Density Functional Theoretical Research Articles

Understanding the Excited State Intramolecular Proton Transfer Phenomena of 2‐Hydroxy‐3‐Naphthaldehyde Thiosemicarbazone

AbstractThe specific objective of this theoretical study is to explore the excited state intramolecular proton transfer (ESIPT) property of 2‐hydroxy‐3‐naphthaldehyde thiosemicarbazone (2H3NS). Proton transfer takes place when the acidic or basic part of a molecule becomes stronger in the excited state which leads to the formation of a tautomer. This takes place via an intramolecular hydrogen bond formation between the two moieties that opens a door for the intramolecular proton transfer process. The present approach utilizes density functional theoretical (DFT) approach to determine the proper geometrical optimization of the molecule, determination of the intramolecular bond distance of O─H during the transition state between the enolic and tautomeric forms, and simulating potential energy curves (PECs) at both the ground and excited states. The excited states explore include the first two singlet states (S1, S2) and the first excited triplet state (T1). The distances of the detachable H from the O atom and the N atom (to which it gets attached) have been used as the unique reaction coordinates to check the variation in the angle O···H···N. The ensuing results help to determine the progress of the prototropic process as both lead to the same species passing through the same transition state. The findings are further corroborated by FTIR spectroscopy through the formation of both O─H and ─N─H bond in the transition state. Frontier molecular orbitals of the tautomer's at the ground state reveals the shifting charge density from ─O─H to N─H region in the HOMO and certifies the stated mechanism.

Smart bio-nano interface derived from zein protein as receptors for biotinyl moiety

Proteinaceous, tunable nanostructures of zein (prolamine of corn) were developed as biotinyl-specific receptors using a molecular imprinting technique. Sacrificial templates, such as latex beads (LB3) and anodized alumina membrane (AAM), have been used to control nanostructural patterns in biotin-imprinted zein (BMZ). Briefly, a methanolic solution of the zein-biotin complex was drop cast upon a self-organized LB3 and AAM templates on Au/quartz surfaces. Subsequent dissolution of these sacrificial templates affords highly oriented, predetermined, and uniformly grown hyperporous (300 nm) and nanowires (150 nm) motifs of zein (BMZ-LB3 and BMZ-AAM), as shown by scanning electron microscopy (SEM). Selective extraction of biotin molecular template cast-off site-selective biotin imprints within these zein nanostructures complementary to biotinyl moieties. Alternatively, biotin-imprinted zein nanoparticles (BMZ-Np) and thin film (BMZ-MeOH) were prepared by coacervation and drop casting methods, respectively. Density functional theoretical (DFT) studies reveal strong hydrogen-bonded interaction of biotin with serine and glutamine residues of zein. Quartz crystal microbalance (QCM) studies show remarkable sensitivity of the hyperporous-BMZ-LB3 and nanowires of BMZ-AAM towards biotin derivative (biotin methyl ester) by five (24.75 ± 1.34 Hz/mM) and four (18.19 ± 0.75 Hz/mM) times, respectively, higher than the BMZ-MeOH. Enhanced permeability features of the zein nanostructures, when templated with LB3, enable the QCM detection of biotin- or its derivatives down to 12.9 ng mL−1 from dairy products (Kefir). The outcome of this study shall be a key aspect in interfacing biological materials with micro-/nano-sensors and electronic devices for detecting pertinent analytes using sustainably developed biopolymer-based nanostructures.

Metallic Metastable Hybrid 1T'/1T Phase Triggered Co,PSnS2 Nanosheets for High Efficiency Trifunctional Electrocatalyst.

The development of trifunctional electrocatalyst for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) with deeply understanding the mechanism to enhance the electrochemical performance is still a challenging task. In this work, the distorted metastable hybrid-phase induced 1T'/1T Co,PSnS2 nanosheets on carbon cloth (1T'/1T Co,PSnS2 @CC) is prepared and examined. The density functional theoretical (DFT) calculation suggests that the distorted 1T'/1T Co,PSnS2 can provide excellent conductivity and strong hydrogen adsorption ability. The electronic structure tuning and enhancement mechanism of electrochemical performance are investigated and discussed. The optimal 1T'/1T Co,PSnS2 @CC catalyst exhibits low overpotential of ≈94 and 219.7mV at 10mA cm-2 for HER and OER, respectively. Remarkably, the catalyst exhibits exceptional ORR activity with small onset potential value (≈0.94V) and half-wave potential (≈0.87V). Most significantly, the 1T'/1T Co,PSnS2 ||Co,PSnS2 electrolyzer required small cell voltages of ≈1.53, 1.70, and 1.82V at 10, 100, and 400mA cm-2 , respectively, which are better than those of state-of-the-art Pt-C||RuO2 (≈1.56 and 1.84V at 10 and 100mA cm-2 ). The present study suggests a new approach for the preparation of large-scalable, high performance hierarchical 3D next-generation trifunctional electrocatalysts.

