Highly sensitive detection of biomolecules with the magneto-optic surface-plasmon-resonance sensor

Abstract

The characteristics of a novel magneto-optic surface-plasmon-resonance (MOSPR) sensor and its use for the detection of biomolecules are presented. This physical transduction principle is based on the combination of the magneto-optic activity of magnetic materials and a surface-plasmon resonance of metallic layers. Such a combination can produce a sharp enhancement of the magneto-optic effects that strongly depends on the optical properties of the surrounding medium, allowing its use for biosensing applications. Experimental characterizations of the MOSPR sensor have shown an increase in the limit of detection by a factor of 3 in changes of refractive index and in the adsorption of biomolecules compared with standard sensors. Optimization of the metallic layers and the experimental setup could result in an improvement of the limit of detection by as much as 1 order of magnitude.

Au/Fe/Au multilayer transducers for magneto-optic surface plasmon resonance sensing

“…5͑a͔͒. This sensitivity increase, however, is still lower than that achieved by Au/Cr/Co multilayer structures, 13 and far from the expected theoretical maximum sensitivity increase ͑of one order of magnitude͒. This is directly originated by the low values experimentally observed ⌬R pp in the Au/Fe/Au system, ten times lower than those predicted in theoretical calculations ͓see Fig.…”

“…In a previous work, a Au/Cr/Co multilayer was employed as MOSPR transducer. 13 The intermediate Cr layer was required to improve the stability of the transducer, due to the lack of adhesion between the Au and Co layers. Contrary to what would be desirable, this layer increases the optical absorption and reduces the MO effect of the multilayer, thus decreasing the sensitivity of the MP transducer.…”

The effect of shape anisotropy on the spectroscopic characterization of the magneto-optical activity of nanostructures

“…The intrinsic MO activity of gold nanodisks was measured along the symmetry axis. Compared to the transmittance spectra, the MO spectra shows a much narrower line width, namely a higher quality factor which suggests characterizing the MO activity might be a promising method for refractive index sensing using plasmonic nanostructures [18][19][20][21]. …”

Intertwined magneto-optical and plasmonic effects in Ag/Co/Ag layered structures

“…This is due to the sharper plasmon resonance of Ag compared to Au, which comes from more negative real part of the dielectric constant of Ag at the working wavelength ͑633 nm͒. 1 This bigger slope has specially relevance in the MO surfaceplasmon resonance sensing applications, 6 where the slope of the resonance is the relevant parameter that may lead to enhanced sensitivity of the device.…”

“…On the one hand, SPP characteristics are strongly dependent on the optical properties of both metal and dielectric media, which makes them useful for the development of biological sensors. [4][5][6] On the other hand, SPP modes are evanescent waves strongly bounded to the metaldielectric interface with the potential to overcome the light diffraction limit and therefore they become suitable candidates for light guiding at the subwavelength scale [7][8][9] or for super resolution far-field optical microscopy. 10,11 One step further in the progress of plasmonics is associated with the development of active plasmonic devices, that is, the realization of materials combinations or configurations that allow the control of SPP properties by an external agent.…”