Electron Transfer Mechanism Research Articles

Peptide-Perovskite Based Bio-Inspired Materials for Optoelectronics Applications.

The growing demand for environmentally friendly semiconductors that can be tailored and developed easily is compelling researchers and technologists to design inherently bio-compatible, self-assembling nanostructures with tunable semiconducting characteristics. Peptide-based bioinspired materials exhibit a variety of supramolecular morphologies and have the potential to function as organic semiconductors. Such biologically or naturally derived peptides with intrinsic semiconducting characteristics create new opportunities for sustainable biomolecule-based optoelectronics devices. Affably, halide perovskite nanocrystals are emerging as potentially attractive nano-electronic analogs, in this vein creating synergies and probing peptide-perovskite-based bio-electronics are of paramount interest. The physical properties and inherent aromatic short-peptide assemblies that can stabilize, and passivate the defects at surfaces assist in improving the charge transport in halide perovskite devices. This review sheds light on how these peptide-perovskite nano-assemblies can be developed for optical sensing, optoelectronics, and imaging for biomedical and healthcare applications. The charge transfer mechanism in peptides along with as an outlook the electron transfer mechanism between perovskite and short peptide chains, which is paramount to facilitate their entry into molecular electronics is discussed. Future aspects, prevailing challenges, and research directions in the field of perovskite-peptides are also presented.

Self-Supported α-MoB/β-MoB2 Ceramic Electrodes for Efficient High-Current-Density Hydrogen Evolution in Acidic, Neutral, and Alkaline pH-Values.

This paper describes the production and high-current-density hydrogen evolution reaction (HER) performance in the whole pH range (from acidic to basic pH values) of self-supported α-MoB/β-MoB2 ceramic electrodes, aiming for use in industrial electrocatalytic water splitting. Tape-casting and phase-inversion process, followed by sintering, were employed to synthesize self-supported β-MoB2 ceramic electrodes, which exhibited well arranged large finger-like pores, providing numerous active sites and channels for electrolyte entry and hydrogen release. The reaction between β-MoB2 and the sintering aid of MoO3 in situ produces α-MoB/β-MoB2 heterojunctions, which significantly improve the electrocatalytic performance. At a current density of 1000 mA·cm-2, the ceramic electrode manifested an overpotential of 289 mV and 294 mV in acidic and alkaline aqueous solutions, respectively, and a stable operation over time (>100 h). The electrode also performed well in a neutral solution, with an overpotential of 354 mV at 100 mA·cm-2. Theoretical (DFT) calculations demonstrated that the α-MoB/β-MoB2 heterojunction alters the electronic configuration of β-MoB2, favoring an effective electron transfer mechanism; thereby, the adsorption free energy of hydrogen ions is close to zero, and the adsorption and dissociation of water molecules under alkaline and neutral conditions are significantly enhanced.

Luminescent Mesoporous Squaraine Copolymers: Probing the Structural, Optical, and Sensing Behaviors

ABSTRACTHerein, we have designed and developed four luminescent mesoporous squaraine copolymers (PSQ‐X) based on substituted diaryl‐1,4‐diamine moiety with various heteroatom “X” such as CH2, O, S, and SO2 to demonstrate the effect of heteroatom on structural, thermal, electrochemical, and optical properties of copolymers. Synthesis has been achieved through a facile single step metal‐free poly‐condensation reaction using commercially available low‐cost monomers. All polysquaraines (PSQs) possess good thermal stability, crystallinity and low bandgap energy (2–3 eV). Utilizing the fluorescent nature of the PSQs, we have explored them as a “turn‐off” sensor for the selective and sensitive detection of picric acid among various nitro‐aromatic explosives via photoinduced electron transfer (PET) and inner filter effect (IFE) mechanism. The Stern–Volmer constant (KSV) for PA has estimated as 1.93 × 104, 1.92 × 104, 0.68 × 104, and 3.57 × 104 M−1 for PSQ‐CH2, PSQ‐O, PSQ‐S, and PSQ‐SO2, respectively, indicating that PA can quench the emission intensity of PSQ‐SO2 most efficiently with the detection limit in the nano‐molar range (LOD = 5.96 nM). Contact mode detection of PA has been also accomplished using economical and transportable fluorescent paper test strip devices for on‐site sensing, which can detect a minimum of 6.9 fg of PA.

