Continuous preparation of pyromellitic dianhydride(PMDA) from durene has been studied using a fixedbed reactor. The reaction was performed using a phosphorus-vanadium-titanium ternary catalyst.Relatively high selectiv...Continuous preparation of pyromellitic dianhydride(PMDA) from durene has been studied using a fixedbed reactor. The reaction was performed using a phosphorus-vanadium-titanium ternary catalyst.Relatively high selectivity and yield of PMDA was obtained. The in-situ characterization was combined with theoretical calculation to reveal the reaction mechanisms, and the remarkable doping effect was discussed.展开更多
MoS2 nanodots are emerging as promising semiconductor materials for optoelectronic devices. However, most of the recent attention is focused on the fabrication of MoS2 nanodots,and the survey for exciton dynamics of M...MoS2 nanodots are emerging as promising semiconductor materials for optoelectronic devices. However, most of the recent attention is focused on the fabrication of MoS2 nanodots,and the survey for exciton dynamics of MoS2 nanodots remains less explored. Herein, we use femtosecond transient absorption spectroscopy to investigate the carrier dynamics of MoS2 nanodots. Our results show that defect-assisted carrier recombination processes are well consistent with the observed dynamics. The photo-excited carriers are captured by defects with at least two different capture rates via Auger scattering. Four processes are deemed to take part in the carrier relaxation. After photoexcitation, carrier cooling occurs instantly within ～0.5 ps. Then most of carriers are fast captured by the defects, and the corresponding time constant increases from ～4.9 ps to ～9.2 ps with increasing pump fluence, which may be interpreted by saturation of the defect states. Next a small quantity of carriers is captured by the other kinds of defects with a relatively slow carrier capture time within ～65 ps.Finally, the remaining small fraction of carriers relaxes via direct interband electron-hole recombination within～1 ns. Our results may lead to deep insight into the fundamentals of carrier dynamics in MoS2 nanodots, paving the way for their further applications.展开更多
基金financial support by the National Natural Science Foundation of China (21878265)。
文摘Continuous preparation of pyromellitic dianhydride(PMDA) from durene has been studied using a fixedbed reactor. The reaction was performed using a phosphorus-vanadium-titanium ternary catalyst.Relatively high selectivity and yield of PMDA was obtained. The in-situ characterization was combined with theoretical calculation to reveal the reaction mechanisms, and the remarkable doping effect was discussed.
基金supported by the National Natural Science Foundation of China (No.11674128, No.21403232, No.11474129,and No.11504129)the Jilin Province Scientific and Technological Development Program, China (Grant No. 20170101063JC)the Thirteenth Five-Year Scientific and Technological Research Project of the Education Department of Jilin Province, China(2016, No. 400)
文摘MoS2 nanodots are emerging as promising semiconductor materials for optoelectronic devices. However, most of the recent attention is focused on the fabrication of MoS2 nanodots,and the survey for exciton dynamics of MoS2 nanodots remains less explored. Herein, we use femtosecond transient absorption spectroscopy to investigate the carrier dynamics of MoS2 nanodots. Our results show that defect-assisted carrier recombination processes are well consistent with the observed dynamics. The photo-excited carriers are captured by defects with at least two different capture rates via Auger scattering. Four processes are deemed to take part in the carrier relaxation. After photoexcitation, carrier cooling occurs instantly within ～0.5 ps. Then most of carriers are fast captured by the defects, and the corresponding time constant increases from ～4.9 ps to ～9.2 ps with increasing pump fluence, which may be interpreted by saturation of the defect states. Next a small quantity of carriers is captured by the other kinds of defects with a relatively slow carrier capture time within ～65 ps.Finally, the remaining small fraction of carriers relaxes via direct interband electron-hole recombination within～1 ns. Our results may lead to deep insight into the fundamentals of carrier dynamics in MoS2 nanodots, paving the way for their further applications.
