Surface plasmon resonance of two-segmented Au–Cu nanorods

Abstract

Two-segmented gold–copper nanorods were electrodeposited inside thepores of polycarbonate track-etched membranes from two separatesolutions. The PCT membranes were dissolved in dichloromethane(CH2Cl2) and the solvent was replaced by methanol solution. Optical absorption spectra oftwo-segmented Au–Cu nanorods dispersed in methanol showed two peaks which wererelated to the transverse mode of copper and the longitudinal mode of gold. By increasingthe length of the gold segment, when the total length of both metals was fixed at1 µm, the copper and gold peaks shifted to the blue and red wavelengths, respectively. Weobserved that the wavelengths of the extinction peaks are not in good agreement with theexpected value obtained from calculations using the nominal dielectric constantof the medium. Therefore, we suggest the effective medium dielectric constant(εmeff) for Cu and Au segments by comparing the experimental data and calculation results. The values ofεmeff decrease by increasing the gold length.