微乳液法制备竹节状纳米管的机理研究

Bamboo-like CdSe nanotubes preparation by inverse microemulsion method and the characterization

通过反相微乳液法制备不同形貌的CdSe纳米晶。利用X-射线衍射(XRD)和透射电子显微镜(TEM)技术对纳米晶的结构和形貌进行表征。结果表明,纳米晶主要由CdSe和Na2SO4组成,根据Sherrer公式计算得到CdSe(100)方向的晶粒尺寸D100=35nm;不同制备条件下,纳米晶的形貌有短链状CdSe纳米晶、项链状和竹节状CdSe纳米管。其形成机理是:由于界面膜处束缚水含量小于水核内部自由水含量,造成CdSe纳米球外层密度小于中心密度,浓度差驱使Se2-与Cd2+向外层扩散形成CdSe空心纳米球;最终在取向附生生长机制下,CdSe空心纳米球生长为项链状和竹节状纳米管。

CdSe nanocrystals wth different morphologies were prepared by using inverse microemulsion method and sodium sulfite, selenium powder and chromium nitrate as the raw material. X-ray diffraction （XRD） and transmission electron microscopy （TEM） techniques are used to characterize the structure and morphology of the nanocrystals. The results show that nanocrystals are mainly composed of CdSe （100） ,CdSe（ll0）, CclSe （112）, Na2 SO4 （111）, Na2 SO4 （113）, Na2 SO4 （220）, Na2 SO4 （153）, Na2 ~~）4 （260）. The grain size of CdSe （100） direction is calculated according to the Sherrer formula to be D^00 ： 35 nm. Short chains-like,necklaces-like and bamboo-like CdSe nanocrystals were prepared under differ- ent conditions. The mechanism is as follows：The content of water in interface membrane bound is less than that of internal free water, which causes the outer density less than the central density of CdSe nanospheres,and the Se2- and Cd2＋ are drived to the outer layer to form CdSe hollow nanospheres by concentration difference. Due to kiekendall effect, a lot of holes are formed in the CdSe nanospheres, cen- ter,and holes are fused into larger voids to form CdSe hollow nanospheres. Because of the small size effect,the CdSe hollow nanospheres become necklace-like nanotubes and ultimately bamboo-like nano- tubes by oriented attachment mechanism and the surface quality diffusion motion.