Abstract
Magneto-optic surface plasmon resonance (MOSPR)-based sensors are highly attractive as next-generation biosensors. However, these sensors suffer from oxidation leading to degradation of performance, reproducibility of the sensor surface, because of the difficulty of removing adsorbed materials, and degradation of the sensor surface during surface cleaning and these limit their applications. In this paper, I propose MOSPR-based biosensors with 0 to 15 nm thick inert polycarbonate laminate plastic as a protective layer and theoretically demonstrate the practicability of my approach in water-medium for three different probing samples: ethanol, propanol, and pentanol. I also investigate microstructure and magnetic properties. The chemical composition and layered information of the sensor are investigated using X-ray reflectivity and X-ray diffraction analyses and these show distinct face-centered-cubic (fcc)-Au (111) phases, as dominated by the higher density of conduction electrons in Au as compared to Co. The magnetic characterization measured with the in-plane magnetic field to the sensor surface for both the as-deposited and annealed multilayers showed isotropic easy axis magnetization parallel to the multilayer interface at a saturating magnetic field of <100 Oersted (Oe). The sensor showed a maximum sensitivity of 5.5 × 104%/RIU (refractive index unit) for water–ethanol media and the highest detection level of 2.5 × 10−6 for water-pentanol media as the protective layer is increased from 0 to 15 nm.
Highlights
Artificially-tailored magneto-optic (MO) Ti/Au/Co/Au structures are interesting materials for investigating magnetic, microstructure, surface plasmon resonance (SPR), and magneto-optics SPR effects arising from the interaction of magnetic field with surface plasmon polariton and correspondingly induced MO properties, and these have huge potential for various applications, for details, see past papers [1,2,3]
New functionality can be achieved from the combined roles of generating surface plasmon oscillations in the artificially tailored MO structures when excited by a TM polarized (p-polarized) optical radiation that is further controlled by external magnetic, H fields [4]
Ti/Au/Co/Au/Pc is one of the most important artificially-tailored MO nanostructured multilayers that has recently seen huge potential in the field of biosensing and imaging [6,7,8,9]
Summary
Artificially-tailored magneto-optic (MO) Ti/Au/Co/Au structures are interesting materials for investigating magnetic (magnetization, magnetic anisotropy, etc.), microstructure (crystal structure, multilayer interface, surface roughness, etc.), surface plasmon resonance (SPR), and magneto-optics SPR effects arising from the interaction of magnetic field with surface plasmon polariton and correspondingly induced MO properties, and these have huge potential for various applications, for details, see past papers [1,2,3]. The choice of Au in this configuration is due to its excellent plasmonic properties arising from the high electron density of about 5.9 × 1022/cm (Au possess an abundance of surface plasmons), its low electrical resistivity, and low chemical reactivity. All these features are essential in reducing attenuation and enhancing plasmon activity. I analyze the MO effect using transfer matrix method similar to what has been described in my prior work [20] Both variations in optical excitation wavelength and probed medium are taken into consideration in the analysis. The proposed sensor configuration is an excellent candidate for developing robust practical biosensors
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