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Hydrotalcite-like layered double hydroxides (LDHs) exhibit distinct microstructures and atomic compositions, and thus, they are expected to be superior microwave absorbing materials. However, preparation of excellent absorbers from LDHs is still a challenging task. Herein, NiCo-LDHs@SiC/C heterostructure composites were designed and then heat-treated to obtain NiCo@SiC/C nanofibers. Finally, with a synergistic effect of dielectric and magnetic losses, the minimum reflection loss value of the sample could reach −56.3 dB with a thickness of 2.7 mm, and the maximum effective bandwidth absorption reached 6.8 GHz at 2.3 mm. Moreover, the simulated radar cross-section indicates that the NiCo@SiC/C nanofibers well suppress the electromagnetic scattering from metal trench structure. This result further indicates the outstanding microwave absorption properties of the nanofibers. This study contributes to the development of LDH materials in the field of wave-absorbing materials, and is an important guideline for exploring efficient microwave absorbers with fibrous structure. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2) is an important two-dimension multifunction material, which is widely used in semiconductor devices due to its special electrical properties. However, the electromagnetic wave absorption performance of MoS 2 is severely limited as a result of the impedance mismatch between the material and free space. To address this issue, effective strategies of phase engineering and in situ growth techniques are employed to synthesize 2 H MoS 2 , 1 T/2 H MoS 2 , SiC@2 H MoS 2 , and SiC@1 T/2 H MoS 2 composites. The electromagnetic absorbing property data reveal that the minimum reflection loss can reach 58.04 dB at 11.16 GHz in a 2.5 mm thick SiC@1 T/2 H MoS 2 nanofiber coating; the effective absorbing bandwidth is up to 5.04 GHz (9.16–14.2 GHz). From the detailed analysis, it can be seen that the dielectric loss strength and the degree of impedance matching are the critical factors impacting the microwave absorption properties. The attenuation mechanisms underlying the excellent microwave absorption performance and related phenomena are explored, opening new directions for synthesizing MoS 2 -based electromagnetic wave absorbing materials with efficient and broadband. • Different phases MoS 2 successfully grow in situ on fibrous SiC with a distinctive structure. • The interface of SiC, 1 T phase and 2 H phase MoS 2 lead to interfacial polarization. • The RL min of SiC@1 T/2 H MoS 2 nanofiber reaches −58.04 dB with the EAB max of 5.04 GHz. • The excellent wave-absorbing properties are attributed to the synergistic effect of double dielectric component. [ABSTRACT FROM AUTHOR]

It is anticipated that the advancement of efficient wave-absorbing materials across diverse frequency bands can meet the demands of covert communication and reduced radar detection, in particular, in the context of active camouflage in the era of electronic information warfare. In this study, a carbon-modified nickel ferrite (NiFe 2 O 4) hybrid fiber was successfully synthesized via electrostatic spinning and in-situ carbothermal reduction. The carbothermal reduction temperature can be used to adjust the carbon content of NiFe 2 O 4 /C hybrid nanofiber, thereby enabling the tuning of the conductance loss. Furthermore, the effective wave-absorption frequency range can be finely adjusted from the Ku-band to the C-band. This is attributed to a deliberate tailoring, which enables the achievement of synergistic and complementary effects of the magnetic and dielectric properties, influencing the impedance matching level of each NiFe 2 O 4 /C hybrid absorber. A large electromagnetic loss indicates a high-efficiency energy conversion, and thus, the excellent microwave absorption properties indicate that this material exhibits promising potential for integration into multifunctional micro–nano electromagnetic devices and weaponry. • Multiscale NiFe 2 O 4 /C hybrid nanofibers were successfully synthesized. • The effective absorption frequency can be finely adjusted from Ku to X and even to C bands. • The optimal reflection loss of hybrid nanofiber reaches –63.05 dB at 8.08 GHz. • The electromagnetic wave attenuation mechanism is analyzed in depth. [ABSTRACT FROM AUTHOR]

