Abstract
In this work we present a surface plasmon resonance sensor based on enhanced optical transmission through sub-wavelength nanohole arrays. This technique is extremely sensitive to changes in the refractive index of the surrounding medium which result in a modulation of the transmitted light. The periodic gold nanohole array sensors were fabricated by high-throughput thermal nanoimprint lithography. Square periodic arrays with sub-wavelength hole diameters were obtained and characterized. Using solutions with known refractive index, the array sensitivities were obtained. Finally, protein absorption was monitored in real-time demonstrating the label-free biosensing capabilities of the fabricated devices.
Highlights
Surface plasmon resonance (SPR) sensors are a common tool for real-time label-free biochemical interaction monitoring due to their ease of use and good performance
The refractive index of aqueous sucrose solutions with concentrations ranging from 0 up-to 40% were measured with a refractometer (DM40, Mettler Toledo, Columbus, OH, USA) and the light transmission spectra through the nanohole arrays in contact with these media recorded
From the slope of this plot, a 126 nm per refractive index unit sensitivity was obtained, which is very close to the sensitivities of arrays with similar characteristics reported in the literature but fabricated with costlier techniques such as focused ion beam (FIB) or electron beam lithography (EBL)
Summary
Surface plasmon resonance (SPR) sensors are a common tool for real-time label-free biochemical interaction monitoring due to their ease of use and good performance. The use of enhanced transmission through metallic sub-wavelength nanohole arrays [2,3,4] to couple the incoming light to surface polaritons has proven to be a very good alternative because it makes use of a simple linear setup and boasts higher spatial resolution [5] Both these characteristics allow for the miniaturization and micro-integration of the sensing device. Ordered nanohole arrays are typically fabricated using focused ion beam (FIB), e.g., [3,6,7,8], or electron beam lithography (EBL) [9] Even though these techniques have very high resolution, the manufacture of arrays requires long processing times and, they are not suitable for mass-production due to their low throughput and the associated high cost. Absorption of bovine serum albumina (BSA) protein onto the gold surface was monitored in real-time without the necessity of labels to demonstrate the biosensing capability of the fabricated device
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