Abstract
The use of thermoresponsive poly(N-isopropylacrylamide)-based hydrogel (pNIPAAm) for rapid tuning of surface plasmon resonance (SPR) is reported. This approach is implemented by using an SPR layer architecture with an embedded indium tin oxide microheater and pNIPAAm film on its top. It takes advantage of rapid thermally induced swelling and collapse of pNIPAAm that is accompanied by large refractive index changes and leads to high thermo-optical coefficient of dn/dT = 2 × 10–2 RIU/K. We show that this material is excellently suited for efficient control of refractive index-sensitive SPR and that it can serve simultaneously as a 3D binding matrix in biosensor applications (if modified with biomolecular recognition elements for a specific capture of target analyte). We demonstrate that this approach enables modulating of the output signal in surface plasmon-enhanced fluorescence spectroscopy biosensors and holds potential for simple time-multiplexing of sensing channels for parallelized readout of fluorescence assays.
Highlights
Plasmonics represents a rapidly developing research and technology area that exploits the tight confinement of electromagnetic field associated with its coupling to surface plasmons−optical waves originating from collective oscillations of the electron plasma on surfaces of metallic nanostructures and thin films.[1]
It takes advantage of rapid thermally induced swelling and collapse of pNIPAAm that is accompanied by large refractive index changes and leads to high thermo-optical coefficient of dn/dT = 2 × 10−2 refractive index units (RIUs)/K. We show that this material is excellently suited for efficient control of refractive index-sensitive surface plasmon resonance (SPR) and that it can serve simultaneously as a 3D binding matrix in biosensor applications. We demonstrate that this approach enables modulating of the output signal in surface plasmon-enhanced fluorescence spectroscopy biosensors and holds potential for simple time-multiplexing of sensing channels for parallelized readout of fluorescence assays
An unmodified pNIPAAm hydrogel film with the thickness in a dry state of dh‐dry = 135 nm was attached to the sensor surface, swollen in water, and probed by resonantly excited long-range surface plasmons (LRSPs) and hydrogel optical waveguide (HOW) modes
Summary
Plasmonics represents a rapidly developing research and technology area that exploits the tight confinement of electromagnetic field associated with its coupling to surface plasmons−optical waves originating from collective oscillations of the electron plasma on surfaces of metallic nanostructures and thin films.[1]. The interfacing of metallic structures with dielectric materials for electro-optical,[2] thermo-optical,[3] magneto-optical,[4] photoinduced,[5] and electrochemical6 -based modulating of refractive index was pursued for rapid tuning of surface plasmon resonance (SPR). These approaches typically allow for only weak refractive index changes (
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