Photothermal Microscopy and
Spectroscopy Webinar

Label-free optical detection schemes commonly rely on specific chemical interactions between receptor and target molecule to facilitate analyte recognition. Here, we present a novel pathway toward fingerprinting proteins via analysis of their motion, i.e., through physical properties such as Stokes radius and polarizability rather than chemical interactions. Single gold nanorods, which are commonly used as labels, can be transformed into high-speed nanoscale sensors by polarization-sensitive bright-field scattering. We perform photothermal spectroscopy on single gold nanorods as a probe of their sensitivity to refractive index changes, and to optimize the signal on a rod-to-rod basis. This way, we achieve detection of single nanoparticles and single protein molecules traversing plasmonic near fields with sub-microsecond time resolution.