Electron Transfer Products Research Articles

(Invited) A CNT Binding Bis(Zinc Porphyrin)Bodipy-C60 Nano Tweezer: Charge Stabilization in Supramolecular C60-Bodipy-(ZnP)2:SWCNT Hybrids

Single-wall carbon nanotubes (SWCNT) coupled with either electron donor or acceptor are promising functional structures for light energy harvesting and molecular optoelectronics applications. For building such hybrids involving SWCNTs, the p-stacking ability of large aromatic compounds is one of the commonly employed approaches.1-2 Often, the desired donor or acceptor entities are functionalized to carry one or more aromatic entities and allowed to interact with CNTs. However, due to close proximity, the role of SWCNTs in stabilizing the electron transfer product has been a challenge.3 Recently, we overcame this hurdle by employing a multi-modular approach to build donor-acceptor hybrids and successfully demonstrated charge stabilization in the presence of SWCNTs.4 In the present study, we have further improved our design by newly synthesizing a nano tweezer comprised of covalently linked BODIPY-C60 carrying two zinc porphyrin arms as shown in the figure. This compound was further allowed to interact with SWCNT(6,5) and SWCNT(7,6) to form the supramolecular C60-BODIPY-(ZnP)2:SWCNThybrids. Upon spectral, electrochemical, and computational characterization, femtosecond pump-probe spectroscopic studies were performed to establish the occurrence of photoinduced charge separation and charge stabilization. Extending the lifetime of the charge-separated states upon SWCNT binding has been successfully demonstrated in the present molecular design strategy. D’Souza, F.; Sandanayaka, A. S. D.; Ito, O. ‘SWNT-Based Supramolecular Nanoarchitectures with Photosensitizing Donor and Acceptor Molecules’ Phys. Chem. Letts. 2010, 1. 2586-2593.B. KC, G. N. Lim, and F. D’Souza, ‘Accelerated Charge Separation in Graphene Decorated Multi-Modular Tripyrene-Subphthalocyanine-Fullerene Donor-Acceptor Hybrids,’ Angew. Chem. Int. Ed. 2015, 54, 5088-5092.Barrejon, L. M. Arellano, F. D’Souza, F. Langa, ‘Bidirectional charge transfer in carbon-based hybrid nanomaterials’ Nanoscale, 2019, 11, 14978-14992.Kazemi, Y. Jang, A. Liyanage, P. A. Karr, and F. D’Souza, A Carbon Nanotube Binding Bis(pyrenylstyryl)BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer, Angew. Chem. Int. Ed. 2022, 61, e202212474 (1-7). Figure 1

Magnetite enhances As immobilization during nitrate reduction and Fe(II) oxidation by Acidovorax sp. strain BoFeN1

Arsenic (As) cycling in groundwater is commonly coupled to the biogeochemical cycling of iron (Fe) and the associated transformation of Fe minerals present. Numerous laboratory studies suggested that Fe minerals can act as nucleation sites for further crystal growth and as catalysts for abiotic Fe(II) oxidation. In view of the widespread existence of magnetite in anoxic environments where As is often dissolved, we firstly exploited magnetite to enhance As immobilization during nitrate-reducing Fe(II) oxidation (NRFO) induced by Acidovorax sp. strain BoFeN1, a mixotrophic nitrate-reducing Fe(II)-oxidizing bacterium that can oxidize Fe(II) through both enzymatic and abiotic pathways. Subsequently, we investigated how magnetite affects NRFO and As immobilization. Results demonstrated a significant increase in As(III) removal efficiency from 75.4 % to 97.2 % with magnetite, attributed to the higher amount of NRFO and As(III) oxidation promoted by magnetite. It was found that magnetite stimulated the production of extracellular polymeric substances (EPS), which could decrease the diffusion of nitrate in the periplasm of bacteria and shield them against encrustation, resulting in a more rapid reduction of nitrate in the system with magnetite than that without magnetite. Meanwhile, Fe(II) was almost completely oxidized in the presence of magnetite during the whole 72 h experiment, while in the absence of magnetite, 47.7 % of Fe(II) remained, indicating that magnetite could obviously accelerate the chemical oxidation of Fe(II) with nitrite (the intermediates of nitrate bioreduction). Furthermore, the formation of labile Fe(III), an intermediate product of electron transfer between Fe(II) and magnetite, was reasonably deduced to be vital for anoxic As(III) oxidation. Additionally, the XPS analysis of the solid phase confirmed the oxidation of 43.8 % of As(III) to As(V). This study helps to understand the biogeochemical cycling of Fe and As in the environment, and provides a cost-effective and environmentally friendly option for in situ remediation of As-contaminated groundwater.

