The photocatalytic decarboxylation ofα-keto acids to generate acyl radicals under mild conditions represents a novel strategy in organic synthesis.However,the quantum efficiency of this process has been underexplored...The photocatalytic decarboxylation ofα-keto acids to generate acyl radicals under mild conditions represents a novel strategy in organic synthesis.However,the quantum efficiency of this process has been underexplored,limiting its practicality.To improve quantum efficiency,detailed analysis of mechanisms and kinetic data for key steps are essential.In this work,using time-resolved emission and absorption spectroscopy,we conducted a mechanistic study focusing on the excited-state properties of representative photocatalysts and their quenching efficiencies during the initial quenching process([Ir(dFCF_(3)ppy)_(2)(dtbbpy)]+(IrIII),Eosin Y(EY),Rose Bengal(RB),and 4CzPN).Our findings revealed that RB is active in its triplet states(^(3)RBH*),with lifetimes of 103 ns(in air)and 3.4µs(in anaerobic conditions),while EY and 4CzPN are active in their singlet states(^(1)EYH*and^(1)4CzPN*),with lifetimes of 2.9 ns and 5.1 ns,respectively.We measured the second-order rate constants for quenching by electron transfer fromα-keto acids:^(1)EYH*,2.3×10^(9)(mol/L)^(-1)·s^(-1);^(3)RBH*,3.2×10^(8)(mol/L)^(-1)·s^(-1)4CzPN*,2.8×10^(8)(mol/L)^(-1)·s^(-1).With our previously reported data for Mil,we established the quenching efficiency relationships for these photocatalysts withα-keto acids concentration.Our steady-state chromatography experiments determined the quantum efficiencies for consumption ofα-keto acids(IrIII>RBH>EYH>4CzPN),correlating these efficiencies with the initial quenching process.The results suggest that IrIII/RBH under anaerobic conditions could be optimal for high quantum efficiency.This study provides a foundation for designing new photocatalyticα-keto acid radical acylation systems with enhanced quantum efficiency.展开更多
The presence of defects/vacancies in nanomaterials influences the electronic structure of materials, and thus, it is necessary to study the correlation between the optoelectronic properties of a nanomaterial and its d...The presence of defects/vacancies in nanomaterials influences the electronic structure of materials, and thus, it is necessary to study the correlation between the optoelectronic properties of a nanomaterial and its defects/vacancies. Herein, we report a facile solvothermal route to synthesize three-dimensional （3D） SnS nanostructures formed by {131} faceted nanosheet assembly. The 3D SnS nanostructures were calcined at temperatures of 350, 400, and 450 ~C and used as counter electrodes, before their photocurrent properties were investigated. First principle computation revealed the photocurrent properties depend on the defect/vacancy concentration within the samples. It is very interesting that characterization with positron annihilation spectrometry confirmed that the density of defects/vacancies increased with the calcination temperature, and a maximum photocurrent was realized after treatment at 400 ℃. Further, the defect/vacancy density decreased when the calcination temperature reached 450℃ as the higher calcination temperature enlarged the mesopores and densified the pore walls, which led to a lower photocurrent value at 450℃ than at 400℃.展开更多
基金supported by the National Key R&D Program of China(No.2022YFA1505400)the National Natural Science Foundation of China(Nos.21933005,21727803,22003005 and 22273007)the Fundamental Research Funds for the Central Universities(No.2233300007).
文摘The photocatalytic decarboxylation ofα-keto acids to generate acyl radicals under mild conditions represents a novel strategy in organic synthesis.However,the quantum efficiency of this process has been underexplored,limiting its practicality.To improve quantum efficiency,detailed analysis of mechanisms and kinetic data for key steps are essential.In this work,using time-resolved emission and absorption spectroscopy,we conducted a mechanistic study focusing on the excited-state properties of representative photocatalysts and their quenching efficiencies during the initial quenching process([Ir(dFCF_(3)ppy)_(2)(dtbbpy)]+(IrIII),Eosin Y(EY),Rose Bengal(RB),and 4CzPN).Our findings revealed that RB is active in its triplet states(^(3)RBH*),with lifetimes of 103 ns(in air)and 3.4µs(in anaerobic conditions),while EY and 4CzPN are active in their singlet states(^(1)EYH*and^(1)4CzPN*),with lifetimes of 2.9 ns and 5.1 ns,respectively.We measured the second-order rate constants for quenching by electron transfer fromα-keto acids:^(1)EYH*,2.3×10^(9)(mol/L)^(-1)·s^(-1);^(3)RBH*,3.2×10^(8)(mol/L)^(-1)·s^(-1)4CzPN*,2.8×10^(8)(mol/L)^(-1)·s^(-1).With our previously reported data for Mil,we established the quenching efficiency relationships for these photocatalysts withα-keto acids concentration.Our steady-state chromatography experiments determined the quantum efficiencies for consumption ofα-keto acids(IrIII>RBH>EYH>4CzPN),correlating these efficiencies with the initial quenching process.The results suggest that IrIII/RBH under anaerobic conditions could be optimal for high quantum efficiency.This study provides a foundation for designing new photocatalyticα-keto acid radical acylation systems with enhanced quantum efficiency.
文摘The presence of defects/vacancies in nanomaterials influences the electronic structure of materials, and thus, it is necessary to study the correlation between the optoelectronic properties of a nanomaterial and its defects/vacancies. Herein, we report a facile solvothermal route to synthesize three-dimensional （3D） SnS nanostructures formed by {131} faceted nanosheet assembly. The 3D SnS nanostructures were calcined at temperatures of 350, 400, and 450 ~C and used as counter electrodes, before their photocurrent properties were investigated. First principle computation revealed the photocurrent properties depend on the defect/vacancy concentration within the samples. It is very interesting that characterization with positron annihilation spectrometry confirmed that the density of defects/vacancies increased with the calcination temperature, and a maximum photocurrent was realized after treatment at 400 ℃. Further, the defect/vacancy density decreased when the calcination temperature reached 450℃ as the higher calcination temperature enlarged the mesopores and densified the pore walls, which led to a lower photocurrent value at 450℃ than at 400℃.
