- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Homogeneous Electron Transfer Reactions of Electrochemically Generated Species in Electrogenerated Chemiluminescence; 電気化学発光における電極反応の後続反応;
摘要： Electrogenerated Chemiluminescence (ECL) involves electrode reactions and the following homogeneous electron transfer reactions which resulted in a light emission. In this integrated research paper, we focused on the homogeneous electron transfer reactions to form excited states of some luminescent molecules. The Marcus theory was used to estimate ratios of the electron-transfer rate constants between a radical cation and anion to generate the lowest excited singlet and triplet states. In addition, the ECL behavior using tripropylamine as a coreactant was demonstrated by simulating the electrochemical and homogeneous electron transfer reactions with a finite element method. Although coreactants are useful to form excited species, because of complicated reactions in bulk, analyzing the ECL response such as relationship between the current-voltage and ECL intensity curves depending on the redox potentials of luminescent molecules and coreactants is quite difficult. It was shown that the simulations were very useful to understand the ECL response depending on the redox potentials of the coreactant and luminescent molecules.
关键词： Marcus theory,homogeneous electron transfer,Electrogenerated Chemiluminescence,tripropylamine,finite element method
更新于2025-09-09 09:28:46
-
Tuning Photoinduced Electron Transfer Efficiency of Fluorogenic BODIPY- <i>α</i> -Tocopherol Analogues
摘要： Fluorogenic analogues of α-tocopherol developed by our group have been instrumental in monitoring reactive oxygen species (ROS) within lipid membranes. Prepared as two-segment trap-reporter (chromanol-BODIPY) probes, photoinduced electron transfer (PeT) was utilized to provide these probes with an off/on switch mechanism warranting the necessary sensitivity. Herein we rationalize within the context of Marcus theory of electron transfer how substituents on the BODIPY core and linker length joining the trap and reporter segments, tune PeT efficiency. DFT and electrochemical studies were used to estimate the thermodynamic driving force of PeT in our constructs. By tuning the redox potential over a 400 mV range, we observed over an order of magnitude increase in PeT efficiency. Increasing the linker length between the chromanol and BODIPY by 2.8 angstroms in turn decreased PeT efficiency 2.7-fold. Our results illustrate how substituent and linker choice enable “darkening” the off state of fluorogenic probes based on BODIPY fluorophores, by favoring PeT over radiative emission from the singlet excited state manifold. Ultimately, our work brings light to the sensitivity ceiling one may achieve in developing fluorogenic antioxidants analogues of α-tocopherol. The work provides general guidelines applicable to those developing fluorogenic probes based on PeT.
关键词： electrochemical studies,α-tocopherol,lipid membranes,reactive oxygen species,redox potential,photoinduced electron transfer,Marcus theory,DFT,Fluorogenic analogues,BODIPY
更新于2025-09-09 09:28:46
-
Background-free fluorescence decay time sensing and imaging of pH with highly photostable diazaoxotriangulenium dyes
摘要： Novel fluorescent diazaoxatriangulenium (DAOTA) pH indicators for lifetime-based self-referenced pH sensing are reported. The DAOTA dyes were decorated with phenolic receptor groups inducing fluorescence quenching via photoinduced electron transfer mechanism. Electron-withdrawing chlorine substituents ensure response in the most relevant pH range (apparent pK’a values ~5 and 7.5 for the p,p-dichlorophenol- and the p-chlorophenol-substituted dyes, respectively). The dyes feature long fluorescence lifetime (17-20 ns), high quantum yield (~60%) and high photostability. Planar optodes are prepared upon immobilization of the dyes into polyurethane hydrogel D4. Apart from the response in the fluorescence intensity, the optodes show pH-dependent lifetime behaviour which makes them suitable for studying 2D pH distribution with help of fluorescence lifetime imaging technique. The lifetime response is particularly pronounced for the sensors with high dye concentration (0.5-1% wt. in respect to the polymer) and is attributed to efficient homo-FRET mechanism.
关键词： pH sensor,photoinduced electron transfer,Decay time,triangulenium,Frequency Domain FLIM,FRET
更新于2025-09-09 09:28:46
-
Ultrafast Excited State Dynamics of a Stilbene–Viologen Charge Transfer Complex and Its Interaction with Alkanediammonium Salts
摘要： The spectral and thermodynamic properties of charge transfer complexes D?A and D?A?D between (E)-bis(18-crown-6)stilbene (D) and 1,1'-bis(2-ammonioethyl)-4,4'-bipyridinium tetraperchlorate (A) in MeCN were studied. The complex D?A is highly stable, while the complex D?A?D is weakly stable. D?A does not fluoresce due to fast intramolecular processes of direct and reverse electron transfer. The efficiency of D?A fluorescence ignition upon adding alkanediammonium salts depends on the length of a carbon chain. The spectral and kinetic characteristics of D?A and D?A?D CT states were obtained by femtosecond transient absorption spectroscopy. It was established that the characteristic time of back electron transfer in the CT state of D?A?D (770 fs) is significantly higher than that in the CT state of D?A (400 fs). In a number of charge transfer complexes, formed by derivatives of 4,4'-bipyridinium and di-(4-pyridinium)-ethylene with ammonioethyl and ammoniopropyl N-substituents, the rate of back electron transfer depends weakly on the acceptor nature, but is determined by the length of the carbon chain of terminal groups.
