Electron Transfer Energy Research Articles

Novel Electrochemical Synthesis and Characterization of Zn(II) Metal Organic Framework for Photo-catalytic and Sensing Applications.

Multidentate 1,3,5-benzenetricarboxylic acid (organic linker), Zn (II) based Zn-BTC has been synthesized via electrochemical method. Quantitative and Qualitative analyses of synthesized metal-organic framework (MOF) have been done using Fourier Transform Infrared (FTIR) Spectroscopy, Energy Dispersive X- Ray Spectroscopy (EDS), and Photoluminescence (PL). Powder X-Ray Diffraction (PXRD) and Scanning Electron Microscopy (SEM) have been used for crystallographic and morphological & topographical analyses, respectively. Crystallographic studies confirm the formation of face-centered cubic (fcc) crystal structure with good crystallinity. Photo-catalytic activity of synthesized MOF has been tested using Methylene Blue (MB) dye as a test contaminant in aqueous media under sunlight irradiation. Recorded results reveal that the synthesized MOF efficiently degrade MB dye upto 96% under sunlight exposure after 270min. Photoluminescence studies indicate that Zn-BTC could be used as an efficient material for sensing of nitroaromatic compounds (NACs): 4-Nitroaniline (4-NA), 2-Nitroaniline (2-NA), 3- Nitroaniline (3-NA), 2,4-Dinitrotoulene (2,4-DNT), 4-Nitrotoulene (4-NT) in N,N'-Dimethylformamide (DMF) by fluorescence quenching and shows maximum quenching efficiency towards 3-NA (72.80%). Notably, the variation in luminescence intensity of 3-NA@Zn-BTC shows a linear relationship over its different concentrations from 0-1000ppb range with KSV = 2.7 × 104M-1 and R2 = 0.9924 with limit of detection 0.889ppb (6.43µM) (LOD). The possible ways of luminescence quenching are successfully explained by the combination of Photoinduced Electron Transfer (PET) and Resonance Energy Transfer (RET) mechanisms. Additionally, the Density Functional Theory (DFT) calculations have been employed to support the experimental results. Zn-BTC fully demonstrates the power of a multi component MOF, which provides a feasible pathway for the design of novel material towards fast responding luminescence sensing and photocatalytic degradation of pollutants.

Kinetics of Initial Charge Separation in the Photosynthetic Reaction Centers of Rhodobacter sphaeroides.

A stochastic kinetic study of the initial electron transfer reaction in the reaction centers of wild-type and different mutants of photosynthetic bacterium Rhodobacter sphaeroides is suggested. The present approach to the disorder-driven complex kinetics skilfully offers an alternative to the earlier dynamic analyses. Exploiting a rational description of the reaction coordinate, effected by the relaxation of the surrounding protein environment, the measured kinetics were reproduced quantitatively. Notably, comparisons of the extracted relative free energies of electron transfer for the selected mutants and the available independent electrochemical estimates show exact agreement in some cases.

Reorganization Energy of Electron Transfer in Ionic Liquids

Bandshape analysis of charge-transfer optical bands in room-temperature ionic liquids (ILs) was performed to extract the reorganization energy of electron transfer. Remarkably, the reorganization energies in ILs are close to those in cyclohexane. This result runs against common wisdom in the field since conducting ILs, which are characterized by an infinite static dielectric constant, and nonpolar cyclohexane fall to the opposite ends of the polarity scale based on their dielectric constants. Theoretical calculations employing structure factors of ILs from molecular dynamics simulations support the low values of the reorganization energy. Standard dielectric arguments do not apply to solvation in ILs, and nonergodic reorganization energies are required for a quantitative analysis.