Halogenated methanesulfonic acids (HMSAs) are an important new class of organic compounds as they were universal in the water cycle and drinking water sources. However, no study has investigated the presence of HMSAs in surface water and sediment from China. The present study reports the occurrence and spatiotemporal distribution of seven HMSAs in water and sediment samples from Hangzhou Bay, China. Trifluoromethanesulfonic acid (TFMSA) was the main contributor to the concentrations of HMSAs in water and sediment samples from spring, summer, autumn and winter which were 30.8–541 ng/L, n. d.-86.6 ng/L, 4.22–70.9 ng/L and 8.86–192 ng/L, separately, while in sediment samples were n. d.-11.1 ng/g, n. d.-12.9 ng/g, n. d.-22.5 ng/g, n. d.-4.60 ng/g, respectively. The levels of HMSAs in water from winter and spring were higher than those in summer and autumn, and the concentrations of the target HMSAs in water presents a seasonal pattern affected by the temperature, the precipitation and river flow variations. Nevertheless, the levels of HMSAs in sediment were highest in the area near the industrial area and the confluences of rivers. Correlation analysis revealed that the concentrations of TFMSA were significantly positively correlated with total organic carbon (TOC) in water samples. Although TFMSA is regarded as low toxic based on the EC 50 value of acute toxicity, the potential risks to aquatic ecology should be paid more attention due to its high concentrations in the aquatic system and the environmental persistency. [Display omitted] • HMSAs were observed in Hangzhou Bay's water and sediment for the first time. • Trifluoromethanesulfonic acid was the main contributor to the concentrations of HMSAs. • Detection frequencies of HMSAs in water were much higher than those in sediment. • The levels of TFMSAs in water showed distinct seasonal patterns. • TOC was the important factor affecting the levels of TFMSAs in water. [ABSTRACT FROM AUTHOR]

QSAR modeling could be a promising tool for guiding the development of novel and cost-effective environmental technologies. As an example, it could be widely used to analyze the degradation rules of organic pollutants in various decomposition methods. However, a lack of systematic research on a particular removal method is significant in revealing the decomposition rule of pollutants more accurately and guiding industrial applications. In this study, six coagulation systems (MnO 2 /Fe(OH) 3 /AlCl 3 /FeCl 3 /CaCl 2 /MgCl 2) were used as examples to remove 38 dyes under three pH conditions, and the characteristics and differences of these systems were explored by QSAR modeling. The results showed that the removal effect by MnO 2 under acidic and neutral conditions and Fe(OH) 3 under acidic conditions were quantitatively described mainly by bond order (BO) and Fukui index (f (+) and f (0)), which reflected that oxidative degradation dominated. In contrast, most of the critical parameters of other systems were molecular descriptors represented by ∑q(O) (the total charge of all the oxygen atoms in the molecule) and SAA (surface area of a molecule), which reflected that electrostatic adsorption and hydrogen-bond adsorption processes dominated. [Display omitted] • The most key parameters of the MnO 2 /Fe(OH) 3 system such as BO x and f (+) n. • The most key parameters of the AlCl 3 /FeCl 3 /CaCl 2 /MgCl 2 system such as SAA and ∑q(H). • The MnO 2 /Fe(OH) 3 system is dominated by oxidative degradation, and various interface adsorptions coexist. • The AlCl 3 /FeCl 3 /CaCl 2 /MgCl 2 system is dominated by electrostatic adsorption, supplemented by hydrogen bond adsorption. [ABSTRACT FROM AUTHOR]

In this study, the adsorption effect by freshly formed ferric hydroxide (FFFH) for the removal of 47 synthetic dye and antibiotic wastewaters under different pH conditions (i.e., pH = 4, 7, and 10) was investigated. The average total organic carbon (TOC) removal rates (R exp) of pollutants under acidic, neutral, and alkaline conditions were 27.10 ± 3.21%, 15.16 ± 2.48%, and 9.72 ± 2.81%, respectively. By analyzing the characteristics of FFFH measured by SEM, XRD, FT-IR, TGA and BET, the properties of pollutants, and the values of R exp , one can conclude that the large specific surface area and rich hydroxyl groups on the surface of FFFH were the reasons for its adsorption capacity for organic pollutants, and the electrostatic adsorption was the main reason for higher removal rate in acidic condition. Subsequently, to better elucidate the intrinsic factors influencing the removal rates at the molecular structure level, three optimal quantitative structure-activity relationship (QSAR) models were established by using multiple linear regression (MLR) analysis. Results of model validations (e.g., regression coefficient, internal and external verifications, and Y-randomization) showed that the established models exhibited excellent stability, reliability, and robustness with the values of R2 = 0.7544, 0.7764, 0.7528, Q2 INT = 0.6451, 0.6836, 0.6228, and Q2 EXT = 0.5890, 0.6029, 0.7298 under acidic, neutral, and alkaline conditions, respectively. The results of quantum parameter analysis revealed that the adsorption mechanism of FFFH for dyes and antibiotics mainly includes the activity of adsorption site, the behavior of electron transfer and the strength of molecular polarity. [Display omitted] • The removal of dyes and antibiotics by freshly formed ferric hydroxide was studied. • Electrostatic adsorption was the main reason for higher R exp under acidic condition. • Three high-quality QSAR models under different pH conditions were developed. • The adsorption mechanism of ferric hydroxide at a molecular level was proposed. [ABSTRACT FROM AUTHOR]

