Electron Transfer Energy Research Articles

Microscopic Origin of Twist-Dependent Electron Transfer Rate in Bilayer Graphene.

Using molecular simulation and continuum dielectric theory, we consider how electrochemical kinetics are modulated by the twist angle in bilayer graphene electrodes. By establishing a connection between the twist angle and the screening length of charge carriers within the electrode, we investigate how tunable metallicity modifies the statistics of the electron transfer energy gap. Constant potential molecular simulations show that the activation free energy for electron transfer increases with screening length, leading to a non-monotonic dependence on the twist angle. The twist angle alters the density of states, tuning the number of thermally accessible channels for electron transfer and the reorganization energy by affecting the stability of the vertically excited state through attenuated image charge interactions. Understanding these effects allows us to express the Marcus rate of interfacial electron transfer as a function of the twist angle in a manner consistent with experimental observations.

Efficient electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3) on metal-free B4@g-C3N4 nanosheet

The combustion of fossil fuels releases substantial amounts of nitric oxide (NO), posing serious environmental and health risks. Addressing NO pollution effectively is, therefore, a pressing need. Conversion of NO into valuable chemicals is an appealing strategy with dual benefits, including waste utilization and sustainable energy transformation. In this study, we investigate the metal-free electrocatalytic reduction of NO (NORR) to NH3 on a B4 atomic cluster supported by a g-C3N4 nanosheet (B4@g-C3N4) using density functional theory (DFT). Our findings reveal that NO is efficiently activated on the B4@g-C3N4 catalyst, favoring side-on and N end-on adsorption configurations. Significant electron transfer and strong adsorption energies confirm the chemisorption of NO. The NORR exhibits an impressively low limiting potential (UL) of −0.29 V in the gas phase, which decreases further under solvent effects and varying charge states (−2e-, −1e-, +1e-, +2e-). Additionally, the high negative UL values for competing side reactions such as H2 (−0.42 V), N2 (−0.29 V), and N2O (−0.72 V) underscore the selectivity of B4@g-C3N4 for ammonia synthesis. These results highlight the promising potential of B4@g-C3N4 nanosheets for eco-friendly ammonia production from NO, providing a theoretical basis for future experimental efforts to combat NO pollution.

Anion substitution strategy for constructing abundant oxygen vacancies in perovskites enables efficient nitrate electroreduction

Perovskite oxides have emerged as promising candidates for electrocatalytic nitrate reduction (ERN) catalysts due to their unique electronic structures and tunable chemical compositions. In this work, we employed a fluorine ion substitution strategy to modulate the oxygen site of LaCoO3 (LCO), resulting in the construction of F-substituted LaCoO3 (LCOF0.5) catalyst for efficient ERN. The incorporation of fluorine ions leads to a weakening of the hybridization between the O 1 s orbital and Co 3d orbital of the catalyst, thereby inducing an increase in oxygen vacancies. The abundant oxygen vacancies can facilitate the electron transfer and surface adsorption energy of the ERN reaction intermediates. This leads to a reduction in the energy barriers for both the reduction of *HNO3 to *NO2 and the reduction of *HNO2 to *NO, thereby enhancing the performance of ERN. As excepted, LCOF0.5 exhibits a rapid reaction rate of k = 5.48 × 10−3 min−1, which is 1.70 times faster than that of pristine LCO, and its catalytic activity approaches that of the state-of-the-art electrocatalysts for ERN. Applying this strategy to LaFeO3 and LaMnO3 also yields similar results, demonstrating its general applicability. The F-anion substitution strategy offers new opportunities for significantly enhancing ERN performance.

A water-stable three-fold interpenetrating Zn-MOFs with nanomolar luminescence turn-off response for Roxarsone

High selectivity and fast response for detrimental and carcinogenic Roxarsone (ROX) is always a challenge. Herein, a new luminescent Zn-based metal-organic frameworks {Zn2(XN)(BDC)2·H2O}n (compound 1) has been successfully harvested (XN: 4′-(4-pyridine)4,2′:2′,4′'-terpyridine, H2BDC: terephthalic acid), exhibiting excellent chemical stability and thermal stability. Moreover, luminescence investigation revealed that compound 1 could present nanomolar luminescence turn-off response to ROX (limit detection: 5.84 nM), which may be attributed to both photo-induced electron transfer (PET) and competitive energy absorption (CEA) between ROX and compound 1. Notably, the extraordinary luminescence quenching response to ROX of compound 1 is almost unaffected by the simulated serum and urine components, various antibiotics and even real chicken feed environment, demonstrating excellent interference immunity and selectivity. Importantly, sensor 1 with preeminent recyclability can be reused at least five times for detecting ROX without significant changes in luminescence intensity and structural integrity. This work provides a new synthetic strategy of recyclable metal-organic frameworks sensor with excellent sensitivity and selectivity, making it possible to detect in actual chicken feed.