Amphiphilic fluorescent nanospheres for quantitative sensing of trinitrophenol in water system

2,4,6-Trinitrophenol (TNP) is an important chemical and widely applied in industry. However, on account of its high toxicity, flammability and explosive nature, just trace amounts of TNP may cause potential threats to ecosystem and human security, so it is significant to establish a rapid and reliable method for the detection of TNP. Herein, a novel amphiphilic fluorescent probe TPE-CD was successfully designed and synthesized by the functionalization of hydrophilic β-cyclodextrin with a hydrophobic Aggregation Induced Emission (AIE) fluorophore. Moreover, spherical nanoparticles formed in H2O/CH3OH solution with the increase of water fraction (fw). Fluorescence titration of TNP indicated that TPE-CD exhibited excellent sensitivity to TNP with LOD = 0.31 μmol L−1 and Ksv = 3.06 × 104 L mol−1. The introduced β-cyclodextrin remarkably enhanced the ability of TPE-CD rather than its precursor TPE-COOH to capture TNP molecules through forming spherical nanoparticles, improving the fluorescence quenching efficiency. Density Functional Theory (DFT) calculations and experimental results confirmed that the response mechanism of TPE-CD to TNP involved Photoinduced Electron Transfer (PET) and Fluorescence Resonance Energy Transfer (FRET) with PET being predominant. Furthermore, the probe showed excellent selectivity and anti-interference to aqueous TNP samples. Moreover, the test strips prepared by soaking in TPE-CD solution also exhibited good sensitivity to TNP, providing a convenient, rapid and reliable method for the detection of TNP.

A Novel Method for the Synthesis of MOF-199 for Sensing and Photocatalytic Applications.

Multifunctional Cu (II)-based Metal Organic Framework (MOF) [Cu3(BTC)2] has been synthesized by a facile electrochemical method. Crystallographic and morphological characterizations of synthesized MOF have been done using Powder X-ray Diffractometer and Scanning Electron Microscope (SEM), respectively, whereas Fourier Transform Infrared Spectroscopy (FT-IR), Energy Dispersive X-ray Spectroscopy (EDS), UV-Vis Absorption Spectroscopy and Energy Resolved Luminescence Spectroscopic studies have been used for the detailed qualitative, quantitative as well as optical analyses. Sharp PXRD peaks indicate the formation of highly crystalline MOF with face centered cubic (fcc) structure. Flakes (average length = 0.71µm and width = 0.10µm) and rods (average aspect ratio = ((0.1:8.3) µm) like morphologies have been observed in SEM micrographs. The presence of C, O and Cu has been confirmed by EDS analysis. Photocatalytic activity potential of the synthesized MOF has been tested using methylene blue dye (MB) as a test contaminant in aqueous media under sunlight irradiation. Selective and sensitive fluorescent sensing of different Nitroaromatic compounds (NACs) like 4-Nitroaniline (4-NA), 2-Nitroaniline (2-NA), 3-Nitroaniline (3-NA), 4-Nitrotoulene (4-NT), 2,4-Dinitrotoulene (2,4-DNT), 1,3-Dinitrobenzene (1,3-DNB), 2,6- Dinitrotoulene (2,6-DNT) has been done by exploring the photoluminescent behaviour of chemically stable Cu3(BTC)2. Synthesized MOF is extremely sensitive towards 4-NA, which is having PL quenching efficiency of 82.61% with highest quenching rate till reported. Indeed, a large quenching coefficient KSV = 34.02 × 10-7M-1 and correlation coefficient R2 = 0.9962 in KSV plot have been elucidated with limit of detection (LOD) = 0.7544ppb. The possible ways of luminescence quenching are successfully explained by the combination of Photoinduced Electron Transfer (PET) and Resonance Energy Transfer (RET) mechanisms. Additionally, the Density Functional Theory (DFT) calculations have been employed to support the experimental results. Cu3(BTC)2 fully demonstrates the power of a multi component MOF, which provides a feasible pathway for the design of novel material towards fast responding luminescence sensing and photocatalytic degradation of pollutants.

A novel hydrolytically stable fluorescent Cd(II) coordination polymer showing solvent-dependent multi-responsive fluorescence sensing to pH and some metal ions

