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Treatment of Trichloroethylene with Photocatalyst-Coated Optical Fiber
摘要： In this present study, we investigated the effect of photocatalyzation on the degradation of trichloroethylene (TCE) in the aqueous phase by a photocatalyst-coated plastic optical fiber (POF). Two light-emitting diodes (LEDs) with low light intensity were used as the light source and TiO2 and ZnO were used as photocatalysts, which were characterized by scanning electron microscope (SEM) and UV-Vis diffuse reflectance spectroscopy (DRS). The para-chlorobenzoic acid (pCBA) was used as the hydroxyl radical probe for kinetic study and for the calculation of hydroxyl radical conversion rate (ROH,UV ). Experimental results show that POF coated with TiO2 exhibited higher degradation efficiency of TCE in basic solution, but POF coated with ZnO performed better in acidic solution. The increase of coating times resulted in the decrease in degradation efficiency of TCE due to increased thickness of the photocatalyst layer. The enhancement of light intensity contributed to the improvement of photocatalytic treatment efficiency. The ROH,UV for TiO2 and ZnO coated POF increased from 2 × 103 to 8 × 103 M s cm2 mJ?1 and from 8 × 102 to 2 × 103 M s cm2 mJ?1, respectively, as the pH increased from 4 to 10.
关键词： trichloroethylene (TCE),optical fiber,photocatalysis,groundwater,hydroxyl radical
更新于2025-09-12 10:27:22
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Propagation Kinetics of Isoprene Radical Homopolymerization Derived from Pulsed Laser Initiated Polymerizations
摘要： The propagation kinetics of isoprene radical polymerizations in bulk and in solution are investigated via pulsed laser initiated polymerizations and subsequent polymer analyses via size-exclusion chromatography, the PLP-SEC method. Because of low polymerization rate and high volatility of isoprene, the polymerizations are carried out at elevated pressure ranging from 134 to 1320 bar. The temperatures are varied between 55 and 105 °C. PLP-SEC yields activation parameters of kp (Arrhenius parameters and activation volume) over a wide temperature and pressure range that allow for the calculation of kp at technically relevant ambient pressure conditions. The kp values determined are very low, e.g., 99 L mol?1 s?1 at 50 °C, which is even lower than the corresponding value for styrene polymerizations. The presence of a polar solvent results in a slight increase of kp compared to the bulk system. The kp values reported are important for determining rate coefficients of other elemental reactions from coupled parameters as well as for modeling isoprene free-radical polymerizations and reversible deactivation radical polymerization with respect to tailored polymer properties and optimizing the polymerization processes.
关键词： polyisoprene,radical polymerization,kinetics,pulsed laser initiated polymerization
更新于2025-09-11 14:15:04
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Anti‐Oxidizing Radical Polymer‐Incorporated Perovskite Layers and their Photovoltaic Characteristics
摘要： A small amount of a radical-bearing redox-active polymer, poly(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl methacrylate) (PTMA), incorporated into the photovoltaic organo-lead halide perovskite layer significantly enhanced durability of both the perovskite layer and its solar cell even exposure to ambient air or oxygen. The radical PTMA polymer acted as an eliminating agent of the superoxide anion radical formed upon light-irradiation on the layer, which can react with the perovskite compound and decompose it to lead halide. A cell fabricated with the PTMA-incorporated perovskite layer and a hole-transporting polytriarylamine layer gave a photovoltaic conversion efficiency of 18.8 % (18.2 % for the control without PTMA). The photovoltaic current was not reduced in the presence of PTMA in the perovskite layer probably owing to a carrier conductivity of PTMA. The incorporated PTMA also worked as a water-repelling coating for the organo-lead halide perovskite layer, providing humidity-resistance to their.
关键词： perovskite solar cell,nitroxide radical,organo-lead halide perovskite,redox polymer,anti-oxidizing agent
更新于2025-09-11 14:15:04
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Equation of motion coupled-cluster for core excitation spectra: Two complementary approaches
摘要： This paper presents core excitation spectra from coupled-cluster (CC) theory obtained from both a time-independent and a new time-dependent formalism. The conventional time-independent CC formulation for excited states is the equation-of-motion (EOM-CC) method whose eigenvalues and eigenvectors describe the core excited states. An alternative computational procedure is offered by a time-dependent CC description. In that case, the dipole transition operator is expressed in the CC effective Hamiltonian form and propagated with respect to time. The absorption spectrum is obtained from the CC dipole autocorrelation function via a Fourier transformation. Comparisons are made among the time-dependent results obtained from second-order perturbation theory, to coupled cluster doubles and their linearized forms (CCD and LCCD), to CC singles and doubles (CCSD) and the linearized form (LCCSD). In the time-independent case, considerations of triples (EOM-CCSDT) and quadruples (EOM-CCSDTQ) are used to approach sub-electron volt accuracy. A particular target is the allyl radical, as an example of an open-shell molecule. As the results have to ultimately be the same, the two procedures offer a complementary approach toward analyzing experimental results.
