Charge transfer as a mechanism for chlorophyll fluorescence concentration quenching.

Highly concentrated solutions of chlorophyll display rapid fluorescence quenching. The same devastating energy loss is not seen in photosynthetic light-harvesting antenna complexes, despite the need for chromophores to be in close proximity to facilitate energy transfer. A promising, though unconfirmed mechanism for the observed quenching is energy transfer from an excited chlorophyll monomer to a closely associated chlorophyll pair that subsequently undergoes rapid nonradiative decay to the ground state via a short-lived intermediate charge-transfer state. In this work, we make use of newly emerging fast methods in quantum chemistry to assess the feasibility of this proposed mechanism. We calculate rate constants for the initial charge separation, based on Marcus free-energy surfaces extracted from molecular dynamics simulations of solvated chlorophyll pairs, demonstrating that this pathway will compete with fluorescence (i.e., drive quenching) at experimentally measured quenching concentrations. We show that the rate of charge separation is highly sensitive to interchlorophyll distance and the relative orientations of chromophores within a quenching pair. We discuss possible solvent effects on the rate of charge separation (and consequently the degree of quenching), using the light-harvesting complex II (LH2) protein from rps. acidophila as a specific example of how this process might be controlled in a protein environment. Crucially, we reveal that the LH2 antenna protein prevents quenching, even at the high chlorophyll concentrations required for efficient energy transfer, by restricting the range of orientations that neighboring chlorophyll pairs can adopt.

From antenna to reaction center: Pathways of ultrafast energy and charge transfer in photosystem II.

The photosystem II core complex (PSII-CC) is the smallest subunit of the oxygenic photosynthetic apparatus that contains core antennas and a reaction center, which together allow for rapid energy transfer and charge separation, ultimately leading to efficient solar energy conversion. However, there is a lack of consensus on the interplay between the energy transfer and charge separation dynamics of the core complex. Here, we report the application of two-dimensional electronic-vibrational (2DEV) spectroscopy to the spinach PSII-CC at 77 K. The simultaneous temporal and spectral resolution afforded by 2DEV spectroscopy facilitates the separation and direct assignment of coexisting dynamical processes. Our results show that the dominant dynamics of the PSII-CC are distinct in different excitation energy regions. By separating the excitation regions, we are able to distinguish the intraprotein dynamics and interprotein energy transfer. Additionally, with the improved resolution, we are able to identify the key pigments involved in the pathways, allowing for a direct connection between dynamical and structural information. Specifically, we show that C505 in CP43 and the peripheral chlorophyll ChlzD1 in the reaction center are most likely responsible for energy transfer from CP43 to the reaction center.

A Robust Pyro-phototronic Route to Markedly Enhanced Photocatalytic Disinfection.

Photocatalysis offers a direct, yet robust, approach to eradicate pathogenic bacteria. However, the practical implementation of photocatalytic disinfection faces a significant challenge due to low-efficiency photogenerated carrier separation and transfer. Here, we present an effective approach to improve photocatalytic disinfection performance by exploiting the pyro-phototronic effect through a synergistic combination of pyroelectric properties and photocatalytic processes. A set of comprehensive studies reveals that the temperature fluctuation-induced pyroelectric field promotes photoexcited carrier separation and transfer and thus facilitates the generation of reactive oxygen species and ultimately enhances photocatalytic disinfection performance. It is worth highlighting that the constructed film demonstrated an exceptional antibacterial efficiency exceeding 95% against pathogenic bacteria under temperature fluctuations and light irradiation. Moreover, the versatile modulation role of the pyro-phototronic effect in boosting photocatalytic disinfection was corroborated. This work paves the way for improving photocatalytic disinfection efficiency by harnessing the synergistic potential of various inherent material properties.

Engineering Directional Charge Carrier Transport Using Ferroelectric Polarization for Enhanced Photoelectrochemical Water Oxidation.

