Semiconductor-cocatalyst interfacial electron transfer has widely been considered as a fast step occurring on picosecond-microsecond timescale in photocatalytic reaction.However,the formed potential barriers severely ...Semiconductor-cocatalyst interfacial electron transfer has widely been considered as a fast step occurring on picosecond-microsecond timescale in photocatalytic reaction.However,the formed potential barriers severely slow this interfacial electronic process by thermionic emission.Although trap-assisted charge recombination can transfer electrons from semiconductor to cocatalyst and can even be evident under weak illumination,the parallel connection with thermionic emission makes the photocatalytic photon utilization encounter a minimum along the variation of light intensity.By this cognition,the light-intensity-dependent photocatalytic behaviors can be predicted by simulating the photoinduced semiconductor-cocatalyst interfacial electron transfer that mainly determines the reaction rate.We then propose a(photo)electrochemical method to evaluate the time constants for occurring this interfacial electronic process in actual photocatalytic reaction without relying on extremely high photon flux that is required to generate discernible optical signal in common instrumental methods based on ultrafast pulse laser.The evaluated decisecond-second timescale can accurately guide us to develop certain strategies to facilitate this rate-determining step to improve photon utilization.展开更多
The development of efficient photocatalytic H2-evolution materials requires both rapid electron transfer and an effective interfacial catalysis reaction for H2 production. In addition to the well-known noble metals, l...The development of efficient photocatalytic H2-evolution materials requires both rapid electron transfer and an effective interfacial catalysis reaction for H2 production. In addition to the well-known noble metals, low-cost and earth-abundant non-noble metals can also act as electron- transfer mediators to modify photocatalysts. However, as almost all non-noble metals lack the interfacial catalytic active sites required for the H2-evolution reaction, the enhancement of the photocatalytic performance is limited. Therefore, the development of new interfacial active sites on metal-modified photocatalysts is of considerable importance. In this study, to enhance the photocatalytic evolution of H2 by Ni-modified TiO2, the formation of NiSx as interfacial active sites was promoted on the surface of Ni nanoparticles. Specifically, the co-modified TiO2/Ni-NiSx photocatalysts were prepared via a two-step process involving the photoinduced deposition of Ni on the TiO2 surface and the subsequent formation of NiSx on the Ni surface by a hydrothermal reaction method. It was found that the TiO2/Ni-NiSx photocatalysts exhibited enhanced photocatalytic H2-evolution activity. In particular, TiO2/Ni-NiSx(30%) showed the highest photocatalytic rate (223.74 μmol h.1), which was greater than those of TiO2, TiO2/Ni, and TiO2/NiSx by factors of 22.2, 8.0, and 2.2, respectively. The improved H2-evolution performance of TiO2/Ni-NiSx could be attributed to the excellent synergistic effect of Ni and NiSx, where Ni nanoparticles function as effective mediators to transfer electrons from the TiO2 surface and NiSx serves as interfacial active sites to capture H+ ions from solution and promote the interfacial H2-evolution reaction. The synergistic effect of the non-noble metal cocatalyst and the interfacial active sites may provide new insights for the design of highly efficient photocatalytic materials.展开更多
Photocatalytic solar fuel generation is currently a hot topic because of its potential for solving the energy crisis owing to its low cost and zero-carbon emissions.However,the rapid bulk recombination of photoexcited...Photocatalytic solar fuel generation is currently a hot topic because of its potential for solving the energy crisis owing to its low cost and zero-carbon emissions.However,the rapid bulk recombination of photoexcited carrier pairs is a fundamental disadvantage.To resolve this problem,we synthesized a dual cocatalysts system of cobalt phosphide(Co P)and molybdenum carbide(Mo_(2)C)embedded on strontium titanate(Sr TiO_(3))nanofibers.Compared with those of pristine SrTiO_(3) and binary samples,the dual cocatalysts system(denoted SCM)showed a significant improvement in the hydrogen evolution and CO_(2) reduction performance.Further,the structure of SCM effectively promoted spatial charge separation and enhanced the photocatalytic performance.In addition,the Schottky junction formed between the SrTiO_(3) and cocatalysts enabled the rapid transfer of photoexcited electrons from SrTiO_(3) to the cocatalysts,resulting in effective separation and prolonged photoexcited electron lifetimes.The electron migration route between SrTiO_(3) and the cocatalysts was determined by in situ irradiation X-ray spectroscopy,and band structures of Sr TiO_(3) and the cocatalysts are proposed based on results obtained from UV-vis diffraction reflection spectroscopy and ultraviolet photoelectron spectroscopy measurements.On the basis of our results,the dual cocatalysts unambiguously boosts charge separation and enhances photocatalytic performance.In summary,we have investigated the flux of photoexcited electrons in a dual cocatalysts system and provided a theoretical basis and ideas for subsequent research.展开更多