Evolution of Natural Ferroan Brucite Under Different Atmospheres

The study on the evolution of natural ferroan brucite (MgFe(OH)[Formula: see text] was beneficial to discovering the function of brucite in the geologic cycle and directing the reasonable utilization of brucite resources. In this study, natural MgFe(OH)2 was characterized in detail and Rietveld refinement was employed to determine the precise content and existing environment of Fe[Formula: see text]. The reaction products of MgFe(OH)2 under various atmospheric conditions, including CO2, O2 and a mixed atmosphere of CO2 and O2 were innovatively investigated to gain insights into the evolution process and the crucial role played by Fe[Formula: see text]. Accordingly, the evolution mechanism of MgFe(OH)2 under different atmospheres was afforded based on the characterization and molecular simulations like electron transfer and binding energy. Fe[Formula: see text] in MgFe(OH)2 layers could be oxidized by O2 easily and give positive layers, CO[Formula: see text] produced by CO2 dissolving in water simultaneously was attracted to finally produce CO[Formula: see text] intercalated MgFe- layered double hydroxides (MgFe-CO[Formula: see text]-LDHs) which could be used as adsorbents, catalysts and so on. This process was supported by thermodynamics and also the dominant evolution route due to the dynamic reason. The existence of Fe[Formula: see text] in MgFe(OH)2 resulted in the diversity of the evolution products. This work highlighted the composition and structure of evolution products of natural MgFe(OH)2 under different environment as well as its possible application field.

Efficient removal of bisphenol A from water using a novel organic–inorganic hybrid heterojunction

Organic-inorganic hybrid heterojunctions have the ability to efficiently remove trace pollutants from water due to efficient photosensitivity. In this work, an organic–inorganic hybrid S-scheme heterojunction photosensitizer (RCP-BW) was successfully fabricated by growing cross-linked β-CD/riboflavin copolymer on the surface of bismuth tungstate (Bi2WO6). The fabrication of the copolymer retains the photosensitivity of riboflavin and the confinement effect of β-CD and forms an internal electric field with Bi2WO6 to enhance the photoelectron transport ability. Photogenerated electrons are transferred and stacked from Bi2WO6 to β-CD/riboflavin copolymers, which greatly enhances the ability of organic copolymers to reduce oxygen and produce superoxide radicals. We combined electrochemistry, free radical chemistry and DFT to study the photoelectron migration mechanism and photocatalytic performance enhancement mechanism in S-scheme heterojunctions. The pseudo-first-order reaction kinetic constant (kRCP-BW = 0.081 min−1) for BPA degradation was four times that of unmodified BW (kBW = 0.020 min−1). β-CD regulates the band structure of riboflavin to match with Bi2WO6, and utilizes charged contaminants and intermediate degradation products to promote the production of reactive oxygen species through interface electron transfer and excited state transition energy transfer. This work provides theoretical support and technical means for photocatalytic oxidation technology to control endocrine disruptors.

The inhibitor activity of some azo compound derivatives using density functional theory and molecular dynamics simulations

