Cation‐Induced Unidirectional Self‐Assembly of Amino‐Terminated Poly(propylene imine) Dendrimers

Abstract

Nanofibers are fabricated by the self‐assembly of poly(propylene imine) (PPI) dendrimers in the presence of cadmium cations in aqueous media. The fibers consist of ribbons of PPI dendrimers linked by the cations. Subsequently, micrometer‐long nanofibers are decorated with gold nanoparticles via wet‐chemical reduction.

Hybrid Nanoalloy: Nanofibers Fabricated by Self‐Assembling Dendrimers Mediate In Situ CdSe Quantum Dots and Their Metallization with Discrete Gold Nanoparticles

“…This is a unique method to fabricate functional nanofibers of supra­molecular hybrid nanostructures formed in aqueous solutions since the CdSe nanoparticles are prepared in situ within the PPI matrices at a moderate pH value and room temperature. Our previous study to form stable micrometer‐long Cd II @PPI dendrimer aggregates,17 using 2 nd –5 th generation PPI dendrimers and a molar complexation ratio of ≥5:1 with excess Cd II against the PPI dendrimer ( Scheme , step a), stimulated us to perform further investigations to form functional nanofibers (Scheme , steps b and c). Applying the in situ approach to prepare the CdSe nanoparticles within the supramolecular Cd II @PPI dendrimer aggregates, a well‐defined 1D nanostructure is formed by controlled electrostatic interactions.…”

“… Schematic illustration of dendrimer self‐assembly resulting in the formation of various hybrid structures. a) Unidirectional self‐assembly of 2 nd –5 th th generation PPI dendrimer as a function of pH and the addition of Cd II salt 17. b) Cd II @PPI dendrimer nanofi bers template CdSe particles into hybrid nanofi bers.…”

“…The PPI@CdSe hybrid nanofibers are prepared by mixing aqueous solutions (0.3 × 10 −3 M ) of the 4 th generation PPI dendrimer (PPI‐G4) and a solution (0.3 M ) of cadmium acetate (Cd(AcO) 2 ) in a specific molar ratio to form Cd II @PPI‐G4 nanofibers (Scheme a) 17. A fresh solution of NaSeH (0.05 M ) is injected into a 10 mL solution of the PPI‐G4 complexed with Cd II ions under inert (N 2 or Ar) atmosphere 20.…”

“…The remaining positive charges increase the repulsive inter‐ and intra‐dendrimer interactions (electrostatic repulsion)19, 23 and thus prevent aggregation at high molar ratios of CdSe/PPI‐G4. Moreover, the competing effects of conformational changes due to increased acidity and the coordination of Cd II ions lead to changes in shape‐ and charge asymmetry within the PPI‐G4 molecule to form Cd II @PPI nanofibers (Figure 1b) 17. Ultimately, the Se precursor (NaHSe) reacts with the Cd II cations to form CdSe nanoparticles.…”

Staged self-assembly of PAMAM dendrimers into macroscopic aggregates with a microribbon structure similar to that of amelogenin

“…For instance, in aqueous solution containing cadmium acetate (Cd-(CH 3 COO) 2 ), fourth generation amino-terminated poly(propylene imine) dendrimers can form a functional nanober by the ion-selective controlled assembly method. [30][31][32] Meanwhile, the poly(amidoamine) (PAMAM) dendrimer has been widely used for self-assembly at the nanoscale. [33][34][35] It has been described to form fractal aggregates through electrostatic interactions between a 3.5 generation carboxylate terminated PAMAM dendrimer and a fourth generation amine terminated PAMAM dendrimer in aqueous solutions.…”