Introducing ferroelectric polarization has shown great potential to facilitate interfacial charge separation in photoelectrochemical (PEC) water splitting. However, unambiguous evidence of the actual influence of spontaneous ferroelectric polarization, as compared to heterojunction formation, on electron extraction and PEC water splitting is still lacking to date. Herein, core-shell BaTiO3/TiO2 nanostructures are designed as photoanodes based on paraelectric cubic and ferroelectric tetragonal phases BaTiO3 (BTO) perovskite. The cubic and tetragonal crystalline phases are stabilized using selected elaboration methods. Compared to the paraelectric cubic (c-BTO), the ferroelectric tetragonal (t-BTO) leads to a favorable ferroelectric polarization, enhancing directional charge separation and as a consequence to increased photocurrent up to a factor of 1.95. More interestingly, the charge separation efficiency can be tuned by applying positive or negative polarization, with the highest charge separation obtained for the positive one. When loading Ni(OH)2 as a cocatalyst on the t-BTO@TiO2 photoanode, the Ni(OH)2/TiO2/t-BTO exhibits a high performance and superior stability toward PEC water oxidation with a photocurrent almost 6.7 times that of the reference SiO2@TiO2. The proposed facilitation may open an avenue to engineer charge separation and transport for high-performance PEC water oxidation.

Band Structure Optimized by Electron-Acceptor Cations for Sensitive Perovskite Single Crystal Self-Powered Photodetectors.

Low-dimensional perovskites afford improved stability against moisture, heat, and ionic migration. However, the low dimensionality typically results in a wide bandgap and strong electron-phonon coupling, which is undesirable for optoelectronic applications. Herein, semiconducting A-site organic cation engineering by electron-acceptor bipyridine (bpy) cations (2,2'-bpy2+ and 4,4'-bpy2+) is employed to optimize band structure in low-dimensional perovskites. Benefiting from the merits of lower lowest unoccupied molecular orbital (LUMO) energy for 4,4'-bpy2+ cation, the corresponding (4,4'-bpy)PbI4 is endowed with a smaller bandgap (1.44 eV) than the (CH3NH3)PbI3 (1.57 eV) benchmark. Encouragingly, an intramolecular type II band alignment formation between inorganic Pb-I octahedron anions and bpy2+ cations favors photogenerated electron-hole pairs separation. In addition, a shortening distance between inorganic Pb-I octahedral chains in (4,4'-bpy)PbI4 single crystal (SC) can effectively promote carrier transfer. As a result, a self-powered photodetector based on (4,4'-bpy)PbI4 SC exhibits 131 folds higher on/off ratio (3807) than the counterpart of (2,2'-bpy)2Pb3I10 SC (29). The presented result provides an effective strategy for exporting novel organic cation-based low-dimensional perovskite SC for high-performance optoelectronic devices.

Construction of Cs2AgBiCl6/COF Heterojunction for Boosted Photocatalytic Thioester Oxidation.

Lead-free halide perovskites as a new kind of potential candidate for photocatalytic organic synthesis have attracted much attention recently. The rational heterojunction construction is regarded as an efficient strategy to delicately regulate their catalytic performances. Herein, a semi-conductive covalent organic framework (COF) nanosheet, C4N, is employed as the functional component to construct Cs2AgBiCl6/C4N (CABC/C4N) heterojunction. It is found that the C4N nanosheets with rich surface functional groups can serve as heterogeneous nucleation sites to manipulate the growth of CABC nanocrystals and afford close contact between each other, therefore facilitate the transfer and spatial separation of photogenerated charge carriers, as verified by in situ X-ray photoelectronic spectroscopy and Kelvin probe force microscopy. Moreover, the oxygen affinity of C4N endows the heterojunctions with outstanding aerobic reactivity, thus improving the photocatalytic performance largely. The optimal CABC/C4N heterojunction delivers a thioanisole conversion efficiency of 100% after 6 h, which is 2.2 and 7.7-fold of that of CABC and C4N. This work provides a new ideal for the design and application of lead-free perovskite heterojunction photocatalysts for organic reactions.

