Enhanced anisotropy of gold nanorods-polymer composite films for optical applications

Abstract

The strong optical absorption, scattering and local electric field enhancement associated with the longitudinal Surface Plasmon Resonance (SPR) of gold nanorods (AuNRs) have important applications in imaging, sensing, nonlinear optics, thermal therapy and data encoding. The longitudinal SPR mode can be optimally excited only in the NRs that are most aligned with the electric field of a linearly polarized incident light. Thus, in cast polymer based nanorod composite films, where the NRs orientation is random, only a fraction of the embedded NRs is actually usable to the maximal extent for the intended applications. To enhance the degree of alignment of the AuNRs by uniaxial stretching and increase the application efficiency, we have improved the polymer matrix with respect to plastic deformation and designed a suitable drawing device to reduce the fracture risks of the polymer. The resulting nanocomposite film was characterized by Scanning Electron Microscopy (SEM) and by spectroscopy using linearly polarized light in the UV-Visible range. The linear dichroic ratio of the stretched nanocomposite film was calculated based on the ratio of the peak absorbance of the incident light parallelly polarized, to that of the light polarized perpendicularly to the NRs long axes.