• Ni/SiC/C nanofibers were synthesized via electrospinning and magnetron sputtering. • Fillers result in Strong microwave absorption with a minimum of −32.3 dB. • Multicomponent composites possess wider absorption bandwidth. • Synergistic between SiC/C and Ni favours microwave absorption. • Magnetic loss contributes more evenly to microwave absorption. Nickel/silicon carbide/carbon (Ni/SiC/C) composite nanofibers were synthesized via electrospinning and sputtering. The introduction of a Ni coating has an obvious sharp effect on the EMW absorption performances of SiC/C nanofibers. The results show that the permittivity and permeability were significantly improved, and the optimal reflection loss (RL) was reached in the C-band. The composite nanofibers/paraffin mixture (10 wt%) with an absorbent thickness of 5 mm presents an RL min of approximately −32.3 dB at 4.3 GHz. The results indicate that the Ni/SiC/C composite nanofiber is a remarkable candidate for use as a high-efficiency and lightweight EMW absorbing material. [ABSTRACT FROM AUTHOR]

• N-containing compounds with various structures were degraded in SCWO process. • Intramolecular and intermolecular synergistic denitrification were discovered. • The TN removal rate of mixture was correlated with monomer compound. • The overall reaction mechanism of synergistic denitrification was proposed. Nitrogen transformation processes have an important impact on human life. In this work, the synergistic denitrification mechanism in the process of supercritical water oxidation (SCWO) was studied. N-containing organic compounds had better denitrification effects than the inorganics because they could produce more active radicals. Nitroaniline had higher total nitrogen (TN) removal rates than those of compounds containing only amino or nitro group due to the intramolecular synergistic denitrification. Meanwhile, intermolecular synergistic denitrification was found between nitro and amino/N-heterocyclic compounds, but its denitrification efficiency was not as good as intramolecular synergistic denitrification. The reaction mechanism of synergistic denitrification was proposed, which was similar to anaerobic ammonia oxidation. In addition, the overall equilibrium process of intermolecular synergistic denitrification was established. It included the rapid reduction of org-N at the early stage of SCWO process, as well as the limiting step of slow denitrification rate of NH 4 + and NO 3 − in the late stage. The relationship between TN removal rate of mixture (k MIX-TN) and monomer compound (k NO2-TN or k NH2-TN) could be expressed by an equation, that was k MIX-TN = 3.3698 k NO2-TN ·k NH2-TN + 0.0901, with R2 of 0.7788, which demonstrated that k MIX-TN was linearly related to k NO2-TN ·k NH2-TN. All these works provided theoretical basis for nitrogen removal in water by SCWO technology. [ABSTRACT FROM AUTHOR]

Developing highly active and non-precious-metal single-atom catalysts (SAC) for electrochemical water splitting is of great significance to the development of renewable energy technology in future. Herein, 10 first-row transition-metal (TM, from Sc to Zn) single atoms anchored on a graphyne (GY) nanosheet (TM@GY) as electrocatalysts for water splitting are explored through computational screening approach. It is found that the single atoms prefer to tightly bind at the acetylenic-ring center of GY. Meanwhile, these TM@GY catalysts show metallic properties or reduced band gap, favoring electron transfer during the electrochemical processes. Moreover, both Co@GY and Mn@GY catalysts present good catalytic performance for hydrogen evolution reaction (HER) with both the acetylenic C and TM atoms being highly active sites. However, only the Co@GY catalyst shows good oxygen evolution reaction (OER) activity with an overpotential of 0.55 V. Thus, Co@GY could serve as a potential bifunctional electrocatalyst for water splitting. Besides, the d-band center of TM atoms on TM@GY can be turned through controlling TM atoms with different d-electron number and be used to predict the OER performance. This work highlights that GY doped with single non-precious-metals can be considered for designing high-active and low-cost bifunctional electrocatalysts for practical electrochemical reactions. Unlabelled Image • 10 TM@GY are explored as potential catalysts for electrochemical water splitting by the means of computational screening. • The best catalyst for HER is Co@GY with the minimum ∆GH* of 0.04 eV. • The Co@GY catalyst is predicted to be a good bifunctional electrocatalyst for water splitting. • The distinct OER performance can be turned via adjusting TM atoms with different d-electron number. [ABSTRACT FROM AUTHOR]