Suppressing Se Vacancies in Sb2Se3 Photocathode by In Situ Annealing with Moderate Se Vapor Pressure for Efficient Photoelectrochemical Water Splitting.

Sb2Se3 emerges as a promising material for solar energy conversion devices. Unfortunately, the common deep-level defect VSe (selenium vacancy) in Sb2Se3 results in a low solar conversion efficiency. The post selenization process has been widely adopted for suppressing VSe. However, the effect of selenization on suppressing VSe is often compromised and even more VSe are induced due to defect-correlation. Herein, high-quality Sb2Se3 films are prepared using an unconventional selenization process, with precisely regulating in situ annealing Se vapor pressure. It is found that moderate Se vapor pressure annealing can efficiently suppress VSe by overcoming defect-correlation, as well as promotes grain growth and forms a better heterojunction band alignment. Consequently, the Sb2Se3 photocathode shows a high-level photocurrent of 19.5 mA cm-2 at 0 VRHE, an onset potential of 0.40 VRHE and a half-cell solar-to-hydrogen conversion efficiency of 1.9%, owing to the inhibited charge recombination, excellent charge transport and interface charge extraction. This work provides a significant insight to suppress deep-level defect VSe by adjusting Se vapor pressure for efficient Sb2Se3 photocathode.

Efficient Charge Separation in Ag/PCN/UPDI Ternary Heterojunction for Optimized Photothermal-Photocatalytic Performance via Tandem Electric Fields.

Charge separation driven by the internal electric field is a research hotspot in photocatalysis. However, it remains challenging to accurately control the electric field to continuously accelerate the charge transfer. Herein, a strategy of constructing a tandem electric field to continuously accelerate charge transfer in photocatalysts is proposed. The plasma electric field, interface electric field, and intramolecular electric field are integrated into the Ag/g-C3N4/urea perylene imide (Ag/PCN/UPDI) ternary heterojunction to achieve faster charge separation and longer carrier lifetime. The triple electric fields function as three accelerators on the charge transport path, promoting the separation of electron-hole pairs, accelerating charge transfer, enhancing light absorption, and increasing the concentration of energetic electrons on the catalyst. The H2 evolution rate of Ag/PCN/UPDI is 16.8 times higher than that of pristine PDI, while the degradation rate of oxytetracycline is increased by 4.5 times. This new strategy will provide a groundbreaking idea for the development of high-efficiency photocatalysts.

Customized Ultrathin Oxygen Vacancy-Rich Bi2W0.2Mo0.8O6 Nanosheets Enabling a Stepwise Charge Separation Relay and Exposure of Lewis Acid Sites toward Broad-Spectrum Photothermal Catalysis.

Designing robust photocatalysts with broad light absorption, effective charge separation, and sufficient reactive sites is critical for achieving efficient solar energy conversion. However, realizing these aims simultaneously through a single material modulation approach poses a challenge. Here, a 2D ultrathin oxygen vacancy (Ov)-rich Bi2W0.2Mo0.8O6 solid solution photocatalyst is designed and fabricated to tackle the dilemma through component and structure optimization. Specifically, the construction of a solid solution with ultrathin structure initially facilitates the separation of photoinduced electron-hole pairs, while the introduction of Ov strengthens such separation. In the meantime, the presence of Ov extends light absorption to the NIR region, triggering a photothermal effect that further enhances the charge separation and accelerates the redox reaction. As such, photoinduced charge carriers in the Ov-Bi2W0.2Mo0.8O6 are separated step by step via the synergistic action of 2D solid solution, OV, and solar heating. Furthermore, the introduction of OV exposes surface metal sites that serve as reactive Lewis acid sites, promoting the adsorption and activation of toluene. Consequently, the designed Ov-Bi2W0.2Mo0.8O6 reveals an enhanced photothermal catalytic toluene oxidation rate of 2445 µmol g-1 h-1 under a wide spectrum without extra heat input. The performance is 9.0 and 3.9 times that of Bi2WO6 and Bi2MoO6 nanosheets, respectively.

