Single Out-of-Resonance Dielectric Nanoparticles as Molecular Sensors.

Light scattering from single nanoparticles and nanostructures is a commonly used readout method for nanosensors. Increasing the spectral sensitivity of resonant nanosensors to changes in their local surrounding has been the focus of many studies. Switching from spectral to intensity monitoring allows one to investigate nonresonant or out-of-resonance dielectric nanoparticles. Here, we systematically compared such dielectric silica nanoparticles with plasmonic gold nanorods by deriving analytical expressions and by performing experiments. The experiments show a similar sensitivity for the detection of an adsorbate layer for both particle types, which is in good agreement with theory. The flat spectral response of dielectric silica nanoparticles simplifies the choice of illumination wavelength. Furthermore, such dielectric nanoparticles can be made from many oxides, polymers, and even biological assemblies, broadening the choice of materials for the nanosensor.