Hierarchical Assemblies of Dendrimers Embedded in Networks of Lanthanide-Based Supramolecular Polyelectrolytes

Abstract

Supramolecular assemblies of dendrimers, with defined structures and tunable functionalities, are promising functional materials. Here we report a ternary system (lanthanide ion/bis-ligand/PAMAM dendrimer) capable of assembling in a cooperative way by forming a complex between anionic (metal–ligand) coordination polymers and the cationic PAMAM dendrimers. In off-stoichiometric mixtures, charge-stabilized spherical nanoparticles of ∼100 nm appear; they have either negative or positive surface charges depending on what the excess component is. Introducing different trivalent lanthanide ions, Ln­(III), in the coordination allows tuning both the luminescence emission spectrum and the magnetic relaxivity without affecting the assembly process or the final structure of the particles; this makes them interesting in the context of application. Moreover, the incorporated dendrimer allows us to add functional nanocargo, for example, Au nanoparticles in the cavities of these molecules, again without disturbing the assembly. In this novel way, we obtain versatile, multilevel hierarchical supramolecular dendrimer-containing assemblies with good control over their structures and functionalities. This is very difficult to achieve with conventional covalent compounds but becomes possible because of the supramolecular nature of the coordination polymers and the strong cooperative assembly.

Dendrimer‐Based Polyion Complex Vesicles: Loops Make Loose

“…The PAMAM dendrimers contain both primary amine groups (pKa ≈ 10.5) at their surface and internal tertiary amines (pKa ≈ 6.5). [29,30] We conducted our experiments at pH = 6.5 (20 mM MES buffer) where the surface amine groups are supposed to be protonated completely. The internal tertiary amines may be partially protonated, but the exact protonation degree is difficult to determine.…”

“…Previous studies have concluded that the compact molecular structure of dendrimers tends to create kinetically trapped PIC vesicles. [30,34,35] In other words, the dendrimer-based vesicles should be salt persistent. We checked this by adding salt to PAMAM/PSS-PEO-PSS vesicle dispersions.…”

Dendrimer‐Based Gold Nanostructures for SERS Detection of Pesticides in Water

“…Previous reports have shown that PAMAM dendrimers might act as colloidal stabilizers and reducing agents in the synthesis of Au nanoparticles , . The enhanced colloidal stabilization has been associated with steric hindrance and electrostatic repulsion due to the coordination sphere network formed around the nanoparticles' surfaces , , .…”

“…Moreover, by the selective change of the surface chemistry of PAMAM dendrimers, the colloidal stability of nanoparticles under variable chemical conditions can be improved. The characteristic surface chemistry along with well‐defined size of PAMAM dendrimers can also be further explored for the blending of more complex systems, which can deliver multifunctionality to the final material …”

Response of metal-coordination-based polyelectrolyte complex micelles to added ligands and metals

“…22 Upon mixing with the cationic blocks, the local concentration of M-LEO in the assemblies increases hundreds of times, which dramatically shifts the equilibria of the coordination structures towards coordination polymers. 23,24 In this study, the Zn/LEO ratio is kept at 1/1, at which Zn-LEO can form linear coordination polymers, such that each coordination site carries a net charge of À2. For lanthanides (Ln), we fix the Ln/LEO ratio at 1/1.5, thereby producing 3D network structures such that each coordination unit carries 3 negative charges 26 (Scheme 1).…”