl methacrylate) by changing the monomer concentration. The library of linear, Y- and Ψ-shaped PDMAEMA and PMMA brushes was used to investigate the possible impact of polymer architecture on the swelling properties as well as the degrafting behavior of these surface-grown polymer films. The swelling of the PDMAEMA and PMMA brushes in PBS, respectively, acetone as a solvent was studied by ellipsometry. These experiments revealed a smaller swelling ratio for Y-shaped polymer brushes, as compared to linear analogues of comparable dry film thickness. Degrafting experiments were conducted with linear, Y- and Ψ-shaped PDMAEMA brushes in PBS. These experiments revealed a 2-fold, respectively, 3-fold increase in the initial rate constant of degrafting for the Y- and Ψ-shaped PDMAEMA brushes as compared to the linear analogues.

Ultrafast and Bright Quantum Emitters from the Cavity-Coupled Single Perovskite Nanocrystals.

Perovskite nanocrystals (NCs) have attracted increasing interest in the realization of single-photon emitters owing to their ease of chemical synthesis, wide spectral tunability, fast recombination rate constant, scalability, and high quantum yield. However, the integration of a single perovskite NC into a photonic structure has yet to be accomplished. In this work, the integration of a highly stable individual zwitterionic ligand-based CsPbBr3 perovskite NC with a circular Bragg grating (CBG) is successfully demonstrated. The far-field radiation pattern of the NC inside the CBG exhibits high directionality toward a low azimuthal angle, which is consistent with the simulation results. A 5.4-fold enhancement in brightness is observed due to an increase in collection efficiency. Moreover, a 1.95-fold increase in the recombination rate constant is achieved. This study offers ultrafast (<100 ps) single-photon emission and an improved brightness of perovskite NCs, which are critical factors for practical quantum optical applications.

Studying the optoelectronic properties and emission quenching dynamics of poly‐TPD by incorporating ZnO nanoparticles and multiwalled carbon nanotubes

AbstractIn this study, the optoelectronic properties and emission dynamic quenching of poly‐TPD were investigated upon incorporating ZnO nanoparticles and multiwalled carbon nanotubes (MWCNTs). A solution blending method was utilized to successfully prepare poly‐TPD incorporated with various contents of ZnO/MWCNT nanocomposites. The optoelectronic properties of the nanocomposites were analyzed using UV–Vis and photoluminescence spectrophotometry. The incorporation of the nanocomposites resulted in a decrease in transmittance, reflectance, and absorption edge, indicating a reduction in the poly‐TPD's bandgap. Parameters such as extinction coefficient, Urbach energy, and charge carrier density also decreased with addition of the nanocomposites, suggesting increased scattering, disorder, and the presence of defect states. The decrease in bandgap from 2.970 to 2.852 eV with increasing the nanocomposite content confirmed the emergence of new electronic states. Furthermore, the nature of the transitions changed from direct allowed for pure poly‐TPD to direct forbidden upon incorporation of the nanocomposites. The inclusion of the nanocomposites also led to a decrease in refractive index and fluorescence intensity. The observed fluorescence quenching primarily exhibited dynamic characteristics, with a Stern–Volmer constant of 5.14 L/g and quenching rate constants surpassing the minimum threshold for efficient quenching. The increase in charge transfer rate constants with the nanocomposite content indicated enhanced quenching efficiency and charge transfer, likely due to the increased surface area and presence of defects. These findings suggest that poly‐TPD incorporated with ZnO/MWCNT nanocomposites displays promising properties for applications in optoelectronic devices.