A novel algorithm was designed and implemented to realize the numerical calculation of the solvent reorganization energy for electron transfer reactions, on the basis of nonequilibrium solvation theory and the dielect...A novel algorithm was designed and implemented to realize the numerical calculation of the solvent reorganization energy for electron transfer reactions, on the basis of nonequilibrium solvation theory and the dielectric polarizable continuum model. Applying the procedure to the well-investigated intramoleeular electron transfer in biphenyl-androstane-naphthyl and biphenyl-androstane-phenanthryl systems, the numerical results of solvent reorganization energy were determined to be around 60 k J/mol, in good agreement with experimental data. Koopman＇s theorem was adopted for the calculation of the electron transfer coupling element, associated with the linear reaction coordinate approximation. The values for this quantity obtained are acceptable when compared with experimental results.展开更多
The photophysical and photochemical behaviors of thioxanthen-9-one(TX)in different solvents have been studied using nanosecond transient absorption spectroscopy.A unique absorption of the triplet state^(3)TX^(∗) is ob...The photophysical and photochemical behaviors of thioxanthen-9-one(TX)in different solvents have been studied using nanosecond transient absorption spectroscopy.A unique absorption of the triplet state^(3)TX^(∗) is observed,which involves two components,^(3)nπ^(∗) and^(3)ππ^(∗) states.The ^(3)ππ^(∗) component contributes more to the^(3)TX^(∗) when increasing the solvent polarity.The self-quenching rate constant ksq of^(3)TX^(∗)is decreased in the order of CH_(3)CN,CH_(3)CN/CH_(3)OH(1:1),and CH_(3)CN/H_(2)O(1:1),which might be caused by the exciplex formed from hydrogen bond interaction.In the presence of diphenylamine(DPA),the quenching of^(3)TX^(∗)happens efficiently via electron transfer,producing the TX^(⋅−) anion and DPA^(⋅+) cation radicals.Because of insignificant solvent effects on the electron transfer,the electron affinity of the ^(3)nπ^(∗) state is proved to be approximately equal to that of the ^(3)ππ^(∗) state.However,a solvent dependence is found in the dynamic decay of TX^(⋅−) anion radical.In the strongly acid aqueous acetonitrile(pH=3.0),a dynamic equilibrium between protonated and unprotonated TX is definitely observed.Once photolysis,^(3)TXH^(+∗) is produced,which contributes to the new band at 520 nm.展开更多
The present work concerns the study of solvent effects on the geometrical structures, as well as one- and two-photon absorption （TPA） processes, for two series of alkyne and alkene π-bridging molecules, within the ...The present work concerns the study of solvent effects on the geometrical structures, as well as one- and two-photon absorption （TPA） processes, for two series of alkyne and alkene π-bridging molecules, within the framework of the polarization continuum model. Particular emphasis was put on the characterization of solvent effects on the molecular geometrical structures and geometric distortion, which were measured by the bond-length-alternation parameter. The π centres in the compounds are seen to play a decisive role in increasing the TPA cross section and nonlinear optical properties. All studied molecules have relatively strong TPA characteristics, while the alkyne π-bridging ones yield larger TPA cross sections.展开更多
