Constant Of Transfer Research Articles

Excited-state hole transfer in quantum dot-ferrocene hybrids: influence of ligand-exchange chemistry on surface loading and charge-transfer dynamics

We investigated how the post-synthesis treatment of tetradecylphosphonic acid-capped CdTe (TDPA-CdTe) QDs with CdCl2 and oleylamine (OAm) affected subsequent ligand-exchange reactions with ferrocenylhexanethiol (FcC6SH) and the dynamics and yield of photoinduced hole transfer from CdTe to adsorbed ferrocenylhexanethiolate (FcC6S-). CdCl2/OAm treatment promoted an 8-fold increase of the average number of adsorbed FcC6S- ligands ( N FcC 6 S − ) per CdTe QD; N FcC 6 S − increased with the concentration of FcC6SH and reached a maximum of 198 ± 5. Higher per-QD loadings of FcC6S- increased the overall ensemble rate constant of CdTe-to-FcC6S- hole transfer (kNht ), which reached (3.0 ± 0.4) × 109 s−1, and the efficiency of hole transfer (ηht ), which reached (98.2 ± 0.3)%. Values of kNht increased monotonically with N FcC 6 S − ; at relatively low loadings of FcC6S−, kNht varied linearly with N FcC 6 S − , indicating that hole-transfer pathways were additive. The intrinsic rate constant of hole transfer per adsorbed FcC6S− (kht ), (2.75 ± 0.19) × 107 s−1, was 10-fold higher for CdCl2/OAm-treated CdTe QDs than for TDPA-CdTe QDs. Surface-anchoring thiolates did not trap photogenerated holes; instead, holes were transferred to the Fe(II) center of FcC6S−. Treatment of CdTe QDs with CdCl2 and OAm thus promoted ligand-exchange with FcC6S−, accelerated excited-state hole transfer, and afforded tunability of charge-transfer dynamics.

Measuring Hydride Transfer Kinetics to Mhat Relevant Catalysts Using Cyclic Voltammetry

The area of organic electrocatalysis has been growing in importance as many new transformations have been developed and previously known transformations are adapted to be accomplished electrochemically. As the field of synthetic organic electrochemistry emerges, it is becoming ever more important to study the mechanisms of these electrocatalytic reactions. Understanding the mechanics of the chemical processes and how they are coupled to the electrode is critical for continuing to expand the synthetic utility of electrocatalysis. Radical based hydrofunctionalization of alkenes through transition-metal catalyzed hydrogen atom transfer (MHAT) mechanisms is a proven, powerful mode of forming C−C, C−O, C−N and C−X bonds. In recent years, new asymmetric MHAT reactions have been enabled through electrocatalysis. The in situ generation of the key metal-hydride species plays a crucial role in both the kinetics and selectivity of the observed products. These high energy metal hydrides are too reactive and too short lived to be isolated, thus the oxidative mechanism leading to their formation is poorly understood. Here, we utilize a model catalytic cycle in which metal hydride formation is the rate determining step. Cyclic voltammetry enables us to extract the rate constant of hydride transfer. The differences in kinetic trends between catalysts and hydride donors indicate separate mechanisms of hydride transfer are operative for different classes of MHAT catalysts. Specific trends in ligand electronics, hydride donor sterics and hydricity for cobalt salen type catalysts allowed us to postulate a possible metal/ligand cooperative mechanism of hydride transfer. In summary, these studies represent a significant step towards understanding the homolytic reactivity of metal hydride species and will help enable the design of new electrosynthetic reactions involving radical intermediates.

Characterization of the Lithium/Solid Electrolyte Interface in the Presence of Nanometer-thin TiOx Layers for All-Solid-State Batteries.