Graphical abstract An efficient S, N-codoped carbon supported isolated single Mo atoms catalyst is computer-aided designed, and shows excellent HER performance. Highlights • The Mo-ISA/S 6 N1C catalyst was computer-aided designed showing excellent HER performance. • The interactions between H and the Mo atoms can be controlled by the N dopent concentration on carbon support. • The Mo-ISA/N1C catalyst showed the best HER performance with small ΔG H* of 0.04 eV. • The competitive effect of the S-induced tensile strain and charge transfer results in an enhanced HER performance. Abstract The high-efficient electrochemical hydrogen evolution reaction (HER) is a promising pathway to provide clean energy. An electrocatalyst was computer-aided designed with Mo isolated single atoms (Mo-ISA) supported on heteroatom S, N-codoped carbon having excellent HER performance. Here, by performing comprehensive density functional theory (DFT) computations, we investigated the influence of the N dopent concentration and the sites of S atom doping on the HER performance. Our computed results demonstrate that the Mo-ISA/N1C and Mo-ISA/S 6 N1C catalysts possess good stability and high HER reactivity. Moreover, the interactions between hydrogen and the Mo atoms could be controlled by the N dopent concentration on carbon support, and the Mo-ISA/N1C catalyst showed best HER reactivity. In particular, the S atom was introduced into Mo-ISA/N1C at the S 6 site showing an enhanced HER performance due to the competitive effect of the S-induced tensile strain and charge transfer. Our DFT computations open up new opportunities for application of S, N-codoped Mo-based high-efficient catalysts for HER. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The adsorption behaviour and oxidation mechanism of Hg0 on monolayer Ti 2 CO 2 (MXenes) were investigated from First Principles. • Hg0 is chemically adsorbed on the Ov-Ti 2 CO 2 monolayer through atomic orbital hybridization and overlap. • HgO displays high chemical reactivity for its adsorption on monolayer Ti 2 CO 2. • Oxygen vacancies from Ti 2 CO 2 monolayer have promoting effects on Hg0 adsorption and oxidation. Abstract Developing low-cost, high adsorption capacity, and recyclable mercury sorbents is an important step for control of mercury in coal-fired flue gas. However, few sorbents meet all the requirements. Herein, we explore the adsorption behavior and oxidation mechanisms of mercury on 2D Ti 2 CO 2 (MXenes) monolayer and defective Ti 2 CO 2 monolayer with an Ov (Ov-Ti 2 CO 2) through first-principles computations based on density functional theory (DFT). Our calculation results show that Hg0 adsorption on Ti 2 CO 2 and Ov-Ti 2 CO 2 monolayers are mainly physisorption and chemisorption mechanisms, respectively. Moreover, the presence of a single oxygen vacancy on Ti 2 CO 2 monolayer can improve the interaction between the mercury and Ov-Ti 2 CO 2 monolayer, thereby enhancing the adsorption energy of mercury by 66 kJ/mol. Hg0 has a strong interaction with Ti atom on Ov-Ti 2 CO 2 monolayer by the atomic orbital hybridization and overlap. The adsorption of HgO molecule on Ti 2 CO 2 and Ov-Ti 2 CO 2 monolayers are chemisorption processes. Furthermore, electron density difference analysis indicates that the remarkable charge accumulation across the interface is closely related to the strong interaction between HgO molecule and Ti 2 CO 2 or Ov-Ti 2 CO 2 monolayers. The three-step reaction processes (Hg0 → Hg(ads) → HgO(ads) → HgO) are taken place on Ti 2 CO 2 and Ov-Ti 2 CO 2 monolayers, resulting in the formation of gaseous HgO molecule. The energy barrier for the Hg0 oxidation reaction step on Ov-Ti 2 CO 2 monolayer (54.85 kJ/mol) is about half of that on Ti 2 CO 2 monolayer (104.73 kJ/mol). The desorption steps of the resultant HgO molecule from Ti 2 CO 2 and Ov-Ti 2 CO 2 monolayers are the rate-determining steps, which need external energies of about 119.3 and 183.2 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting to hydrogen is considered as a promising approach for clean H 2 production. However, developing highly active and inexpensive electrocatalysts is an important part of the hydrogen evolution reaction (HER). Herein, we present a multifaceted atom (sp2-and sp-hybridized boron) doping strategy to directly fine-modify the electronic structures of the active site and the HER performance by the density functional theory calculations. It is found that the binding strength between the Co atom and the B doped graphyne nanosheets can be enhanced by doping B atoms. Meanwhile, the Co@B 1 -GY and Co@B 2 -GY catalysts exhibit good thermodynamic stability and high HER catalytic activity. Interestingly, the Co@B 2 -GY catalyst has an ideal HER performance with the ΔG H* value of −0.004 eV. Moreover, the d-band center of the Co atoms is upshifted by the sp2-or sp-hybridized B dopants. The concentrations of the sp-hybridized B atoms have a positive effect on the electrons transformation of the Co atoms. The interaction between the H and Co atoms becomes strong with the increase of the concentrations of the sp-hybridized B atoms and thus the corresponding catalysts show sluggish HER kinetics. This investigation could provide useful guidance for the experimental groups to directly and continuously control the catalytic activity towards HER by precisely doping multifaceted atoms. The sp-hybridized B atoms doped Co@GY (Co@B 2 -GY) catalyst delivers excellent catalytic activity toward HER with the calculated hydrogen adsorption free energy of −0.004 eV. Image 1 • A sp-hybridized B atom doping strategy is performed to the HER electrocatalysis by the DFT calculations. • Doping of sp-hybridized B displays good thermodynamic stability in the HER catalytic process. • Co@B 2 -GY has an ideal HER performance with the ΔG H* value of −0.004 eV. • The d -band center of Co is upshifted by the sp2-or sp-hybridized B dopants. • The interactions between the H and Co atoms are tuned by concentrations of the sp-hybridized B atom. [ABSTRACT FROM AUTHOR]