Systematic Constructing FeOCl/BiVO4 Hetero-Interfacial Hybrid Photoanodes for Efficient Photoelectrochemical Water Splitting.

Bismuth vanadate (BiVO4), as a promising photoanode for photoelectrochemical (PEC) water splitting, suffers from poor charge separation efficiency and light absorption efficiency. Herein, iron oxychloride (FeOCl) is introduced as a novel cocatalyst simply grafted on BiVO4 to construct an integrated photoanode, enhancing PEC performance. The optimized FeOCl/BiVO4 photoanode exhibits a superior photocurrent density value of 5.23 mA cm-2 at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5G illuminations. From experimental analysis, such high PEC performance is ascribed to the unique properties of FeOCl, facilitating charge transport, increasing light absorption efficiency, and promoting water oxidation kinetics. Density functional theory calculations further confirm that FeOCl optimizes the Gibbs free energy of H and O-containing intermediates (OOH*) during PEC processes, boosting the catalytic kinetics of PEC water splitting. This work presents FeOCl as a promising catalyst for constructing high efficient PEC water-splitting photoanodes.

Achieving Long-Lived Charge Separated State through Ultrafast Interfacial Hole Transfer in Redox Sites-Isolated CdS Nanorods for Enhanced Photocatalysis.

As opposed to natural photosynthesis, a significant challenge in a semiconductor-based photocatalyst is the limited hole extraction efficiency, which adversely affects solar-to-fuel efficiency. Recent studies have demonstrated that photocatalysts featuring spatially isolated dual catalytic oxidation/reduction sites can yield enhanced hole extraction efficiencies. However, the decay dynamics of excited states in such photocatalysts have not been explored. Here a ternary barbell-shaped CdS/MoS2/Cu2S heterostructure is prepared, comprising CdS nanorods (NRs) interfaced with MoS2 nanosheets at both ends and Cu2S nanoparticles on the sidewall. By using transient absorption (TA) spectra, highly efficient charge separation within the CdS/MoS2/Cu2S heterostructure are identified. This is achieved through directed electron transfer to the MoS2 tips at a rate constant of >8.3 × 109 s-1 and rapid hole transfer to the Cu2S nanoparticles on the sidewall at a rate of >6.1 × 1010 s-1, leading to an exceptional overall charge transfer constant of 2.3 × 1011 s-1 in CdS/MoS2/Cu2S. The enhanced hole transfer efficiency results in a remarkably prolonged charge-separated state, facilitating efficient electron accumulation within the MoS2 tips. Consequently, the ternary CdS/MoS2/Cu2S heterostructure demonstrates a 22-fold enhancement in visible-light-driven H2 generation compare to pure CdS nanorods. This work highlights the significance of efficient hole extraction in enhancing the solar-to-H2 performance of semiconductor-based heterostructure.

S-Modified Graphitic Carbon Nitride with Double Defect Sites For Efficient Photocatalytic Hydrogen Evolution.

Graphitic carbon nitride (gC3N4) is an attractive photocatalyst for solar energy conversion due to its unique electronic structure and chemical stability. However, gC3N4 generally suffers from insufficient light absorption and rapid compounding of photogenerated charges. The introduction of defects and atomic doping can optimize the electronic structure of gC3N4 and improve the light absorption and carrier separation efficiency. Herein, the high efficiency of carbon nitride photocatalysis for hydrogen evolution in visible light is achieved by an S-modified double-deficient site strategy. Defect engineering forms abundant unsaturated sites and cyano (─C≡N), which promotes strong interlayer C─N bonding interactions and accelerates charge transport in gC3N4. S doping tunes the electronic structure of the semiconductors, and the formation of C─S─C bonds optimizes the electron-transfer paths of the C─N bonding, which enhances the absorption of visible light. Meanwhile,C≡N acts as an electron trap to capture photoexcited electrons, providing the active site for the reduction of H+ to hydrogen. The photocatalytic hydrogen evolution efficiency of SDCN (1613.5 µmol g-1 h-1) is 31.5 times higher than that of pristine MCN (51.2 µmol g-1 h-1). The charge separation situation and charge transfer mechanism of the photocatalysts are investigated in detail by a combination of experimental and theoretical calculations.