Noncatalytic Reductive Deiodination of Thyroid Hormones. Electrochemistry and Quantum Chemical Calculations

AbstractNoncatalytic processes may occur spontaneously leading often to undesired products. Electrochemical measurements provide data for thermodynamic calculations. Cyclic voltammetry of thyroxine (T4) and 3,3’,5‐triiodothyronine (T3) in N,N‐dimethylformamide (DMF) and alkaline aqueous solutions of pH 10–14 on glassy carbon electrodes yielded the values of redox potentials for the reduction leading to deiodination of those thyroid hormones under noncatalytic conditions. The first step of T4 deiodination occurs in DMF at −1.93 V vs. Fc+/Fc and for T3 at −1.95 V, which was confirmed by quantum‐chemical calculations at DFT and DLPNO‐CCSD(T) levels. In alkaline aqueous solutions, owing to poor solubility of these compounds, it was possible to determine only approximate values equal to −1.6 to −1.7 V vs. Ag/AgCl for the first step of deiodination. The reduction potentials do not depend on pH under these conditions. As shown by calculations, further steps exhibit very close reduction potentials. The radicals formed as products of concerted dissociative electron transfer to T4 and T3 are relatively kinetically stable which leads to side reactions initiated by radicals in uncatalyzed deiodination processes.

Panchromatic Light-Capturing Bis-styryl BODIPY-Perylenediimide Donor-Acceptor Constructs: Occurrence of Sequential Energy Transfer Followed by Electron Transfer.

Two wide-band-capturing donor-acceptor conjugates featuring bis-styrylBODIPY and perylenediimide (PDI) have been newly synthesized, and the occurrence of ultrafast excitation transfer from the 1 PDI* to BODIPY, and a subsequent electron transfer from the 1 BODIPY* to PDI have been demonstrated. Optical absorption studies revealed panchromatic light capture but offered no evidence of ground-state interactions between the donor and acceptor entities. Steady-state fluorescence and excitation spectral recordings provided evidence of singlet-singlet energy transfer in these dyads, and quenched fluorescence of bis-styrylBODIPY emission in the dyads suggested additional photo-events. The facile oxidation of bis-styrylBODIPY and facile reduction of PDI, establishing their relative roles of electron donor and acceptor, were borne out by electrochemical studies. The electrostatic potential surfaces of the S1 and S2 states, derived from time-dependent DFT calculations, supported excited charge transfer in these dyads. Spectro-electrochemical studies on one-electron-oxidized and one-electron-reduced dyads and the monomeric precursor compounds were also performed in a thin-layer optical cell under corresponding applied potentials. From this study, both bis-styrylBODIPY⋅+ and PDI⋅- could be spectrally characterizes and were subsequently used in characterizing the electron-transfer products. Finally, pump-probe spectral studies were performed in dichlorobenzene under selective PDI and bis-styrylBODIPY excitation to secure energy and electron-transfer evidence. The measured rate constants for energy transfer, kENT , were in the range of 1011 s-1 , while the electron transfer rate constants, kET , were in the range of 1010 s-1 , thus highlighting their potential use in solar energy harvesting and optoelectronic applications.