CO2 hydrogenation to formic acid on Pd-Cu nanoclusters: a DFT study.

Carbon dioxide (CO2) hydrogenation to formic acid is a promising method for the conversion of CO2 to useful organic products. The interaction of CO2 with hydrogen (H2) on PdmCun (m + n = 4, 8 and 13) clusters to form formic acid (HCOOH) has been explored using density functional theoretical (DFT) calculations. Pd2Cu2, Pd4Cu4 and 13-atom Pd12Cu clusters are found to be the most stable among all of the PdmCun (m + n = 4, 8 and 13) clusters with binding energies of -1.75, -2.16 and -2.40 eV per atom, respectively. CO2 molecules get adsorbed on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters in an inverted V-shaped way with adsorption energies of -0.91, -0.96 and -0.44 eV, respectively. The hydrogenation of CO2 to form formate goes through a unidentate structure that rapidly transforms into the bidentate structure. To determine the transition state structures and minimum energy paths (MEPs) for CO2 hydrogenation to formic acid, the climbing image nudge elastic band (CI-NEB) method has been adopted. The activation barriers for the formation of formic acid from formate on Pd2Cu2 and Pd4Cu4 are calculated to be 0.79 and 0.68 eV, respectively whereas that on the Pd12Cu cluster is 1.77 eV. The enthalpy for the overall process of CO2 hydrogenation to formic acid on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters are found to be 0.83, 0.48 and 0.63 eV, respectively. Analysis of the density of states (DOS) spectra show that the 4d orbital of Pd, the 3d orbital of Cu, and the 2p orbitals of C and O atoms are involved in the bonding between CO2 molecules and the Pd2Cu2 clusters. The CO2 adsorption on the PdmCun (m + n = 4 and 8) clusters has also been explained in terms of the charge density distribution analysis.

Sugar moiety driven adsorption of nucleic acid on graphene quantum dots: Photophysical, thermodynamic and theoretical evidence

Integration of biologically important molecules with graphene quantum dots (GQDs) as a new class of luminescent water-soluble carbon materials, has drawn considerable attention for recent exciting progress on its biomedical applications. In order to avoid toxic semiconductor QDs, GQDs have shown great promise in detection of DNA and other biological applications and hence, fundamental understanding of processes of interactions is important and necessary. The present work establishes the significant role of sugar residue of nucleic acids in adsorption of graphene materials through experimental estimation of binding thermodynamics concomitant with density functional theoretical (DFT) simulation and a detailed evaluation of photophysical parameters. Maximum quenching efficiency of adenosine moiety coupled with the shift in the vibrations of the five-member ring of D-ribose demonstrates the adsorption of DNA on GQDs framework through sugar moieties. The observed experimental results are consistent with the favorable Gibb’s free energy calculated through theoretical simulation. DFT presenting orbital interactions and bonding mechanism of DNAs on GQDs confirms that adsorption on GQDs surface involves charge transfer from nucleobases to GQDs and adenosine, in particular, binds strongly through charge transfer of 0.032e from nitrogen atom to carbon of GQDs. The present investigation will provide insights in understanding the possible role of GQDs in cellular imaging, biosensing and as carriers in targeted drug delivery.

