| Abstract
| - Citrate-capped gold nanoparticles as well as planar gold surfaces can be efficiently grafted witha covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surfacewith dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shownby UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies. The hydrophilicpolymer-coated gold colloids can be freeze-dried and stored as powders that can be subsequently dissolvedto yield stable aqueous dispersions, even at very large concentrations. They allow for applying filtrations,gel permeation chromatography, or centrifugation. They do not suffer from undesirable nonspecific adsorptionof proteins while allowing the diffusion of small species within the hydrogel surface coating. In addition,specific properties of the original hydrophilic polymers are retained such as a lower critical solutiontemperature. The latter feature could be useful to enhance optical responses of functionalized gold surfacestoward interaction with various substrates.
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