Optical and electrochemical properties of multilayer polyelectrolyte thin films incorporating spherical, gold colloid nanomaterials |
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Authors: | Tran T Doan Robert W Day Michael C Leopold |
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Affiliation: | (1) Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, VA 23173, USA; |
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Abstract: | Polyelectrolyte multilayer (PEM) films incorporating various types of spherical, gold nanomaterials (NMs) were investigated
to assess the existence of electrochemical and/or optical signal enhancement effects directly attributable to embedded NMs
and the relationship of these effects to film structure and composition. Specifically, electrostatically assembled films of
cationic poly-l-lysine (PLL) and anionic poly(4-styrene sulfonate) (PSS) incorporating one of four types of spherical, gold colloid NMs were
constructed on 3-(aminopropyl)trimethoxysilane (3-APTMS)-modified glass substrates for optical studies or 11-mercaptoundecanoic
(MUA)-modified gold electrodes for electrochemical studies. The NMs inserted into the PEM films include citrate-stabilized
gold nanoparticles, thioctic acid-stabilized gold nanoparticles (TAS-NPs), MUA-modified monolayer protected gold clusters,
and hollow gold nanoshells (Au-NSs). Optical sensitivity of the NM-embedded films, in terms of absorbance, surface plasmon
band shifts, and the dependence of these optical responses on film thickness, varied depending on the type of NM within the
film (e.g., TAS-NPs versus Au-NSs) but exhibited no corresponding electrochemical effects in the diffusional voltammetry of
a ferricyanide redox probe. While not correlated to optical responses, the increased Faradaic current achieved during voltammetry
at NM-embedded PEM films suggested that electrochemical effects of NMs were less dependent on the type of NMs and were, instead,
more related to their location within the film and the electrostatic interactions built into the interfacial chemistry of
the films. These results should prove useful for developing strategies constructing thin films with NMs that are specifically
designed for optical or electrochemical sensing, taking full advantage of the signal enhancements provided by individual types
of NMs. |
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