Enhanced visible light assisted peroxymonosulfate process by biochar in-situ enriched with γ-Fe2O3 for p-chlorophenol degradation: performance, mechanism and DFT calculation

In this study, a novel γ-Fe2O3/biochar (BFγ) composite by a plant in-situ enrichment and one-step pyrolysis strategy was prepared, which was applied as a photocatalyst to activate peroxymonosulfate (PMS) for the degradation of p-chlorophenol (4-CP) under visible light irradiation (BFγ/PMS/Vis) system. The characterization results exhibited that γ-Fe2O3 with localized carbon doping was evenly embedded in biochar during the pyrolysis. BFγ exhibited better photoresponse properties than biochar (BC) and γ-Fe2O3. The removal efficiency of this system for 4-CP reached 96.41% under optimal conditions. This system showed high removal efficiency with a wide pH range (3.0–13.0) and under conditions of different organic pollutants. It also showed strong resistance to interference with co-existing inorganic ions and humic acid (HA). Electron paramagnetic resonance (EPR) and radical scavenging experiments revealed that the reactive oxygen species (ROS) in this system included SO4-·, ·OH, ·O2- and 1O2. The density functional theoretical (DFT) calculations further revealed the promotion of localized carbon doping in γ-Fe2O3 on electron transfer and photoresponse, including C-O bond (d=1.29 Å), C-Fe bond (d=1.80 Å) and band gap value (Egap < 0.72 eV). This study provides new insights into constructing environmentally-friendly catalysts and the possibility of the solid waste recycling for other wetland plants.

Dual Responsive Optical Sensor for The Detection of Zn2+and Al3+: Supportive Single‐Crystal X‐ray Structure of its Ni(II) Complex and DFT Studies

AbstractA tripodal pentadentate mono‐imine derivative, 2‐({2‐[bis‐(2‐amino‐ethyl)‐amino]‐ethylimino}‐methyl)‐phenol (L2) is employed for ‘turn on’ fluorescence recognition of Zn2+and Al3+at two different wavelengths. Chelation‐enhanced fluorescence (CHEF) assisted inhibition of excited‐state intramolecular proton transfer (ESIPT) is proposed as the sensing mechanism. The1HNMR, mass, IR spectral data, Jobs experiment and single crystal X‐ray structure of the [Ni(II)‐L2] complex (N1) strongly support the structure of L2 and its interaction with Zn2+and Al3+. Density functional theoretical (DFT) studies indicate higher stability of the Zn2+and Al3+adducts over free L2. The recognition of Zn2+and Al3+at two different emission wavelengths allows to construct a binary logic gate. Moreover, L2 is useful for determination unknown concentration of Al3+in real water samples. The complex N1 catalyses the catechol oxidation reaction.

Aggregation Behavior of Nitrilotriacetamide (NTAmide) Ligands in Thorium(IV) Extraction from Acidic Medium: Small-Angle Neutron Scattering, Fourier Transform Infrared, and Theoretical Studies.

Two tripodal amides obtained from nitrilotriacetic acid with n-butyl and n-octyl alkyl chains (HBNTA(LI) and HONTA(LII), respectively) were studied for the extraction of Th(IV) ions from nitric acid medium. The effect of the diluent medium, i.e., n-dodecane alone and a mixture of n-dodecane and 1-decanol, onto aggregate formation were investigated using small angle neutron scattering (SANS) studies. In addition, the influence of the ligand structure, nitric acid, and Th(IV) loading onto ligand aggregation and third-phase formation tendency was discussed.The LI/LII exist as monomers (aggregarte radius for LI: 6.0 Å; LII:7.4 Å) in the presence of 1-decanol, whereas LII forms dimers (aggregarte radius for LII:9.3 Å; LI does not dissolve in n-dodecane) in the absence of 1-decanol. The aggregation number increases for both the ligands after HNO3 and Th(IV) loading. The maximum organic concentration (0.050 ± 0.004 M) of Th(IV) was reached without third-phase formation for 0.1 M LI/LII dissolved in 20% isodecanol +80% n-dodecane. The interaction of 1-decanol with LII and HNO3/Th(IV) with amidic oxygens of LI/LII results in shift of carbonyl stretching frequency, as shown by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) studies. The structural and bonding information of the Th-LI/LII complex were derived from the density functional theoretical (DFT) studies. The molecular dynamics (MD) simulations suggested that the aggregation behavior of the ligand in the present system is governed by the population of hydrogen bonds by phase modifier around the ligand molecules. Although the theoretical studies suggested higher Gibbs free energy of complexation for Th4+ ions with LI than LII, the extraction was found to be higher with the latter, possibly due to the higher lipophilicity and solubility of the Th-LII aggregate in the nonpolar media.

