Infrared dichroism of gold nanorods controlled using a magnetically addressable mesophase

TL;DR

This study demonstrates how gold nanorods embedded in a lamellar mesophase can be magnetically aligned to produce tunable infrared dichroism, enabling the creation of soft, addressable optical elements with anisotropic properties.

Contribution

It introduces a method to control the optical anisotropy of gold nanorods in a mesophase using magnetic fields, resulting in tunable infrared dichroism.

Findings

Magnetic field aligns nanorods within the mesophase.

Significant infrared absorption dichroism observed at the plasmon peak.

The system enables soft, addressable optical elements.

Abstract

Gold nanorods have unique optical properties, which make them promising candidates for building nano-structured materials using a "bottom-up" strategy. We formulate stable bulk materials with anisotropic optical properties by inserting gold and iron oxide nanorods within a lamellar mesophase. Quantitative measurements of the order parameter by modelling the absorbance spectra show that the medium is macroscopically aligned in a direction defined by an external magnetic field. Under field, the system exhibits significant absorption dichroism in the infrared range, at the position of the longitudinal plasmon peak of the gold nanorods (about 1200 nm), indicating strong confinement of these particles within the water layers of the lamellar phase. This approach can yield soft and addressable optical elements.