• FeN 3 -C as an excellent sorbent for Hg0 adsorption is proposed by DFT study. • The incorporated FeN 3 in C endows the carbon with magnetic and metallic properties. • Hg0 can be efficiently adsorbed on FeN 3 -C via the chemisorption mechanism. • The unoccupied Fe d -orbital accepts electron and hybridizes with Hg s -, d -orbitals. • Hg0 adsorption on FeN 3 -C is beneficial at low temperature. The control of mercury (Hg0) is one of the most important environmental problems but a long-standing challenge in environment. Current research efforts for mercury removal mainly focus on the development of economical, effective, and recyclable sorbents, while the carbon-based metal sorbents with magnetism have been rarely studied. Here, we proposed the FeN 3 -embedded carbon (FeN 3 -C) as the efficient sorbent for Hg0 adsorption from first-principles computations. Our calculation results show that the incorporated FeN 3 in carbon endows the carbon with magnetic and metallic properties and that the gas phase Hg0 can be efficiently adsorbed on FeN 3 -C through the chemisorption mechanism with the adsorption energy of −66.27 kJ/mol. Moreover, the unoccupied d -orbital of Fe in FeN 3 -C can hybridize with the Hg s - and d -orbitals and accept electron density from the Hg s - and d -orbitals, which is the "acceptance" process between Hg0 and FeN 3 -C. Additionally, according to the equilibrium constant, Hg0 adsorption on FeN 3 -C is beneficial at low temperature. Our theoretical study not only reveals that the nonprecious FeN 3 -embedded carbon possesses great promise to serve as an efficient sorbent for Hg0 adsorption, but also provides a coordination-engineered strategy for searching more efficient carbon-based metal sorbents. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 41 kinds of nitrogenous organics were conducted by supercritical water oxidation. • Reaction temperature at which the TN removal efficiency is 50% (T TN 50 ) was studied. • QSAR models were established by quantum chemical parameters and removal behaviors. • The proposed models could accurately predict reaction rate and reaction temperature. • A three factor theory was proposed based on the optimal models. Abstract Supercritical water oxidation (SCWO), in which hazardous wastes are removed from water at high temperature and pressure, is an effective method for wastewater treatment. To gain a better understanding of the removal rules for nitrogenous organics in SCWO, a Quantitative-Structure-Activity-Relationship (QSAR) approach was applied to establish the relationship between quantum chemical parameters and removal behaviors. In this study, 41 nitrogenous organics were used to study the removal behaviors, including the reaction rate constants of total nitrogen (k TN ) and the temperature at which the total nitrogen removal efficiency is 50% (T TN 50 ). QSAR models were subsequently developed and evaluated. The two optimal models for k TN and T TN 50 were stable, robust and accurate, with the associated statistical indices of R2 = 0.725 and 0.951, q2 = 0.568 and 0.931, Q ext 2 = 0.847 and 0.987, respectively. The two optimal models both contained f (-) n , E gap , q N and BO x , but varied in the correlation between these four parameters and dependent variables. A three factors theory was thus proposed based on the two optimal models: the selectivity of active site, the transfer of electrons, and the breaking of chemical bond. These two models not only offer theoretical methods for predicting k TN and T TN 50 , but also have predictive power for the removal behaviors of other nitrogenous organics in SCWO, reducing the need for further experiments. [ABSTRACT FROM AUTHOR]

The ozonation process is an effective method for removing hazardous wastes in water. To better characterize and understand the factors influencing the reaction rate constants of organic compounds during the ozonation process, a quantitative-structure–activity-relationship (QSAR) model was developed using the principal component analysis and multiple linear regression (PCA-MLR) method. In principal component analysis, five of the seven components were found to mechanistically and statistically affect the reaction rate constants. Component 1 was represented by the number of oxygen atoms ( n O ) and minimum value of bond order ( BO n ), component 2 was represented by the energy of the highest occupied molecular orbital ( E HOMO ), and component 3 and 4 were dominated by the largest change in the charge of each atom during nucleophilic attack ( f ( + ) x ) and the energy of the lowest unoccupied molecular orbital ( E LUMO ), respectively. The temperature ( T ) was the most important factor for component 7. The optimal model was l n k O 3 = 4.102 + 0.007 T - 3.419 BO n + 1.765 f ( + ) x + 5.698 E LUMO - 4.016 E HOMO - 0.241 n O , with the following evaluation index values: squared correlation coefficient ( R 2 ) = 0.916, internal validation ( q 2 ) = 0.895 and external validation ( Q ext 2 ) = 0.962. Based on these evaluation indices, Y-randomization validation and the definition of the applicability domain, the optimal model was stable, robust and predictive. We anticipate that our work will provide a credible theoretical foundation for estimating the reaction rate constants for degradation of high-molecular weight organic compounds during ozonation over a temperature range from 25 to 60 °C. [ABSTRACT FROM AUTHOR]

