Plasmonic metal nanostructures, in
colloidal or surface-supported
forms, have been extensively studied in the context of metamaterials
design and applications, in particular as refractometric sensing platforms.
Recently, high refractive index (high-<i>n</i>) dielectric
subwavelength structures have been experimentally shown to support
strong Mie scattering resonances, predicted to exhibit analogous refractive
index sensing capabilities. Here we present the first experimental
demonstration of the use of supported high-<i>n</i> dielectric
nano/microparticle ensembles as refractive index sensing platforms,
using cuprous oxide as a model high-<i>n</i> material. Single-crystalline
Cu<sub>2</sub>O particles were deposited on transparent substrates
using a chemical deposition scheme, showing well-defined electric
and magnetic dipolar resonances (EDR and MDR, respectively) in the
visible range, which change in intensity and wavelength upon changing
the medium refractive index (<i>n</i><sub>m</sub>). The
significant modulation of the MDR intensity when <i>n</i><sub>m</sub> is modified appears to be the most valuable empirical
sensing parameter. The Mie scattering properties of Cu<sub>2</sub>O particles, particularly the spectral dependence of the MDR on <i>n</i><sub>m</sub>, are theoretically modeled to support the
experimental observations. MDR extinction changes (i.e., refractive
index sensitivity) per particle are >100 times higher compared
to
localized surface plasmon resonance (LSPR) changes in supported Au
nanoislands, encouraging the evaluation of Cu<sub>2</sub>O and other
high-<i>n</i> dielectric particles and sensing modes in
order to improve the sensitivity in optical (bio)sensing applications
