ja206611s_si_001.pdf (10.6 MB)
Ion-Selective Controlled Assembly of Dendrimer-Based Functional Nanofibers and Their Ionic-Competitive Disassembly
journal contribution
posted on 2012-02-22, 00:00 authored by Matteo Garzoni, Nicolas Cheval, Amir Fahmi, Andrea Danani, Giovanni M. PavanThe 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.