关键词： fluorescence,charge transfer complex,ultrafast electron transfer,transient absorption spectroscopy,bis-crown ether
更新于2025-09-04 15:30:14
-
The Quantum Efficiency of Charge Transfer Competing Against Non-Exponential Processes: The Case of Electron Transfer from CdS Nanorods to Hydrogenase
摘要： Photoexcited charge transfer from semiconductor nanocrystals to charge acceptors is a key step for photon energy conversion in semiconductor nanocrystal-based light-harvesting systems. Charge transfer competes against relaxation processes within the nanocrystals, and this competition determines the quantum efficiency of charge transfer. The quantum efficiency is a critical design element in photochemistry, but in nanocrystal–acceptor systems its extraction from experimental data is complicated by sample heterogeneity and intrinsically non-exponential excited-state decay pathways. In this manuscript, we systematically explore these complexities using TA spectroscopy over a broad range of timescales to probe electron transfer from CdS nanorods to the redox enzyme hydrogenase. To analyze the experimental data, we build a model that quantifies the quantum efficiency of charge transfer in the face of competing, potentially non-exponential, relaxation processes. Our approach can be applied to calculate the efficiency of charge or energy transfer in any donor–acceptor system that exhibits non-exponential donor decay and any ensemble distribution in the number of acceptors provided that donor relaxation and charge transfer can be described as independent, parallel decay pathways. We apply this analysis to our experimental system and unveil the connections between particle morphology and quantum efficiency. Our model predicts a finite quantum efficiency even when the mean recombination time diverges, as it does in CdS nanostructures with spatially separated electron–hole pairs that recombine with power-law dynamics. We contrast our approach to the widely-used expressions for the quantum efficiency based on average lifetimes, which for our system overestimate the quantum efficiency. The approach developed here is straightforward to implement and should be applicable to a wide range of systems.
关键词： electron transfer,quantum efficiency,semiconductor nanocrystals,non-exponential processes,charge transfer,hydrogenase,CdS nanorods
更新于2025-09-04 15:30:14
-
Spectro-electrochemical Studies on [Ru(TAP) <sub/>2</sub> (dppz)] <sup>2+</sup> —Insights into the Mechanism of its Photosensitized Oxidation of Oligonucleotides
摘要： [Ru(TAP)2(dppz)]2+ (TAP = 1,4,5,8-tetraazaphenanthrene; dppz = dipyrido[3,2-a:2′,3′-c]phenazine) is known to photo-oxidize guanine in DNA. Whether this oxidation proceeds by direct photoelectron transfer or by proton-coupled electron transfer is still unknown. To help distinguish between these mechanisms, spectro-electrochemical experiments have been carried out with [Ru(TAP)2(dppz)]2+ in acetonitrile. The UV?vis and mid-IR spectra obtained for the one-electron reduced product were compared to those obtained by picosecond transient absorption and time-resolved infrared experiments of [Ru(TAP)2(dppz)]2+ bound to guanine-containing DNA. An interesting feature of the singly reduced species is an electronic transition in the near-IR region (with λmax at 1970 and 2820 nm). Density functional and time-dependent density functional theory simulations of the vibrational and electronic spectra of [Ru(TAP)2(dppz)]2+, the reduced complex [Ru(TAP)2(dppz)]+, and four isomers of [Ru(TAP)(TAPH)(dppz)]2+ (a possible product of proton-coupled electron transfer) were performed. Significantly, these predict absorption bands at λ > 1900 nm (attributed to a ligand-to-metal charge-transfer transition) for [Ru(TAP)2(dppz)]+ but not for [Ru(TAP)(TAPH)(dppz)]2+. Both the UV?vis and mid-IR difference absorption spectra of the electrochemically generated singly reduced species [Ru(TAP)2(dppz)]+ agree well with the transient absorption and time-resolved infrared spectra previously determined for the transient species formed by photoexcitation of [Ru(TAP)2(dppz)]2+ intercalated in guanine-containing DNA. This suggests that the photochemical process in DNA proceeds by photoelectron transfer and not by a proton-coupled electron transfer process involving formation of [Ru(TAP)(TAPH)(dppz)]2+, as is proposed for the reaction with 5′-guanosine monophosphate. Additional infrared spectro-electrochemical measurements and density functional calculations have also been carried out on the free TAP ligand. These show that the TAP radical anion in acetonitrile also exhibits strong broad near-IR electronic absorption (λmax at 1750 and 2360 nm).