Abstract Synergistic oxidation of ozone (O 3) and hydrogen peroxide (H 2 O 2) is an effective water treatment for the elimination of organic pollutants. In this study, 23 organic compounds were conducted to study the reaction rate constants during O 3 -H 2 O 2 oxidation. Then, two- and three-dimensional quantitative structure-activity relationship (QSAR) models were established to investigate the factors influencing the reaction rate constants by using multiple linear regression method and comparative molecular similarity index analysis (CoMSIA) method, respectively. Both of the two models showed good performance on predicting the reaction rate constants, the associated statistical indices of 2D-QSAR and 3D-QSAR models were R 2 = 0.898 and 0.952, q 2 = 0.841 and 0.951, Q e x t 2 = 0.968 and 0.970, respectively. But varied in the influence factors, as for the 2D-QSAR model, three quantum chemical parameters, included dipole moment, the largest change of charge in each atom during the nucleophilic attack, the maximum positive partial charge on a hydrogen atom linked with a carbon atom affected the reaction rate. While in the 3D-QSAR model, the electrostatic field played the most important role in evaluating the reaction rate with the contribution of 35.8%, followed by hydrogen bond acceptor and hydrophobic fields with the contribution of 24.9% and 23.2%, respectively. These two models provided predictive tools to study the influencing factors for the degradation of organics and might potentially be applied for estimating the removal properties of unknown organics in O 3 -H 2 O 2 oxidation process. Graphical abstract Image 1 Highlights • 23 organics were conducted to study the kinetics degradation by O 3 -H 2 O 2 oxidation. • A two-dimensional QSAR model was developed by quantum chemical parameters. • A three-dimensional QSAR model was established by molecular force fields. • The factors affecting the reaction rate were analyzed by 2D- and 3D-QSAR models. • Molecular modifications were performed to validate the results of 3D-QSAR model. [ABSTRACT FROM AUTHOR]

Extracellular vesicles (EVs) are important participants in numerous pathophysiological processes, and could be used as valuable biomarkers to detect and monitor various diseases. However, facile EV isolation methods are the essential and preliminary issue for their downstream analysis and function investigation. In this work, a polyhedral oligomeric silsesquioxanes (POSS) based hybrid monolith combined metal affinity chromatography (MAC) and distearoyl phospholipid ethanolamine (DSPE) function was developed via photo-initiated thiol-ene polymerization. This synthesis process was facile, simple and convenient, and the obtained hybrid monolith could be applied to efficiently isolate EVs from bio-samples by taking advantages of the specific bond of Ti4+ and phosphate groups on the phospholipid membrane of EVs and the synergistic effect of DSPE insertion. Meanwhile, the eluted EVs could maintain their structural integrity and biological activity, suggesting they could be used for downstream application. Furthermore, 75 up-regulated proteins and 56 down-regulated proteins were identified by comparing the urinary EVs of colorectal cancer (CRC) patients and healthy donors, and these proteins might be used as potential biomarkers for early screening of CRC. These results demonstrated that this hybrid monolith could be used as a simple and convenient tool for isolating EVs from bio-samples and for wider applications in biomarker discovery. [Display omitted] • Hybrid monolith with synergistic effect of DSPE insertion and MAC was prepared via photo-initiated polymerization. • The EV isolation method based on hybrid monolith is successfully developed. • The hybrid monolithic materials-based isolation method for EVs exhibited excellent capture efficiency with short time. • The EVs isolated by hybrid monolith materials could maintain their structural integrity and biological activity. [ABSTRACT FROM AUTHOR]