It is still unclear which role space charge layers (SCLs) play within an all-solid-state battery during operation with high current densities, as well as to which extent they form. Herein, we use a solid electrolyte with a known SCL formation and investigate it in a symmetric cell under non-blocking conditions with Li metal electrodes. Since the used LICGC™ electrolyte is known for its instability against lithium, it is protected from rapid degradation by nanometer-thin layers of TiOx deployed by atomic layer deposition. Close attention is given to the interfacial properties, as now additional Li+ can traverse through the interface depending on the applied bias potential. The interlayer's impedance response shows efficient lithium-ion conduction for low bias potentials and a diffusion-limiting effect towards high positive and negative potentials. SCLs grow up to a thickness of 5.1 μm. Additionally, estimating the apparent rate constant of the charge transfer across the interface indicates that the potentials where kinetics are hindered coincide with the widest SCLs. In conclusion, the investigation under higher steady-state currents was only possible because of the improved stability due to the interlayer. No chemo-physical failure could be observed after 800+ hours of cycling. However, an ex-situ SEM study shows a new phase at the interface, which grows into the electrolyte.

The Hydroxylated Carbon Nanotubes as the Hole Oxidation System in Electrocatalysis.

The hydroxylated carbon nanotubes (CNTs-OH), due to their propensity to trap electrons, are considered in many applications. Despite many case studies, the effect of the electronic structure of the CNT-OH electrode on its oxidation properties has not received in-depth analysis. In the present study, we used Fe(CN)63-/4- and Ru(NH3)63+/2+ as redox probes, which differ in charge. The CNT-OH and CNT electrodes used in the cyclic voltammetry were in the form of freestanding films. The concentration of holes in the CNTs-OH, estimated from the upshift of the Raman G-feature, was 2.9×1013 cm-2. The standard rate constant of the heterogeneous electron transfer (HET) between Fe(CN)63-/4- and the CNTs-OH electrode was 25.9×10-4 cm·s-1. The value was more than four times higher than the HET rate on the CNT electrode (ks=6.3×10-4 cm·s-1), which proves excellent boosting of the redox reaction by the holes. The opposite effect was observed for the Ru(NH3)63+/2+ redox couple. While the redox reaction rate constant at the CNT electrode was 1.4×10-4 cm·s-1, there was a significant suppression of the redox reaction at the CNT-OH electrode (ks<0.1×10-4 cm·s-1). Based on the DFT calculations and the Gerischer model, we find that the boosting of the HET from the reduced form of the redox couple to CNT-OH occurs when the reduced forms of the redox couples are negatively charged and the occupied reduced states are aligned with acceptor states of the nanotube electrode.

Multifunctional MoS2 membrane for integrated solar-driven water evaporation and water purification

Solar-driven interfacial water evaporation shows great potential to address the global water crisis, but its efficient implementation in the presence of organic wastewater remains challenging. Here, we achieved integrated water evaporation and organic compound degradation by designing a multifunctional MoS2 membrane. Under 1.0 sun irradiation, the membrane exhibits an evaporation rate of 2.07 kg m−2 h−1 and 82% degradation efficiency of organic pollutants, with negligible organic pollutant residues in the condensate. The high performance is attributed to the thermal energy generated by the evaporation process of MoS2 membrane. This promotes an increase in the rate constant of interfacial electron transfer during the photocatalytic reaction, accelerating the generation of free radicals and facilitating the removal of organic pollutants. The study demonstrated that fresh water can be collected from high-salinity wastewater at a rate of 1.56 kg m−2 h−1. The MoS2 membrane provides a sustainable approach to addressing the water crisis.

Understanding first electron transfer kinetic process of electrochemical nitrate reduction to ammonia on Fe2O3 nanorods array

Electroreduction reaction of nitrate (NO3RR) to ammonia (NH3) using reproducible energy is an effective alternative strategy to energy-intensive Haber-Bosch process and potentially energy storage. However, the reaction needs coupling of multiple electrons and protons, considering it a grand challenge to NH3 yield and selectivity affected by slow electron transfer kinetic processes. Herein, we investigate the electrode kinetics process by Tafel plots on Fe2O3 nanorods array electrocatalysts, confirming that the process of the first electron transfer is involved in the rate-determining step (RDS) for NO3RR. The reaction rate constant (k) of the first electron transfer (NO3– + e-→*NO3) indicates that Fe2O3 electrocatalyst treated at 450 ℃ has a faster electron transfer kinetic and thus exhibits a higher NH3 yield. Furthermore, operando EIS and in situ Raman spectroscopic characterizations demonstrate that electron gaining and losing process of Fe promotes the transfer of the first electron to NO3–, thus substantially accelerating the kinetic process of the RDS. These results provide key insight into the metal oxide-based electrocatalysts kinetic processes on the performance of NO3RR.

