核壳复合材料.pdf

第二部分 核－壳复合材料 核 壳 核 壳 核 壳 通过核－壳复合手段，一方面可以使原本 不稳定或不太稳定的核稳定化 ，另一方面还可 以获得核和壳材料本身不具备的功能和特性， 或者可以获得新的物质存在形态 。 2.1 半导体纳米粒子核－壳结构 CdSe核-ZnS壳以及包覆的三辛基氧化膦的结构示意图 QD = Quantum Dot （量子点） CdSe-ZnS 核－壳复合纳米材料制备 Step 1: Pyrolysis of the organometallic precursors, dimethylcadmium and trioctylphosphine selenide, in a coordinating solvent, trioctylphosphine oxide (TOPO), at temperatures ranging from 340 to 360 °C, leads to formation of small dots which grow at temperatures between 290 and 300 °C. →CdSe dots. Step 2: TOPO was heated to 190 °C under vacuum for several hours and then cooled to 60 °C after which trioctylphosphine (TOP) was added. CdSe dots dispersed in hexane was transferred into the reaction vessel, and the solvent was pumped off. → CdSe dots in TOPO and TOP. Step 3: Diethylzinc (ZnEt ) and hexamethyldisilathiane ((TMS) S) are 2 2 dissolved in TOP. CdSe dots dispersed in TOPO and TOP are heated, and the Zn and S precursors are added dropwise. The overcoated particles are stored in their growth solution to ensure that the surface of the dots remained passivated with TOPO. →CdSe@ZnS. Transmission electron micrographs of (A) one “bare” CdSe nanocrystallite and (B) one CdSe nanocrystallite with a 2.6 monolayer ZnS shell. B. O. Dabbousi et. al., J. Phys. Chem. B, 1997, 101,9463. (Top) Emission spectra of several sizes of CdSe-ZnS quantum dots, with excitation at 350 nm in all cases. (Bottom) Idealized mixed-surface QD- protein conjugate. Antibodies labeled with biotin(生物素) bind efficiently to QD surfaces due to the great strength of their interaction with bridging avidin(抗生物 素蛋白)molecules A fluorescence resonance energy transfer-derived s