Facet dependence of electrocatalytic furfural hydrogenation on palladium nanocrystals

AbstractElectrocatalytic hydrogenation (ECH) offers a sustainable route for the conversion of biomass-derived feedstocks under ambient conditions; however, an atomic-level understanding of the catalytic mechanism based on heterogeneous electrodes is lacking. To gain insights into the relation between electrocatalysis and the catalyst surface configuration, herein, the facet dependence of the ECH of furfural (FAL) is investigated on models of nanostructured Pd cubes, rhombic dodecahedrons, and octahedrons, which are predominantly enclosed by {100}, {110}, and {111} facets, respectively. The facet-dependent specific activity to afford furfuryl alcohol (FOL) follows the order of {111}>{100}>{110}. Experimental and theoretical kinetic analyses confirmed the occurrence of a competitive adsorption Langmuir-Hinshelwood mechanism on Pd, in which the ECH activity can be correlated with the difference between the binding energies of chemisorbed H (*H) and FAL (*FAL) based on density functional theoretical (DFT) calculations. Among the three facets, Pd{111} exhibiting the strongest *H but the weakest *FAL showed the copresence of the *H and *FAL intermediates on the Pd surface for subsequent hydrogenation, experimentally confirming its high ECH activity and Faradaic efficiency. The free energies determined using DFT calculations indicated that *H addition to the carbonyl of FAL on Pd{111} was thermodynamically preferred over desorption to gaseous H2, contributing to efficient ECH to afford FOL at the expense of H2 evolution. The obtained insights into the facet-dependent ECH underline that surface bindings assist ECH or H2 evolution considering their competitiveness. These findings are expected to deepen the fundamental understanding of electrochemical refinery and broaden the scope of electrocatalyst exploration.

Design of tandem CuO/CNTs composites for enhanced tetracycline degradation and antibacterial activity

The increasingly complex situation of the water environment has put forward higher requirements for the development of functional materials for comprehensive water environmental management. Here, a facile microwave self-assembly strategy was proposed to construct a tandem copper oxide/carbon nanotube (CuO/CNTs) composite. The characterization of the structure shows that the CNTs have been associated with porous CuO nanospheres, forming an interpenetrating architecture. We identified generated reactive oxygen species including sulfate radicals (SO4−), hydroxyl radicals (OH), singlet oxygen (1O2), and superoxide radical (O2−), which can rapidly improve the degradation of tetracycline (TC). Compared with individual CuO microspheres or CNTs, the reaction rate of TC on the CuO/CNTs is improved 1.9 and 6.5 times, respectively. In addition, we confirmed that the reactive oxygen species produced had an effectively inhibitory effect on common types of bacteria. Density functional theoretical (DFT) calculations show that the adsorption energy of PMS on the opposite side of graphene is favorable (−0.517 eV). The CuO/CNTs catalysts with excellent intrinsic properties suggest its wide potential applications in wastewater treatment.

Dielectric response and density functional theory assessment of fluorinated dicationic pyridinium ionic liquids

AbstractThis study represent the synthesis and electrical conductivity of two focused dicationic pyridinium ionic liquids (DiILs) carrying tetrafluoroborate and/or hexafluorophosphate as counter anion. Thus, the synthesis required quaternization of the pyridine nitrogen atoms first, followed by a metathetical exchange reaction to produce the task‐specific ILs bearing tetrafluoroborate and hexafluorophosphate as counter anions. The resulting DiILs were characterized by NMR and MS spectroscopy. The dielectric constant and the conductivity of the targeted DiILs were analyzed in detail, within a frequency‐range of 1 KHz to 0.3 MHz and a temperature range of 25–100°C. Density functional theoretical (DFT) calculations were also carried out at the base site, B3LYP 6–311 g (d,p), for the Syn/E isomers of the investigated ionic liquids (ILs). We found non‐coplanar molecular geometries with a twist angle of the Schiff base, dependent on the type of counter ion present. The energy levels and differences of the frontier molecular orbitals (FMOs) were also predicted using DFT calculations. The results revealed that the ILs incorporating BF4− as counter anions showed high HOMO and LUMO values with a higher energy gap, while low FMOs with a lower energy gap were recorded for the derivative encompassing PF6− counter anions. These findings were used to help explain the dielectric properties of the investigated DiILs.