Prediction and optimization of frying conditions of air fried pork rind using a direct linking model

The properties of puffed food change significantly, primarily due to temperature-induced changes in water vaporization during frying. This study aimed to establish a linking model that compiles data from moisture content and air temperature to determine the optimal frying conditions for making hot air-fried pork rind. The kinetics of pork rind drying were observed using a simple first-order reaction model to match the experimental data, indicating a decrease in moisture content during air frying. A model that considers mass and heat transfer during air frying was developed to predict the moisture content, water activity, puffing ratio, breaking force, appearance, and the optimized frying time for pork rind. The precision of the predictive model was examined by comparing simulated and measured values of the physical properties of fried pork rind during air frying. The simulation of the physical qualities of fried pork rind during air frying. The simulation of the physical qualities of fried pork rind could be directly associated with moisture content and air temperature. The minimum breaking force of the pork rind was observed at a frying temperature of 180 °C. Furthermore, the time required to reach this minimum breaking force was found to be 10.0, 3.5, 2.5, and 1.5 min as the moisture rate constant increased to 4.50 × 10−3, 1.20 × 10−2, 1.95 × 10−2, and 2.70 × 10−2 1/s, respectively. Based on the high determination coefficient values, the direct linking model accurately predicted the properties of fried pork rind. Thus, we successfully developed a method to optimize the frying time and moisture rate constant. It is evident that the optimized time decreases as the moisture rate constant increases. Consequently, a frying optimization strategy was developed for predicting the frying performance of pork rind, using optimized time, for industrial-scale production.

Interactive effects of microbial functional diversity and carbon availability on decomposition – A theoretical exploration

Microbial functional diversity in litter and soil has been hypothesized to affect the rate of decomposition of organic matter and other soil ecosystem functions. However, there are no clear theoretical expectations on how these effects might change with substrate availability, heterogeneity in the substrate chemistry, and different aspects of functional diversity itself (number of microbial groups vs. distribution of functional traits). To explore how these factors shape the decomposition-diversity relation, we carry out numerical experiments using a flexible reaction network comprising microbial processes and interactions with bioavailable carbon (extracellular degradation, uptake, respiration, growth, and mortality), and ecological processes (competition among the different groups). We also considered diverse carbon substrates, in terms of varying nominal oxidation state of carbon (NOSC). The reaction network was used to test the effects of (i) number of microbial groups, (ii) number of carbon pools, (iii) microbial functional diversity, and (iv) amount of bioavailable carbon. We found that the decomposition rate constant increases with increasing substrate concentration and heterogeneity, as well as with increasing microbial functional diversity or variance of microbial traits, albeit these biological factors are less important. The multivariate dependence of the decomposition rate constant (and other decomposition and microbial growth metrics) on substrate and microbial factors can be described using power laws with exponents lower than one, indicating that diversity effects on decomposition and microbial growth are reduced at high substrate concentration and heterogeneity, or at high microbial diversity.

Synthesis and Characterization of CdO/CdS Nanocomposite for the Degradation of Methyl Orange Dye

CdO/CdS nanocomposites have been synthesized via the solution combustion route. These nanocomposites have been characterized in terms of XRD, FESEM, EDS, UV-visible and FTIR spectroscopy. The crystallinity and the crystallite size of the as-synthesized CdO/CdS nanocomposites were calculated from XRD, whereas the surface morphology and chemical purity were obtained from FESEM and EDS analysis. Further, all the samples were used as photocatalyst for the degradation of methyl orange (MO) dye under UV-Visible irradiation. The rate constant, [Formula: see text], was obtained by the Langmuir–Hinshelwood model. From [Formula: see text] values, it can be observed that the rate constant increases on increasing the amount of photocatalyst due to an increase in surface area. The rate constant value for CdO/CdS nanocomposite annealed at 615[Formula: see text]C was found to be very low, which may be largely due to loss in crystallinity at this higher temperature. Further, we compared our results with those reported in the literature and it was observed that CdO/CdS nanocomposites act as a better photocatalyst than others.

Effect of post-treatment on photocatalytic activity of anodic titania photonic crystals

One of the possible ways to enhance photocatalytic activity is the use of photonic band gap (PBG) materials. Anodic titania photonic crystals (PhCs) are promising PBG structures, whose structure can be tuned easily by anodizing conditions. However, the effect of various doping approaches on the photocatalytic activity of anodic titania PhCs has never been studied before. Here anodic titania PhCs were synthesized by cycling anodizing of titanium with voltage versus charge density modulation followed by annealing at 450 °C in air. The PhCs were post-treated by electrochemical reduction in 0.1 M Na2SO4, annealing in H2/Ar mixture or NH3. The phase composition and structure of titania PhCs were studied by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy. Photocatalytic activity of PhCs in the degradation of the methylene blue dye decreases after electrochemical reduction and annealing in NH3, whereas the annealing in H2/Ar at 600 °C for 2 h leads to an increase in the degradation rate constant by 60%.