Enhanced Spin-Polarized Electric Field Modulating p-Band Center on Ni-Doped CdS for Boosting Photocatalytic Hydrogen Evolution.

It is a challenge to regulate charge separation dynamics and redox reaction kinetics at the atomic level to synergistically boost photocatalytic hydrogen (H2) evolution. Herein, a robust Ni-doped CdS (Ni-CdS) photocatalyst is synthesized by incorporating highly dispersed Ni atoms into the CdS lattice in substitution for Cd atoms. Combined characterizations with theoretical analysis indicate that local lattice distortion and S-vacancy of Ni-CdS induced by Ni incorporation lead to an increased dipole moment and enhanced spin-polarized electric field, which promotes the separation and transfer of photoinduced carriers. In this contribution, charge redistribution caused by enhanced internal electric field results in the downshift of the S p-band center, which is conducive to the desorption of intermediate H* for boosting the H2 evolution reaction. Accordingly, the Ni-CdS photocatalyst shows a remarkably improved photocatalytic performance with an H2 evolution rate of 20.28 mmol g-1 h-1 under visible-light irradiation, which is 5.58 times higher than that of pristine CdS. This work supplied an insightful understanding that the enhanced polarization electric field governs the p-band center for efficient photocatalytic H2 evolution activity.

Directional Charge Pumping from Photoactive P-doped CdS to Catalytic Active Ni2P via Funneled Bandgap and Bridged Interface for Greatly Enhanced Photocatalytic H2 Evolution.

Loading cocatalysts onto semiconductors is one of the most popular strategies to inhibit charge recombination, but the efficiency is generally hindered by the localized built-in electric field and the weakly connected interface. Here, this work designs and synthesizes a 1D P-doped CdS nanowire/Ni2P heterojunction with gradient doped P to address the challenges. In the composite, the gradient P doping not only creates a funneled bandgap structure with a built-in electric field oriented from the bulk of P-CdS to the surface, but also facilitates the formation of a tightly connected interface using the co-shared P element. Consequently, the photogenerated charge carriers are enabled to be pumped from inside to surface of the P-CdS and then smoothly across the interface to the Ni2P. The as-obtained P-CdS/Ni2P displays high visible-light-driven H2 evolution rate of ≈8265 µmol g-1 h-1, which is 336 times and 120 times as that of CdS and P-CdS, respectively. This work is anticipated to inspire more research attention for designing new gradient-doped semiconductor/cocatalyst heterojunction photocatalysts with bridged interface for efficient solar energy conversion.

Direct Observation of Z-Scheme Route in Cu31S16/ZnxCd1-xS Heteronanoplates for Highly Efficient Photocatalytic Hydrogen Evolution.

Although photocatalytic hydrogen production from water holds great potential as a renewable and sustainable energy alternative, the practical application of the technology demands cost-effective, simple photocatalytic systems with high efficiency in hydrogen evolution reaction (HER). Herein, the synthesis and characterization of Cu31S16/ZnxCd1-xS heterostructured nanoplates (Cu31S16/ZnCdS HNPs) as a high photocatalytic system are reported. The cost-effective, hierarchical structures are easily prepared using the Cu31S16 NPs as the seed by the epitaxial growth of the ZnCdS nanocrystals (NCs). The Cu31S16/ZnCdS without the noble metal cocatalyst exhibits a high HER rate of 61.7 mmol g-1 h-1, which is 8,014 and 17 times higher than that of Cu31S16 and ZnCdS, respectively, under visible light irradiation. The apparent quantum yield (AQY) of Cu31S16/ZnCdS reaches 67.9% at 400 nm with the highest value so far in the reported ZnCdS-based photocatalysts. The excellent activity and stability of the Cu31S16/ZnCdS are attributed to the formation of a strong internal electric field (IEF) and the Z-scheme pathway. The comprehensive experiments and theoretical calculations provide the direct evidences of the Z-scheme route. This work may offer a way for the design and development of efficient photocatalysts to achieve solar-to-chemical energy conversion at a practically useful level.