3D printed bionic self-powered sensing device based on fern-shaped nitrogen doped BiVO4 photoanode with enriched oxygen vacancies

A portable three-dimensional (3D) printed bionic sensing device with enhanced photoelectric response was fabricated for sensitive detection of Bisphenol A (BPA). The proposed sensor is operated upon by using a highly reactive dual-electrode system to generate electrical output and provide the sensing signal under photoirradiation, without an external power source. The fern-shaped nitrogen doped BiVO4 photoanode with enriched oxygen vacancies (Ov) bismuth vanadate (N/Ov/BiVO4) photoanode was first synthesized and applied to construct a bionic sensing device. Density functional theoretical (DFT) calculation shows that the synergistic of nitrogen doping and Ov on the surface of photoanode leads to the emergence of impurity levels in BiVO4’s electronic structure, promoting the effective separation of photogenerated electron-hole pairs. Impressively, the unique fern-shaped bionic structure enhances the mass transfer efficiency of the sensing system and provides abundant binding sites of aptamer, realizing signal amplification. Moreover, a portable sensing device for automatic sample injection and detection is developed by integrating the detection system into a micromodel based on micro-nano 3D printing technology. Benefit from this ingenious design, the proposed bionic aptasensor displayed excellent electricity output and achieved high sensitivity and selectivity of BPA detection with a low limit of detection (0.025 nM) and broad linear range from 0.1 nM to 100 μM, paving a new way for the development of portable and on-site sensing devices.

DFT analysis on the adsorption of melamine in Ga12-N12/P12 nanocages: solvent effects, SERS analysis, reactivity properties

Due to its negative effects on people, melamine contamination in food products are detected and filtered. Amongst several sensory schemes for the screening of melamine poisoning, one of the most promising techniques is the use of nanomaterial based sensing for real time applicability in industries. In the current work, we have looked into the way melamine binds to Ga12-N12/P12 nanocages. Surface-enhanced Raman scattering (SERS), a successful spectroscopic technique is used to monitor melamine. Density functional theoretical (DFT) computations were used to study the sensing properties of melamine (Me) with Ga12-N12/P12 nanocages. Reactivity and Mulliken charge analyses show charge transfer from melamine to nanocage. Me-Ga12-N12 and Me-Ga12P12 clusters have adsorption energies of −47.54 and −33.12 kcal/mol, respectively. All nanocage-Me systems have a significant increase in polarizability. The electron densities revealed non-covalent interactions in the adsorbed systems. All adsorption energies in aqueous media are negative, indicating an attractive and exothermic reaction, with maximum value in water for Me-Ga12N12 and in acetone for Me-Ga12P12. Evidence of SERS is observed due to the enhancement of different vibrational modes. Communicated by Ramaswamy H. Sarma

CO2 Hydrogenation to Methanol on Indium Oxide-Supported Rhenium Catalysts: The Effects of Size

In this work, CO2 hydrogenation over In2O3-supported rhenium (Re) catalysts was found to be highly size-dependent. When the Re loading was less than 1 wt %, the strong interaction between Re and In2O3 caused atomically dispersed Re species with a positive charge, resulting in high activity for CO2 hydrogenation to methanol with enhanced stability at elevated temperatures. The space–time yield of methanol over the 1 wt % Re/In2O3 catalyst reached 0.54 gMeOH gcat–1 h–1 with a methanol selectivity of 72.1% at 5 MPa and 573 K. With increasing Re loading, the In2O3 supported Re catalysts become more favored for CO2 methanation. Under the same experimental conditions, the methane selectivity is close to 100.0% over the 10 wt % Re/In2O3 catalyst. Catalyst characterizations and density functional theoretical (DFT) calculations further confirm that the size of the Re/In2O3 catalyst has a significant effect on hydrogen activation and the selectivity of the CO2 hydrogenation reaction. Due to the strong Re–In2O3 interaction, the atomically dispersed Re in the In2O3 surface lattice not only stabilizes oxygen vacancies but also results in Hδ+ formation upon hydrogen adsorption. This significantly promotes methanol synthesis from CO2 hydrogenation. Meanwhile, the 10 wt % Re/In2O3 catalyst with supported Re nanoclusters induces Hδ- formation, which eventually leads to more methane production. The present study demonstrates the atomically dispersed Re/In2O3 catalyst is promising for CO2 hydrogenation to methanol.