A general distance synergy of single Ag atoms doped MoS 2 in catalysing HER presents a volcanic trend between the adsorption free energy of hydrogen and the inter-Ag distance, resulting in the optimum HER activity on MoS 2 basal plane. [Display omitted] • A general distance synergy of single Ag atoms doped MoS 2 in catalyzing HER was presented. • A volcanic trend between ΔG H* and the inter-Ag distance was found. • The optimum HER activity with the minimum ΔG H* of 0.03 eV is at the neighboting in-plane S sites. • A proper inter-Ag distance could moderately alter the charge of the S atoms adjacent to the Ag atoms. Doping heteroatoms into the 2D MoS 2 lattice provides an opportunity for regulating the electronic structures of the MoS 2 basal plane and further activating the inert in-plane S atoms for efficient hydrogen evolution reaction (HER). However, the most appropriate type and distribution of the doping atoms in MoS 2 induced the optimum HER performance remains a big challenge. Herein, through the density functional theory calculations, we present a general distance synergy of single Ag atoms doped MoS 2 in catalyzing HER, resulting in the optimum HER activity at the in-plane S sites neighbored to and between the Ag atoms. A general distance synergy between the doped Ag atoms in modifying the HER reactivity of in-plane S atoms adjacent to the Ag atoms is found via the control of the distance between the Ag atoms. This distance synergy shows a volcanic trend between the adsorption free energy of hydrogen (ΔG H*) and the inter-Ag distance, where the Ag d6.38 (the initial distances of 6.38 Å between two Ag atoms doped in the MoS 2 lattice) electrocatalyst with a ΔG H* value of 0.03 eV locates at the top of the volcano. Moreover, the stability and HER catalytic mechanism of the Ag d6.38 electrocatalyst as well as the doping density of Ag atoms in MoS 2 are discussed. This investigation offers useful guidance for the experimental groups to trigger the activity of the MoS 2 basal plane by precisely controlling the distance between the doped heteroatoms. [ABSTRACT FROM AUTHOR]

The reaction with hydroxyl radicals (•OH) is an important way to remove the most volatile organic compounds (VOCs) in atmospheric environment. Thus, the reaction rate constant (k OH) is important for assessing the persistence and exposure risk of VOCs, and is of great significance in evaluating the ecological risk of volatile organic chemicals. Fukui indices and bond order have a large effect on the degradation of VOCs, but so far, quantitative structure activity relationship (QSAR) models for VOCs degradation have rarely been considered these two factors. In this study, these two momentous factors will be considered along with other relevant quantitative parameters. A total of 180 substances are divided into training set (144 substances) and test set (36 substances), which are used to build and validate quantitative structure activity relationship (QSAR) models, respectively. Internal, external verification and y-randomization tests showed that the established model had excellent stability and reliability. The energy of the highest occupied molecular orbital (E HOMO), the possibility of being attacked by radicals (f (0) n) and the breaking of chemical bonds (BO x) are the main factors affecting VOCs removal. Finally, the scope of the application domain was determined and the robustness of the model was further verified. Unlabelled Image • A new QSAR for predicting the rate constant of OH radical degradation of VOCs • E HOMO , f (0) n and BO x have great influence on the degradation of VOCs. • The proposed model has been verified internally and externally. • Recommended model has broader applicability domains. [ABSTRACT FROM AUTHOR]

• An optimal one-parameter 2D-QSAR model was established for the OPFRs degradation. • Two distinct degradation mechanisms were proposed based on the distribution of LUMO. • Two 3D-QSAR models were successfully developed using CoMFA and CoMSIA methods. • Steric field was more important than electrostatic field in the CoMFA model. • Hydrophobic field was the dominant factor in the CoMSIA model. Organophosphate flame retardants (OPFRs) have been increasingly utilized as flame retardants in various fields due to the phasing out of polybrominated diphenyl ethers. To achieve a better understanding of the degradation of OPFRs undergoing supercritical water oxidation (SCWO) process, two-dimensional and three-dimensional quantitative structure-activity relationship (2D-QSAR and 3D-QSAR) models were established to investigate the factors influencing the total carbon degradation rates (k T O C). Results of the QSAR models demonstrated reliable results to estimate the k T O C values, but varied in the influencing factors. Two distinct degradation mechanisms were subsequently proposed based on the distribution of LUMO in molecules for the 2D-QSAR model. CoMFA and CoMSIA methods were applied to develop the 3D-QSAR models. Steric fields were observed to influence k T O C values more than electrostatic fields in the CoMFA model with the contribution rates of 87.2% and 12.8%, respectively. In the CoMSIA model, influence on k T O C values varies between different types of fields with the hydrophobic field being the most influential at 62.1%, followed by the steric field at 25.7% and then the electrostatic field at 10.8%. Results from this study generated critical knowledge of influencing factors on OPFRs degradation and yielded theoretical basis for estimating removal behaviors of OPFRs undergoing SCWO process. [ABSTRACT FROM AUTHOR]

• SCWO removed 50% to >70% TN of nitro and amino/N-heterocyclic mixtures. • The synergetic effect was pronounced for a pair with similar TOC removal rate. • Molecular descriptors, like E HOMO and E LUMO , largely affected TN removal. Supercritical water oxidation (SCWO) of 20 N-containing mixtures was investigated under 24 MPa, 450 °C and reaction time from 0.5 min to 6 min, with initial concentration of 1 mM. TN removal of the mixtures obtained a sharp improvement as reaction time increased from 0.5 min to 3 min, the TN removal efficiencies was over 50% at 6 min. The TN degradation rate of the mixture (k M-TN) was higher than that of the initial nitro, amino or N-heterocyclic compound. Interestingly, k M-TN was largely affected by the TOC degradation rates (k TOC) of the initial N-containing compounds, which implied that the nitro and amino/N-heterocyclic compounds, containing similar k TOC , would lead to a high value of k M-TN after mixing. Distribution of N-containing products showed that org-N made a main contribution to the formation of N 2. Molecular descriptors, like E HOMO , E LUMO and q N, largely influenced k M-TN. [ABSTRACT FROM AUTHOR]