Herein, the assembly between the multi-functional 2-amino-4-sulfonyl-benzoic acid (H2asba) and Cd(II) in the presence of the hydrophobic ligand 4-bis[(2-methyl-1H-imidazole-1-yl)methyl]benzene (2-mmzm) results in a novel hydrolytically sTable 1D Cd(II)-FCP, {[Cd(asba)(2-mmzm)(H2O)2]·3H2O}n (1). The water tetramer-based hydrogen-bonded ring R22 (8) bridges the chains into a 2D supramolecular layer. The novel discrete water decamer further links the layers into a 3D supramolecular network.1 shows extremely acidic and basic resistance in a wide pH range of 1.0–12.0. More importantly, 1 exhibits accurate sensing of pH of the artificial gastric juices. Interestingly, 1 demonstrates solvent-dependent multi-responsive fluorescence sensing behavior to metal ions. 1 can sense Fe3+/Cu2+/Tb3+ in water, Fe3+/Cu2+/Tb3+/Co2+ in MeOH and Fe3+/Cu2+/Tb3+/Co2+/Ba2+ in ethanol, respectively. The fluorescence sensing of 1 toward Fe3+/Tb3+/Ba2+ is resulted from the structural collapse in the corresponding solvents. However, 1 keeps integrity and shows higher chemical resistance to Cu2+ and Co2+ in the corresponding solvents. The fluorescence sensing of Cu2+ can be ascribed to the photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) mechanism. The sensing of Co2+ can be attributed to the PET mechanism. The solvents have great influence on the sensing sensitivities to Cu2+ and Co2+. 1 shows the highest sensing sensitivity to Cu2+ and Co2+ in ethanol.

Molecular Geometry Dependent Electronic Coupling and Reorganization Energy for Electron Transfer between Dye Molecule Adsorbed on TiO2 Electrode and Co Complex in Electrolyte Solutions

Molecular Geometry Dependent Electronic Coupling and Reorganization Energy for Electron Transfer between Dye Molecule Adsorbed on TiO₂ Electrode and Co Complex in Electrolyte Solutions

Surface and interface chemistry in metal‐free electrocatalysts for electrochemical CO2 reduction

AbstractThe electrochemical reduction of carbon dioxide (CO2) into value‐added fuels and chemicals presents a sustainable route to alleviate CO2 emissions, promote carbon‐neutral cycles and reduce the dependence on fossil fuels. Considering the thermodynamic stability of the CO2 molecule and sluggish reaction kinetics, it is still a challenge to design highly efficient electrocatalysts for the CO2 reduction reaction (CO2RR). It has been found that the surface and interface chemistry of electrocatalysts can modulate the electronic structure and increase the active sites, which is favorable for CO2 adsorption, electron transfer, mass transport, and optimizing adsorption strength of reaction intermediates. However, the effect of surface and interface chemistry on metal‐free electrocatalysts (MFEs) for CO2RR has not been comprehensively reviewed. Herein, we discuss the importance of the surface and interface chemistry on MFEs for improving the electrochemical CO2RR performance based on thermodynamic and kinetic views. The fundamentals and challenges of CO2RR are firstly presented. Then, the recent advances of the surface and interface chemistry in improving reaction rate and overcoming reaction constraints are reviewed from regulating electronic structure, active sites, electron transfer, mass transport, and intermediate binding energy. Finally, the research challenges and prospects are proposed to suggest the future designs of advanced MFEs in CO2RR.

A spatial and temporal characterisation of single proton acoustic waves in proton beam cancer therapy.

An in vivo range verification technology for proton beam cancer therapy, preferably in real-time and with submillimeter resolution, is desired to reduce the present uncertainty in dose localization. Acoustical imaging technologies exploiting possible local interactions between protons and microbubbles or nanodroplets might be an interesting option. Unfortunately, a theoretical model capable of characterising the acoustical field generated by an individual proton on nanometer and micrometer scales is still missing. In this work, such a model is presented. The proton acoustic field is generated by the adiabatic expansion of a region that is locally heated by a passing proton. To model the proton heat deposition, secondary electron production due to protons has been quantified using a semi-empirical model based on Rutherford's scattering theory, which reproduces experimentally obtained electronic stopping power values for protons in water within 10% over the full energy range. The electrons transfer energy into heat via electron-phonon coupling to atoms along the proton track. The resulting temperature increase is calculated using an inelastic thermal spike model. Heat deposition can be regarded as instantaneous, thus, stress confinement is ensured and acoustical initial conditions are set. The resulting thermoacoustic field in the nanometer and micrometer range from the single proton track is computed by solving the thermoacoustic wave equation using k-space Green's functions, yielding the characteristic amplitudes and frequencies present in the acoustic signal generated by a single proton in an aqueous medium. Wavefield expansion and asymptotic approximations are used to extend the spatial and temporal ranges of the proton acoustic field.