Extending Infrared Emission via Energy Transfer in a CsPbI3-Cyanine Dye Hybrid.

Directing energy flow in light harvesting assemblies of nanocrystal-chromophore hybrid systems requires a better understanding of factors that dictate excited-state processes. In this study, we explore excited-state interactions within the CsPbI3-cyanine dye (IR125) hybrid assembly through a comprehensive set of steady-state and time-resolved absorption and photoluminescence (PL) experiments. Our photoluminescence investigations reveal the quenching of CsPbI3 emission alongside the simultaneous enhancement of IR125 fluorescence, providing evidence for a singlet energy transfer. The evaluation of both photoluminescence (PL) quenching and PL decay measurements yield ∼94% energy transfer efficiency for the CsPbI3-IR125 hybrid assembly. Transient absorption spectroscopy further unveils that this singlet energy transfer process operates on an ultrafast time scale, occurring within 400 ps with a rate constant of energy transfer of 1.4 × 1010 s-1. Our findings highlight the potential of the CsPbI3-IR125 hybrid assembly to extend the emission of halide perovskites into the infrared region, paving the way for light energy harvesting and display applications.

Truxene-to-Fluorenone Energy Transfer in a Robust Mesoporous Zn-MOF.

A new metal-organic framework (MOF; [Zn4O(hett)4/3(fluo)1/2(bdc)1/2]n; TFT-MOF) constructed on chromophoric ligands 5,5',10,10',15,15'-hexaethyltruxene-2,7,12-triacetate (hett), 9-fluorenone-2,7-dicarboxylate (fluo), terephthalate (bdc), and the Zn4O node has been prepared and identified by powder X-ray diffraction. This luminescent MOF exhibits large mesoporous pores of 2.7 nm based on computer modeling using density functional theory (DFT) calculations. The steady-state and time-resolved fluorescence spectra and photophysical parameters of TFT-MOF have been investigated and compared with those of the free ligands and their basic chromophores. All in all, TFT-MOF exhibits particularly efficient singlet-singlet energy-transfer processes described as 1(hett)* → (fluo) and 1(bdc)* → (fluo), leading to fluorescence arising for the fluo lumophore operating only through Förster resonance energy transfer (FRET) with an efficiency of transfer of up to >95%. This experimental conclusion was corroborated by DFT and time-dependent DFT (TDDFT). For the 1(hett)* → (fluo) process, the approximated overall rate constant of energy transfer was evaluated to be at most 2.04 × 1010 s-1 (using a Stern-Volmer approach of solution data and the relationship between distance and concentration). This process was analyzed using the Förster theory, where two intrapore energy transfer paths of center-to-center distances of 13 and 25 Å have been identified. TFT-MOF photosensitizes the formation of singlet oxygen (1O2 (1Σg)) as detected by its phosphorescence signal at 1275 nm.

Trap or Triplet? Excited-State Interactions in 2D Perovskite Colloids with Chromophoric Cations.

Movement of energy within light-harvesting assemblies is typically carried out with separately synthesized donor and acceptor species, which are then brought together to induce an interaction. Recently, two-dimensional (2D) lead halide perovskites have gained interest for their ability to accommodate and assemble chromophoric molecules within their lattice, creating hybrid organic-inorganic compositions. Using a combination of steady-state and time-resolved absorption and emission spectroscopy, we have now succeeded in establishing the competition between energy transfer and charge trapping in 2D halide perovskite colloids containing naphthalene-derived cations (i.e., NEA2PbX4, where NEA = naphthylethylamine). The presence of room-temperature triplet emission from the naphthalene moiety depends on the ratio of bromide to iodide in the lead halide sublattice (i.e., x in NEA2Pb(Br1-xIx)4), with only bromide-rich compositions showing sensitized emission. Photoluminescence lifetime measurements of the sensitized naphthalene reveal the formation of the naphthalene triplet excimer at room temperature. From transient absorption measurements, we find the rate constant of triplet energy transfer (kEnT) to be on the order of ∼109 s-1. At low temperatures (77 K) a new broad emission feature arising from trap states is observed in all samples ranging from pure bromide to pure iodide composition. These results reveal the interplay between sensitized triplet energy transfer and charge trapping in 2D lead halide perovskites, highlighting the need to carefully parse contributions from competing de-excitation pathways for optoelectronic applications.