Pilot-scale study of UVC-based AOPs towards implementation at the outlet of domestic WWTPs.

The degradation of a mixture of ibuprofen, naproxen, and diclofenac in various effluents by UVC/H2O2 or UVC/S2O82- was studied to assess the impact of the matrix composition and of the oxidant precursor on process efficiency. Experiments were carried out in a 20-L laboratory pilot (a scaled-down version of a full-scale pilot). In effluents collected during dry weather, the rural constructed wetland effluent allowed faster degradation than the urban conventional WWTP effluent, regardless of the nature of the targets or of the oxidant precursor. This was mainly attributed to a three-times higher chemical oxygen demand in the urban effluent, likely to quench the oxidative species. UV fluences to reach 90% degradation of the three compounds were 3,800 and 5,500 mJ cm-2 in the rural effluent, whereas they were 6,600 and 6,100 mJ cm-2 in the urban effluent with H2O2 and S2O82-, respectively. After a rainfall event, the rural effluent composition was not significantly affected compared to that of the urban effluent that underwent the dilution effect. Therefore, the stability of the rural effluent composition allowed comparable degradation efficiency, whereas the dilution effect led to a significant increase in the degradation rate constants in the urban effluent (up to four times higher).

Peptide Nucleic Acids Containing Cationic/Amino-Alkyl Modified Bases Promote Enhanced Hybridization Kinetics and Thermodynamics with Single-Strand DNA.

Peptide nucleic acids (PNAs) are antisense molecules with excellent polynucleotide hybridization properties; they are resistant to nuclease degradation but often have poor cell permeability leading to moderate cellular activity and limited clinical results. The addition of cationic substitutions (positive charges) to PNA molecules greatly increases cell permeability. In this report, we describe the synthesis and polynucleotide hybridization properties of a novel cationic/amino-alkyl nucleotide base-modified PNA (OPNA). This study was designed to quantitate the effect the cationic/amino-alkyl nucleotide base modification had on the kinetic and thermodynamic properties of OPNA-DNA hybridization using surface plasmon resonance and UV thermal melt studies. Kinetic studies reveal a favorable 10-30 fold increase in affinity for a single cationic modification on the base of an adenine, cytosine, or guanidine OPNA sequence compared to the nonmodified PNA strand. The increase in affinity is correlated directly with a favorable decrease in the dissociation rate constant and increase in the association rate constant. Introducing additional amino-alkyl base modifications further favors a decrease in the dissociation rate (3-10-fold per amino-alkyl). The thermodynamics driving the OPNA hybridization is promoted by an additional favorable -80 kJ/mol enthalpy of binding for a single amino-alkyl modification compared to the PNA strand. This increase in enthalpy is consistent with an ion-ion interaction with the DNA strand. These kinetic and thermodynamic hybridization studies reveal for the first time that this type of cationic/amino-alkyl base-modified PNA has favorable hybridization properties suitable for development as an antisense oligomer.

Facilely Tuning the First-Shell Coordination Microenvironment in Iron Single-Atom for Fenton-like Chemistry toward Highly Efficient Wastewater Purification.

Precisely identifying the atomic structures in single-atom sites and establishing authentic structure-activity relationships for single-atom catalyst (SAC) coordination are significant challenges. Here, theoretical calculations first predicted the underlying catalytic activity of Fe-NxC4-x sites with diverse first-shell coordination environments. Substituting N with C to coordinate with the central Fe atom induces an inferior Fenton-like catalytic efficiency. Then, Fe-SACs carrying three configurations (Fe-N2C2, Fe-N3C1, and Fe-N4) fabricate facilely and demonstrate that optimized coordination environments of Fe-NxC4-x significantly promote the Fenton-like catalytic activity. Specifically, the reaction rate constant increases from 0.064 to 0.318 min-1 as the coordination number of Fe-N increases from 2 to 4, slightly influencing the nonradical reaction mechanism dominated by 1O2. In-depth theoretical calculations unveil that the modulated coordination environments of Fe-SACs from Fe-N2C2 to Fe-N4 optimize the d-band electronic structures and regulate the binding strength of peroxymonosulfate on Fe-NxC4-x sites, resulting in a reduced energy barrier and enhanced Fenton-like catalytic activity. The catalytic stability and the actual hospital sewage treatment capacity also showed strong coordination dependency. This strategy of local coordination engineering offers a vivid example of modulating SACs with well-regulated coordination environments, ultimately maximizing their catalytic efficiency.

