Ion-Selective Controlled Assembly of Dendrimer-Based Functional Nanofibers and Their Ionic-Competitive Disassembly

Abstract

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(CH(3)COO)(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., CdCl(2), CdSO(4)) 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.

In situ functionalization of self-assembled dendrimer nanofibers with cadmium sulfide quantum dots through simple ionic-substitution

“…In turn, this controls the directional selfassembly of the dendrimers into supramolecular fibers. 28 The obtained 1D assemblies are of particular technological interest. In fact, since these formations are created by ions, they can also be easily disassembled by the addition of NaCl salt in solution due to ionic competition.…”

Nano Molecular‐Platform: A Protocol to Write Energy Transmission Program Inside a Molecule for Bio‐Inspired Supramolecular Engineering

“…[7][8][9][10] Screening a dendrimer from its environment is considered a critical issue. [11][12][13][14] In addition to rotor dynamics, screening is associated with the synchronized energy transport between rotors (MR) and doped controller. Synchronization ensures a noise-free energy transport between two energy levels, however, it is an unfamiliar potential of a dendritic box, [ 15 ] which enables us to look beyond the unitary objective of dendrimer as drug delivery agent.…”

Filamentous supramolecular structures with polyelectrolyte and cadmium sulfide

“…This, however, is not possible in the system investigated herein: due to the size and the strong branching of a ninth generation dendrimer, the G9 is not as flexible and therefore, unlike smaller generation dendrimers, retains its spherical shape 24,25 where it is impossible to locate all primary amino groups on the poles of the dendrimer. An interpretation given by Garzoni et al 13 is based on the counterion acetate from Cd(CH 3 COO) 2 , introducing anisotropy to the generation 4 PPI dendrimer due to hydrophobicity and thus causing fiber formation. As in the present study nitrate was used as counterion, having no hydrophobic properties, this cannot be the case here either.…”

“…11 In terms of self-assembly, recently the possibility of dendrimeric macromolecules to assemble into fibrous structures under certain reaction conditions has been shown. The process of fiber-formation with poly(propylene imine) (PPI) dendrimer of the fourth generation (G4) and cadmium acetate was discussed by Fahmi et al and Garzoni et al 12,13 On the one hand, a mechanism was proposed which is based on the flexibility of the G4 dendrimer becoming interconnected by Cd 2+ , yielding fibers that can subsequently be turned into chains of CdSe nanoparticles connected by dendrimer macromolecules. 12 On the other hand, Garzoni suggests that the reason for fiber formation lies in the hydrophobic effect of the acetate counterion, which induces anisotropy within the dendrimer.…”

“…12 On the other hand, Garzoni suggests that the reason for fiber formation lies in the hydrophobic effect of the acetate counterion, which induces anisotropy within the dendrimer. 13 In the present study a system of a poly(amido amine) (PAMAM) dendrimer of the ninth generation (G9) in combination with cadmium nitrate and sodium sulfide was investigated, yielding fibrous structures. Subsequently, the fibers were further interconnected by ionic dye molecules leading to a novel type of ternary nanoparticle-dendrimer-dye supramolecular structure.…”