Theoretical study of glycoluril by highly symmetrical magnesium oxide Mg12O12 nanostructure: adsorption, detection, SERS enhancement, and electrical conductivity study.

Using metal substrates that are nanoscale in size, surface-enhanced Raman scattering (SERS) is a technique for enhancing the Raman signal of biomolecules. Numerous industries including sensing materials, adsorption and medical devices, use nanomaterials like nanocages and nanoclusters. To discover a possible novel sensor platform involving a small metal cluster and a curved rigid substrate, we used density functional theoretical (DFT) simulations to explore the adsorption of glycoluril (GLC), a prospective drug intermediate, on a pure magnesium oxide cage (Mg12O12). This well defined cage was used as (i) an exact probable structure that could be used as well as (ii) a general model for MgO nanostructures. We also investigated the mono Al-doped Mg12O12 nanocage version Mg11AlO12. All computations were performed at the M06-2X level of theory. The GLC binds to the Mg12O12 nanocage by way of strong donor-acceptor interactions. The adsorption is releasing - 45.80kcalmol-1 of energy. Due to Al doping, the energy gap of GLC-Mg11AlO12 (1.91eV) is reduced from that of GLC-Mg12O12 (4.28eV) and hence there is an increase in electrical conductivity of GLC-Mg11AlO12. The electronic change in the nanocage's conductivity can be transformed into an electrical signal which can be used to detect the presence of the drug analyte. In addition, when a GLC molecule is present, the work function of the nanocage is also reduced. The MgO nanocage, we conclude, is a work function type as well as a possible electronic sensor for GLC drug detection. GLC desorption from the Mg11AlO12 surface recovers more quickly in comparison with Mg12O12 recovery time. The AIM and NCIs assessed in this study were performed to help analyze the electronic structures of the complexes. Our findings pave the possibility for Mg11AlO12 nanostructures to be used in drug recognition.

A metal alkynyl molecular wire with PN ligands: Synthesis, isomerization, physical properties and single-molecule conductance

As new candidates for organometallic molecular wires, we designed a ruthenium trans-di(alkynyl) molecular wire 1H, trans-Ru(PN)2(C≡CC≡C-H)2, with the two mixed phosphine-pyridine supporting ligands (PN: 2-diphenylphosphinomethyl-6-methylpyridine). While two stereo-isomers with the syn and anti configurations were possible, the syn isomers of triisopropylsilylbutadiynyl precursors syn-1TIPS and syn-1H were prepared in direct and stereo-selective manners. Electrochemical analysis of syn-1TIPS revealed a virtually reversible redox wave with the potential cathodically shifted compared to that of the bis(diphosphine) analogue 2TMS, trans-Ru(dppe)2(C≡CC≡C-SiMe3)2. The density functional theoretical (DFT) study supports the similarity of the electronic structures of 1 and 2 with the HOMOs being close to the Fermi energy level of gold electrodes. STM-break junction measurements of Au-syn-1-Au (Au: gold electrode) revealed high single-molecule conductance (1.9 × 10–2G0), which is comparable to that of Au-2-Au. Calculations on the basis of the DFT-non equilibrium Green’s function method also support the experimental results. Notably, the molecular junction Au- syn-1-Au can be formed from syn-1H through C-H activation and formation of Au-C bonds without any pre-functionalization in contrast to the bis(diphosphine) analogue 2H, which requires terminal gold functionalization.

Molecular levels unveil the membrane fouling mitigation mechanism of a superpotent N-rGO catalytic ozonation membrane: Interfacial catalytic reaction pathway and induced EfOM transformation reactions

This study investigated the membrane fouling self-cleaning of N-doped reduced graphene oxide (N-rGO)-tailored ceramic membrane with ozone (N-rGO-CM-O/F) at the molecular level. Density functional theoretical (DFT) revealed the principle of interfacial catalytic reaction, and the transformation of foulants was probed using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and various spectroscopic techniques. Results showed that ozone could be aggregated on the N-rGO-CM surface and formed abundant •OH. This made humic acid-like substances blocking membrane pores to be sufficiently and preferentially removed in N-rGO-CM-O/F by 18-types reactions of catalytic ozonation. Conversely, CM-O/F preferentially removed protein-like substances that formed the cake layer. Due to the stronger catalytic ozonation ability and efficient fouling mitigation behavior, N-rGO-CM-O/F showed higher water flux as 1.96 times than that of CM-O/F. Overall, this study provided molecular insight into the mechanism of membrane fouling mitigation, which will facilitate the design and application of advanced catalytic membranes.

