Spherical Gold-Nanoparticle Assemblies with Tunable Interparticle Distances Mediated by Multifunctional RAFT Polymers

Abstract

A strategy for the controlled assembly of gold nanocrystals into dispersed three-dimensional superstructures is presented. A multifunctional RAFT agent was used to prepare multiblock polystyrene (4.4−17.8 kDa) with trithiocarbonate groups as junctions between the individual blocks. Addition of these polymers to two-phase Brust−Schiffrin gold nanoparticles (4.1 nm) resulted in the formation of stable gold-nanoparticle assemblies dispersed in toluene. TEM analysis revealed that the interparticle distances in these superstructures can be tuned over an unprecedented wide range by employing multiblock polymers with an adjusted degree of polymerization and thus tailored trithiocarbonate distances. Cross-linking of the gold nanoparticles in the assemblies by multifunctional trithiocarbonates was proven by AFM showing partly preserved globular shape after deposition on a solid substrate. The reported strategy is expected to prove useful when interparticle distances in nanoparticle assemblies need to be tuned in a liquid phase or on surfaces. I n recent years, colloidal superparticles 1 attracted growing attention due to potential applications ranging from but not limited to sensing, 2 photothermal therapy, 3 and surfaceenhanced Raman spectroscopy. 4 One of the central requirements for the design and understanding of such particle assemblies is the ability to control the spatial arrangement of the individual particles. 5−7 Due to the chemical stability and facile surface modification of gold nanoparticles (AuNPs), their spherical assemblies in particular are regarded as canonical model superstructures and are explored extensively. 5,7−16 Their formation is driven through cross-linking of individual particles mediated by a variety of distinct interactions, such as salt bridges, 5 hydrogen bonding, 8,9,16 π-π-interactions, 11 metal coordination, 13 dipole− dipole-interactions, 14 halogen bonding, 15 and thiol−gold 12 and thioether−gold interactions. 7,10 The cross-linking species can take the form of dendrimers, 5 small molecules, 7,10−15 DNA, 8 polypeptides, 16 and synthetic polymers. 9 Because small molecules as cross-linking agents suffer from their inherent limitations, 17 polymers are attractive candidates for fulfilling the dual function of (1) providing good particle/assembly dispersion through steric stabilization and (2) directing selfassembly. Moreover, because there are tools available to control complex macromolecular architectures (like reversible-deactivation radical polymerization (RDRP) techniques), it can be envisaged to translate the macromolecular design to the structure of nanoparticle assemblies. 18 Of all RDRP techniques, RAFT polymerization 19 is an attractive means of polymer fabrication in the context of gold nanoparticle chemistry, because RAFT polymers inherently contain the thiocarbonylthio moiety, which can be used as an anchoring group for the attachment to gold surfaces. 20 Our lab recently examined in detail a strategy to prepare multiblock (co)polymers with trithiocarbonate (TTC) groups in...

Nanohybrids of Gold Particles

“…[10] He found that controlled structures are formed, when multiblock oligomers were employed in the functionalization. [11] By the degree of oligomerization, the spatial distances in the produced colloidal superparticles [12][13][14] can be fine-tuned.…”

“…In order to quantify this kind of evaluation, the position of the maximum V max,SEC and the full width at half maximum w SEC of the signals are listed for all examined nanohybrid samples in Table 8 11 . This shows that all nanoparticles are well separated from each other and are not interconnected by the multiblock polymers.…”

Biomimetic glycopolymers tethered gold nanoparticles: Preparation, self-assembly and lectin recognition properties

“…Recently, hybrid nanoparticles composed of an inorganic core and an organic polymer shell have received considerable attention as a new class of nanoscale materials [1][2][3][4][5]. The hybrid nanoparticles have held a significant promise in the areas of sensing, catalysis, and biomedical applications [6][7][8][9][10][11][12].…”

Kontrollierte Herstellung von Planet‐Satellit‐Nanostrukturen durch RAFT‐Sternpolymere

“…Verbindung 2 wurde analog zu einer kürzlich beschriebenen Methode [18] synthetisiert, und die Struktur von 2 wurde durch NMR-Spektroskopie bestätigt (Abbildungen S1 und S2). RAFT-Agens 1 [13] wurde verwendet, um PN i PAAM mit linearer Topologie zu erhalten. Sämtliche Polymerproben wurden durch dreifaches Ausfällen gereinigt und mittels Grçßenausschlusschromato- [19] In vorangegangenen Studien konnten wir Korrekturfaktoren für verschiedene Sternpolymere (darunter solche mit vier Armen), die mittels einer gegen lineare Standards geeichten SEC-Anlage analysiert wurden, bestimmen.…”

“…(Abbildung S6 zeigt eine exemplarische TEMAufnahme, Abbildung S7 die Durchmesserhistogramme für beide Partikelsorten, welche keine Überlappung zeigen). TOAB kann leicht durch konkurrierende Liganden verdrängt werden, [13,21] was eine geringe Bindungsstärke von TOAB zu Gold und daraus folgende mangelnde kolloidale Stabilität impliziert. Deshalb wurde 10 Minuten nach Zugabe der BSPartikel lineares PNiPAAM hinzugefügt, um die Außenseiten der Satellit-Partikel, die vom zentralen Planet-Partikel abgewandt sind, zu stabilisieren.…”