Design and Fabrication of Biomass Derived Black Carbon Modified g-C3N4/FeIn2S4 Heterojunction as Highly Efficient Photocatalyst for Wastewater Treatment.

The environmental deterioration caused by dye wastewater discharge has received considerable attention in recent decades. One of the most promising approaches to addressing the aforementioned environmental issue is the development of photocatalysts with high solar energy consumption efficiency for the treatment of dye-contaminated water. In this study, a novel low-cost π-π biomass-derived black carbon modified g-C3N4 coupled FeIn2S4 composite (i.e., FeInS/BC-CN) photocatalyst is successfully designed and fabricated that reveals significantly improved photocatalytic performance for the degradation of Eosin Yellow (EY) dye in aqueous solution. Under dark and subsequent visible light irradiation, the amount optimized composite reveals 99% removal performance for EY dye, almost three-fold compared to that of the pristine FeInS and BC-CN counterparts. Further, it is confirmed by means of the electron spin resonance spectrometry, quenching experiments, and density functional theory (DFT) calculations, that the hydroxyl radicals (•OH) and superoxide radicals (•O2 -) are the dominant oxidation species involved in the degradation process of EY dye. In addition, a systematic photocatalytic degradation route is proposed based on the resultant degradation intermediates detectedduring liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. This work provides an innovative idea for the development of advanced photocatalysts to mitigate water pollution.

Metal Cocatalyst Engineering in Metal-Semiconductor Hybrid Photocatalysts Achieves a Fivefold Enhancement of Hydrogen Evolution.

This study explores the optimal morphology of photochemical hydrogen evolution catalysts in a one-dimensional system. Systematic engineering of metal tips on precisely defined CdSe@CdS dot-in-rods is conducted to exert control over morphology, composition, and both factors. The outcome yields an optimized configuration, a Au-Pt core-shell structure with a rough Pt surface (Au@r-Pt), which exhibits a remarkable fivefold increase in quantum efficiency, reaching 86 % at 455 nm and superior hydrogen evolution rates under visible and AM1.5 G irradiation conditions with prolonged stability. Kinetic investigations using photoelectrochemical and time-resolved measurements demonstrate a greater extent and extended lifetime of the charge-separated state on the tips as well as rapid water reduction kinetics on high-energy surfaces. This approach sheds light on the critical role of cocatalysts in hybrid photocatalytic systems for achieving high performance.

Excited-State Dynamics in Segregated Donor-Acceptor Stacks Versus a Peri-Bisdonor-Acceptor System.

