2 research outputs found
Self-Assembly of Nanoparticle Amphiphiles with Adaptive Surface Chemistry
We investigate the self-assembly of amphiphilic nanoparticles (NPs) functionalized with mixed monolayers of hydrophobic and hydrophilic ligands in water. Unlike typical amphiphilic particles with âfixedâ surface chemistries, the ligands used here are not bound irreversibly but can rearrange dynamically on the particlesâ surface during their assembly from solution. Depending on the assembly conditions, these adaptive amphiphiles form compact micellar clusters or extended chain-like assemblies in aqueous solution. By controlling the amount of hydrophobic ligands on the particlesâ surface, the average number of nearest neighborsî¸that is, the preferred coordination numberî¸can be varied systematically from âź1 (dimers) to âź2 (linear chains) to âź3 (extended clusters). To explain these experimental findings, we present an assembly mechanism in which hydrophobic ligands organize dynamically to form discrete patches between proximal NPs to minimize contact with their aqueous surroundings. Monte Carlo simulations incorporating these adaptive hydrophobic interactions reproduce the three-dimensional assemblies observed in experiment. These results suggest a general strategy based on reconfigurable âstickyâ patches that may allow for tunable control over particle coordination number within self-assembled structures
Integration of Gold Nanoparticles into Bilayer Structures via Adaptive Surface Chemistry
We
describe the spontaneous incorporation of amphiphilic gold nanoparticles
(Au NPs) into the walls of surfactant vesicles. Au NPs were functionalized
with mixed monolayers of hydrophilic (deprotonated mercaptoundecanoic
acid, MUA) and hydrophobic (octadecanethiol, ODT) ligands, which are
known to redistribute dynamically on the NP surface in response to
changes in the local environment. When Au NPs are mixed with preformed
surfactant vesicles, the hydrophobic ODT ligands on the NP surface
interact favorably with the hydrophobic core of the bilayer structure
and guide the incorporation of NPs into the vesicle walls. Unlike
previous strategies based on small hydrophobic NPs, the present approach
allows for the incorporation of water-soluble particles even when
the size of the particles greatly exceeds the bilayer thickness. The
strategy described here based on inorganic NPs functionalized with
two labile ligands should in principle be applicable to other nanoparticle
materials and bilayer structures