Corrosion poses a significant challenge for metals and alloys, carrying considerable economic and safety consequences. Various manufacturing processes, including surface preparation techniques, further exacerbate it. While corrosion inhibitors are employed to safeguard these materials from corrosion, they can also induce oxidative damage. This study aims to determine the corrosion inhibition efficiency of the specified materials. Density Functional Theory (DFT) and molecular dynamics simulations (MDS) were used to investigate the electronic characteristics of diverse compounds. The study included key parameters including highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), energy gap (Eg) between ELUMO and EHOMO, dipole moment, global hardness, softness (σ), ionization energy (I), electron affinity (A), electronegativity (χ), back-donation energy Eb-d, global electrophilicity (ω), electron transfer, global nucleophilicity (ε), and total energy (sum of electronic and zero-point energies). The calculations were executed utilizing the DFT method, employing a 6-311G++(d,p) basis set at the B3LYP level. Our research aimed to rank materials based on their effectiveness in inhibiting corrosion by considering EHOMO, ELUMO, and Eg. The order of effectiveness was found to be as follows: S4 > S3 > S1 > Mad1 > Mad3 > Mad4 > P-azo > Bad4. Additionally, our Investigation delved into alterations in electron affinity (A) and ionization potential (I) within different solvent phases, highlighting their importance in determining the chemical reactivity and stability of the studied compounds. The reactive sites were selected using Fukui indices, and the molecular electrostatic potential (MESP) surface was characterized—a Monte Carlo simulation to further understand these chemicals' adsorption behavior on Fe (110) surfaces. Our findings revealed that these compounds exhibit corrosion inhibition potential due to their high EHOMO, A, σ, ΔN, ΔE-back-donation, and low Eg, ELUMO, I, and η. Moreover, our MESP surface analysis demonstrated their ability to donate electrons to the metal's d-orbitals and receive electrons through back-donation. The compounds investigated in this study exhibit the potential to be employed as corrosion inhibitors in various industrial sectors. As a result, through the use and determination of quantum computational chemistry parameters, the level of corrosion resistance was as follows S3 > S1 > Bad4 > Mad4 > Mad3 > S4 > Mad1 > P-azo.

Multidimensional detection of roxarsone via AIE-based sulfates

Improper abuse of roxarsone (ROX) in industrial production leads to harmful effects on water, soil, food, and living creatures. It is significant to detect its concentration in the environment and biosystem. Herein, two aggregation-induced emission (AIE)-active fluorescence probes, TPE-TPE and TPE-TPE-CN, are successfully synthesized via a sulfur (VI) fluoride exchange (SuFEx) click reaction and first employed to detect ROX in the environment and living 3T3 cells. These two probes can selectively detect ROX in water due to the synergistic effect of photoinduced electron transfer (PET) and fluorescence resonance energy transfer (FRET) between the probes and ROX. The detection limit of TPE-TPE and TPE-TPE-CN is 0.154 and 0.385 μmol/L, respectively, much lower than the safety concentration stipulated by the World Health Organization (WHO). In addition, with the aid of a color discrimination application in a smartphone, these two probes can also detect ROX in real samples (such as water, soil, and cabbage), demonstrating their excellent potential for monitoring ROX in a practical environment.

Solvent-free oxidation of benzylic C(sp3)–H bond over MA3Bi2Br9 perovskite photocatalyst by efficient singlet oxygen generation

Photocatalytic selective oxidation under solvent-free conditions plays a pivotal role in green chemistry, which can diminish pollutant production and minimize resource consumption in chemical reactions. In this process, the activation of molecular oxygen (O2) plays a crucial role. Here, we demonstrate the efficient oxidation of C(sp3)–H bond in pure toluene to produce oxygenated products of benzaldehyde (BAD) and benzyl alcohol (BA) using O2 as an oxidant over lead-free MA3Bi2Br9 perovskite. Systematic spectroscopic characterizations and controlled experiments validate that MA3Bi2Br9 enables the activation of O2 to superoxide radical (•O2−) and singlet oxygen (1O2) via charged electron transfer and excitonic energy transfer, respectively. Significantly, 1O2 emerges as an important active species. The optimal photocatalytic performance delivered by MA3Bi2Br9 reaches a BAD generation rate of 10756 µmol g−1h−1, with a BAD product selectivity of 81.5 %. The performance is greater than most classical photocatalysts, representing one of the best photocatalytic activities available in the literature. The lead-free feature of MA3Bi2Br9 perovskite coupled with its impressive catalytic performance makes it promising for practical applications.

Liquid-Liquid Phase Separation-Mediated Photocatalytic Subcellular Hybrid System for Highly Efficient Hydrogen Production.

Plant chloroplasts have a highly compartmentalized interior, essential for executing photocatalytic functions. However, the construction of a photocatalytic reaction compartment similar to chloroplasts in inorganic-biological hybrid systems (IBS) has not been reported. Drawing inspiration from the compartmentalized chloroplast and the phenomenon of liquid-liquid phase separation, herein, a new strategy is first developed for constructing a photocatalytic subcellular hybrid system through liquid-liquid phase separation technology in living cells. Photosensitizers and in vivo expressed hydrogenases are designed to coassemble within the cell to create subcellular compartments for synergetic photocatalysis. This compartmentalization facilitates efficient electron transfer and light energy utilization, resulting in highly effective H2 production. The subcellular compartments hybrid system (HM/IBSCS) exhibits a nearly 87-fold increase in H2 production compared to the bare bacteria/hybrid system. Furthermore, the intracellular compartments of the photocatalytic reactor enhance the system's stability obviously, with the bacteria maintaining approximately 81% of their H2 production activity even after undergoing five cycles of photocatalytic hydrogen production. The research brings forward visionary prospects for the field of semi-artificial photosynthesis, offering new possibilities for advancements in areas such as renewable energy, biomanufacturing, and genetic engineering.

