Wang Hai, Wang Xiaosong, Winnik Mitchell A, Manners Ian
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
J Am Chem Soc. 2008 Oct 1;130(39):12921-30. doi: 10.1021/ja8028558. Epub 2008 Sep 3.
Detailed studies of a new approach to the synthesis and encapsulation of silver and silver halide nanoparticles inside shell-cross-linked cylindrical block copolymer polyisoprene-block-polyferrocenyldimethylsilane (PI-b-PFS) micelles (1) through in situ redox reactions are reported. The cylindrical nanostructures 1 were prepared by the solution self-assembly of the PI-b-PFS diblock copolymer in the PI-selective solvent hexane followed by Pt(0)-catalyzed PI shell-cross-linking hydrosilylation reactions. The partial preoxidation of the swollen PFS core using tris(4-bromophenyl)aminium hexachloroantimonate [p-BrC6H4)3N][SbCl6] (2, Magic Blue) followed by redox reaction between the remaining Fe(II) centers in the PFS core and Ag(+) cations led to the formation of silver nanoparticles. High-resolution scanning transmission electron microscopy images of the resulting peapod structures provided a clear indication that the nanoparticles were encapsulated inside the micelles. The composition of the nanoparticles was analyzed by energy-dispersive X-ray spectroscopy (EDX). By combining the evolution of the UV-vis spectra of the reaction mixture and EDX measurements, we surprisingly found that silver halide seed particles were formed through a precipitation reaction at an early stage of the encapsulation process. The size of the silver nanoparticles varied with different amounts of silver ions added to the micelle solution. When I2 was used as the preoxidant, AgI nanoparticles were formed and encapsulated inside the cylinders through the precipitation reaction between iodide anions and silver ions. The packing density of the resulting AgI nanoparticles was increased by an iterative addition method, which utilizes the reversible redox properties of PFS. The small encapsulated AgI nanoparticles were also shown to serve as seeds for the formation of larger Ag nanoparticles when a silver salt was subsequently added.
报道了通过原位氧化还原反应在壳交联圆柱形嵌段共聚物聚异戊二烯-嵌段-聚二茂铁二甲基硅烷（PI-b-PFS）胶束（1）内合成和封装银及卤化银纳米颗粒的新方法的详细研究。圆柱形纳米结构1是通过PI-b-PFS二嵌段共聚物在PI选择性溶剂己烷中的溶液自组装，然后进行Pt(0)催化的PI壳交联硅氢化反应制备的。使用三（4-溴苯基）铵六氯锑酸盐[（对溴苯基）3N][SbCl6]（2，魔蓝）对溶胀的PFS核进行部分预氧化，随后PFS核中剩余的Fe(II)中心与Ag(+)阳离子之间发生氧化还原反应，导致形成银纳米颗粒。所得豆荚状结构的高分辨率扫描透射电子显微镜图像清楚地表明纳米颗粒被封装在胶束内部。通过能量色散X射线光谱（EDX）分析纳米颗粒的组成。通过结合反应混合物的紫外-可见光谱的演变和EDX测量，我们惊讶地发现卤化银种子颗粒是在封装过程的早期通过沉淀反应形成的。银纳米颗粒的尺寸随添加到胶束溶液中的银离子量的不同而变化。当使用I2作为预氧化剂时，通过碘离子和银离子之间的沉淀反应形成AgI纳米颗粒并封装在圆柱体内。通过利用PFS的可逆氧化还原性质的迭代添加方法提高了所得AgI纳米颗粒的堆积密度。当随后添加银盐时，还显示出小的封装AgI纳米颗粒可作为形成更大银纳米颗粒的种子。