A novel overtone peak self-referencing fluorescent sensor based on a bipyridine-linked covalent organic framework for highly sensitive copper ion detection.

This study reports a novel ratiometric fluorescence sensor based on a tetraphenylethylene-bipyridine covalent organic framework (TPE-Bpy-COF) for the sensitive detection of Cu2+, leveraging the unique coordination properties of the bipyridine moieties. The interaction between Cu2+ and the nitrogen atoms in the bipyridine units induces fluorescence quenching at 500 nm through an efficient host-guest electron transfer mechanism, where excited-state electrons from the COF framework are transferred to the vacant orbitals of Cu2+. Upon excitation at 410 nm, the sensor exhibits a primary emission peak at 500 nm, which is quenched in the presence of Cu2+, while an overtone peak at 820 nm remains stable, serving as an internal reference for ratiometric measurements and significantly enhancing the accuracy and reliability of the sensor. The detection limit for Cu2+ is 0.1 μM, with the dual-emission system and the strong affinity of the bipyridine units for Cu2+, further improving the sensor's sensitivity and selectivity. Additionally, the sensor demonstrated excellent recovery rates in real water samples, confirming its practical applicability in environmental monitoring.

CuS/Nitrogen-biomass derived carbon composites for heterogeneous Fenton-like degradation of dyes: C-, N- and S-mediated electron transfer mechanism for redox cycling of Cu(I)/Cu (II) couple

CuS/Nitrogen-biomass derived carbon composites for heterogeneous Fenton-like degradation of dyes: C-, N- and S-mediated electron transfer mechanism for redox cycling of Cu(I)/Cu (II) couple

Amplification of O-D stimulated Raman scattering in DMSO-D2O solution via intense laser-driven electron transfer.

In this study, we investigated in detail the regulation mechanism of electron transfer under laser-induced breakdown (LIB) on weak O-D stimulated Raman scattering (SRS) in DMSO-D2O solutions. Significantly, the Raman activity of O-D vibrations was greatly enhanced by two orders of magnitude due to electron transfer in DMSO molecules. Density functional theory (DFT) calculations showed that the O-D Raman activity was significantly enhanced in the DMSO-D2O dimer compared to the D2O dimer. Additionally, the high-order (third-order) SRS peaks originating from the O-D vibration and the characteristic peaks representing the ice-like structure were detected, which were due to the Raman-enhanced four-wave mixing (FWM) process induced by the hydrated electron and intramolecular electron transfer. It was hoped that our results could provide a meaningful reference for the development of multi-wavelength and significant frequency-shifted Raman lasers.

A One Stone Three Birds Paradigm of Photon‐Driven Pyroptosis Dye for Amplifying Tumor Immunotherapy

AbstractActivating the pyroptosis pathway of tumor cells by photodynamic therapy (PDT) for immunogenic cell death (ICD) is considered a valid strategy in pursuit of antitumor immunotherapy, but it remains a huge challenge due to the lack of reliable design guidelines. Moreover, it is often overlooked that conventional PDT can exacerbate the development of tumor immunosuppressive microenvironment, which is apparently unfavorable to clinical immunotherapy. The endoplasmic reticulum's (ER) pivotal role in cellular homeostasis and its emerging link to pyroptosis have galvanized interest in ER‐centric imaging and therapeutics. Herein, using the targeted group‐assisted strategy (TAGS), an intriguing cyclooxygenase‐2‐targeted photodynamic conjugate, Indo‐Cy, strategically created, which exploits the enzyme's overabundance in the tumoral ER, especially under proinflammatory hypoxic conditions. This conjugate, with its highly precise ER imaging, embodies a trifunctional strategy: i) innovating an electron transfer mechanism, converting the hemicyanine moiety into an oxygen‐independent type I photosensitizer, thereby navigating around the hypoxia constraints of traditional PDT; ii) executing precise ER‐targeted PDT, amplifying caspase‐1/GSDMD‐mediated pyroptosis for ICD; 3) attenuating immunosuppressive pathways by inhibiting cyclooxygenase‐2 downstream factors, including HIF‐1α, PGE2, and VEGF. Indo‐Cy's multimodal approach potently induces in vivo tumor pyroptosis and bolsters antitumor immunity, underscoring cyclooxygenase‐2‐targeted dyes' potential as a versatile oncotherapeutics.

