Characterization of Au/Fe/Au and Au/Co/Au Magneto-Plasmonic Multilayers as an Ethanol Vapor Sensor

Abstract

In this paper, we investigate the sensing performance of Au/Fe/Au and Au/Co/Au magneto-plasmonic nanostructures as transducers as well as the performance of TiO2 thin film and TiO2 NPs as sensing layers. A comparison between sensing performance of the traditional surface plasmon resonance (SPR) and the magneto-optic (MO) SPR (MOSPR) transducing techniques is presented here. The surface plasmon wave vector in these transducers which are consisted of metallic and magnetic materials is modulated by external magnetic field in the transverse configuration. Magneto-plasmonic structures show a great enhancement of an MO Kerr effect when the SPR condition is satisfied. As such enhancement strongly depends on the excitation conditions of the surface plasmon polariton (SPP) and, therefore, on the refractive index of the dielectric in contact with the metal layer, we use this enhanced MO signal as the sensing magnitude for investigating molecular interactions between ethanol vapor and TiO2 nanostructures onto the transducers. Besides, when the SPP is excited, applied magnetic field would modulate the SPP wave vector. The modulated nature of MOSPR signal would lead to a higher sensing performance in terms of sensitivity and signal-to-noise ratio with respect to the traditional SPR signal. Moreover, our results show that using TiO2 NPs in the vicinity of multilayer transducers creates a better sensing performance which is caused by porosity and enhancement in the surface area of absorbent layer.