关键词： proton-coupled electron transfer,DNA oxidation,photoelectron transfer,Ruthenium complexes,spectro-electrochemistry
更新于2025-09-04 15:30:14
-
Tuning the Crystal Packing and Semiconductor Electronic Properties of 7,7’-Diazaisoindigo by Side-Chain Length and Halogenation
摘要： In the last years, the 7,7’-diazaisoindigo has emerged as a promising building block for semiconductor materials. In this work, we have studied different electronic properties which can be related to the semiconducting character of a family of 7,7’-diazaisoindigo derivatives. Concretely, we have analyzed the role of halogen substituents and different-length side chains on these properties calculated by means of the Density Functional Theory. In total, sixteen halogenated and non-halogenated diazaisoindigo derivatives were investigated. Four of these compounds were also synthetized and their X-ray structures were employed as starting points for the calculation of crystal structure of the rest of the novel compounds. In general, high electron transfer rate constants and electron mobilites were calculated for the studied 7,7’-diazaisoindigo derivatives, especially for bromine derivatives and compounds with long-side chains. The origin of these high rate constants mainly resides in the strong electronic couplings found for diazaisoindigo crystals in the π-stacking direction.
关键词： 7,7’-diazaisoindigo,side chains,electron mobilities,halogen substituents,Density Functional Theory,semiconductor materials,electron transfer rate constants,π-stacking direction
更新于2025-09-04 15:30:14
-
Mechanistic insights into light-activated catalysis for water oxidation
摘要： The development of catalysts for water oxidation to oxygen has been the subject of intense investigation in the last decade. In parallel to the search for high catalytic performance, many works have focused on the mechanistic analysis of the process. In this perspective, the oxidation of water through light-assisted cycles composed of an electron acceptor (EA), a photosensitizer (PS), and a water oxidation catalyst (WOC) can provide insightful and complementary information with respect to the use of chemical oxidants or to electrochemical techniques. In this microreview, we discuss the mechanistic aspects of the EA/PS/WOC photoactivated cycles, and in particular: (i) the general elementary steps; (ii) the required features and the nature of the PS employed; (iii) the electron transfer processes and kinetics from the WOC to PS+ (hole scavenging); (iv) the detrimental quenching of the PS by the WOC and the alternative mechanistic routes; (v) the identification of WOC intermediates and, finally, (vi) the transposition of the above processes into a dye-sensitized photoanode embedding a WOC.
关键词： reaction mechanisms,intermediates,water oxidation,Electron transfer,photocatalysis
更新于2025-09-04 15:30:14
-
Specific electron-transfer and surface plasmon resonance integrated boosting visible-light photoelectrochemical sensor for 4-chlorophenol
摘要： Emerging analytical technologies are being developed to provide advanced methods for monitoring 4-chlorophenol (4-CP) in the environment. Herein, a label-free, sensitive, and rapid photoelectrochemical (PEC) 4-CP detection system was constructed based on ternary composites of Ag nanoparticles, graphitic carbon nitride (GCN) and carbon spheres (CS) (Ag/GCN/CS). The proposed ternary composites were synthesized by a simple hydrothermal method. In this process, ascorbic acid (AA) played a crucial role in reducing Ag+ to metallic Ag, and provided a carbon source for CS. Due to synergistic promotion by the surface plasmon resonance (SPR) effect of Ag nanoparticles and electron-transfer behavior of CS, the ternary composites exhibited a broad visible light response and fast charge transfer, leading to a tremendously enhanced PEC response. Based on the promotion of the PEC response, a PEC sensor for 4-CP was designed by detecting the photocurrent signals of the PEC electrode after adding 4-CP to solution. Under optimal conditions, the PEC sensor exhibited a wide linear range for 4-CP from 16 to 1104 ng mL–1, with a limit of detection (LOD) of 5.33 ng mL–1. In particular, the present work may provide assist in better understanding the synergistic effect between the SPR effect of Ag nanoparticles and electron-transfer properties of CS. The results can also be applied to other PEC and photocatalytic systems in conjunction with high-performance photoactive materials.
关键词： PEC sensor,Carbon materials,Electron-transfer,SPR,Ternary composite
更新于2025-09-04 15:30:14
-
Effective quenching and excited-state relaxation of a Cu(I) photosensitizer addressed by time-resolved spectroscopy and TDDFT calculations
摘要： Homogenous photocatalytic systems based on copper photosensitizers are promising candidates for noble metal free approaches in solar hydrogen generation. To improve their performance, a detailed understanding of the individual steps is needed. Here, we study the interaction of a heteroleptic copper (I) photosensitizer with an iron catalyst by time-resolved spectroscopy and ab initio calculations. The catalyst leads to rather efficient quenching of the 3MLCT state of the copper complex, with a bimolecular rate being about three times smaller than the collision rate. Using control experiments with methyl viologen, an appearing absorption band is assigned to the oxidized copper complex demonstrating that an electron transfer from the sensitizer to the iron catalyst occurs and the system reacts along an oxidative pathway. However, only about 30% of the quenching events result in an electron transfer while the other 70% experience deactivation indicating that the photocatalytic performance might suffer from geminate recombination.
关键词： Solar hydrogen generation,Time-resolved spectroscopy,Ab initio calculations,Copper photosensitizers,Electron transfer
更新于2025-09-04 15:30:14