The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction,both in terms of practical applications(e.g.models of combustion or atmosphere chemistry...The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction,both in terms of practical applications(e.g.models of combustion or atmosphere chemistry)in understanding the fundamental mechanisms of such chemical reactions.A global ground state potential energy surface for the dissociation reaction of deuterated alkyl halide CD_(3)CH_(2)F was computed at the CCSD(T)/CBS//B3 LYP/aug-cc-p VDZ level of theory for all species.The decomposition of CD_(3)CH_(2)F is controversial concerning C-F bond dissociation reaction and molecular(HF,DF,H_(2),D_(2),HD)elimination reaction.RiceRamsperger-Kassel-Marcus(RRKM)calculations were applied to compute the rate constants for individual reaction steps and the relative product branching ratios for the dissociation products were calculated using the steady-state approach.At the different energies studied,the RRKM method predicts that the main channel for DF or HF elimination from1,2-elimination of CD_(3)CH_(2)F is through a four-center transition state,whereas D_(2) or H_(2) elimination from 1,1-elimination of CD_(3)CH_(2)F occurs through a direct three-center elimination.At 266,248,and 193 nm photodissociation,the main product CD_(2)CH_(2)+DF branching ratios are computed to be 96.57%,91.47%,and 48.52%,respectively;however,at 157 nm photodissociation,the product branching ratio is computed to be 16.11%.Based on these transition state structures and energies,the following photodissociation mechanisms are suggested:at 266,248,193 nm,CD_(3)CH_(2)F→absorption of a photon→TS5→the formation of the major product CD_(2)CH_(2)+DF;at 157 nm,CD_(3)CH_(2)F→absorption of a photon→D/F interchange of TS1→CDH_(2)CDF→H/F interchange of TS2→CHD_(2)CHDF→the formation of the major product CHD_(2)+CHDF.展开更多
Electron transfer （ET） reactions between 1,8-dihydroxyanthraquinone （DHAQ） and two DNA bases, adenine （A） and cytosine （C）, have been investigated in CH3CN/H20 solution with nanosecond time-resolved laser flas...Electron transfer （ET） reactions between 1,8-dihydroxyanthraquinone （DHAQ） and two DNA bases, adenine （A） and cytosine （C）, have been investigated in CH3CN/H20 solution with nanosecond time-resolved laser flash photolysis. After irradiation at 355 nm, the triplet DHAQ is produced via intersystem crossing and reacts with two nucleobases. ET processes for both reactions have been definitely identified, in which two bases play a significant role of electron donor. Based on the measured decay dynamics of various intermediates and the corresponding quenching rates, an initial ET process followed by a secondary proton-transfer reaction is suggested for both the overall reactions. By plotting the observed quenching rate against the concentration of two DNA bases, the bimolecular quenching rate constants are determined as 9.0-10s L/（mol.s） for the 3DHAQ＊＋C reaction and 3.3x10^8 L/（mol.s） for the 3DHAQ＊＋A reaction, respectively.展开更多
Although many ionic liquids have been reported, their polarity is not completely understood. Different empirical polarity scales for molecular solvents always lead to different polarity orders when they are applied on...Although many ionic liquids have been reported, their polarity is not completely understood. Different empirical polarity scales for molecular solvents always lead to different polarity orders when they are applied on ionic liquids. Based on a literature survey, this review summarizes the recent polarity scales of ionic liquids according to the following 4 classes:(1) equilibrium and kinetic rate constants of chemical reactions;(2) empirical polar parameters of ionic liquids;(3) spectral properties of probe molecules;(4) multiparameter approaches. In addition, their interrelations are presented. A systematic understanding of the relationship between different polarity parameters of ionic liquids is of great importance for finding a universal set of parameters that can be used to predict the polarities of ionic liquids quantitatively. The potential utilization of the electron paramagnetic resonance in this field is also addressed.展开更多
Highly efficient,low-cost,and portable wastewater treatment and purification solutions are urgently needed for aqueous pollution removal,especially at remote sites.Synergistic photocatalytic (PC) and persulphate (PS) ...Highly efficient,low-cost,and portable wastewater treatment and purification solutions are urgently needed for aqueous pollution removal,especially at remote sites.Synergistic photocatalytic (PC) and persulphate (PS) degradation under visible light offers an exceptional alternative for this purpose.In this work,we coupled a TiO^(2-)based PC system with a PS oxidation system into a portable advanced oxidation device for rapid and deep degradation of organic contaminants in wastewater.Using hydrogenation,we fabricated hydrogenated anatase branched-rutile TiO_(2) nanorod (H-AB@RTNR) photocatalysts which enable the PC degradation to occur under visible light and improve the utilization of solar energy.We also discovered that the addition of PS resulted in the synergistic degradation of tenacious and persistent organics,dramatically improving the extent and kinetics of the degradation.A degradation rate of 100%and a reaction rate constant of 0.0221 min^(-1)for degrading 1 L rhodamine B(20 mg L^(-1)) were achieved in 120 min in a specially designed thin-layer cell under visible light irradiation.The superior performance of the synergistic PC and PS degradation system was also demonstrated in the degradation of real industrial wastewater.Both remarkable performances can be attributed to the heterophase junction and oxygen vacancies in the photocatalyst that facilitate the catalytic conversion of PS anions into highly active radicals (·SO_(4)-and·OH).This work suggests that the as-proposed synergistic degradation design is a promising solution for building a portable wastewater treatment system.展开更多
