The exposed crystal facet of TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent ga...The exposed crystal facet of TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties. In this paper, TiO2 nanoplates with defective{001}facets were synthesized by chemical etching via one-step hydrothermal method. We carefully explored the gas-sensing performance of TiO2 nanoplates with defective and complete{001}facets towards acetone. The results show that the sensing response of TiO2 nanoplates with complete{001}facets is 70%higher than that of defective TiO2 nanoplates, which proves that the{001}facets plays a vital role in improving the gas sensing performance of TiO2. It is speculated that the poor gas sensitivity of defective TiO2 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 TiO2 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 TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties. In this paper, TiO2 nanoplates with defective{001}facets were synthesized by chemical etching via one-step hydrothermal method. We carefully explored the gas-sensing performance of TiO2 nanoplates with defective and complete{001}facets towards acetone. The results show that the sensing response of TiO2 nanoplates with complete{001}facets is 70%higher than that of defective TiO2 nanoplates, which proves that the{001}facets plays a vital role in improving the gas sensing performance of TiO2. It is speculated that the poor gas sensitivity of defective TiO2 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 TiO2 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.