Methionine-Derived Fluorescent Probes Targeting Mitochondria: A Tool for Real-Time Oxidative Stress Monitoring in Live Cells.

Reactive oxygen species (ROS) play crucial roles in both cell signaling and defense mechanisms. Hypochlorous acid (HOCl), a strong oxidant, aids the immune response by damaging pathogens. In this study, we developed two pyridinium-based fluorophores PSSM and PSSE for selective hypochlorite detection. Out of these two fluorescent probes, PSSM shows a strong turn-on emission via a photoinduced electron transfer (PeT) mechanism, excellent mitochondrial localization, and rapid response to HOCl with high selectivity among reactive oxygen species by achieving a detection limit of 2.41 μM. It successfully detects both exogenous and endogenous HOCl in live cells, enabling the study of HOCl's role at the organelle level. Structural analysis of PSSM via thioether oxidation confirmed by HPLC, NMR and HRMS further supports its specificity. Confocal imaging and flow cytometry studies further highlights its utility in investigating oxidative stress, positioning this fluorophore as a valuable tool for monitoring HOCl imbalances in biological systems.

Palladium Nanosheet Enables Synergistic Electrocatalytic Dehalogenation via Direct and Indirect Electron Transfer Mechanisms.

Electrocatalytic dehalogenation is a promising method for the remediation of chlorinated organic pollutants. The dehalogenation performance is controlled by catalytic activity, and the underlying electrocatalytic dehalogenation mechanisms need to be carefully investigated for guiding the design of catalyst. Here we report the preparation of a new Pd-based catalyst with a nanosheet structure (Pd NS) by a simple wet-chemical reduction method. This Pd NS catalyst showed a superior electrocatalytic activity toward the reductive dehalogenation of a chlorinated organic pollutant (e.g., 4-chlorophenol) with the dehalogenation rate of 0.324 h-1. Importantly, the obtained Pd NS catalyst had a good durability that could operate well over 30 h under high concentration of 4-chlorophenol with removal efficiency beyond 82%. Experimental results confirmed the simultaneous occurrence of direct electrocatalytic dehalogenation and H*-mediated indirect electron transfer mechanisms in the dehalogenation process, and their quantitative contributions to the dehalogenation performance were established based on the cyclic voltammetry and quenching experiments. This study provides a promising dehalogenation catalyst and sheds light on the mechanism of electrocatalytic dehalogenation as well as the development of a dual-functional electrocatalyst.

Genetic investigation of hydrogenases in Thermoanaerobacterium thermosaccharolyticum suggests that redox balance via hydrogen cycling enables high ethanol yield.

Our study elucidates the crucial role of electron flow and redox balancing mechanisms in improving ethanol yields from renewable biomass. We delve into the mechanism of electron transfer, highlighting the potential of key genes to be leveraged for enhanced ethanol production in anaerobic microbial species. We suggest by genetic investigation the existence of a novel Ferredoxin:NADP+ Oxidoreductase (FNOR) reaction, comprising HfsD, HydAB, and NfnAB enzymes, as a promising avenue for achieving balanced stoichiometry and efficient ethanol synthesis. Our findings not only advance the understanding of microbial metabolism but also offer practical insights for developing strategies to improve bioenergy production and sustainability.