关键词： time-independent formalism,time-dependent formalism,TD-EOM-CC,open-shell molecule,core excitation spectra,allyl radical,coupled-cluster theory,EOM-CC
更新于2025-09-11 14:15:04
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Protective characterization of low dose sodium nitrite on yak meat myoglobin in a hydroxy radical oxidation environment: Fourier Transform Infrared spectroscopy and laser Micro-Raman spectroscopy
摘要： The effect of NaNO2 in hydroxyl radical-mediated oxidative damage of yak meat myoglobin was investigated. Laser micro-Raman spectroscopy and Fourier Transform Infrared spectroscopy were used to assess protein (carbonyls, total sulfhydryl and Disulfide bonds) oxidation, atomic (or molecular) interactions and secondary structural changes. The addition of NaNO2 during the oxidation of myoglobin significantly reduced the content of carbonyl and disulfide bonds and protected the sulfhydryl groups from hydroxyl radical oxidation (P < 0.05). There was no significant difference in the secondary structure of myoglobin between the control group and the SN treatment group(P > 0.05). At the same time, NaNO2 had an inhibitory effect on the expansion of the hemoglobin center size and the transition of Fe from a low spin state to a high spin state caused by radical-oxidized. These findings suggest that NaNO2 has potential for treatment effects in a hydroxyl radical-oxidized myoglobin.
关键词： Secondary structure,Hydroxyl radical,Raman spectroscopy,NaNO2,Myoglobin
更新于2025-09-11 14:15:04
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High-Resolution Threshold Photoelectron Spectroscopy by Vacuum Ultraviolet Laser Velocity-Map-Imaging Method
摘要： We have obtained the high-resolution threshold photoelectron (TPE) spectra of chlorobenzene C6H5Cl (X 1A1), propargyl radical C3H3 (X 2B1), and allyl radical C3H5 (X 2A1) by employing the vacuum ultraviolet (VUV) laser velocity-map-imaging-TPE (VUV-VMI-TPE) method. The photoelectron energy resolution of 1(cid:0)2 cm?1 observed for the VUV-VMI-TPE method is comparable to that achieved in VUV laser pulsed-field ionization-photoelectron (VUV-PFI-PE) measurements. Similar to VUV-PFI-PE measurements, the energy resolutions for VUV-VMI-photoelectron (VUV-VMI-PE) and VUV-VMI-TPE measurements are found to depend on the dc electric field F in V/cm used at the photoionization region for electron extraction. The decrease of the ionization thresholds of C6H5Cl and C3H3 observed as a function of F shows that the Stark shift correction for VUV-VMI-TPE measurements F in cm?1, which is half of the classical prediction of F in cm?1. We have also measured the VUV-VMI-PE spectra of C6H5Cl and C3H5 at VUV energies near their ionization thresholds. The cationic vibrational bands observed in the VUV-VMI-PE measurements were assigned to be the vibrational progression, nv7 (n=0(cid:0)3), for C3H+ 5 . The higher experimental sensitivity and similar energy resolutions achieved in VUV-VMI-TPE compared to VUV-PFI-PE measurements make the VUV-VMI-TPE method an excellent alternative for high-resolution VUV-PFI-PE measurements.
关键词： Velocity-map imaging,Photoionization,Threshold photoelectron,Radical
更新于2025-09-11 14:15:04
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Radical induced cationic frontal twin polymerization of Si-spiro compound in combination with bisphenol-A-diglycidylether
摘要： The radical induced cationic frontal polymerization (RICFP) of the twin monomer with 2,2’-spirobi[4H-1,3,2-benzodioxasiline] combination (SPIRO) in bisphenol-A-diglycidylether (BADGE) has been developed to fabricate nanostructured hybrid material with domain sizes of 2–5 nm. In one reaction step, an interpenetrating network of phenolic resin, SiO2 and the epoxy resin is formed in a very short time period, initiated by UV light. That indicates that both polymerization reactions take place simultaneously. The influence of monomer composition on molecular structure was investigated by means of solid state NMR spectroscopies. The envisaged nanostructure of the resulting organic-inorganic hybrid materials is proven by transmission electron microscopy high-angle annular dark-field scanning (HAADF-STEM). The thermal properties of the hybrid materials are comparable to “state of the art” materials with the advantage that the silica quantity can be adjusted on demand.