• A computer-aided design of high-efficient Co@N 1 -GY catalyst for electrochemical water splitting is presented. • The N-induced charge redistribution on the catalysts greatly affects the HER and OER performances. • A feasible strategy for fine-tuning the charge density of the catalysts is provided. Developing inexpensive and high-active electrocatalysts for overall water splitting is important to the development of future clean energy technologies. Many non-noble metal single-atom catalysts (SACs) present unsatisfactory water-splitting catalytic performance because of their intrinsic electronic structures. Here, through the density functional theory calculations, a nitrogen atom doping strategy is applied to directly tune the electronic structure of the SAC and boost their catalytic activities towards both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). By precisely manipulating N doping modes in graphyne supported single Co atom catalyst (Co@GY), the stability, electronic properties, and HER, as well as OER catalytic activities of these N-doped Co@GY catalysts are investigated. It is found that the N-induced charge redistribution on the surface of the N-doped Co@GY catalysts greatly affects their HER and OER performances. The N-induced charge density not only increases the number of active sites of Co@N 1 -GY and enhances its catalytic activity for HER, but also weakens the chemisorption of oxygenated species and decreases distinctly the over-potential for OER, making Co@N 1 -GY a promising bifunctional electrocatalyst for water splitting. This work offers a feasible strategy for experimental groups to properly tune the electronic structures of catalysts and improve catalytic activity. [ABSTRACT FROM AUTHOR]

Oxidation is an attractive treatment method to effectively remove organic contaminants in water. In this study, degradation of 30 organic compounds in different oxidation systems was evaluated, including oxygen (O 2), hydrogen peroxide (H 2 O 2), ozone (O 3) and hydroxyl radical (HO). First, a quantitative structure-activity relationship (QSAR) model for oxidation-reduction potentials (ORPs) of organics was developed and exhibited a good performance to predict ORP values of organics with evaluation indices of squared correlation coefficient ( R 2 ) = 0.866, internal validation ( q 2 ) = 0.811 and external validation ( Q e x t 2 ) = 0.669. Four quantum parameters, including f (+) n , f (−) n , E H O M O and E B 3 L Y P dominate the ORP values. Subsequently, a relationship between reaction rates (k) and the difference of ORP for oxidants and organics (Δ E o x i − o r g ) was established, however, which was limited ( R 2 = 0.697). Therefore, two new predictors (slopes and intercepts) are proposed based on the linear relationships between k values and ORPs of oxidants. These new predictors can be applied to estimate the reaction rates and minimum oxidation potential for organic compounds. Afterwards, to express the two predictors, QSAR models were established. The two optimal QSAR models fitted very well with experimental values and were demonstrated to be stable and accurate based on R 2 (0.982 and 0.965), q 2 (0.950 and 0.950) and Q e x t 2 (0.985 and 0.989). B O x , q (H) + and q (C) x were main factors influencing the slopes and intercepts. This study developed methods to predict ORPs of organics and established two new predictors to estimate the reaction rates undergoing different oxidation processes, offering new insights into the oxidant selection. Image 1 • 30 organics were conducted to evaluate the kinetics in four oxidation systems. • A QSAR model was developed to predict the redox potential of organics. • Relationships between reaction rates and abilities of oxidant were established. • Two new predictors were proposed to better predict the degradation of organics. • QSAR models were built to accurately predict the two new predictors. [ABSTRACT FROM AUTHOR]

• 2D Pc monolayer is a promising support for SACs. • 2D Mo-Pc monolayer can capture N 2 selectively and activate N 2 effectively. • NNR on 2D Mo-Pc monolayer prefers to proceed through distal pathway with biggest energy barrier of 0.70 eV. The current remarkable catalysts for natural and artificial ammonia (NH 3) synthesis are transition-metal (TM) atoms as binding site and catalytic center. Herein several TM atoms were embedded regularly and separately on phthalocyanine monolayer as N 2 capture and reduction catalysts and theirs catalytic activity were investigated in this work by performing density functional theory simulations. The results showed that single molybdenum atom embedded phthalocyanine monolayer exhibited outstanding performances on N 2 capture and reduction to NH 3 at ambient conditions. N 2 reduction reaction prefers to proceed through distal reaction pathway with a rate determining barrier 0.70 V, suggesting its good catalytic performance for N 2 reduction. Our work also demonstrated the Pc monolayers can act as an excellent substrate for the design of single-atom catalysts. Our study provides a novel pathway for achieving conversion of N 2 into NH 3 at ambient conditions. [ABSTRACT FROM AUTHOR]