Jump to main content
Jump to site search

Issue 11, 2017
Previous Article Next Article

Out-of-plane orientation alignment and reorientation dynamics of gold nanorods in polymer nanocomposite films

Author affiliations

Abstract

In this work, we develop a novel, in situ characterization method to measure the orientation order parameter and investigate the reorientation and reshaping dynamics of polymer grafted gold nanorods (AuNRs) in polymer nanocomposite (PNC) thin films. The long aspect-ratio of AuNRs results in two well-defined plasmon resonance modes, allowing the optical properties of the PNC to be tuned over a wide spectral range. The alignment of the AuNRs in a particular direction can also be used to further tune these optical properties. We utilize variable angle spectroscopic ellipsometry as a unique technique to measure the optical properties of PNC films containing AuNRs at various angles of incidence, and use effective index of refraction analysis of the PNC to relate the birefringence in the film due to changes of the plasmon coupling to the orientation order parameter of AuNRs. Polymer thin films (ca. 70 nm) of either polystyrene (PS) or poly(methyl methacrylate) (PMMA) containing PS grafted AuNRs are probed with ellipsometry, and the resulting extinction coefficient spectra compare favorably with more traditional analytical techniques, electron microscopy (EM) and optical absorbance (vis-NIR) spectroscopy. Furthermore, variable angle spectroscopic ellipsometry measures optical birefringence, which allows us to determine the in- and out-of plane order of the AuNRs, a property that is not easily accessible using other measurement techniques. Additionally, this technique is applied in situ to demonstrate that AuNRs undergo a rapid (ca. 1–5 hours) reorientation before undergoing a slower (ca. 24 hours) rod to sphere shape transition. The reorientation behavior is different depending on the polymer matrix used. In the athermal case (i.e. PS matrix), the AuNRs reorient isotropically, while in PMMA the AuNRs do not become isotropic, which we hypothesize is due to PMMA preferentially wetting the silica substrate, leaving less vertical space for the AuNRs to reorient.

Graphical abstract: Out-of-plane orientation alignment and reorientation dynamics of gold nanorods in polymer nanocomposite films

Back to tab navigation

Supplementary files

Publication details

The article was received on 24 Oct 2016, accepted on 17 Feb 2017 and first published on 17 Feb 2017


Article type: Paper
DOI: 10.1039/C6SM02403C
Soft Matter, 2017,13, 2207-2215

  •   Request permissions

    Out-of-plane orientation alignment and reorientation dynamics of gold nanorods in polymer nanocomposite films

    E. C. Glor, R. C. Ferrier, C. Li, R. J. Composto and Z. Fakhraai, Soft Matter, 2017, 13, 2207
    DOI: 10.1039/C6SM02403C

Search articles by author

Spotlight

Advertisements