Ion-Selective Controlled Assembly of Dendrimer-Based Functional Nanofibers and Their Ionic-Competitive Disassembly
Ion-Selective Controlled Assembly of Dendrimer-Based Functional Nanofibers and Their Ionic-Competitive Disassembly
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DOI：
10.1021/ja206611s
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发表时间：
2012-02-22
影响因子：
15
通讯作者：
Pavan, Giovanni M.
中科院分区：
文献类型：
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作者：
Garzoni, Matteo;Cheval, Nicolas;Pavan, Giovanni M.
通过分子构建块(例如树枝状大分子)的受控自组装来构建分级材料代表了以方便的方式产生功能纳米器件的独特机会。众所周知，过渡金属化合物能够与阳离子树枝状大分子相互作用，生成具有有趣集体性质的各种超分子结构，如纳米纤维。在这项工作中，分子动力学模拟(MD)表明，解离的Cd(CH3COO)(2)中的乙酸根离子通过对树枝状大分子表面的疏水修饰选择性地生成阳离子PPI-树枝状大分子功能纤维。树枝状大分子的疏水聚集是由醋酸酯阴离子(ACO-)的不对称性质引发的，而不是由精确的过渡金属(CD)引发的。组装的方向性还受溶液中ACO-离子浓度的控制。原子力显微镜(AFM)和透射电子显微镜(TEM)证实了这些结果。这种明确的阳离子树枝状大分子的定向组装对于不同的具有对称阴离子的镉衍生物(即，氯化镉、硫酸镉)来说是不存在的。此外，由于这些纳米纤维的形成完全由所选择的阴离子控制，因此可以通过氯化钠盐的简单离子竞争来触发纤维分解。离子是一种简单而经济的工具，可以主动驱动和控制这种基于树枝状大分子的功能纳米材料的组装和拆解。
The construction of hierarchical materials through controlled self-assembly of molecular building blocks (e.g., dendrimers) represents a unique opportunity to generate functional nanodevices in a convenient way. Transition-metal compounds are known to be able to interact with cationic dendrimers to generate diverse supramolecular structures, such as nanofibers, with interesting collective properties. In this work, molecular dynamics simulation (MD) demonstrates that acetate ions from dissociated Cd(CH3COO)(2) selectively generate cationic PPI-dendrimer functional fibers through hydrophobic modification of the dendrimer's surface. The hydrophobic aggregation of dendrimers is triggered by the asymmetric nature of the acetate anions (AcO-) rather than by the precise transition metal (Cd). The assembling directionality is also controlled by the concentration of AcO- ions in solution. Atomic force (AFM) and transmission electron microscopy (TEM) prove these results. This well-defined directional assembly of cationic dendrimers is absent for different cadmium derivatives (i.e., CdCl2, CdSO4) with symmetric anions. Moreover, since the formation of these nanofibers is controlled exclusively by selected anions, fiber disassembly can be consequently triggered via simple ionic competition by NaCl salt. Ions are here reported as a simple and cost-effective tool to drive and control actively the assembly and the disassembly of such functional nanomaterials based on dendrimers.