基金supported by the National Natural Science Foundation of China(No.91641116,No.21433004,No.91753103,and No.21933010)the NYU Global Seed Grantthe Laboratory and Equipment Management Office of ECNU。
文摘The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction,both in terms of practical applications(e.g.models of combustion or atmosphere chemistry)in understanding the fundamental mechanisms of such chemical reactions.A global ground state potential energy surface for the dissociation reaction of deuterated alkyl halide CD_(3)CH_(2)F was computed at the CCSD(T)/CBS//B3 LYP/aug-cc-p VDZ level of theory for all species.The decomposition of CD_(3)CH_(2)F is controversial concerning C-F bond dissociation reaction and molecular(HF,DF,H_(2),D_(2),HD)elimination reaction.RiceRamsperger-Kassel-Marcus(RRKM)calculations were applied to compute the rate constants for individual reaction steps and the relative product branching ratios for the dissociation products were calculated using the steady-state approach.At the different energies studied,the RRKM method predicts that the main channel for DF or HF elimination from1,2-elimination of CD_(3)CH_(2)F is through a four-center transition state,whereas D_(2) or H_(2) elimination from 1,1-elimination of CD_(3)CH_(2)F occurs through a direct three-center elimination.At 266,248,and 193 nm photodissociation,the main product CD_(2)CH_(2)+DF branching ratios are computed to be 96.57%,91.47%,and 48.52%,respectively;however,at 157 nm photodissociation,the product branching ratio is computed to be 16.11%.Based on these transition state structures and energies,the following photodissociation mechanisms are suggested:at 266,248,193 nm,CD_(3)CH_(2)F→absorption of a photon→TS5→the formation of the major product CD_(2)CH_(2)+DF;at 157 nm,CD_(3)CH_(2)F→absorption of a photon→D/F interchange of TS1→CDH_(2)CDF→H/F interchange of TS2→CHD_(2)CHDF→the formation of the major product CHD_(2)+CHDF.
文摘Electron transfer （ET） reactions between 1,8-dihydroxyanthraquinone （DHAQ） and two DNA bases, adenine （A） and cytosine （C）, have been investigated in CH3CN/H20 solution with nanosecond time-resolved laser flash photolysis. After irradiation at 355 nm, the triplet DHAQ is produced via intersystem crossing and reacts with two nucleobases. ET processes for both reactions have been definitely identified, in which two bases play a significant role of electron donor. Based on the measured decay dynamics of various intermediates and the corresponding quenching rates, an initial ET process followed by a secondary proton-transfer reaction is suggested for both the overall reactions. By plotting the observed quenching rate against the concentration of two DNA bases, the bimolecular quenching rate constants are determined as 9.0-10s L/（mol.s） for the 3DHAQ＊＋C reaction and 3.3x10^8 L/（mol.s） for the 3DHAQ＊＋A reaction, respectively.
基金supported by the National Natural Science Foundation of China (21573196)the Program for Zhejiang Leading Team of S&T Innovation (2011R50007)the Fundamental Research Funds of the Central Universities
文摘Although many ionic liquids have been reported, their polarity is not completely understood. Different empirical polarity scales for molecular solvents always lead to different polarity orders when they are applied on ionic liquids. Based on a literature survey, this review summarizes the recent polarity scales of ionic liquids according to the following 4 classes:(1) equilibrium and kinetic rate constants of chemical reactions;(2) empirical polar parameters of ionic liquids;(3) spectral properties of probe molecules;(4) multiparameter approaches. In addition, their interrelations are presented. A systematic understanding of the relationship between different polarity parameters of ionic liquids is of great importance for finding a universal set of parameters that can be used to predict the polarities of ionic liquids quantitatively. The potential utilization of the electron paramagnetic resonance in this field is also addressed.
基金supported by Griffith University PhD scholarshipsthe National Natural Science Foundation of China (22078118)the Natural Science Foundation of Guangdong Province (2019A1515011138)。
文摘Highly efficient,low-cost,and portable wastewater treatment and purification solutions are urgently needed for aqueous pollution removal,especially at remote sites.Synergistic photocatalytic (PC) and persulphate (PS) degradation under visible light offers an exceptional alternative for this purpose.In this work,we coupled a TiO^(2-)based PC system with a PS oxidation system into a portable advanced oxidation device for rapid and deep degradation of organic contaminants in wastewater.Using hydrogenation,we fabricated hydrogenated anatase branched-rutile TiO_(2) nanorod (H-AB@RTNR) photocatalysts which enable the PC degradation to occur under visible light and improve the utilization of solar energy.We also discovered that the addition of PS resulted in the synergistic degradation of tenacious and persistent organics,dramatically improving the extent and kinetics of the degradation.A degradation rate of 100%and a reaction rate constant of 0.0221 min^(-1)for degrading 1 L rhodamine B(20 mg L^(-1)) were achieved in 120 min in a specially designed thin-layer cell under visible light irradiation.The superior performance of the synergistic PC and PS degradation system was also demonstrated in the degradation of real industrial wastewater.Both remarkable performances can be attributed to the heterophase junction and oxygen vacancies in the photocatalyst that facilitate the catalytic conversion of PS anions into highly active radicals (·SO_(4)-and·OH).This work suggests that the as-proposed synergistic degradation design is a promising solution for building a portable wastewater treatment system.