Antioxidant activity of erlotinib and gefitinib: theoretical and experimental insights

Erlotinib and gefitinib are quinazoline derivatives with antineoplastic properties. Usually, intake of antineoplastic agents results in much a greater degree of oxidative stress, i.e. the production of free radicals, than induced by cancer itself. Hence, anticancerous drugs must also exhibit antioxidant activity but this has not been studied thus far. In this study, the antioxidant activity of erlotinib and gefitinib was examined by experimental and computational studies. It was found that erlotinib and gefitinib exhibit good 2,2-dipheny l-1-picrylhydrazyl (DPPH) radical and hydroxyl radical scavenging (HRS) activities. In DPPH assay, the IC50 for erlotinib and gefitinib were 0.584 and 0.696 mM, respectively, while IC50 for HRS assay were 0.843 and 1.03 mM for erlotinib and gefitinib, respectively. Structural characteristics such as frontier molecular orbitals (FMOs), molecular electrostatic potential maps (MESPs), and global descriptive parameters were calculated at DFT/B3LYP/6-311++G (d,p) on the optimized geometries of erlotinib and gefitinib. UV–visible spectroscopy revealed the possible electronic transitions between the FMOs and their associated excitation energies of both drugs and found that erlotinib has π to π* transitions while gefitinib has π to π* and σ to π* transitions. To elucidate the antioxidant activity of erlotinib and gefitinib, three mechanisms namely hydrogen atom transfer (HAT), single electron transfer proton transfer (SETPT), and sequential proton-loss electron-transfer (SPLET) were employed and articulated the results in arithmetic parameters like bond dissociation energy (BDE), proton affinity (PA), ionization potential (IP), electron transfer enthalpy (ETE), and proton dissociation enthalpy (PDE). Further, molecular docking studies have been carried out to have a better understanding of binding sites and modes of interaction with a well-known antioxidant target protein monoamine oxidase-B (MAO-B) employing docking scores and types of interactions. All the calculated parameters point out that though gefitinib and erlotinib were interchangeable, erlotinib requires a lesser amount of energy for proton transfer and electron transfer, moreover it scavenges radicals easily.

Construction of Two-Dimensional Fluorescent Covalent Organic Framework Nanosheets for the Detection and Removal of Nitrophenols.

In this work, we synthesized a two-dimensional fluorescent covalent-organic framework (TFPB-TTA COF) nanosheet by selecting and designing reactive monomers to realize the dual-functional processing of nitrophenols. The staggered benzene ring, triazine structure, and imine bond (C═N) of the TFPB-TTA COF can capture free nitrophenols through hydrogen bonding and conjugation interaction, and then, the photoinduced electron transfer and fluorescence resonance energy transfer (FRET) between the TFPB-TTA COF and nitrophenols affects the fluorescence emission of the TFPB-TTA COF, realizing the fluorescence sensing of nitrophenols. The large Ksv values and the low detection limit suggest that the TFPB-TTA COF can serve as sensitive and selective fluorescence sensors for nitrophenol detection in an aqueous system. At the same time, the strong interaction combined with the porous network structure of the TFPB-TTA COF facilitates the efficient adsorption and removal of nitrophenols. Especially for 2,4,6-trinitrophenol, the maximum adsorption capacity can reach 1045.53 mg/g with good recyclability and high structural stability of the TFPB-TTA COF. This work proposed a simple synthetic method for the construction of a fluorescent COF platform for the sensitive determination and efficient adsorption of nitrophenols.

Luminescent Two-Dimensional Metal-Organic Framework Nanosheets with Large π-Conjugated System: Design, Synthesis, and Detection of Anti-Inflammatory Drugs and Pesticides.