Mo-doped Ni3S4 nanosheets grown on carbonized wood as highly efficient and durable electrocatalysts for water splitting

Rational design and fabrication of nonprecious metal-based electrocatalysts with high activity and excellent stability for overall water splitting (OWS) is still a grand challenge. Here we report a novel electrocatalyst constructed by incorporating molybdenum into the Ni3S4 lattices grown on carbonized wood (denoted as Mo-Ni3S4/CW). Experimental results and density functional theory (DFT)-based calculations demonstrate that lattice expansion of Ni3S4 caused by Mo doping optimizes adsorption energy of hydrogen/oxygen species and regulates local charge density of active sites, which promote the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Also, a nickel (oxy)hydroxide (Ni-OOH) layer generated via surface reconstruction of Ni3S4 nanosheets improves the intrinsic activity for OER. Moreover, the 3D low-tortuosity porous CW substrate increases the exposure of active specific surface, accelerates the rates of electron transfer, electrolyte diffusion, and gas products escaping. Accordingly, an optimized electrocatalyst (Mo-Ni3S4/CW-0.4) exhibits ultralow overpotentials of 17 and 240 mV for HER and OER at 10 mA cm−2, respectively. Besides, an electrolyzer composed of Mo-Ni3S4/CW-0.4 electrodes as both the anode and cathode shows a low cell voltage of 1.46 V at 10 mA cm−2 while maintaining superior durability over 50 h for OWS. Further, it requires only 0.19 V to achieve 10 mA cm−2 for hydrazine oxidation-assisted water electrolysis, indicating highly attractive potential for economical hydrogen production coupling with pollutants treatment.

Synthesis, characterization and electrochemistry of mono- and dirhodium(I) meso-diaryl dibenzoporphyrin(2.1.2.1) complexes

A series of mono- and dirhodium(I) meso-diaryl dibenzoporphyrin(2.1.2.1) complexes containing [Formula: see text]-tolyl, phenyl or pentafluorophenyl meso-substiuents were synthesized and characterized as to their electrochemical and spectroscopic properties in organic solvents and the data compared to that for same series of free base dibenzoporphyrins in their neutral and protonated forms. The redox behavior of the free base, mono- and di-metallic porphyrins was measured by cyclic voltammetry (CV) in methylene chloride or pyridine before and after the addition of acid in the form of TFA and the products of electron transfer are proposed on the basis of the CV data combined with results from thin-layer UV-visible spectroelectrochemistry. X-ray crystal structures of the dirhodium(I) complexes are also reported.

Elucidating the mechanism of photocatalytic reduction of bicarbonate (aqueous CO2) into formate and other organics

The photocatalytic reduction of CO2 under solar irradiation is an ideal approach to mitigating global warming, and reducing aqueous forms of CO2 that interact strongly with a catalyst (e.g., HCO3−) is a promising strategy to expedite such reductions. This study uses Pt-deposited graphene oxide dots as a model photocatalyst to elucidate the mechanism of HCO3− reduction. The photocatalyst steadily catalyzes the reduction of an HCO3− solution (at pH = 9) containing an electron donor under 1-sun illumination over a period of 60 h to produce H2 and organic compounds (formate, methanol, and acetate). H2 is derived from solution-contained H2O, which undergoes photocatalytic cleavage to produce •H atoms. Isotopic analysis reveals that all of the organics formed via interactions between HCO3− and •H. This study proposes mechanistic steps, which are governed by the reacting behavior of the •H, to correlate the electron transfer steps and product formation of this photocatalysis. This photocatalysis achieves overall apparent quantum efficiency of 27% in the formation of reaction products under monochromatic irradiation at 420 nm. This study demonstrates the effectiveness of aqueous-phase photocatalysis in converting aqueous CO2 into valuable chemicals and the importance of H2O-derived •H in governing the product selectivity and formation kinetics.

Neutrophils and their friends.

Neutrophils and their friends.

