The ordering alignment of gold nanorods in liquid crystals and its applications to polarization-sensitive SERS

Abstract

Gold nanorods (GNRs) were synthesized, coated with poly(ethylene glycol) (PEG) chains, and uniformly dispersed into the lyotropic nematic liquid crystal (LC) matrix by our proposed method. The GNRs-LC composites were found to exhibit good stability over days and have high density of GNRs. The extinction spectra of the composites were found to be polarization sensitive when the shearing force were applied, due to the alignment of GNRs driven by the LC molecules, which was also in accordance to the simulation results. A type of Raman reporter, 3,3'-diethylthiatricarbocyanine iodide (DTTC), was co-conjugated onto the GNRs with PEG molecules, and then incorporated into the LC matrix. Thus, its Raman signals could be enhanced by the localized surface plasmon resonance (LSPR) of the GNRs. These surface-enhanced Raman scattering (SERS) signals were found to be polarization sensitive when the shearing force was applied, due to the polarization sensitive enhancement of the local field of GNRs. The nanocomposites with tunable SPR peaks and SERS signals have potential applications in optoelectronic devices.