Two-dimensional (2D) metal-organic framework (MOF) nanosheets, with largely exposed surface area and highly accessible active sites, have emerged as a novel kind of sensing material. Here, a luminescent 2D MOF nanosheet was designed and synthesized by a facile top-down strategy based on a three-dimensional (3D) layered MOF {[Zn(H2L)(H2O)2]·H2O}n (Zn-MOF; H4L = 3,5-bis(3',5'-dicarboxyphenyl)-1H-1,2,4-triazole). With a large π-conjugated system and rigid planar structure, ligand H4L was elaborately selected to construct the bulk Zn-MOF, which can be readily exfoliated into 2D nanosheets, owing to the weak interlayer interactions and easy-to-release H2O molecules in the interspaces of 2D layers. Given the great threat posed to the ecological environment by anti-inflammatory drugs and pesticides, the developed luminescent Zn-MOF nanosheets were utilized to determine these organic pollutants, achieving highly selective and sensitive detection of diclofenac sodium (DCF) and tetramethylthiuram disulfide (TMTD). Compared to the detection limits of 3D Zn-MOF (7.72 ppm for DCF, 6.01 ppm for TMTD), the obviously lower detection limits for 2D Zn-MOF nanosheets toward DCF (0.20 ppm) and TMTD (0.18 ppm) further revealed that the largely exposed surface area with rigid planar structure and ultralarge π-conjugated system greatly accelerated electron transfer, which brought about a vast improvement in response sensitivity. The remarkable quenching performance for DCF and TMTD stems from a combined effect of photoinduced electron transfer and competitive energy absorption. The possible sensing mechanism was systematically investigated by the studies of powder X-ray diffraction, UV-vis, luminescence lifetime, and density functional theory calculations.

Water use efficiency and photosynthesis of Calamagrostis angustifolia leaves under drought stress through CO2 concentration increase

ABSTRACT The effects of elevated CO2 concentration on photosynthetic gas exchange parameters and chlorophyll fluorescence parameters in leaves of Calamagrostis angustifolia seedlings under drought stress were studied through control of different CO2 concentrations (370 and 700 μmol·mol−1) with an artificial OTC climate chamber. The results demonstrated that: Under non-drought conditions, although the stomatal conductance (G s) and transpiration rate (T r) decreased slightly as the CO2 concentration increased, while the net photosynthetic rate (P n) increased significantly, resulting in a significant increase in leaf water use efficiency (WUE). However, the effect of elevated CO2 concentration on PSII reaction center activity was insignificant under non drought conditions. Under severe drought stress, the amount of active reaction centers per unit area and the proportion of PSII absorbed light energy for photosynthetic electron transfer increased, while the proportion of PSII absorbed light energy for heat dissipation decreased, providing energy guarantee for effective fixation of CO2 as dark reaction. In conclusion, elevated CO2 concentration could improve the water use efficiency of C. angustifolia seedlings under normal water and drought stress, and the elevated CO2 concentration could improve the drought resistance ability of C. angustifolia seedlings through PSII function improvement under severe drought stress.

Rational Design and Facile Synthesis of Dual-State Emission Fluorophores: Expanding Functionality for the Sensitive Detection of Nitroaromatic Compounds.

Six novel benzimidazole-based D-π-A compounds 4 a-4 f were concisely synthesized by attaching different donor/acceptor units to the skeleton of 1,3-bis(1H-benzimidazol-2-yl)benzene on its 5-position through an ethynyl link. Due to the twisted conformation and effective conjugation structure, these dual-state emission (DSE) molecules show intense and multifarious photoluminescence, and their fluorescence quantum yields in solution and solid state can be up to 96.16 and 69.82 %, respectively. Especially, for excellent photostability, obvious solvatofluorochromic and extraordinary wide range of solvent compatibility, DSE molecule 4 a is a multifunctional fluorescent probe for the visual detection of nitroaromatic compounds (NACs) with the limit of detection as low as 10-7 M. The quenching mechanism has been proved as the results of photoinduced electron transfer and fluorescence resonance energy transfer processes. Importantly, probe 4 a can sensitively detect NACs not only in real water samples, but also on 4 a-coated strips and 4 a@PBAT thin films.

Kinetics and Energetics of Intramolecular Electron Transfer in Single-Point Labeled TUPS-Cytochrome c Derivatives.