Carbon nanotubes accelerates the bio-induced vivianite formation

Vivianite widely existed in digested sludge and activated sludge as a potential phosphate resource recovered from wastewater treatment plants (WWTPs). As an important product of extracellular electron transfer (EET) and biological iron reduction, the production of vivianite can be enhanced by conductive materials. Carbon nanotubes (CNTs) with excellent electrical conductivity have been reported to promote electron transfer, which was applied in wastewater treatment to accelerate the degradation of the contaminants. However, the impact of CNTs on vivianite formation was barely reported. In this study, the iron reduction, vivianite recovery, and the biotoxicity of CNTs were investigated in order to determine the influence of CNTs towards the vivianite production. The enhancement of vivianite production after CNTs adding reached up to 17 % by promoting the electron transfer between dissimilative iron-reducing bacteria (DIRB) and Fe(III). However, at the initial stage (0–24 h), Fe(III) reduction efficiency decreased by 81 % after inoculating with sewage sludge, which was attributed to CNTs destroying of the cell membrane (as indicated by SEM, CLSM and AFM analysis). The biotoxicity of CNTs stimulated DIRB to secret extracellular polymeric substances (EPS) and form bio-flocs to resist the physical puncture. After 48 h, the proportion of living DIRB in 1000 mg/L CNTs batch increased to 98 %, which was 79 % higher than 12 h. As a result, the vivianite recovery of raw sewage with 1000 mg/L CNTs increased to 44 ± 1 %, which was 33 % higher than that in the CNT-0.

Carbamazepine degradation and genome sequencing of a novel exoelectrogen isolated from microbial fuel cells

Extracellular electron transfer and pharmaceutical products degradation mechanisms of electrochemical active microbial are helpful in optimizing electricity generation and biotoxic contaminants removal for microbial fuel cells (MFCs). An exoelectrogenic bacterial strain (designated as LYK-6) capable of degrading carbamazepine was first isolated from MFCs operated with carbamazepine as unique fuel. The strain LYK-6 was identified as the member of Pseudomonas genus according to morphological characteristics and 16S rRNA gene sequence analysis. Carbamazepine degradation rate of the strain LYK-6 was determined as 56.28% in inorganic salt medium using carbamazepine as sole carbon source. There were two oxidation peaks located at −0.044 V and 0.288 V revealed with differential pulse voltammetry analysis of the strain LQK-6. The maximum voltage of MFCs inoculated the strain LYK-6 reached to 187 mV when the MFCs fed with carbamazepine. The complete genome of the strain LYK-6 was of 4,454,672 bp in length and encoding 4209 protein genes. Genome annotation and functional gene analysis showed that the strain LYK-6 had significant genes encoding proteins responsible for the degradation of carbamazepine. The results demonstrated that the strain LYK-6 was promising application for the treatment of carbamazepine contaminant water by MFCs. This finding increases the known diversity of exoelectrogens.

Control of Photoinduced Electron Transfer Using Complex Formation of Water-Soluble Porphyrin and Polyvinylpyrrolidone.

Inspired by the natural photosynthetic system in which proteins control the electron transfer from electron donors to acceptors, in this research, artificial polymers were tried to achieve this control effect. Polyvinylpyrrolidone (PVP) was found to form complex with pigments 5,10,15,20-tetrakis-(4-sulfonatophenyl) porphyrin (TPPS) and its zinc complex (ZnTPPS) quantitatively through different interactions (hydrogen bonds and coordination bonds, respectively). These complex formations hinder the interaction between ground-state TPPS or ZnTPPS and an electron acceptor (methyl viologen, MV2+) and could control the photoinduced electron transfer from TPPS or ZnTPPS to MV2+, giving more electron transfer products methyl viologen cationic radical (MV+•). Other polymers such as PEG did not show similar results, indicating that PVP plays an important role in controlling the photoinduced electron transfer.

Photoinduced Charge Separation Prompted Intervalence Charge Transfer in a Bis(thienyl)diketopyrrolopyrrole Bridged Donor-TCBD Push-Pull System.

Intervalence charge transfer (IVCT), a phenomenon observed in molecular systems comprised of two redox centers differing in oxidation states by one unit, is reported in a novel, newly synthesized, multi-modular donor-acceptor system comprised of central bis(thienyl)diketopyrrolopyrrole (TDPP) hosting two phenothiazine-tetracyanobutadiene (PTZ-TCBD) entities on the opposite sides. One-electron reduction of TCBD promoted electron exchange between the two TCBD resulting in IVCT transition in the near-infrared region. The stabilization energy, -ΔGcom and comproportionation equilibrium constant, Kcom calculated from peak potentials of the split reduction waves were found to be 1.06×104 J mol-1 , and 72.3 M-1 , respectively. Further, the IVCT transition was also witnessed during the process of thermodynamically feasible electron transfer upon excitation of the TDPP entity in the system, and served as a diagnostic marker to characterize the electron transfer product. Subsequent transient absorption spectral studies and data analysis by Global and Target analyses revealed occurrence of ultrafast charge separation (kcs ≈1010 s-1 ) owing to the close proximity and good communication between the entities of the multi-modular donor-acceptor system. The role of central TDPP in promoting IVCT is borne out from the present investigation.

