title: Cascade synthesis of a gold nanoparticle-network polymer composite.
abstract: The multi-step, cascade synthesis of a self-supporting, hierarchically-structured gold nanoparticle hydrogel composite is described. The composite is spontaneously prepared from a non-covalent, lamellar lyotropic mesophase composed of amphiphiles that support the reactive constituents, a mixture of hydroxyl- and acrylate-end-derivatized PEO117-PPO47-PEO117 and [AuCl4](-). The reaction sequence begins with the auto-reduction of aqueous [AuCl4](-) by PEO117-PPO47-PEO117 which leads to both the production of Au NPs and the free radical initiated polymerization and crosslinking of the acrylate end-derivatized PEO117-PPO47-PEO117 to yield a network polymer. Optical spectroscopy and TEM monitored the reduction of [AuCl4](-), formation of large aggregated Au NPs and oxidative etching into a final state of dispersed, spherical Au NPs. ATR/FT-IR spectroscopy and thermal analysis confirms acrylate crosslinking to yield the polymer network. X-ray scattering (SAXS and WAXS) monitored the evolution of the multi-lamellar structured mesophase and revealed the presence of semi-crystalline PEO confined within the water layers. The hydrogel could be reversibly swollen without loss of the well-entrained Au NPs with full recovery of composite structure. Optical spectroscopy shows a notable red shift (Δλ ∼ 45 nm) in the surface plasmon resonance between swollen and contracted states, demonstrating solvent-mediated modulation of the internal NP packing arrangement.
authors.affiliation: Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Simonida
authors.initials: S
authors.lastname: Grubjesic
authors.affiliation: Los Alamos National Laboratory, Los Alamos, NM 87545, USA. firestone@lanl.gov.
authors.forename: Bryan S
authors.initials: BS
authors.lastname: Ringstrand
authors.affiliation: Sandia National Laboratories, Albuquerque, NM 87185, USA.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Jungjohann
authors.affiliation: Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Brombosz
authors.affiliation: Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Sönke
authors.initials: S
authors.lastname: Seifert
authors.affiliation: Los Alamos National Laboratory, Los Alamos, NM 87545, USA. firestone@lanl.gov.
authors.forename: Millicent A
authors.initials: MA
authors.lastname: Firestone