Entropy-Enthalpy Compensation in Electron-Transfer Processes.

Solvent reorganization energies, free energies, and entropies are obtained for photoexcitation of three molecules that exhibit strong solvatochromism [Nile red, 5-(dimethylamino)-5'-nitro-2,2-bisthiophene, and Reichardt's dye B30] by measuring their optical absorption spectra at temperatures between 150 and 300 K in solvents with a range of polarities. Energies, free energies, and entropies of solvent reorganization are also obtained from computer simulations of three intramolecular electron-transfer reactions (charge separation and recombination in Zn-porphyrin-quinone cyclophane and charge transfer in a bis-biphenylandrostane radical anion). Entropy-enthalpy compensation in the solvent reorganization free energy for photoexcitation or electron transfer is found to be essentially complete (having nearly equal and opposite contributions from entropic and enthalpic effects) for all of the processes with solvent reorganization energies less than about 0.1 eV. Compensation becomes less complete as the reorganization energy becomes larger. A semiclassical treatment of the solvent reorganization entropy can rationalize these results.

Fluorescence response of metalo-hydrogen-bonded organic framework (MHOF) with room temperature phosphorescence to organic pollutants

For health, environmental and safety reasons, it is necessary to conduct highly sensitive detection of organic contaminant antibiotics (sulfathiazole) and nitro explosive drugs (o-nitroaniline) in water. In this work, metal-hydrogen bonded organic framework (MHOF), {[Co(Ad)2(H2O)4]·(H2L)·2.5H2O}n (1), was synthesized by a one-pot hydrothermal method with 2,6-bis(3,5-dicarboxyphenoxy) pyridine (H4L) and adenine (Ad). This MHOF shows a 4-fold interpenetrated three-dimensional (3D) network structure. Importantly, 1 has excellent fluorescence properties and can be used as fluorescent chemical sensor to detect sulfathiazole (STZ) and 2-nitroanilin (2-NA) with limit of detection (LOD) 203 ppb and 6.8 ppb, respectively. By UV-vis absorption/emission spectroscopic measurements and DFT calculations, it is found that photoinduced electron transfer (PET) and fluorescence resonance energy transfer (FRET) are two potential quenching processes. This is the first report of metal-hydrogen bond organic frameworks (MHOFs) as a promising new fluorescent chemical sensor for the detection of organic pollutants in water.

Engineering hybrid conductive electrochemically active biofilms enable efficient interfacial electron transfer and syntrophic carbon metabolism

Supply of carbon-based nanomaterials (e.g., carbon nanotubes, CNTs) to develop highly conductive electrochemically active biofilms (EABs) is a potential strategy for facilitating extracellular electron transfer (EET) in bioelectrochemical systems (BESs). Understanding of the underlying CNTs-mediated EET behaviors is helpful to further advance the practical application of BESs. Here, the cognitive influence of CNTs on bioelectrocatalytic activity and electron transfer efficiency of EABs were elucidated. CNTs can be embedded into EABs to form hybrid conductive biofilms (CNTs/EABs), achieving a high current density (7.4 ± 1.40 A m−2) and excellent coulombic recovery (46.0 ± 2.70 %) over 100 days of steady operation. The supply of CNTs can mitigate the dependence of exoelectrogens (such as Geobacter) on outer membrane cytochromes (OMCs) and conductive pili due to their down-regulated genes expression in CNTs/EABs, but it can significantly improve microbial carbon metabolism because physically high-conductive CNTs can establish rapid EET pathways, which may reduce the necessity for cells to invest metabolic energy in producing conductive pili and cytochromes that are required in the absence of CNTs. Such enhancement in electron transfer rate may be caused by the interfacial interaction between OMCs and CNTs, resulting in an order of magnitude higher than in the control (5.5 ± 1.60 s−1vs. 0.28 ± 0.04 s−1) and without compromising of mass diffusion. This study provides comprehensive insight into the role of carbon-based nanomaterials in provoking interfacial electron transfer and renewable energy recovery.