Photoinduced Charge Separation Prompted Intervalence Charge Transfer in a Bis(thienyl)diketopyrrolopyrrole Bridged Donor‐TCBD Push‐Pull System

AbstractIntervalence charge transfer (IVCT), a phenomenon observed in molecular systems comprised of two redox centers differing in oxidation states by one unit, is reported in a novel, newly synthesized, multi‐modular donor‐acceptor system comprised of central bis(thienyl)diketopyrrolopyrrole (TDPP) hosting two phenothiazine‐tetracyanobutadiene (PTZ‐TCBD) entities on the opposite sides. One‐electron reduction of TCBD promoted electron exchange between the two TCBD resulting in IVCT transition in the near‐infrared region. The stabilization energy, −ΔGcom and comproportionation equilibrium constant, Kcom calculated from peak potentials of the split reduction waves were found to be 1.06×104 J mol−1, and 72.3 M−1, respectively. Further, the IVCT transition was also witnessed during the process of thermodynamically feasible electron transfer upon excitation of the TDPP entity in the system, and served as a diagnostic marker to characterize the electron transfer product. Subsequent transient absorption spectral studies and data analysis by Global and Target analyses revealed occurrence of ultrafast charge separation (kcs≈1010 s−1) owing to the close proximity and good communication between the entities of the multi‐modular donor‐acceptor system. The role of central TDPP in promoting IVCT is borne out from the present investigation.

Structure-Dependent Electron Transfer Rates for Dihydrophenazine, Phenoxazine, and Phenothiazine Photoredox Catalysts Employed in Atom Transfer Radical Polymerization.

Organic photocatalysts (PCs) are gaining popularity in applications of photoredox catalysis, but few studies have explored their modus operandi. We report a detailed mechanistic investigation of the electron transfer activation step of organocatalyzed atom transfer radical polymerization (O-ATRP) involving electronically excited organic PCs and a radical initiator, methyl 2-bromopropionate (MBP). This study compares nine N-aryl modified PCs possessing dihydrophenazine, phenoxazine, or phenothiazine core chromophores. Transient electronic and vibrational absorption spectroscopies over subpicosecond to nanosecond and microsecond time intervals, respectively, track spectroscopic signatures of both the reactants and products of photoinduced electron transfer in N,N-dimethylformamide, dichloromethane, and toluene solutions. The rate coefficients for electron transfer exhibit a range of values up to ∼1010 M-1 s-1 influenced systematically by the PC structures. These rate coefficients are an order of magnitude smaller for catalysts with charge transfer character in their first excited singlet (S1) or triplet (T1) states than for photocatalysts with locally excited character. The latter species show nearly diffusion-limited rate coefficients for the electron transfer to MBP. The derived kinetic parameters are used to model the contributions to electron transfer from the S1 state of each PC for different concentrations of MBP. Comparisons of singlet and triplet reactivity for one of the phenoxazine PCs reveal that the rate coefficient kET(T1) = (2.7 ± 0.3) × 107 M-1 s-1 for electron transfer from the T1 state is 2 orders of magnitude lower than that from the S1 state, kET(S1) = (2.6 ± 0.4) × 109 M-1 s-1. The trends in bimolecular electron transfer rate coefficients are accounted for using a modified Marcus theory for dissociative electron transfer.