Electrochemically Exfoliated Graphene Oxide for Simple Fabrication of Cocaine Aptasensors.

Transducers made from graphene-type materials are widely used in sensing applications. However, utilization of graphene oxide obtained from electrochemical exfoliation of graphite (EGO) has remained relatively unexplored. In this study, electrochemical cocaine aptasensors based on large-size EGO flakes were investigated. In particular, the influence of the following parameters on the sensor performance was examined: (i) aptamer's terminal group (-NH2 vs -OH), (ii) functionalization of EGO with the aptamer via physical adsorption and covalent immobilization, and (iii) intrinsic electrochemical properties of EGO such as the electrochemical surface area (ESA) and standard rate constant of electron transfer (k0). The results demonstrate that EGO-based electrochemical aptasensors fabricated by physical adsorption with an NH2-modified aptamer have very good reproducibility, shelf-life stability, and high sensitivity for detecting cocaine with a detection limit of 50 nM. Their performance is comparable to that of the aptasensors prepared using the covalent immobilization. Additionally, it is shown that EGO materials with high ESA and k0 can enhance the sensing performance. The fast (less than 10 min) and strong adsorption of the NH2-modified cocaine aptamer on the surface of large EGO flakes makes the fabrication of the sensing platform simple and rapid. This simple approach has the potential to simplify the fabrication of sensors.

Bodipy−corrole tetrads as heavy−atom−free triplet photosensitizers: Study of the energy transfer and application in triplet−triplet annihilation upconversion

Free base corrole can generate triplet state without invoking of heavy−atom effect, however, its weak and narrow absorption band in the visible spectral range make corrole not an ideal triplet photosensitizer. Herein, novel Bodipy−corrole tetrads were prepared by attaching visible light-harvesting antennae of Bodipy or electron spin converter with fullerene units (2B−Tur−Cor and B−C60−Tur−Cor) to solve the above problems, which show a stronger and broader absorption band in the visible region, and the maximum molar absorption coefficient is up to 2.58 × 105 M−1 cm−1 at 504 nm for 2B−Tur−Cor. By using of fluorescence spectroscopy, steady-state and time-resolved transient absorption spectroscopic methods, the singlet energy transfer progress from the Bodipy moiety to the corrole moiety was confirmed. Through fluorescence lifetimes and fluorescence excitation spectrum study, the rate constant of the singlet energy transfer was calculated as 9.58 × 107 s−1 for 2B−Tur−Cor and 2.45 × 108 s−1 for B−C60−Tur−Cor, respectively. The TD−DFT computation suggests that the first and second triplet state is localized in the corrole moiety and the Bodipy moiety for 2B−Tur−Cor, respectively, and the triplet state energy was calculated to be 1.37 eV and 1.61 eV, respectively. Nanosecond time−resolved transient difference absorption spectra show that the triplet excited states of these tetrads are localized on corrole unit, the lifetime of 2B−T−Cor is up to 143 μs, however, the lifetime of B−C60−Tur−Cor is only 3.3 μs. Long-lived triplet excited states play important role in applications of the triplet photosensitizers in photocatalysis or other photophysical processes concerning triplet–triplet−energy−transfer. As a proof of concept, these tetrads were used as heavy−atom−free organic triplet photosensitizers for triplet−triplet annihilation based upconversion. The upconversion quantum yield was up to 5.86% for 2B−Tur−Cor, however, it is only 0.52% for B−C60−Tur−Cor.