Photodynamic therapy(PDT)as a non-invasive anticancer modality has received increasing attention due to its advantages of noninvasiveness,high temporospatial selectivity,simple and controllable operation,etc.PDT mainl...Photodynamic therapy(PDT)as a non-invasive anticancer modality has received increasing attention due to its advantages of noninvasiveness,high temporospatial selectivity,simple and controllable operation,etc.PDT mainly relies on the generation of toxic reactive oxygen species(ROS)by photosensitizers(PSs)under the light irradiation to cause cancer cell apoptosis and death.However,solid tumors usually exhibit an inherent hypoxic microenvironment,which greatly limits the PDT efficacy of these high oxygen-dependent conventional type II PSs.Therefore,it is of great importance to design and develop efficient type I PSs that are less oxygen-dependent for the treatment of hypoxic tumors.Herein,a new strategy for the preparation of efficient type I PSs by introducing the photoinduced electron transfer(PET)mechanism is reported.DR-NO_(2) is obtained by introducing 4-nitrobenzyl to(Z)-2-(5-(4-(diethylamino)-2-hydroxybenzylidene)-4-oxo-3-phenylthiazolidin-2-ylidene)malononitrile(DR-OH)with aggregation-induced emission(AIE)feature.The AIE feature ensures their high ROS generation efficiency in aggregate,and the PET process leads to fluorescence quenching of DR-NO_(2) to promote triplet state formation,which also promotes intramolecular charge separation and electron transfer that is conducive for type I ROS particularly superoxide radicals generation.In addition,DR-NO_(2) nanoparticles are prepared by nanoprecipitation to possess nanoscaled sizes,high cancer cell uptake,and excellent type I ROS generation ability,which results in an excellent performance in PDT ablation of MCF-7 cancer cells.This PET strategy for the development of type I PSs possesses great potential for PDT applications against hypoxic tumors.展开更多
Transition metal alloy electrocatalysts have sparked intense interest for their use in oxygen reduction reaction(ORR).However,there is almost no corresponding research on the alloy active sites.In this study,CoNi allo...Transition metal alloy electrocatalysts have sparked intense interest for their use in oxygen reduction reaction(ORR).However,there is almost no corresponding research on the alloy active sites.In this study,CoNi alloy nanoparticles embedded in bamboo-like N-doped carbon nanotubes(CoNi-NCTs)as catalysts constructed by a facile pyrolysis of Prussian blue analogs were investigated.The density functional theory calculation reveals that the oxygen molecules are more easily adsorbed on the Ni sites in these catalysts,while the Co sites favor the formation of OOH★intermediates during ORR.In addition,the cooperation of the CoNi alloys with the N-doped carbon benefits electron transfer and promotes electrocatalytic activity.The optimized CoNi-NCT shows remarkable ORR catalytic activity with an half-wave potential(E1/2)of 0.83 V,an onset potential(Eonset)of 0.97 V,and superior durability,all of which surpass the commercial Pt/C catalysts.The assembled zinc-air battery delivers a small charge/discharge voltage gap of 0.86 V at 10 mA cm^(-2),a high-power density of 167 mW cm^(-2),and good stability(running stably over 900 cycles).展开更多
The mechanisms of reactions between CC13OO? radical and quercetin, rutin and epigallocatechin gallate (EGCG) have been studied using pulse radiolytic technique. It is suggested that the electron transfer reaction is t...The mechanisms of reactions between CC13OO? radical and quercetin, rutin and epigallocatechin gallate (EGCG) have been studied using pulse radiolytic technique. It is suggested that the electron transfer reaction is the main reaction between CC13OO? radical and rutin, EGCG, but there are two main pathways for the reaction of CC13OO? radical with quercetin, one is the electron transfer reaction, the other is addition reaction. The reaction rate constants were determined. It is proved that quercetin and rutin are better CC13OO? radical scavengers than EGCG.展开更多
文摘Semiconductor-cocatalyst interfacial electron transfer has widely been considered as a fast step occurring on picosecond-microsecond timescale in photocatalytic reaction.However,the formed potential barriers severely slow this interfacial electronic process by thermionic emission.Although trap-assisted charge recombination can transfer electrons from semiconductor to cocatalyst and can even be evident under weak illumination,the parallel connection with thermionic emission makes the photocatalytic photon utilization encounter a minimum along the variation of light intensity.By this cognition,the light-intensity-dependent photocatalytic behaviors can be predicted by simulating the photoinduced semiconductor-cocatalyst interfacial electron transfer that mainly determines the reaction rate.We then propose a(photo)electrochemical method to evaluate the time constants for occurring this interfacial electronic process in actual photocatalytic reaction without relying on extremely high photon flux that is required to generate discernible optical signal in common instrumental methods based on ultrafast pulse laser.The evaluated decisecond-second timescale can accurately guide us to develop certain strategies to facilitate this rate-determining step to improve photon utilization.
