Photo-induced proton coupled electron transfer(PCET)is essential in the biological,photosynthesis,catalysis and solar energy conversion processes.Recently,p-nitrophenylphenol(HO-Bp-NO2)has been used as a model compoun...Photo-induced proton coupled electron transfer(PCET)is essential in the biological,photosynthesis,catalysis and solar energy conversion processes.Recently,p-nitrophenylphenol(HO-Bp-NO2)has been used as a model compound to study the photo-induced PCET mechanism by using ultrafast spectroscopy.In transient absorption spectra both singlet and triplet states were observed to exhibit PCET behavior upon laser excitation of HO-Bp-NO2.When we focused on the PCET in the triplet state,a new sharp band attracted us.This band was recorded upon excitation of HO-Bp-NO2 in aprotic polar solvents,and has not been observed for p-nitrobiphenyl which is without hydroxyl substitution.In order to find out what the new band represents,acidic solutions were used as an additional proton donor considering the acidity of HO-Bp-NO2.With the help of results in strong(~10^-1 mol/L)and weak(~10^-4 mol/L)acidic solutions,the new band is identified as open shell singlet O-Bp-NO2H,which is generated through protonation of nitro O in 3HO-Bp-NO2 followed by deprotonation of hydroxyl.Kinetics analysis indicates that the formation of radical·OBp-NO2 competes with O-Bp-NO2H in the way of concerted electron-proton transfer and/or proton followed electron transfers and is responsible for the low yield of O-Bp-NO2H.The results in the present work will make it clear how the3HO-Bp-NO2 deactivates in aprotic polar solvents and provide a solid benchmark for the deeply studying the PCET mechanism in triplets of analogous aromatic nitro compounds.展开更多
Charge breeding technique is used for RIB （radioactive ion beam） production in order of optimizing the re-acceleration of the radioactive isotopes produced by a primary beam in a thick target. Charge breeding is ach...Charge breeding technique is used for RIB （radioactive ion beam） production in order of optimizing the re-acceleration of the radioactive isotopes produced by a primary beam in a thick target. Charge breeding is achieved by means of a device capable of increasing the ion charge state from 1＋ to a desired value n＋. In some experiments, a continuous RIB of a given energy may be required. To reach this goal, a charge breeding device based on a hollow gun EBIS （electron beam ion source） has been proposed by the author recently. That EBIS, in principle, can be capable to realize a CW （continuous wave） operation. A sufficiently high focusing magnetic field could reduce to zero the hole radius in the EBIS electron beam. However, a smaller efficiency in the ion charge state increase should be expected. A code developed for studying the ion selective containment in a EBIS has been modified and used to simulate the ion charge state breeding. The effects of the hollow electron beam on the breeding rate have been studied.展开更多
Perovskite quantum-dot-based light-emitting diodes(QLEDs)are highly promising for future solid-state lightings and high-definition displays due to their excellent color purity.However,their device performance is easil...Perovskite quantum-dot-based light-emitting diodes(QLEDs)are highly promising for future solid-state lightings and high-definition displays due to their excellent color purity.However,their device performance is easily affected by charge accumulation induced luminescence quenching due to imbalanced charge injection in the devices.Here we report green perovskite QLEDs with simultaneously improved efficiency and operational lifetime through balancing the charge injection with the employment of a bilayered electron transport structure.The charge-balanced QLEDs exhibit a color-saturated green emission with a full-width at half-maximum(FWHM)of 18 nm and a peak at 520 nm,a low turn-on voltage of2.0 V and a champion external quantum efficiency(EQE)of 21.63%,representing one of the most efficient perovskite QLEDs so far.In addition,the devices with modulated charge balance demonstrate a nearly 20-fold improvement in the operational lifetime compared to the control device.Our results demonstrate the great potential of further improving the device performance of perovskite QLEDs toward practical applications in lightings and displays via rational device engineering.展开更多
基金supported by the National Natural Science Foundation of China(No.21973082)。
文摘Photo-induced proton coupled electron transfer(PCET)is essential in the biological,photosynthesis,catalysis and solar energy conversion processes.Recently,p-nitrophenylphenol(HO-Bp-NO2)has been used as a model compound to study the photo-induced PCET mechanism by using ultrafast spectroscopy.In transient absorption spectra both singlet and triplet states were observed to exhibit PCET behavior upon laser excitation of HO-Bp-NO2.When we focused on the PCET in the triplet state,a new sharp band attracted us.This band was recorded upon excitation of HO-Bp-NO2 in aprotic polar solvents,and has not been observed for p-nitrobiphenyl which is without hydroxyl substitution.In order to find out what the new band represents,acidic solutions were used as an additional proton donor considering the acidity of HO-Bp-NO2.With the help of results in strong(~10^-1 mol/L)and weak(~10^-4 mol/L)acidic solutions,the new band is identified as open shell singlet O-Bp-NO2H,which is generated through protonation of nitro O in 3HO-Bp-NO2 followed by deprotonation of hydroxyl.Kinetics analysis indicates that the formation of radical·OBp-NO2 competes with O-Bp-NO2H in the way of concerted electron-proton transfer and/or proton followed electron transfers and is responsible for the low yield of O-Bp-NO2H.The results in the present work will make it clear how the3HO-Bp-NO2 deactivates in aprotic polar solvents and provide a solid benchmark for the deeply studying the PCET mechanism in triplets of analogous aromatic nitro compounds.
文摘Charge breeding technique is used for RIB （radioactive ion beam） production in order of optimizing the re-acceleration of the radioactive isotopes produced by a primary beam in a thick target. Charge breeding is achieved by means of a device capable of increasing the ion charge state from 1＋ to a desired value n＋. In some experiments, a continuous RIB of a given energy may be required. To reach this goal, a charge breeding device based on a hollow gun EBIS （electron beam ion source） has been proposed by the author recently. That EBIS, in principle, can be capable to realize a CW （continuous wave） operation. A sufficiently high focusing magnetic field could reduce to zero the hole radius in the EBIS electron beam. However, a smaller efficiency in the ion charge state increase should be expected. A code developed for studying the ion selective containment in a EBIS has been modified and used to simulate the ion charge state breeding. The effects of the hollow electron beam on the breeding rate have been studied.
基金supported by the National Natural Science Foundation of China (51922049, 61604074)the National Key Research and Development Program of China (2016YFB0401701)+2 种基金the Natural Science Foundation of Jiangsu Province (BK20180020)the Fundamental Research Funds for the Central Universities (30920032102)PAPD of Jiangsu Higher Education Institutions
文摘Perovskite quantum-dot-based light-emitting diodes(QLEDs)are highly promising for future solid-state lightings and high-definition displays due to their excellent color purity.However,their device performance is easily affected by charge accumulation induced luminescence quenching due to imbalanced charge injection in the devices.Here we report green perovskite QLEDs with simultaneously improved efficiency and operational lifetime through balancing the charge injection with the employment of a bilayered electron transport structure.The charge-balanced QLEDs exhibit a color-saturated green emission with a full-width at half-maximum(FWHM)of 18 nm and a peak at 520 nm,a low turn-on voltage of2.0 V and a champion external quantum efficiency(EQE)of 21.63%,representing one of the most efficient perovskite QLEDs so far.In addition,the devices with modulated charge balance demonstrate a nearly 20-fold improvement in the operational lifetime compared to the control device.Our results demonstrate the great potential of further improving the device performance of perovskite QLEDs toward practical applications in lightings and displays via rational device engineering.
