The exposed crystal facet of TiO_(2) is a crucial factor influencing the gas sensing properties.TiO_(2) with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excelle...The exposed crystal facet of TiO_(2) is a crucial factor influencing the gas sensing properties.TiO_(2) with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties.In this paper,TiO_(2) nanoplates with defective{001}facets were synthesized by chemical etching via one-step hydrothermal method.We carefully explored the gas-sensing performance of TiO_(2) nanoplates with defective and complete{001}facets towards acetone.The results show that the sensing response of TiO_(2) nanoplates with complete{001}facets is 70%higher than that of defective TiO_(2) nanoplates,which proves that the{001}facets plays a vital role in improving the gas sensing performance of TiO_(2).It is speculated that the poor gas sensitivity of defective TiO_(2) can be contributed to fewer adsorption sites and blocked electron transfer.This work presents a more direct evidence for explaining the important role of the complete{001}crystal facets in high sensitivity of TiO_(2) and also provides a new insight for preparing high sensitivity sensing materials.展开更多
A six-step synthesis of （-）-clausenamide is described. Optically pure （R,E）-1,3-diphenylallylic alcohol was ac-etylated and then subjected to an Ireland-Claisen rearrangement, giving the γ,δ-unsaturated acid, wh...A six-step synthesis of （-）-clausenamide is described. Optically pure （R,E）-1,3-diphenylallylic alcohol was ac-etylated and then subjected to an Ireland-Claisen rearrangement, giving the γ,δ-unsaturated acid, which underwent a substrate-induced stereoselective bromolactonization to afford the expected all-equatorial substituted bromo-δ-lac-one. An unusual chemo-selective aminolysis of the lactone resulted in the formation of a γ,δ-epoxy-amide in stereospecific manner. Base-promoted cyclization of this intermediate and the subsequent Davis oxidation furnished the synthesis, delivering the final product in 〉99% ee and up to 34% overall yield.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51773226,61701514)the Natural Science Foundation of Hunan Province(No.2018JJ3603)
文摘The exposed crystal facet of TiO_(2) is a crucial factor influencing the gas sensing properties.TiO_(2) with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties.In this paper,TiO_(2) nanoplates with defective{001}facets were synthesized by chemical etching via one-step hydrothermal method.We carefully explored the gas-sensing performance of TiO_(2) nanoplates with defective and complete{001}facets towards acetone.The results show that the sensing response of TiO_(2) nanoplates with complete{001}facets is 70%higher than that of defective TiO_(2) nanoplates,which proves that the{001}facets plays a vital role in improving the gas sensing performance of TiO_(2).It is speculated that the poor gas sensitivity of defective TiO_(2) can be contributed to fewer adsorption sites and blocked electron transfer.This work presents a more direct evidence for explaining the important role of the complete{001}crystal facets in high sensitivity of TiO_(2) and also provides a new insight for preparing high sensitivity sensing materials.
文摘A six-step synthesis of （-）-clausenamide is described. Optically pure （R,E）-1,3-diphenylallylic alcohol was ac-etylated and then subjected to an Ireland-Claisen rearrangement, giving the γ,δ-unsaturated acid, which underwent a substrate-induced stereoselective bromolactonization to afford the expected all-equatorial substituted bromo-δ-lac-one. An unusual chemo-selective aminolysis of the lactone resulted in the formation of a γ,δ-epoxy-amide in stereospecific manner. Base-promoted cyclization of this intermediate and the subsequent Davis oxidation furnished the synthesis, delivering the final product in 〉99% ee and up to 34% overall yield.