Activationless Electron Transfer of Redox-DNA in Electrochemical Nanogaps.

Our recent discovery of decreased reorganization energy in electrode-tethered redox-DNA systems prompts inquiries into the origin of this phenomenon and suggests its potential use to lower the activation energy of electrochemical reactions. Here, we show that the confinement of the DNA chain in a nanogap amplifies this effect to an extent to which it nearly abolishes the intrinsic activation energy of electron transfer. Employing electrochemical atomic force microscopy (AFM-SECM), we create sub-10 nm nanogaps between a planar electrode surface bearing end-anchored ferrocenylated DNA chains and an incoming microelectrode tip. The redox cycling of the DNA's ferrocenyl (Fc) moiety between the surface and the tip generates a measurable current at the scale of ∼10 molecules. Our experimental findings are rigorously interpreted through theoretical modeling and original molecular dynamics simulations (Q-Biol code). Several intriguing findings emerge from our investigation: (i) The electron transport resulting from DNA dynamics is many times faster than predicted by simple diffusion considerations. (ii) The current in the nanogap is solely governed by the electron transfer rate at the electrodes. (iii) This rate rapidly saturates as overpotentials applied to the nanogap electrodes increase, implying near-complete suppression of the reorganization energy for the oxidation/reduction of the Fc heads within confined DNA. Furthermore, evidence is presented that this may constitute a general, previously unforeseen, behavior of redox polymer chains in electrochemical nanogaps.

Molecular modelling of fullerene C60 functionalized by nitric oxide for use in biological environment

The unique potential of fullerene C60 for various biological applications has ignited significant interest. However, its inherent non-polarity poses a critical challenge for its effective integration within biological systems. This study delves into the intricate physicochemical characteristics of the innovative [C60 + NO] complex using density functional theory and time-dependent density functional theory. The computational analyses encompass molecular charge, surface electrostatic potential, and dipole moment evaluations. Impressively, the dipole moment of the [C60 + NO] complex significantly increases to 12.92 D. Meticulous surface analysis reveals a subtle interplay between molecular structures, indicating weak interactions. The analysis of the absorption spectrum unveils a noteworthy red-shift of 200 nm subsequent to complex formation. To elucidate the electron transfer mechanisms, we explore photo-induced electron transfer through CAM-B3LYP. This exploration elucidates intricate pathways governing electron transfer, with complementary insights gleaned from Marcus theory's outputs, especially the Gibbs free energy of electron transfer. Changes in the physicochemical properties of approaching C60 and NO molecules reveal interesting results compared to separate molecules. These findings resonate profoundly in the context of potential biological and pharmaceutical utilization. With implications for the biomedical area, the outcomes linked to the [C60 + NO] complex kindle optimism for pioneering biomedical applications.

Effect of temperature on lanthanide charge transition levels and vacuum referred binding energies

Location of lanthanide levels in the bandgap, vacuum referred binding energy (VRBE) in the lanthanide ground state and energy of lanthanide charge transition levels (CTLs) are just three different namings for the same concept. A concept of importance for the performance of lanthanide activated compounds. Energy differences of CTLs with the conduction band bottom and valence band top are important when it concerns e.g. lanthanide luminescence, charge carrier trapping, and valence stability. Effect of temperature on CTL energy or VRBE has so far never been addressed despite that luminescence application and thermoluminescence studies may span a temperature range from 10 K to 1000 K. In this work information on the bandgap (or energy of host exciton creation) around 10 K and at RT in compounds is gathered to demonstrate that bandgap decreases by 0.1 eV to 0.3 eV when temperature increases to RT. A similar decrease will be demonstrated for the energy of electron transfer from the VB to a trivalent lanthanide. The findings have consequences for VRBE-diagram construction, i.e. the experimental parameters for such construction should all apply to the same temperature. They also have consequences on how to relate luminescence thermal quenching energy barriers and TL derived electron and hole trap depths with a VRBE diagram. By proper evaluating the effects of temperature, accuracy of VRBE diagrams and consistency with luminescence and thermoluminescence data can be improved.

Linear scaling relationships in homogeneous photoredox catalysis

In the photoredox catalytic cycle of CO2 reduction with organic chromophores, this work observes a linear relationship between the energies of (desirable) electron transfer to CO2 and (undesirable) carboxylation of the chromophore radical anion.