Degradation of emerging per- and polyfluoroalkyl substances (PFAS) using an electrochemical plug flow reactor

In recent years, shorter-chain fluorinated compounds have been manufactured as alternatives to legacy per- and polyfluoroalkyl substances (PFAS) after a global ban on some long-chain PFAS. This study is the first to investigate the degradability of emerging PFAS by an electrochemical plug flow reactor (EPFR). Ten different emerging PFAS, representing classes of fluorotelomer alcohol, perfluoroalkyl ether carboxylate, polyfluoroalkyl ethersulfonic acids, perfluoroalkyl ether/polyether carboxylates, perfluoroether sulfonate, N-alkyl perfluoroalkylsulfonamido carboxylate, fluoroalkyl phosphonic acid, and perfluoro alkane sulfonamide were investigated. The process kinetics was performed. The degradation of parent compounds increased with increasing retention time (RT). At 45.2 min of RT, the degradation of parent compounds ranged between 68%−100% with a current density of 17.2 mA/cm2. A linear increase in pseudo-first order rate constants was observed for all PFAS with increasing current density from 5.7 to 28.7 mA/cm2 (R2 > 0.91). The effect of pH, natural organic matter, and bicarbonate on the degradation, defluorination, and fluorine mass balance are reported. Alkaline pH (11) caused a decrease in degradation for all PFAS. While the presence of natural organic matter (NOM) significantly decreased the degradation and defluorination processes, the presence of bicarbonate at all studied concentrations (25, 50, and 100 mg/L) did not affect the process efficiency. The defluorination reduced to 34% from 81% with 15 mg/L NOM. The unknown/undetected fluorine fraction also increased in the presence of 15 mg/L NOM indicating the formation of NOM-PFAS complexes. Additionally, C2-C8 perfluoro carboxylic acids (PFCAs), one perfluoro sulfonic acid (PFSA), two H-PFCAs, and 4:2 fluorotelomer sulfonate (FTS) were identified as degradation byproducts in suspect screening. The electrical energy per order for PFAS ranged between 1.8 and 19.4 kWh/m3. This study demonstrates that emerging types of PFAS can potentially be degraded using an EPFR with relatively low electrical energy requirements.

Optimizing dual-scale wettability of epoxy resin on large-tow carbon fiber via tension-driven capillary wicking

Benefiting from the cost-performance advantage, large-tow carbon fiber (LCF) is under the rapid development and shows great application potential in various products like wind turbine blade and hydrogen storage cylinder. However, the numerous and densely stacked monofilaments of LCF require further researches on wetting behavior, laying the foundation for improving the mechanical strength of composite. Here, the established strategy for optimizing the wettability of LCF at dual-scale reveals the microscopic wetting mechanism driven by surface energy and capillary wicking. Firstly, at microscale, the relationship between surface energy and dynamic wetting behavior of single fiber is accurately established by dynamic contact angle and molecular kinetic theory (MKT), and the positive correlation between wettability and interfacial strength is verified. At macroscale, the quantification of fiber bundle wettability is achieved by infiltration rate constant. Meanwhile, the overall wettability of fiber bundle is evaluated and improved through the capillary wicking theory and tension-driven optimization mechanism. Such mechanism is further validated by an increase in infiltration rate constant of 144.7% and composites tensile strength of 16.4%, demonstrating that tension-driven optimization mechanism opened viable opportunities and inspirations for the enhancement of mechanical properties in LCF reinforced polymers.