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Title: Mechanism of Nanoparticle Actuation by Responsive Polymer Brushes: From Reconfigurable Composite Surfaces to Plasmonic Effects

Abstract

The mechanism of nanoparticle actuation by stimuli-responsive polymer brushes triggered by changes in the solution pH was discovered and investigated in detail in this study. The finding explains the high spectral sensitivity of the composite ultrathin film composed of a poly(2-vinylpyridine) (P2VP) brush that tunes the spacing between two kinds of nanoparticles-gold nanoislands immobilized on a transparent support and gold colloidal particles adsorbed on the brush. The optical response of the film relies on the phenomenon of localized surface plasmon resonances in the noble metal nanoparticles, giving rise to an extinction band in visible spectra, and a plasmon coupling between the particles and the islands that has a strong effect on the band position and intensity. Since the coupling is controlled by the interparticle spacing, the pH-triggered swelling-shrinking transition in the P2VP brush leads to pronounced changes in the transmission spectra of the hybrid film. It was not established in the previous publications how the actuation of gold nanoparticles within a 10-15 nm interparticle distance could result in the 50-60 nm shift in the absorbance maximum in contrast to the model experiments and theoretical estimations of several nanometer shifts. In this work, the extinction band was deconvoluted into four spectrallymore » separated and overlapping contributions that were attributed to different modes of interactions between the particles and the islands. These modes came into existence due to variations in the thickness of the grafted polymeric layer on the profiled surface of the islands. In situ atomic force microscopy measurements allowed us to explore the behavior of the Au particles as the P2VP brush switched between the swollen and collapsed states. In particular, we identified an interesting, previously unanticipated regime when a particle position in a polymer brush was switched between two distinct states: the particle exposed to the surface of the collapsed layer and the particle engulfed by the swollen brush. On average, the characteristic distance between the particles and the islands increased upon the brush swelling. The observed behavior was a result of the anchoring of the particles to polymeric chains that limited the particles vertical motion range. The experimental findings will be used to design highly sensitive optical nanosensors based on a polymer-brush-modulated interparticle plasmon coupling.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) Center for Functional Nanomaterials
Sponsoring Org.:
DOE - OFFICE OF SCIENCE
OSTI Identifier:
1034090
Report Number(s):
BNL-94845-2012-JA
R&D Project: NC-001; KC020401H; TRN: US1200745
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Nanoscale
Additional Journal Information:
Journal Volume: 4; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ATOMIC FORCE MICROSCOPY; DESIGN; FASTENING; GOLD; ISLANDS; PLASMONS; POLYMERS; SENSITIVITY; SPECTRA; SWELLING; THICKNESS; VISIBLE SPECTRA; polymer brushes; plasmonic sensors; functional nanomaterials

Citation Formats

Tokarev, I., Nykypanchuk, D., Roiter, Y., Minko, I., and Minko, S. Mechanism of Nanoparticle Actuation by Responsive Polymer Brushes: From Reconfigurable Composite Surfaces to Plasmonic Effects. United States: N. p., 2011. Web.
Tokarev, I., Nykypanchuk, D., Roiter, Y., Minko, I., & Minko, S. Mechanism of Nanoparticle Actuation by Responsive Polymer Brushes: From Reconfigurable Composite Surfaces to Plasmonic Effects. United States.
Tokarev, I., Nykypanchuk, D., Roiter, Y., Minko, I., and Minko, S. Mon . "Mechanism of Nanoparticle Actuation by Responsive Polymer Brushes: From Reconfigurable Composite Surfaces to Plasmonic Effects". United States.
@article{osti_1034090,
title = {Mechanism of Nanoparticle Actuation by Responsive Polymer Brushes: From Reconfigurable Composite Surfaces to Plasmonic Effects},
author = {Tokarev, I. and Nykypanchuk, D. and Roiter, Y. and Minko, I. and Minko, S.},
abstractNote = {The mechanism of nanoparticle actuation by stimuli-responsive polymer brushes triggered by changes in the solution pH was discovered and investigated in detail in this study. The finding explains the high spectral sensitivity of the composite ultrathin film composed of a poly(2-vinylpyridine) (P2VP) brush that tunes the spacing between two kinds of nanoparticles-gold nanoislands immobilized on a transparent support and gold colloidal particles adsorbed on the brush. The optical response of the film relies on the phenomenon of localized surface plasmon resonances in the noble metal nanoparticles, giving rise to an extinction band in visible spectra, and a plasmon coupling between the particles and the islands that has a strong effect on the band position and intensity. Since the coupling is controlled by the interparticle spacing, the pH-triggered swelling-shrinking transition in the P2VP brush leads to pronounced changes in the transmission spectra of the hybrid film. It was not established in the previous publications how the actuation of gold nanoparticles within a 10-15 nm interparticle distance could result in the 50-60 nm shift in the absorbance maximum in contrast to the model experiments and theoretical estimations of several nanometer shifts. In this work, the extinction band was deconvoluted into four spectrally separated and overlapping contributions that were attributed to different modes of interactions between the particles and the islands. These modes came into existence due to variations in the thickness of the grafted polymeric layer on the profiled surface of the islands. In situ atomic force microscopy measurements allowed us to explore the behavior of the Au particles as the P2VP brush switched between the swollen and collapsed states. In particular, we identified an interesting, previously unanticipated regime when a particle position in a polymer brush was switched between two distinct states: the particle exposed to the surface of the collapsed layer and the particle engulfed by the swollen brush. On average, the characteristic distance between the particles and the islands increased upon the brush swelling. The observed behavior was a result of the anchoring of the particles to polymeric chains that limited the particles vertical motion range. The experimental findings will be used to design highly sensitive optical nanosensors based on a polymer-brush-modulated interparticle plasmon coupling.},
doi = {},
journal = {Nanoscale},
number = 1,
volume = 4,
place = {United States},
year = {2011},
month = {11}
}