Photooxidation by a long-lived photoexcited state of a triflic acid-bound Mn(IV)-oxo complex with the highest quantum efficiency

The photoexcited state of high-valent metal-oxo complexes binding protons would show the much enhanced oxidizing reactivity, providing a new way to achieve a photochemical oxidation of thermally inert substrates. However, there has been only one example for the long-lived photoexcited state of a MnIV-oxo complex binding scandium ion that is a rare-earth metal element. We report herein the formation of a long-lived photoexcited state of a MnIV-oxo complex binding triflic acid, composed of only earth-abundant elements, which exhibits the highest oxidizing reactivity among the high-valent metal-oxo species, including the excited state, reported so far. Photoexcitation of a triflic acid-bound MnIV-oxo complex (1, [(N4Py)MnIV(O)]2+–(HOTf)2) in a deaerated trifluoroethanol/acetonitrile resulted in the formation of a long-lived photoexcited state with a lifetime of 21 μs, which oxidized toluene to produce benzyl alcohol that was further oxidized to benzaldehyde. The driving force dependence of the rate constant of the photoinduced electron transfer from electron donors to the long-lived 2E excited state of 1 afforded a small reorganization energy of electron transfer (λ = 0.53 eV), since the 2E excited state of 1 may be composed of the ligand-to-metal charge-transfer (LMCT) state and the efficient electron transfer to the excited sate of 1 occurs at the ligand center. The quantum efficiency of 200% was achieved for the photochemical four-electron oxidation of toluene by 1, being the highest among various photooxidation reactions reported so far. The photodynamics were measured by laser-induced transient absorption spectroscopy to clarify the photooxidation mechanism of 1.

Electrochemical Biosensing of L-DOPA Using Tyrosinase Immobilized on Carboxymethyl Starch-Graft-Polyaniline@MWCNTs Nanocomposite

The electrochemical behavior of the immobilized tyrosinase (Tyrase) on a modified glassy carbon electrode with carboxymethyl starch-graft-polyaniline/multi-walled carbon nanotubes nanocomposite (CMS-g-PANI@MWCNTs) was investigated. The molecular properties of CMS-g-PANI@MWCNTs nanocomposite and its morphological characterization were examined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). A simple drop-casting method was employed to immobilize Tyrase on the CMS-g-PANI@MWCNTs nanocomposite. In the cyclic voltammogram (CV), a pair of redox peaks were observed at the potentials of +0.25 to -0.1 V and E°' was equal to 0.1 V and the apparent rate constant of electron transfer (Ks) was calculated at 0.4 s-1. Using differential pulse voltammetry (DPV), the sensitivity and selectivity of the biosensor were investigated. The biosensor exhibits linearity towards catechol and L-dopa in the concentration range of 5-100 and 10-300 μM with a sensitivity of 2.4 and 1.11 μA μΜ-1 cm-2 and limit of detection (LOD) 25 and 30 μM, respectively. The Michaelis-Menten constant (Km) was calculated at 42 μΜ for catechol and 86 μΜ for L-dopa. After 28 working days, the biosensor provided good repeatability and selectivity, and maintained 67% of its stability. The existence of -COO- and -OH groups in carboxymethyl starch, -NH2 groups in polyaniline, and high surface-to-volume ratio and electrical conductivity of multi-walled carbon nanotubes in the CMS-g-PANI@MWCNTs nanocomposite cause good Tyrase immobilization on the surface of the electrode.

Characterization of the solid/electrolyte interphase at hard carbon anodes via scanning (electrochemical) probe microscopy

Nanostructural properties impacting ion and electron transfer processes at the electrolyte-electrode interface are of pivotal importance for the overall performance of rechargeable batteries such as sodium-ion batteries (SIBs). Compared to lithium-ion batteries (LIBs), less is known about the solid electrolyte interphase (SEI) formation at the negative electrode of SIBs. In this contribution, we present conductive atomic force microscopy (AFM), AFM-based nanomechanical mappings and AFM-scanning electrochemical microscopy (AFM-SECM) measurements addressing the interphase formation on hard carbon (HC) providing insight on the effect of additives like 4-fluoro-1,3-dioxolan-2-one (FEC) and the potential cumulative impact of the electrochemical and nanomechanical properties. The additive strongly influences the adhesion forces, whereas in contrast the Young's modulus appears significantly increased after cycling independent of an added additive to the electrolyte solution. AFM-SECM images before and after cycling clearly indicate the formation of an electrically insulating interphase layer. In addition, the effective heterogeneous rate constant of electron transfer was determined at single HC particles.

How Clustered DNA Damage Can Change the Electronic Properties of ds-DNA-Differences between GAG, GAOXOG, and OXOGAOXOG.