关键词： Nanostructured hybrid material,HAADF-STEM,Solid state NMR spectroscopy,Radical induced cationic frontal polymerization,Twin polymerization
更新于2025-09-11 14:15:04
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Stable (BIII-Subporphyrin-5-yl)dicyanomethyl Radicals
摘要： Stable BIII-subporphyrin-substituted dicyanomethyl radicals were synthesized by SNAr reaction of meso-bromo or meso-chlorosubporphyrins with malononitrile followed by oxidation with PbO2. Different from previously reported dicyanomethyl radicals that underwent s- or π-dimer formation both in the solid state and in solutions, subporphyrin-stabilized dicyanomethyl radicals exist as monomers in solutions even at low temperature. DFT calculations revealed efficient spin delocalization over the whole subporphyrin. In the solid state, these radicals form weak π-dimers with antimagnetic interactions depending on the crystal packing structures.
关键词： porphyrinoid,dynamic covalent bond,subporphyrin,dicyanomethyl radical,stable radical
更新于2025-09-10 09:29:36
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Preparation of Nb2O5-decorated hierarchical porous ZnO microspheres with enhanced photocatalytic degradation of palm oil mill effluent
摘要： In the present work, Nb2O5-decorated hierarchical porous ZnO microspheres (ZnO/Nb2O5) were successfully prepared through a facile surfactant-free method. The as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy and Brunauer–Emmett–Teller surface area analyses. Under UV light irradiation, the ZnO/Nb2O5 composites degraded palm oil mill effluent (POME) efficiently and demonstrated much higher photocatalytic activity compared to those of pure ZnO and Nb2O5. The enhanced photocatalytic degradation performance of ZnO/Nb2O5 composites was attributed to the high charge separation efficiency and hydroxyl radical generation ability as verified by the photoluminescence spectra. Phytotoxicity test upon the POME degradation over ZnO/Nb2O5 photocatalysis considerably decreased through the measurement of radicle lengths of Vigna radiata. Moreover, the ZnO/Nb2O5 composites were reused several times without appreciable loss of activity. This work revealed that the as-prepared ZnO/Nb2O5 composites have great potential for practical applications in the field of wastewater treatment.
关键词： Nb2O5-decorated hierarchical porous ZnO microspheres,Photocatalytic degradation,Charge separation efficiency,Palm oil mill effluent,Hydroxyl radical generation
更新于2025-09-10 09:29:36
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Nitrate Removal via Formate Radical-induced Photochemical Process
摘要： Removal of excess nitrate is critical to balance the nitrogen cycle in aquatic systems. This study investigated a novel denitrification process by tailoring photochemistry of nitrate with formate. Under UV light irradiation, short-lived radicals (i.e., HO·, NO2· and CO3·-) generated from nitrate photolysis partially oxidized formate to highly reductive formate radical (CO2·-). CO2·- further reduced nitrogen intermediates generated during photochemical denitrification (mainly NO·, HNO, and N2O) to gas-phase nitrogen (i.e., N2O and N2). The degradation kinetics of total dissolved nitrogen was mainly controlled by the photolysis rates of nitrate and nitrite. The distribution of final products was controlled by the reaction between CO2·- and N2O. To achieve a simultaneous and complete removal of dissolved nitrogen (i.e., nitrate, nitrite, and ammonia) and organic carbon, the formate-to-nitrate stoichiometry was determined as 3.1 ± 0.2 at neutral pH in deionized water. Solution pH impacted the removal rates of nitrate and nitrite, but not that of total dissolved nitrogen or formate. The presence of dissolved organic matter at levels similar to groundwater had a negligible impact on the photochemical denitrification process. A high denitrification efficiency was also achieved in a synthetic groundwater matrix. Outcome from this study provides a potential denitrification technology for decentralized water treatment and reuse facilities to abate nitrate in local water resources.
关键词： denitrification,water treatment,nitrate removal,photochemical process,formate radical
更新于2025-09-10 09:29:36