A computational mechanistic study of the hydrolytic degradation of three common pyrethroid insecticides

The hydrolytic evolution mechanisms of three pyrethroid insecticides: Imiprothrin, deltamethrin and tetramethrin, commonly applied in bug sprays, were investigated via density functional theoretical (DFT) modelling. Whereas for deltamethrin, hydrolysis terminates after cleavage of the ester linkage in the starting compound via an asynchronously formed four membered cyclic transition state, for the other two compounds, the final transition state result in the release of formaldehyde and a cyclic amide via a five membered cyclic activated complex. Furthermore, though the mechanisms for all compounds are limited by the ester hydrolysis step; the first for deltamethrin and tetramethrin, the hydrolytic evolution for imiprothrin commences with a water catalysed tautomerization process. The limiting activation free energy barrier, for all three compounds: ΔGǂ = 221–290 kJ mol−1, is such that their residence time in air should be several months; the shortest of which would be that for deltamethrin followed by tetramethrin.

Vibrational and electronic absorption spectroscopic and density functional theoretical studies on the 2(3H)-benzothiazolone and its anion

In this paper, 2(3H)-benzothiazolone(2-BTO) was investigated in crystalloid using infrared, and Raman spectroscopies combining with density functional theoretical (DFT) calculation. Further using the steady absorption spectra, the dimer and anion structures were characterized combining with the time-dependent density functional theoretical (TD-DFT) calculations. Our results indicated that in the crystalline the dimer was stabilized due to the strong intermolecular hydrogen bonds (HBs) by vibrational spectroscopic and DFT calculation, and even in methanol and water solvents, the hydrogen bonds between BTO and methanol, even and water could not catch up with the HBs strength of the dimer. However, only was the base doped into methanol and water, hydrogen bonds between the dimer would be cleavage to further produce the monomer anion, which can be determined by the steady UV–Vis absorption spectroscopy and TD-DFT calculation. A simple, convenient and pratical method is proposed to detect the structure and optical properties of benzothiazolones and its anion.

Exploring the Mechanism of Ionic Liquids to Improve the Extraction Efficiency of Essential Oils Based on Density Functional Theory and Molecular Dynamics Simulation.

Highlights According to the design of the experiment (DoE), multivariate analysis models were used to optimize the critical process parameters combined with multi-objective optimization.Based on the optimized operating conditions, the MILT-HD method not only enhances the extraction efficiency from Amomi fructus but also reduces energy demands and CO2 emissions.Based on the density functional theoretical (DFT) and molecular dynamics (MD) simulations, the mechanisms for ionic liquids (ILs) to improve the extraction efficiency of essential oil was comprehensively revealed. In this paper, Amomi fructus (Latin) was used to explore the mechanism of ionic liquids (ILs) in improving the extraction efficiency of essential oils. Microwave assisted ionic liquid treatment followed by a hydro-distillation (MILT-HD) process for isolating Amomi fructus essential oil was optimized by multi-objective optimization. Under optimum operating conditions, the IL-assisted extraction method not only enhances extraction efficiency but also reduces energy demands and CO2 emissions. Since the hydrogen bond structure network of cellulose in the cell wall is an important reason for hindering diffusion of essential oils, the mechanism of ILs was explored by density functional theoretical (DFT) and molecular dynamics (MD) simulations. According to DFT calculations, ILs can facilitate the cleavage of cellulose chains and have strong non-covalent interactions with cellulose. Based on the MD simulations, the degree of destruction of the cellulose hydrogen bond structure was explored. According to the DFT and MD simulations, the ILs can significantly destroy cellulose structure, thereby promoting essential oil release from the plant. These results were confirmed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). This work is conducive to better understand the MILT-HD process for isolating essential oil and comprehensively understand the mechanism of ILs in the extraction process.