The Redox Properties of Germylenes Stabilized by N‐Donor Ligands

AbstractGermylenes, organic compounds of divalent germanium, are often considered as promising catalytic systems efficient in reactions of oxidative addition and reductive elimination, including SET reactions. However, the systematic studies of their redox properties, allowing for the quantitative evaluation of the levels of frontier molecular orbitals and the stability of single electron transfer products, are extremely limited in number. In this work, a series of germylenes with various types of stabilization: N−Ge−N, (N→)C−Ge−C(←N), N−Ge−N(←N), O−Ge−O(←N) и (N→)O−Ge−O(←N) (“−“ ‐a covalent bond, stabilization is achieved by p‐donation of a lone pair of electrons of N or O, “→” ‐donor‐acceptor bond) were characterized by cyclic voltammetry. The results were compared with UV/Vis spectroscopy data and DFT calculations. All germylenes studied in MeCN and THF with Bu4NPF6 as a supporting electrolyte are chemically irreversibly oxidized in the potential range of 0.5–1.4 V vs. Ag/AgCl. In all cases, as estimated by the quantum chemical calculations, the HOMO remains at the covalently unsaturated germanium center although being significantly redistributed over the molecular system. In turn, electroreduction of germylenes is possible only in the presence of a strong electron‐withdrawing substituent or a pyridine ring depleted in electron density donated to germanium. In both cases, the LUMO is localized exactly on these moieties and is absent on the germanium. Thus, the use of stabilizing groups makes it possible both to improve germylene stability and to fine‐tune their HOMO level that determines their ability to participate in oxidative addition reactions.

Photoacoustic-Based Miniature Device with Smartphone Readout for Point-of-Care Testing of Uric Acid.

Real-time and rapid detection of various biomarkers in body fluids has important significance for early disease diagnosis, efficient monitoring of treatment, and evaluation of prognosis. However, traditional detection methods not only require bulky and costly instruments but also are not suitable for the analysis of heterogeneous samples (e.g., serum and urine), limiting their applications in point-of-care testing (POCT). Herein, an integrated photoacoustic (PA) device with a smartphone as the acoustic signal readout has been constructed, greatly reducing the volume and cost of the instrument, and providing a potential miniature platform for POCT of clinical samples. By exploiting the electron transfer product of 3,3',5,5'-tetramethylbenzidine (TMB) (i.e., TMB++) as the PA probe and hemin-graphene oxide (H-GO) complex as the peroxidase, quantitative analysis of uric acid was successfully performed by using only 30 μL of a sample solution. Due to the favorable stability of artificial enzymes, reaction reagents could be effectively embedded in agar gel to make a portable "test strip". Therefore, operators just need to drop clinical samples on the "test strip" for PA analysis, which is user friendly without requiring complex sample preparation steps. In addition, since the acoustic change mainly comes from the PA effect, it has a lower background signal than UV-vis and fluorescence analysis, greatly improving the analytical performance. The simplicity, low cost, and broad adaptability make this miniature PA device attractive for on-site detection, particularly in resource-limited settings.

Photoinduced Electron Transfer in Axially Coordinated Supramolecular Zinc Tetrapyrrole Bis(styryl)BODIPY Donor‐Acceptor Conjugates

AbstractPhotoinduced electron transfer (PET) in newly assembled dyads formed via metal‐ligand axial coordination of phenylimidazole‐functionalized bis(styryl)BODIPY (BODIPY(Im)2) and zinc tetrapyrroles, that is, zinc tetratolylporphyrin (ZnP), zinc tetra‐t‐butyl phthalocyanine (ZnPc) and zinc tetra‐t‐butyl naphthalocyanine (ZnNc), in non‐coordinating o‐dichlorobenzene (DCB) is investigated using both steady‐state and time‐resolved transient absorption techniques. The structure of the BODIPY(Im)2 was identified by using single crystal X‐ray structural analysis. The newly formed supramolecular dyads were fully characterized by spectroscopic, computational and electrochemical methods. The binding constants measured from optical absorption spectral studies were in the range of ∼104 M−1 for the first zinc tetrapyrrole binding and suggested that the two imidazole entities of bis(styryl)BODIPY behave independently in the binding process. The energy level diagram established using spectral and electrochemical studies suggested PET to be thermodynamically unfavorable in the ZnP‐bearing complex while for ZnPc‐ and ZnNc‐bearing complexes such a process is possible when zinc tetrapyrrole is selectively excited. Consequently, occurrence of efficient PET in the latter two dyads was possible to establish from femtosecond transient absorption studies wherein the electron transfer products, that is, the radical cation of zinc tetrapyrrole and the radical anion of BODIPY(Im)2, was possible to spectrally identify. From target analysis of the transient data, time constants of circa 3 ns for ZnPc⋅+:BODIPY⋅− and circa 0.5 ns for ZnNc⋅+:BODIPY⋅− were obtained indicating persistence of the radical ion‐pair to some extent. The electron acceptor property of bis(styryl)BODIPY in donor‐acceptor conjugates is borne out from the present study.