The investigation of impact of through-space/through-bond electronic interaction among chromophores on photoexcited-state properties has immense potential owing to the distinct emergent photophysical pathways. Herein, the photoexcited-state dynamics of homo-sorted π-stacked aggregates of a naphthalenemonoimide and perylene-based acceptor-donor (NI-Pe) system and a fork-shaped acceptor-bisdonor (NI-Pe2) system possessing integrally stacked peri-substituted donors was examined. Femtosecond transient absorption (fsTA) spectra of NI-Pe monomer recorded in chloroform displayed spectroscopic signatures of the singlet state of Pe; 1Pe*, the charge-separated state; NI-⋅-Pe+⋅, and the triplet state of Pe; 3Pe*. The examination of ultrafast excited-state processes of NI-Pe aggregate in chloroform revealed faster charge recombination ( τ C R a ${{\tau }_{CR}^{a}}$ =1.75 ns) than the corresponding monomer ( τ C R m ${{\tau }_{CR}^{m}}$ =2.46 ns) which was followed by observation of a broad structureless band attributed to an excimer-like state. The fork-shaped NI-Pe2 displayed characteristic spectroscopic features of the NI radical anion (λmax~450 nm) and perylene dimer radical cation (λmax~520 nm) upon photoexcitation in non-polar toluene solvent in the nanosecond transient absorption (nsTA) spectroscopy. The investigation highlights the significance of intrinsic close-stacked arrangement of donors in ensuring a long-lived photoinduced charge-separated state ( τ C R ${{\tau }_{CR}}$ =1.35 µs) in non-polar solvents via delocalization of radical cation between the donors.

Photoinduced Energy and Electron Transfer in a 'Two-Point' Bound Panchromatic, Near-Infrared-Absorbing Bis-styrylBODIPY(Zinc Porphyrin)2 - Fullerene Self-Assembled Supramolecular Conjugate.

Structurally well-defined self-assembled supramolecular multi-modular donor-acceptor conjugates play a significant role in furthering our understanding of photoinduced energy and electron transfer events occurring in nature, e. g., in the antenna-reaction centers of photosynthesis and their applications in light energy harvesting. However, building such multi-modular systems capable of mimicking the early events of photosynthesis has been synthetically challenging, causing a major hurdle for its growth. Often, multi-modularity is brought in by combining both covalent and noncovalent approaches. In the present study, we have developed such an approach wherein a π-extended conjugated molecular cleft, two zinc(II)porphyrin bearing bisstyrylBODIPY (dyad, 1), has been synthesized. The binding of 1 via a 'two-point' metal-ligand coordination of a bis-pyridyl fulleropyrrolidine (2), forming a stable self-assembled supramolecular complex (1 : 2), has been established. The self-assembled supramolecular complex has been fully characterized by a suite of physico-chemical methods, including TD-DFT studies. From the established energy diagram, both energy and electron transfer events were envisioned. In dyad 1, selective excitation of zinc(II)porphyrin leads to efficient singlet-singlet excitation transfer to (bisstyrly)BODIPY with an energy transfer rate constant, kEnT of 2.56×1012 s-1. In complex 1 : 2, photoexcitation of zinc(II)porphyrin results in ultrafast photoinduced electron transfer with a charge separation rate constant, kCS of 2.83×1011 s-1, and a charge recombination rate constant, kCR of 2.51×109 s-1. For excitation at 730 nm corresponding to bisstyrylBODIPY, similar results are obtained, where a biexponential decay yielded estimated values of kCS 3.44×1011 s-1 and 2.97×1010 s-1, and a kCR value of 2.10×1010 s-1. The newly built self-assembled supramolecular complex has been shown to successfully mimic the early events of the photosynthetic antenna-reaction center events.

Spontaneous Charge Separation at the Metal-Water Interface.

Reactions at the metal-water interface are essential in a range of fundamental and technological processes. Using Density Functional Theory calculations, we demonstrate that water substantially affects the adsorption of H and O2 on Cu(111), Ag(111), Au(111), Pd(111) and Pt(111). In water, H is found to undergo a spontaneous charge separation, where a proton desorbs to the water solution while an electron is donated to the surface. The reaction is exothermic over Au and Pt and associated with low barriers. The process is facile also over Pd, albeit slightly endothermic. For O2, water is found to increase the metal-to-adsorbate charge transfer, enhancing the adsorption energy and O-O bond length as compared to the adsorption in the absence of water. The magnitudes of the effects are system dependent, which implies that calculations should treat water explicitly. The results elucidate previous experimental results and highlights the importance of charge-transfer effects at the metal-water interface; both to describe the potential energy landscape, and to account for alternative reaction routes in the presence of water.