Design of plasmonic grating structures towards optimum signal discrimination for biosensing applications

Abstract

Sensors based on surface plasmon resonances (SPRs) have proven themselves as promising devices for molecular investigations -still there is potential to determine the geometrical parameter set for optimal sensing performance. Here we propose a comprehensive design rule for one-dimensional plasmonic grating structures. We present an analytical approach, which allows for estimation of the grating parameters for best SPR coupling efficiency for any geometry and design wavelength. On the example of sinusoidal gratings, we expand this solution and discuss numerically and experimentally, how the grating modulation depth can be refined to achieve optimal signal resolution. Finally, we propose a benchmark factor to assess the sensor performance, which can be applied to any sensing scheme utilizing resonances, allowing for comparison of different technological platforms.

Transformation optics approach to singular metasurfaces

“…This paper will explore in detail the nature of the plasmonic excitations, their ability to generate large concentrations of optical energy, and the transition from the discrete excitation spectrum of a non-singular surface to the continuous spectrum of a singular metasurface. Sub-wavelength metal gratings couple external light into surface plasmons, efficiently localizing the electromagnetic energy and finding applications in optical bio-sensing and photovoltaics [4][5][6][7][8]. These can be used to control external radiation using metasurfaces [9,10].…”

Designing Plasmonic Gratings with Transformation Optics

“…The same properties are of interest in biosensing applications, where the strong-field confinement and enhancement aid detection of changes in the refractive index of the grating's environment. Several experimental and theoretical studies, which try to optimize the gratings' design to enhance sensing, exist [3][4][5]. Here, we propose a different method to study gratings based on transformation optics.…”

Reversible plasmonic biosensors based on aptamers and hydrogels

“…Split aptamer sequences that specifically bind to adenosine and ATP were adopted from studies reported in the literature. 55,56 In the presence of the target analyte, the segment S2-AF647 forms a complex with tethered S1-Biotin, whereas in the absence of the target analyte the segments do not interact. The S2-AF647 binding events triggered by the presence of the target analyte were monitored by probing of the gold sensor surface with resonantly excited surface plasmons -PSPs.…”

“…SPPs can also be excited through grating coupling of a light beam. Here, a metal surface with corrugations with the appropriate periodicity and depth that allows phase matching is exploited [56]. Since this architecture was not applied in this thesis, it will not be further detailed.…”

“…We report herein the implementation of PEF as a sensitive readout method for reversible split aptamerbased fluorescence biosensing. A split DNA aptamer 55,56 that binds to ATP and adenosine was chosen for a proof of concept demonstration of real-time continuous monitoring of concentration changes without the need of regeneration.…”