Exploiting halide perovskites for heavy metal ion detection.

Heavy metal ions such as mercury (Hg), copper (Cu), and cadmium (Cd) pose significant threats to ecosystems and human health due to their toxicity and bioaccumulation potential. With growing environmental concerns over heavy metal ion pollution, there is an urgent need to develop efficient detection methods for safeguarding public health and the environment. Various materials, including polymers, nanomaterials, and porous substances, have been used for heavy metal ion detection and have shown promising performance for different scenarios. However, each of these materials has certain limitations as probes. Metal halide perovskites (MHPs), known for their exceptional optoelectronic properties and high structural and chemical tunability, have gained great attention in applications such as photovoltaics and LEDs. Yet, their potential as metal ion probes remains rarely explored. This review assesses MHPs as prospective materials for heavy metal ion detection, taking their structure, chemical properties, and responses to external stimuli into consideration. Three key detection mechanisms-cation exchange (CE), electron transfer (ET), and fluorescence resonance energy transfer (FRET), are explored to understand how metal ions trigger fluorescence changes on perovskites, enabling their detection. Finally, current avenues of developing perovskite probes are discussed, which include exploration of lead-free perovskites to mitigate environmental concerns arising from lead leakage and the pursuit of achieving high-sensitivity and stable detection in aqueous media, summarizing the existing and promising strategies in this field.

Antiferromagnetism and insulator-metal transition of alkali metal-loaded sodalite.

Alkali metal clusters with a single unpaired s-electron can be arranged three-dimensionally in a sodalite crystal by loading the guest alkali atoms. Na, K, and K-Rb alloy clusters are known to be Mott insulators and to exhibit antiferromagnetic ordering. The Néel temperature increases from about 50 K to about 100 K in this order. In this study, Li-Na alloy, Na-K alloy, and pure Rb samples were newly prepared and their magnetic, electrical conductivity, and optical properties were investigated, including those of previous samples. The Na-K alloy samples showed antiferromagnetic properties, which were intermediate between those of the Na and K samples. However, the Rb sample showed a non-magnetic metallic state. The shallower ionization potential in Rb is thought to cause an insulator-metal transition (Mott transition) due to weaker on-site Coulomb repulsion between electrons and larger electron transfer energy between neighboring clusters. On the other hand, the Li-Na alloy sample showed a non-magnetic insulating state. It is thought that the two electrons form a spin-singlet pair due to the strong electron-lattice interaction. In terms of electron correlations and polaron effects, the full picture of the element species dependence of the alkali metal-loaded sodalite is reviewed.

Evaluation of the photosensitizer activity of hydrophobic phosphorus(V)porphyrins using the absorption spectral change of 1-benzyl-1,4-dihydronicotinamide

Under visible light irradiation, water-insoluble P(V)porphyrins oxidized 1-benzyl-1,4-dihydronicotinamide (BNADH), a model compound for nicotinamide adenine dinucleotide, and diminished the typical absorption of BNADH at around 340 nm. A singlet oxygen quencher, sodium azide, partially inhibited photosensitized BNADH oxidation. This BNADH oxidation photosensitized by P(V)porphyrins in the presence of sodium azide can be explained by electron transfer oxidation from BNADH to the photoexcited P(V)porphyrins. The quantum yields of BNADH oxidation via electron transfer by these P(V)porphyrins were larger than those of a singlet oxygen mechanism. Redox potential measurements supported the electron transfer mechanism from a thermodynamic point of view, and fluorescence lifetime measurement also suggests this mechanism. The process of this electron transfer oxidation involves the radical formation of BNADH and the further reaction of this radical to the oxidized form (cationic form of BNADH). Analysis of the quantum yields of BNADH photooxidation by P(V)porphyrins suggests that the photoinduced electron transfer from BNADH to photoexcited P(V)porphyrins triggers the radical chain reaction of BNADH oxidation. The electron transfer rate coefficient and this efficiency were increased with an increase in the Gibbs energy of electron transfer from tryptophan to photoexcited P(V)porphyrins (−ΔG). However, the BNADH oxidation quantum yield via electron transfer decreased with an increase in the -ΔG of electron transfer. These results suggest that reverse electron transfer inhibits the decomposition of BNAD radicals. This assay using BNADH can be used to evaluate the photosensitizer activity of water-insoluble compounds. These P(V)porphyrins may be used as photosensitizers for photodynamic therapy in a relatively hydrophobic environment in cancer tissues.