基金supported by the National Natural Science Foundation of China(21477094)the Fundamental Research Funds for the Central Universities(WUT 2017IB002)~~
文摘The development of efficient photocatalytic H2-evolution materials requires both rapid electron transfer and an effective interfacial catalysis reaction for H2 production. In addition to the well-known noble metals, low-cost and earth-abundant non-noble metals can also act as electron- transfer mediators to modify photocatalysts. However, as almost all non-noble metals lack the interfacial catalytic active sites required for the H2-evolution reaction, the enhancement of the photocatalytic performance is limited. Therefore, the development of new interfacial active sites on metal-modified photocatalysts is of considerable importance. In this study, to enhance the photocatalytic evolution of H2 by Ni-modified TiO2, the formation of NiSx as interfacial active sites was promoted on the surface of Ni nanoparticles. Specifically, the co-modified TiO2/Ni-NiSx photocatalysts were prepared via a two-step process involving the photoinduced deposition of Ni on the TiO2 surface and the subsequent formation of NiSx on the Ni surface by a hydrothermal reaction method. It was found that the TiO2/Ni-NiSx photocatalysts exhibited enhanced photocatalytic H2-evolution activity. In particular, TiO2/Ni-NiSx(30%) showed the highest photocatalytic rate (223.74 μmol h.1), which was greater than those of TiO2, TiO2/Ni, and TiO2/NiSx by factors of 22.2, 8.0, and 2.2, respectively. The improved H2-evolution performance of TiO2/Ni-NiSx could be attributed to the excellent synergistic effect of Ni and NiSx, where Ni nanoparticles function as effective mediators to transfer electrons from the TiO2 surface and NiSx serves as interfacial active sites to capture H+ ions from solution and promote the interfacial H2-evolution reaction. The synergistic effect of the non-noble metal cocatalyst and the interfacial active sites may provide new insights for the design of highly efficient photocatalytic materials.
文摘Photocatalytic solar fuel generation is currently a hot topic because of its potential for solving the energy crisis owing to its low cost and zero-carbon emissions.However,the rapid bulk recombination of photoexcited carrier pairs is a fundamental disadvantage.To resolve this problem,we synthesized a dual cocatalysts system of cobalt phosphide(Co P)and molybdenum carbide(Mo_(2)C)embedded on strontium titanate(Sr TiO_(3))nanofibers.Compared with those of pristine SrTiO_(3) and binary samples,the dual cocatalysts system(denoted SCM)showed a significant improvement in the hydrogen evolution and CO_(2) reduction performance.Further,the structure of SCM effectively promoted spatial charge separation and enhanced the photocatalytic performance.In addition,the Schottky junction formed between the SrTiO_(3) and cocatalysts enabled the rapid transfer of photoexcited electrons from SrTiO_(3) to the cocatalysts,resulting in effective separation and prolonged photoexcited electron lifetimes.The electron migration route between SrTiO_(3) and the cocatalysts was determined by in situ irradiation X-ray spectroscopy,and band structures of Sr TiO_(3) and the cocatalysts are proposed based on results obtained from UV-vis diffraction reflection spectroscopy and ultraviolet photoelectron spectroscopy measurements.On the basis of our results,the dual cocatalysts unambiguously boosts charge separation and enhances photocatalytic performance.In summary,we have investigated the flux of photoexcited electrons in a dual cocatalysts system and provided a theoretical basis and ideas for subsequent research.
文摘A novel algorithm was designed and implemented to realize the numerical calculation of the solvent reorganization energy for electron transfer reactions, on the basis of nonequilibrium solvation theory and the dielectric polarizable continuum model. Applying the procedure to the well-investigated intramoleeular electron transfer in biphenyl-androstane-naphthyl and biphenyl-androstane-phenanthryl systems, the numerical results of solvent reorganization energy were determined to be around 60 k J/mol, in good agreement with experimental data. Koopman＇s theorem was adopted for the calculation of the electron transfer coupling element, associated with the linear reaction coordinate approximation. The values for this quantity obtained are acceptable when compared with experimental results.
基金supported by the Educational Commission of Anhui Province of China (No.KJ2018A0491)financial support of Anhui Natural Science Foundation (No.1908085MB50)
文摘The photophysical and photochemical behaviors of thioxanthen-9-one(TX)in different solvents have been studied using nanosecond transient absorption spectroscopy.A unique absorption of the triplet state^(3)TX^(∗) is observed,which involves two components,^(3)nπ^(∗) and^(3)ππ^(∗) states.The ^(3)ππ^(∗) component contributes more to the^(3)TX^(∗) when increasing the solvent polarity.The self-quenching rate constant ksq of^(3)TX^(∗)is decreased in the order of CH_(3)CN,CH_(3)CN/CH_(3)OH(1:1),and CH_(3)CN/H_(2)O(1:1),which might be caused by the exciplex formed from hydrogen bond interaction.In the presence of diphenylamine(DPA),the quenching of^(3)TX^(∗)happens efficiently via electron transfer,producing the TX^(⋅−) anion and DPA^(⋅+) cation radicals.Because of insignificant solvent effects on the electron transfer,the electron affinity of the ^(3)nπ^(∗) state is proved to be approximately equal to that of the ^(3)ππ^(∗) state.However,a solvent dependence is found in the dynamic decay of TX^(⋅−) anion radical.In the strongly acid aqueous acetonitrile(pH=3.0),a dynamic equilibrium between protonated and unprotonated TX is definitely observed.Once photolysis,^(3)TXH^(+∗) is produced,which contributes to the new band at 520 nm.
