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Issue 19, 2014
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Gold nanorod length controls dispersion, local ordering, and optical absorption in polymer nanocomposite films

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Abstract

The dispersion, local orientation and optical absorption of polystyrene (PS, degree of polymerization P) nanocomposites containing PS-grafted gold nanorods (Au NRs, PS degree of polymerization N), with aspect ratios (ν = length/diameter) ranging from 2.5 to 6.3, are studied using quantitative scanning electron microscopy (SEM) and optical spectroscopy. The experimentally observed nanorod assemblies and optical absorptions are compared with predictions from self-consistent field theory (SCFT) and finite difference time domain (FDTD) calculations, respectively. A pair correlation function for Au NRs is calculated from SEM images, and contains no correlation peaks for P/N = 0.9, indicating nanorods are dispersed within the nanocomposite. Large correlation peaks are observed for P/N = 7.6, representative of interparticle separation distances within nanorod aggregates, which do not vary with ν. On the basis of SCFT calculations, aggregation is attributed to significant depletion–attraction forces in the composite for P/N > 1. When Au NRs disperse, the longitudinal surface plasmon resonance (LSPR) peak red shifts from the visible into the near-IR as ν increases. No shift in the dispersed LSPR position is observed for v = 2.5 and 3.3 upon aggregation because the ratio of the interparticle distance to the nanorod length is too large for surface plasmon coupling. However, for v = 6.3, significant coupling between surface plasmons leads to a blue shift of the LSPR by approximately 140 nm, in agreement with FDTD calculations.

Graphical abstract: Gold nanorod length controls dispersion, local ordering, and optical absorption in polymer nanocomposite films

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Publication details

The article was received on 25 Sep 2013, accepted on 07 Mar 2014 and first published on 07 Mar 2014


Article type: Paper
DOI: 10.1039/C3SM52514G
Citation: Soft Matter, 2014,10, 3404-3413

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    Gold nanorod length controls dispersion, local ordering, and optical absorption in polymer nanocomposite films

    D. Wang, M. J. A. Hore, X. Ye, C. Zheng, C. B. Murray and R. J. Composto, Soft Matter, 2014, 10, 3404
    DOI: 10.1039/C3SM52514G

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