Probing the orientation and membrane permeation of rhodamine voltage reporters through molecular simulations and free energy calculations.

The transmembrane potential of plasma membranes and membrane-bound organelles plays a fundamental role in cellular functions such as signal transduction, ATP synthesis, and homeostasis. Rhodamine voltage reporters (RhoVRs), which operate based on the photoinduced electron transfer (PeT) mechanism, are non-invasive, small-molecule voltage sensors that can detect rapid voltage changes, with some of them specifically targeting the inner mitochondrial membrane. In this work, we conducted extensive molecular dynamics simulations and free-energy calculations to investigate the physicochemical properties governing the orientation as well as membrane permeation barriers of three RhoVRs. Our results indicate that the positioning of the most polarized functional group relative to the hydrophobic molecular wire dictates the alignment of RhoVRs with the membrane normal, thereby, significantly affecting their voltage sensitivity. Free-energy calculations in different membrane systems identify significantly higher barriers against the permeation of RhoVR 1 compared to SPIRIT RhoVR 1, explaining their distinct subcellular localization profiles. Subsequent free-energy calculations of the distinguishing components from the two different RhoVRs provide additional insight into the physicochemical properties governing their membrane permeation. The connection between chemical composition and membrane orientation, as well as permeation behaviors of RhoVRs revealed by our calculations provides general guiding principles for the rational design of PeT-based fluorescent dyes with enhanced voltage sensitivity and desired subcellular distribution.

Surface Engineering of 2D Metal-Porphyrin Metal-Organic Frameworks Z-Scheme Heterostructure for Boosting and Stable Photocatalytic Hydrogen Evolution.

How to improve the stability and activity of metal-organic frameworks is an attractive but challenging task in energy conversion and pollutant degradation of metal-organic framework materials. In this paper, a facile method is developed by fabricating titanium dioxide nanoparticles (TiO2 NPs) layer on 2D copper tetracarboxylphenyl-metalloporphyrin metal-organic frameworks with zinc ions as the linkers (ZnTCuMT-X, "Zn" represented zinc ions as the linkers, the first "T" represented tetracarboxylphenyl-metalloporphyrin (TCPP), "Cu" represented the Cu2+ coordinated into the porphyrin macrocycle, "M" represented metal-organic frameworks, the second "T" represented TiO2 NPs layer, and "X" represented the added volume of n-tetrabutyl titanate (X = 100, 200, 300 or 400)). It is found that the optimized ZnTCuMT-200 showed greatly and stably enhanced H2 generation, which is ≈28.2 times and 47.0 times as high as those of the original ZnTCuM and TiO2, respectively. Combined with the results of free radical capture, X-ray photoelectron spectra (XPS), electron spin resonance (ESR), and theoretical calculation, a direct Z-scheme electron transfer mechanism is achieved to fully explain the enhanced photocatalytic performance. It demonstrates that facilely designing Z-scheme heterostructures based on porphyrin MOFs modified with an inorganic semiconductor layer can be an advantageous strategy for enhancing the stability and activity of photocatalytic hydrogen evolution.

Highly effective catalytic degradation of bisphenol a through activation of peroxymonosulfate by an Fe-Nx structure anchored on novel lignin-based graphitic biochar: Electron transfer mechanism

A lignin-based Fe/N co-doped carbonaceous catalyst was synthesized via freeze-drying followed by pyrolysis to activate peroxymonosulfate (PMS) for efficient degradation of bisphenol A (BPA). The Fe/N co-doped biochar exhibited a high specific surface area (364.84 m2/g), hierarchical porous structures, and abundant oxygen-containing functional groups (hydroxyl and carboxyl groups), which enhancing the dispersion of Fe3O4 nanoparticle and exposure of catalytic site. The Fe8-N10-C/PMS system achieved 100 % BPA degradation within 20 min with a corresponding first-order reaction rate constant (kobs) of 0.4056 min−1, which outperformed most reported catalysts in efficiency. Quenching and EPR analyses revealed that both free radicals (•OH, SO4•−, and O2•−) and non-radical (1O2) were rate-limiting steps, while graphitic N and Fe-Nx structures facilitated direct electron transfer from BPA to PMS in electrochemical tests. XPS results confirmed that pyrrolic N, rather than pyridinic N, played a crucial role in forming the Fe-Nx structure. Moreover, the catalyst showed excellent stability, regeneration capability, and adaptability under diverse conditions, highlighting the potential of the Fe-N-C/PMS system for practical wastewater treatment applications.