Every 24 h, roughly 3 × 1017 incidences of DNA damage are generated in the human body as a result of intra- or extra-cellular factors. The structure of the formed lesions is identical to that formed during radio- or chemotherapy. Increases in the clustered DNA damage (CDL) level during anticancer treatment have been observed compared to those found in untreated normal tissues. 7,8-dihydro-8-oxo-2'-deoxyguanosine (OXOG) has been recognized as the most common lesion. In these studies, the influence of OXOG, as an isolated (oligo-OG) or clustered DNA lesion (oligo-OGOG), on charge transfer has been analyzed in comparison to native oligo-G. DNA lesion repair depends on the damage recognition step, probably via charge transfer. Here the electronic properties of short ds-oligonucleotides were calculated and analyzed at the M062x/6-31++G** level of theory in a non-equilibrated and equilibrated solvent state. The rate constant of hole and electron transfer according to Marcus' theory was also discussed. These studies elucidated that OXOG constitutes the sink for migrated radical cations. However, in the case of oligo-OGOG containing a 5'-OXOGAXOXG-3' sequence, the 3'-End OXOG becomes predisposed to electron-hole accumulation contrary to the undamaged GAG fragment. Moreover, it was found that the 5'-End OXOG present in an OXOGAOXOG fragment adopts a higher adiabatic ionization potential than the 2'-deoxyguanosine of an undamaged analog if both ds-oligos are present in a cationic form. Because increases in CDL formation have been observed during radio- or chemotherapy, understanding their role in the above processes can be crucial for the efficiency and safety of medical cancer treatment.

Probability of charge transport through al/GaAs interfaces system using quantum model

The focus of this paper is on the investigation and the understanding of transition probability of charge at the metal/semiconductor interface depending on the calculation of the rate constant. For this system we can suppose two localized quantum vector states system with a conduction electron state vector l 〉 interacting with an acceptor state vector l 〉 of electron in band of metal with the interacting described by the coupling matrix element. Expression of rate constant of charge transfer for metal/semiconductor system derived upon the quantum model and perturbation theory for transition between l 〉 and I state when the coupling matrix element coefficient smaller than . The probability of the charge transfer rate constant for the metal/semiconductor interface in this context, is basically defined as a relatively to potential barrier between a metal and a semiconductor The probability of charge transfer rate constant evaluated with reorganization energy using a matlap program. Theoretical results obtained for our mode show that the probability of charge transfer is more probable with decreasing the reorganization energy.

How Pendant Groups Dictate Energy and Electron Transfer in Perovskite–Rhodamine Light Harvesting Assemblies

Energy and electron transfer processes allow for efficient manipulation of excited states within light harvesting assemblies for photocatalytic and optoelectronic applications. We have now successfully probed the influence of acceptor pendant group functionalization on the energy and electron transfer between CsPbBr3 perovskite nanocrystals and three rhodamine-based acceptor molecules. The three acceptors─rhodamine B (RhB), rhodamine isothiocyanate (RhB-NCS), and rose Bengal (RoseB)─contain an increasing degree of pendant group functionalization that affects their native excited state properties. When interacting with CsPbBr3 as an energy donor, photoluminescence excitation spectroscopy reveals that singlet energy transfer occurs with all three acceptors. However, the acceptor functionalization directly influences several key parameters that dictate the excited state interactions. For example, RoseB binds to the nanocrystal surface with an apparent association constant (Kapp = 9.4 × 106 M-1) 200 times greater than RhB (Kapp = 0.05 × 106 M-1), thus influencing the rate of energy transfer. Femtosecond transient absorption reveals the observed rate constant of singlet energy transfer (kEnT) is an order-of-magnitude greater for RoseB (kEnT = 1 × 1011 s-1) than for RhB and RhB-NCS. In addition to energy transfer, each acceptor had a subpopulation of molecules (∼30%) that underwent electron transfer as a competing pathway. Thus, the structural influence of acceptor moieties must be considered for both excited state energy and electron transfer in nanocrystal-molecular hybrids. The competition between electron and energy transfer further highlights the complexity of excited state interactions in nanocrystal-molecular complexes and the need for careful spectroscopic analysis to elucidate competitive pathways.