Peptoid-Conjugated Magnetic Field-Sensitive Exciplex System at High and Low Solvent Polarities.

The magnetic field effect (MFE) in exciplex emission (ExE) has been studied for decades, but it has been observed to occur only in solvents with a limited range of polarity. This limitation is mainly due to the reversible interconversion collapse between two quenching products of the photoinduced electron transfer, the exciplex and magnetic field-sensitive radical ion pair (RIP) beyond that polarity range. In a nonpolar solvent, the formation of RIPs is suppressed, whereas in a polar solvent, the probability of their re-encounter forming the exciplexes decreases. In this study, we developed new exciplex-forming (phenyl-phenanthrene)-(phenyl-N,N-dimethylaniline)-peptoid conjugates (PhD-PCs) to overcome this limitation. The well-defined peptoid structure allows precise control of the distance and the relative orientation between two conjugated moieties. Steady-state and time-resolved spectroscopic data indicate that the PhD-PCs can maintain the reversibility, which allows MFEs in ExE regardless of the solvent polarity. Subtle differences between the ExEs of the PhD-PCs were observed and explained by their exciplex geometries obtained through time-dependent density functional theory (TD-DFT) calculations.

Activation of peroxymonosulfate by Fe0@Fe3O4 core-shell nanowires for sulfate radical generation: Electron transfer and transformation products

Nanoscale zero-valent iron (nZVI) is highly promising for oxidative removal of micropollutants by initiating advanced oxidation processes, but its vulnerability to deactivation due to the surface oxidation is challenging. In this study, we propose Fe0@Fe3O4 core–shell nanowires (CSNWs) as a novel activator to generate radicals for atrazine, a representative micropollutant, degradation via the activation of peroxymonosulfate (PMS). Fe0@Fe3O4 CSNWs with a shell thickness of around 5 nm were synthesized using a facile chemical reduction approach and were comprehensively characterized using a series of surface sensitive techniques. The results showed that the Fe0@Fe3O4 CSNW had great reactivity for atrazine degradation via the activation of PMS; near complete degradation of atrazine was achieved after reaction for only 2 min. Under identical conditions, the pseudo-first order rate constant with Fe0@Fe3O4 was more than 36 times greater than that with nano Fe3O4. The surface activation of PMS contributed only a small proportion to the overall degradation. Instead, the iron released from Fe0@Fe3O4 CSNWs primarily activated PMS to generate SO4∙- that degraded atrazine. The Fe0@Fe3O4 CSNWs were stable and no deactivation was observed after exposing Fe0@Fe3O4 CSNWs to air for 3 months. The results from this study demonstrate a stable nZVI for oxidative removal of organic contaminants.

Electrocatalytic Oxidation of Hydroxide Ions by Co3O4 and Co3O4@SiO2 Nanoparticles Both at Particle Ensembles and at the Single Particle Level

AbstractWe report that the Co3O4 nanoparticle‐mediated electrochemical oxidation under alkaline conditions of the hydroxide ion on a glassy carbon macroelectrode leads to hydrogen peroxide as the initial oxidation product of electron transfer. The latter is inferred to subsequently partially decompose to dioxygen by catalytic chemical reaction at the nanoparticles. At the single particle level, electrochemical particle‐electrode impacts point out the rate‐determining step and the limiting kinetics of the reaction. Furthermore, particles with a core‐shell structure of a Co3O4 core and SiO2 shell are synthesised, and their electrochemical behaviour is studied and compared with bare Co3O4 nanoparticles, suggesting the very likely broken or highly porous state of the silica shell, which is not otherwise easily distinguished, for example, by electron microscopy.