Molecular dynamics （MD） simulations were performed to stretch the rectangular graphene sheets doped with silicon, nitrogen or boron atoms. Young＇s modulus, ultimate stress （strain） and energy absorption were measured for the graphene sheets with the doping concentration （DC） ranging from 0 to 5%. The emphasis was placed on the distinct effects of each individual dopant on the fundamental mechanical properties of graphene. The results indicated that incorpo- rating the dopants into graphene led to an almost linear decrease in Young＇s modulus. Monotonic reductions in ultimate strength, ultimate strain and energy absorption were also observed. Such doping effects were found to be most significant for silicon, less pronounced for boron, and small or negligible for nitrogen. The outputs provide an important guidance for the development and optimization of novel nanoscale devices, and facilitate the development of graphene-based M/NEMS.
Difluoromethylation of 2-hydroxychalcones using sodium 2-chloro-2,2-difluoroacetate as the difluoro- methylating agent was developed. Under facile conditions, a wide range of aryl difluoromethyl ethers were obtained in yields of 36%--80%. It is noteworthy that the new addition products, 2,2-difluoro-2H-benzofuran derivatives, were also synthesized in the reactions. The yield of 2,2-difluoro-2H-benzofuran derivative could be up to 35% when 3-methyl-2-hydroxychalcone was used as the reactant. A plausible reaction mechanism was proposed.
WANG WeiHUA MingqingHUANG YanZHANG QiZHANG XiaoyanWU JingboZHANG Qi