文摘The present work concerns the study of solvent effects on the geometrical structures, as well as one- and two-photon absorption （TPA） processes, for two series of alkyne and alkene π-bridging molecules, within the framework of the polarization continuum model. Particular emphasis was put on the characterization of solvent effects on the molecular geometrical structures and geometric distortion, which were measured by the bond-length-alternation parameter. The π centres in the compounds are seen to play a decisive role in increasing the TPA cross section and nonlinear optical properties. All studied molecules have relatively strong TPA characteristics, while the alkyne π-bridging ones yield larger TPA cross sections.
文摘Photodynamic therapy(PDT)as a non-invasive anticancer modality has received increasing attention due to its advantages of noninvasiveness,high temporospatial selectivity,simple and controllable operation,etc.PDT mainly relies on the generation of toxic reactive oxygen species(ROS)by photosensitizers(PSs)under the light irradiation to cause cancer cell apoptosis and death.However,solid tumors usually exhibit an inherent hypoxic microenvironment,which greatly limits the PDT efficacy of these high oxygen-dependent conventional type II PSs.Therefore,it is of great importance to design and develop efficient type I PSs that are less oxygen-dependent for the treatment of hypoxic tumors.Herein,a new strategy for the preparation of efficient type I PSs by introducing the photoinduced electron transfer(PET)mechanism is reported.DR-NO_(2) is obtained by introducing 4-nitrobenzyl to(Z)-2-(5-(4-(diethylamino)-2-hydroxybenzylidene)-4-oxo-3-phenylthiazolidin-2-ylidene)malononitrile(DR-OH)with aggregation-induced emission(AIE)feature.The AIE feature ensures their high ROS generation efficiency in aggregate,and the PET process leads to fluorescence quenching of DR-NO_(2) to promote triplet state formation,which also promotes intramolecular charge separation and electron transfer that is conducive for type I ROS particularly superoxide radicals generation.In addition,DR-NO_(2) nanoparticles are prepared by nanoprecipitation to possess nanoscaled sizes,high cancer cell uptake,and excellent type I ROS generation ability,which results in an excellent performance in PDT ablation of MCF-7 cancer cells.This PET strategy for the development of type I PSs possesses great potential for PDT applications against hypoxic tumors.
基金the National Key R&D Program of China(2018YFE0201704)the National Natural Science Foundation of China(21771059,21631004 and 91961111)the Natural Science Foundation of Heilongjiang Province(YQ2019B007)。
文摘Transition metal alloy electrocatalysts have sparked intense interest for their use in oxygen reduction reaction(ORR).However,there is almost no corresponding research on the alloy active sites.In this study,CoNi alloy nanoparticles embedded in bamboo-like N-doped carbon nanotubes(CoNi-NCTs)as catalysts constructed by a facile pyrolysis of Prussian blue analogs were investigated.The density functional theory calculation reveals that the oxygen molecules are more easily adsorbed on the Ni sites in these catalysts,while the Co sites favor the formation of OOH★intermediates during ORR.In addition,the cooperation of the CoNi alloys with the N-doped carbon benefits electron transfer and promotes electrocatalytic activity.The optimized CoNi-NCT shows remarkable ORR catalytic activity with an half-wave potential(E1/2)of 0.83 V,an onset potential(Eonset)of 0.97 V,and superior durability,all of which surpass the commercial Pt/C catalysts.The assembled zinc-air battery delivers a small charge/discharge voltage gap of 0.86 V at 10 mA cm^(-2),a high-power density of 167 mW cm^(-2),and good stability(running stably over 900 cycles).
基金Acknowledgements This work was supported by the Foundation of Qimingxing Program of Shanghai, China (Grant No. 99QA14034).
文摘The mechanisms of reactions between CC13OO? radical and quercetin, rutin and epigallocatechin gallate (EGCG) have been studied using pulse radiolytic technique. It is suggested that the electron transfer reaction is the main reaction between CC13OO? radical and rutin, EGCG, but there are two main pathways for the reaction of CC13OO? radical with quercetin, one is the electron transfer reaction, the other is addition reaction. The reaction rate constants were determined. It is proved that quercetin and rutin are better CC13OO? radical scavengers than EGCG.
