Hydrogel nanostructures for plasmonic and biosensor applications
Plasmonics is recently emerged nanophotonics research area that focuses at sub-wavelength confinement of light energy by its coupling to surface plasmons - collective oscillations in charge density and associated electromagnetic field at surfaces of metals. Hybrid responsive polymer-metallic nano...
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Online Access: | http://hdl.handle.net/10356/69968 |
| Summary: | Plasmonics is recently emerged nanophotonics research area that focuses at sub-wavelength
confinement of light energy by its coupling to surface plasmons - collective oscillations in
charge density and associated electromagnetic field at surfaces of metals. Hybrid responsive
polymer-metallic nanostructures represent an attractive class of materials with actively
tunable plasmonic properties. Such characteristics may enable new applications of plasmonics
in analytics that utilize direct or optical spectroscopy-based detection of molecular
analytes as well as in development of novel miniaturized plasmonic components. This thesis
describes novel implementations ofthermo-responsive N-isopropylacrylamide (pNIPAAm) based
hydrogel to metallic nanostructures that support surface plasmons. It reports means
of structuring a photo-crosslinkable pNIPAAm layer with features exhibiting size as small as
lOOnm by nano-imprint lithography and laser interference lithography. A new technique
for in situ observation of swelling characteristics of such nanoscopic soft matter objects that
are arranged in a period array was developed based on optical waveguide mode-enhanced
diffraction measurements. pNIPAAm periodic structures highly swell in water (swelling ratio
up to 10) and they can be prepared on around 1 cm2 area on a gold surface. A structure that
acts as a tunable plasmonic crystal was prepared and by its reversible swelling and collapsing
a plasmonic bandgap can be open and closed. In addition, responsive pNIPAAm material was
employed as a "glue" in plasmonic structures. Firstly, it was employed to serve as a responsive
cushion that tethers a thin metallic film with arrays of nanoholes to a solid glass surface. The
swelling and collapsing of the cushion is demonstrated to mediate the extraordinary transmission
and potentially offer a new means of the implementation of nanohole arrays surface
plasmon resonance biosensor with flow-through architecture. Lastly, pNIPMm was used as a
glue in order to form a composite film with high density of nanoparticles that were imprinted
with a low molecular weight organic molecule. The composite film exhibited highly open
architecture through which the target analyte L-Boc-phenylalanine-anilide (L-BFA) can freely
diffuse and become affinity capture. Direct detection of affinity binding at concentrations
around uM was carried by optical waveguide spectroscopy as the composite film can serve at
the same time as large capacity affinity binding matrix and an optical waveguide. |
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