Insight into nitrogen-doped biochar prepared from Chinese medicine compound residue for peracetic acid activation in sulfamethoxazole degradation: Electron transfer mechanism

Insight into nitrogen-doped biochar prepared from Chinese medicine compound residue for peracetic acid activation in sulfamethoxazole degradation: Electron transfer mechanism

Direct and Indirect Interfacial Electron Transfer at a Plasmonic p-Cu7S4/CdS Heterojunction.

Plasmonic semiconductors exhibit significant potential for harvesting near-IR solar energy, although their mechanisms of plasmon-induced hot electron transfer (HET) are poorly understood. We report a transient absorption study of plasmon-induced HET in p-Cu7S4/CdS type II heterojunctions. Near-IR excitation of the p-Cu7S4 plasmon band at ∼1400 nm leads to ultrafast HET into the CdS conduction band with a time constant of <150 fs and a quantum efficiency of ∼0.054%. The injected hot electrons remain in CdS with an amplitude-weighted average lifetime of 1.9 ± 0.5 ns, significantly longer than that in Au/CdS heterostructures, suggesting that plasmonic semiconductors can slow down charge recombination due to the presence of a bandgap. The excited near-IR plasmon does not decay by coupling to the interfacial charge transfer transition, likely due to its energy mismatch. This study provides a detailed mechanistic understanding and possible directions for improving plasmonic HET in plasmonic semiconductor heterojunctions.

Engineering mechanisms of proton-coupled electron transfer to a titanium-substituted polyoxovanadate-alkoxide.

Metal oxides are promising catalysts for small molecule hydrogen chemistries, mediated by interfacial proton-coupled electron transfer (PCET) processes. Engineering the mechanism of PCET has been shown to control the selectivity of reduced products, providing an additional route for improving reductive catalysis with metal oxides. In this work, we present kinetic resolution of the rate determining proton-transfer step of PCET to a titanium-doped POV, TiV5O6(OCH3)13 with 9,10-dihydrophenazine by monitoring the loss of the cationic radical intermediate using stopped-flow analysis. For this reductant, a 5-fold enhanced rate (k PT = 1.2 × 104 M-1 s-1) is accredited to a halved activation barrier in comparison to the homometallic analogue, [V6O7(OCH3)12]1-. By switching to hydrazobenzene as a reductant, a substrate where the electron transfer component of the PCET is thermodynamically unfavorable (ΔG ET = +11 kcal mol-1), the mechanism is found to be altered to a concerted PCET mechanism. Despite the similar mechanisms and driving forces for TiV5O6(OCH3)13 and [V6O7(OCH3)12]1-, the rate of PCET is accellerated by 3-orders of magnitude (k PCET = 0.3 M-1 s-1) by the presence of the Ti(iv) ion. Possible origins of the accelleration are considered, including the possibility of strong electronic coupling interactions between TiV5O6(OCH3)13 with hydrazobenzene. Overall, these results offer insight into the governing factors that control the mechanism of PCET in metal oxide systems.

Unraveling proton-coupled electron transfer in cofactor-free oxidase- and oxygenase-catalyzed oxygen activation: a theoretical view.