Electron transfer within and between proteins is a fundamental biological phenomenon, in which efficiency depends on several physical parameters. We have engineered a number of horse heart cytochrome c single-point mutants with cysteine substitutions at various positions of the protein surface. To these cysteines, as well as to several native lysine side chains, the photoinduced redox label 8-thiouredopyrene-1,3,6-trisulfonate (TUPS) was covalently attached. The long-lived, low potential triplet excited state of TUPS, generated with high quantum efficiency, serves as an electron donor to the oxidized heme c. The rates of the forward (from the label to the heme) and the reverse (from the reduced heme back to the oxidized label) electron transfer reactions were obtained from multichannel and single wavelength flash photolysis absorption kinetic experiments. The electronic coupling term and the reorganization energy for electron transfer in this system were estimated from temperature-dependent experiments and compared with calculated parameters using the crystal and the solution NMR structure of the protein. These results together with the observation of multiexponential kinetics strongly support earlier conclusions that the flexible arm connecting TUPS to the protein allows several shortcut routes for the electron involving through space jumps between the label and the protein surface.

Ab Initio Nonadiabatic Surface-Hopping Trajectory Simulations of Photocatalytic Water Oxidation and Hydrogen Evolution with the Heptazine Chromophore.

In the past decade, polymeric carbon nitrides consisting of heptazine (Hz) building blocks emerged as highly promising materials for photocatalytic hydrogen evolution from water or sacrificial electron donors with near-ultraviolet light. However, the complexity of these materials and their poor characterization at the atomic level are detrimental to the unraveling of the detailed mechanisms of the reactions leading to hydrogen evolution. Recently, it has been shown that a derivative of the Hz molecule, trianisole-heptazine (TAHz), is a potent photobase, which readily oxidizes various derivatives of phenol and even water by an excited-state proton-coupled electron-transfer (PCET) reaction. Energy profiles along minimum-energy reaction paths and relaxed PCET potential-energy surfaces, which previously were computed with ab initio electronic-structure methods for complexes of Hz and TAHz with protic substrates, led to qualitative insights. To obtain more quantitative insight, reaction dynamics simulations are required. In the present work, the time scales of the electron and proton transfer processes and the branching ratios of competing channels were explored with ab initio on-the-fly quasiclassical surface-hopping trajectory simulations for the hydrogen-bonded Hz-H2O complex. By the analysis of representative trajectories, detailed insight into the interplay of various nonadiabatic electronic transitions, electron transfer, proton transfer, and vibrational energy relaxation is obtained. The HzH radicals which are formed by the photoreduction of Hz can disproportionate to Hz and HzH2 in an exothermic reaction with a low reaction barrier. The time scales and branching ratios of competing channels in H-atom photodetachment from the HzH2 molecule also were explored with ab initio surface-hopping simulations. These results delineate for the first time a quantitatively supported scenario of water oxidation and hydrogen evolution with a molecular carbon nitride photocatalyst.

Photosensitized Protein Damage by DiethyleneglycoxyP(V)tetrakis(p-n-butoxyphenyl)porphyrin Through Electron Transfer: Activity Control Through Self-aggregation and Dissociation.

DiethyleneglycoxyP(V)tetrakis(p-n-butoxyphenyl)porphyrin (EGP(V)TBPP) forms a self-aggregation in an aqueous solution, and the photoexcited state of this molecule was effectively deactivated. Association with human serum albumin (HSA), a water-soluble protein, causes dissociation of the self-aggregation, resulting in recovery of the photosensitizer activity of EGP(V)TBPP. Under visible light irradiation, EGP(V)TBPP photosensitized HSA oxidation. The photosensitized singlet oxygen-generating activity of EGP(V)TBPP was confirmed by near-infrared emission measurement. A singlet oxygen quencher, sodium azide, partially inhibited the HSA photodamage; however, the quenching effect was estimated to be 57%. Another 43% of the HSA photodamage could be explained by the electron transfer mechanism. The redox potential of EGP(V)TBPP and the calculated Gibbs energy of electron transfer from tryptophan to photoexcited EGP(V)TBPP demonstrated the possibility of HSA oxidation through electron extraction. Fluorescence lifetime measurements of EGP(V)TBPP verified the electron transfer from HSA. The photosensitizer activity of EGP(V)TBPP can be controlled through an association with biomolecules, such as protein, and the electron transfer-mediated biomolecule photooxidation plays an important role in photodynamic therapy under hypoxia.