Charge Carrier Dynamics of CsPbBr3/g-C3N4 Nanoheterostructures in Visible-Light-Driven CO2-to-CO Conversion

The photon energy-dependent selectivity of photocatalytic CO2-to-CO conversion by CsPbBr3 nanocrystals (NCs) and CsPbBr3/g-C3N4 nanoheterostructures (NHSs) was demonstrated for the first time. The surficial capping ligands of CsPbBr3 NCs would adsorb CO2, resulting in the carboxyl intermediate to process the CO2-to-CO conversion via carbene pathways. The type-II energy band structure at the heterojunction of CsPbBr3/g-C3N4 NHSs would separate the charge carriers, promoting the efficiency in photocatalytic CO2-to-CO conversion. The electron consumption rate of CO2-to-CO conversion for CsPbBr3/g-C3N4 NHSs was found to intensively depend on the rate constant of interfacial hole transfer from CsPbBr3 to g-C3N4. An in situ transient absorption spectroscopy investigation revealed that the half-life time of photoexcited electrons in optimized CsPbBr3/g-C3N4 NHS was extended two times more than that in the CsPbBr3 NCs, resulting in the higher probability of charge carriers to carry out the CO2-to-CO conversion. The current work presents important and novel insights of semiconductor NHSs for solar energy-driven CO2 conversion.

Theory of electron transmission probability at metal/semiconductor Interface system

We focus in this review on the theoretical description of the probability of electron transmission at metal/semiconductor at the interface depending on the quantum theory and density functional theory .Electronic devices technology largely rely on metal/ semiconductor system interfaces, whose most important coefficient parameters for the probability of electron transmission such that :reorientation free energy , potential barrier height ( ),work function ,affinity of semiconductor ,coupling coefficient matrix element, concentration of electron ,volume of unit cell for semiconductor ,petration factor , and temperature T(K) . The probability of electron transport rate constant in Au/ Ge ,and Au/Si interface system has been calculated and the transmission through interface is examined .A Mat lab program has been used to calculate the rate constant of electron transfer and all parameters of transmission by solvingthe suitable formulas .Our results data show that the probability of the rate constant for electron transfer increases with the increasing of the coupling coefficient and temperature, and decreasing of the reorganization energy

Acceleration of Nonradiative Charge Recombination Reactions at Larger Distances in Kinked Donor-Bridge-Acceptor Molecules.

Photoinduced electron transfer in donor-bridge-acceptor (D-B-A) molecular systems can occur via tunneling over long distances (rDA) of well over 10 Å. We commonly observe decreasing rates of electron transfer with increasing distances, a result of a decrease in the electronic coupling of the donor and acceptor moiety. In the study of D-B-A molecules with Ru(bpy)32+ as a bridge/core, Kuss-Petermann and Wenger observed the opposite trend (J. Am. Chem. Soc.2016, 138, 1349); a maximum rate constant of electron transfer was observed at an intermediate electron transfer distance. Within the high-temperature limit of the classical Marcus equation, their observation was qualitatively explained by a sharp distance dependence of outer sphere (or solvent) reorganization energy, as predicted by Sutin and co-workers (J. Am. Chem. Soc.1984, 106, 6858), and almost distance-independent electronic couplings. Here, we report another example of such an underexplored behavior with three kinked D-B-A systems of rDA ∼ 10-19 Å, showing increasing rates of nonradiative charge recombination with increasing rDA. The three D-B-A systems are based on boron dipyrromethene and triphenylamine as electron acceptor and donor groups, respectively, with aryl bridges where the donor and acceptor moieties are connected at meso-positions. These D-B-A molecules exhibit radiative electron transfer reactions (or charge-transfer emission), which enables us to experimentally determine the solvent reorganization energy and the electronic couplings. The analysis of charge-transfer emission that explicitly considers electron-vibration coupling, in conjunction with the temperature-dependent analysis and computational method, revealed that the solvent reorganization energy indeed increases with distance, and at the same time, the electronic coupling decreases with distance expectedly. Therefore, under the right conditions for solvent reorganization energy and electronic coupling values, our results show that we can observe the acceleration of electron transfer reactions with increasing distance, even when we have the expected distance dependence of electronic coupling. This work indicates that the acceleration of electron transfer with increasing distance may be achieved with a fine-tuning of molecular design.