Oxygen plays a crucial role in the metabolic processes of non-anaerobic organisms. However, a detailed understanding of how triplet oxygen participates in the enzymatic oxidation of organic compounds involved in life processes is still lacking. It is noteworthy that recent studies have found that cofactor-free oxidase- and oxygenase-catalyzed oxygen activation occurs through proton-coupled electron transfer (PCET), which is significantly different from the previously proposed single electron transfer (SET) mechanism. Herein, we summarize the recent advances in the general mechanism of catalytic activation reactions of triplet oxygen by these enzymes. We believe that this review not only helps in providing a deep understanding of the processes involved in oxygen metabolism in organisms but also provides valuable theoretical reference data for designing more efficient enzyme mutants for treating diseases and handling environmental pollution in the future.

Exploring graphene's impact on graphite/PANI matrix composites: high-pressure fabrication and enhanced thermal-electrical properties.

This study investigates the effects of the graphene content and applied pressure on the electrical and thermal conductivities of graphite/polyaniline (GP) and graphite/graphene/polyaniline (GGP) composites produced via direct mixing method. Based on the electrical and thermal conductivity results, 14 wt% graphene content was found to be the crucial threshold, beyond which extra graphene additions exhibited different behaviors in pressed and unpressed samples. While the electrical conductivity of the unpressed samples increased up to 14 wt% graphene addition, the thermal conductivity increased further after 14 wt% graphene addition. The addition of graphene induced notable changes in the electronic configurations of quinoid and benzenoid rings, as evidenced by ATR-FT-IR spectroscopy. Based on XPS data, the addition of graphene to the graphite/PANI-CSA matrix affected the electronic distribution and charge transfer mechanisms within the GGP composites, particularly showing the impact of graphene addition on the electronic structure of PANI-CSA in the GGP-14 527 MPa sample. Importantly, the interlocking of graphene and graphite layers observed in the GGP-14 sample pressed at 527 MPa (according to Raman and XRD data) led to enhanced thermal (2253 W m-1 K-1) and electrical (210 S cm-1) conductivity. The interlocked configuration of graphene and graphite in GGP-14 527 MPa facilitated efficient electron and phonon flow throughout the hexagonal CC rings and partially charged nitrogen and oxygen atoms of PANI-CSA. In future work, the concept of interlocked graphene and graphite layers can be used to further enhance the thermal and electrical properties in thermoelectric material applications.

Oxygen, light, and mechanical force mediated radical polymerization toward precision polymer synthesis.

The synthesis of polymers with well-defined composition, architecture, and functionality has long been a focal area of research in the field of polymer chemistry. The advancement of controlled radical polymerization (CRP) has facilitated the synthesis of precise polymers, which are endowed with new properties and functionalities, thereby exhibiting a wide range of applications. However, radical polymerization faces several challenges, such as oxygen intolerance, and common thermal initiation methods may lead to side reactions and depolymerization. Therefore, we have developed some oxygen-tolerant systems that directly utilize oxygen for initiating and regulating polymerization. We utilize oxygen/alkylborane as an effective radical initiator system in the polymerization, and also as a reductant for the removal of polymer chain ends. Moreover, we employ the gentler photoinduced CRP to circumvent side reactions caused by high temperatures and achieve temporal and spatial control over the polymerization. To enhance the penetration of the light source for polymerization, we have developed near-infrared light-induced atom transfer radical polymerization. Additionally, we have extended photochemistry to reversible addition-fragmentation chain transfer polymerization involving ion-pair inner-sphere electron transfer mechanism, metal-free radical hydrosilylation polymerization, as well as carbene-mediated polymer modification through C-H activation and insertion mechanisms. Furthermore, we propose a new method for polymerization initiation synergistically triggered by oxygen and mechanical energy. This review not only showcases the current advancements in CRP but also outlines future directions, such as the potential for 3D printing and surface coatings, and the exploration of new heteroatom radical polymerizations. By expanding the boundaries of polymer synthesis, these innovations could lead to the creation of new materials with enhanced functionality and applications.

The influence of functional groups on the triboelectric properties of chitosan derivatives and the electron transfer mechanism of insulators

The influence of functional groups on the triboelectric properties of chitosan derivatives and the electron transfer mechanism of insulators