1 research outputs found
Optoplasmonic Effects in Highly Curved Surfaces for Catalysis, Photothermal Heating, and SERS
Surface curvature can be used to focus light and alter
optical
processes. Here, we show that curved surfaces (spheres, cylinders,
and cones) with a radius of around 5 Ī¼m lead to maximal optoplasmonic
properties including surface-enhanced Raman scattering (SERS), photocatalysis,
and photothermal processes. Glass microspheres, microfibers, pulled
fibers, and control flat substrates were functionalized with well-dispersed
and dense arrays of 45 nm Au NP using polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) and chemically
modified with 4-mercaptobenzoic acid (4-MBA, SERS reporter), 4-nitrobenzenethiol
(4-NBT, reactive to plasmonic catalysis), or 4-fluorophenyl isocyanide
(FPIC, photothermal reporter). The various curved substrates enhanced
the plasmonic properties by focusing the light in a photonic nanojet
and providing a directional antenna to increase the collection efficacy
of SERS photons. The optoplasmonic effects led to an increase of up
to 1 order of magnitude of the SERS response, up to 5 times the photocatalytic
conversion of 4-NBT to 4,4ā²-dimercaptoazobenzene when the diameter
of the curved surfaces was about 5 Ī¼m and a small increase in
photothermal effects. Taken together, the results provide evidence
that curvature enhances plasmonic properties and that its effect is
maximal for spherical objects around a few micrometers in diameter,
in agreement with a theoretical framework based on geometrical optics.
These enhanced plasmonic effects and the stationary-phase-like plasmonic
substrates pave the way to the next generation of sensors, plasmonic
photocatalysts, and photothermal devices