Boosting the lattice oxygen activity of Fe-catalyst for producing 2,5-diformylfuran from 5-hydroxymethylfurfural

In this work, a novel bimetallic catalyst FeCu@CN was built by calcination of a Fe-Cu/cellulosic polymer framework precursor, which can be observed as FeCuOx nanoparticles well distributed on biochar. The as-synthesized FeCu@CN showed outstanding catalytic performance for producing 2,5-diformylfuran (DFF) via selective oxidation of 5-hydroxymethylfurfural (HMF), which showed better performance compared to Fe-based catalysts once reported. With high TOF of 19.62 h1 for the formation of DFF by using FeCu@CN, 98% of HMF conversion and 95% yield of DFF were effectively obtained using O2 as the oxidant in acetonitrile. The results and catalyst characterization revealed that the Cu sites and urea modification significantly increased the Fe valence and improved activity of lattice oxygen in the parallelogram carbon frame, thereby reducing the electronic transfer energy to preference Fe-HMF interaction. In this oxidative process, Fe3+ played a pivotal catalytic performace by the redox cycle of Fe2+ and Fe3+, while Cu acted as a co-catalyst to facilitate it by the redox cycle of Cu2+ and Cu+ with Mars-van Krevelen oxidation mechanism.

Synthesis of Copper Metal Organic Framework Based on Schiff Base Tricarboxylate Ligand for Highly Selective and Sensitive Detection of 2,4,6-Trinitrophenol in Aqueous Medium.

By using Schiff base tricarboxylate ligand 5-(4-carboxybenzylideneamino)isophthalic acid (H3CIP), a new imine functionalized copper metal organic framework (MOF) has been synthesized solvothermally. It was fully characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and elemental mapping techniques. The as-synthesized MOF has been utilized as fluorescent probe for detection of nitro aromatic explosives (NAEs). The results show that the copper MOF can be developed into highly selective and sensitive sensor for detection of TNP in the aqueous medium via the "turn-off" quenching response. The linear fitting of the Stern-Volmer plot for TNP offered large quenching constant of 1.07 × 104 M-1 for Cu-MOF indicating the high sensitivity of the sensing process. Outstanding sensitivity of prepared material towards TNP detection was further validated by the low detection limit of 80 ppb (0.35 µM). The detailed mechanistic studies for their mode of action and density functional theory (DFT) calculations reveals that photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) processes, as well as electrostatic interactions (i.e. H-bonding) are the key factors for the turn-off response toward TNP by this fluorescent sensor. Thus, this new LMOF owing to their high water stability and remarkable functional features are potential candidates which can be developed into selective and sensitive TNP detection devices.

Fomesafen drift affects morphophysiology of sugar beet

Fomesafen is an herbicide used in soybean production, and sugar beet is a sensitive crop to fomesafen. When the herbicide is sprayed in the field, it is easy to cause floating and depositing on non-target crops, resulting in crop poisoning and reducing yield. There are few on the phenomenon and mechanism of fomesafen herbicide drift on sugar beet. There are few reports on the phenomenon and mechanism of ether herbicide migration on phytotoxicity of sugar beet. Therefore, in this experiment, indoor potted plants were used to simulate the dose of fomesafen drift deposited on sugar beet in the field to study the effects of fomesafen on the growth, photosynthetic system, and physiological indexes of seedlings for sugar beet were studied. The results showed that fomesafen at the dose of 225 g a.i. ha−1 significantly inhibited the plant height, root length, and biomass of sugar beet. Compared with the control, the net photosynthetic rate, stoma conductance, transpiration rate, and total chlorophyll pigment content of leaves were reduced by 77.16%, 83.84%, 64.00%, and 28.13%, respectively. Treatment with a dose of 225 g a.i. ha−1 also damaged the photosynthetic system II of the leaves, lowering the performance index on absorption energy, maximum quantum yield and, the energy of electron transfer, causing photoinhibition and photodamage. In addition, fomesafen significantly increased the content of malondialdehyde and the activity of peroxidase in leaves of sugar beet, reducing the activities of superoxide dismutase and catalase. Overall, this study is helpful to understand the drift and deposition of fomesafen on sugar beet and to discuss the phytotoxicity risk and dose of fomesafen on the beet, as a result of controlling the dose of fomesafen sprayed in the field.