Correlative microscopy of single self-assembled nanorod dimers for refractometric sensing.

Single metallic particles and dimers of nanospheres have been used extensively for sensing, but dimers of particles provide attractive advantages because they exhibit multiple modes that can be tuned by the dimer geometry. Here, we employ correlative microscopy of single self-assembled dimers of gold nanorods to study their performance as refractometric sensors. The correlation between atomic force microscopy and single-particle white-light spectroscopy allows us to relate the measured sensitivity to numerical simulations taking into account the exact geometry of the construct.

Spatially Resolved Sensitivity of Single-Particle Plasmon Sensors.

The high sensitivity of localized surface plasmon resonance sensors to the local refractive index allows for the detection of single-molecule binding events. Though binding events of single objects can be detected by their induced plasmon shift, the broad distribution of observed shifts remains poorly understood. Here, we perform a single-particle study wherein single nanospheres bind to a gold nanorod, and relate the observed plasmon shift to the binding location using correlative microscopy.

All-Optical Imaging of Gold Nanoparticle Geometry Using Super-Resolution Microscopy.

We demonstrate the all-optical reconstruction of gold nanoparticle geometry using super-resolution microscopy. We employ DNA-PAINT to get exquisite control over the (un)binding kinetics by the number of complementary bases and salt concentration, leading to localization accuracies of ∼5 nm. We employ a dye with an emission spectrum strongly blue-shifted from the plasmon resonance to minimize mislocalization due to plasmon-fluorophore coupling.

Stochastic protein interactions monitored by hundreds of single-molecule plasmonic biosensors.

We present a plasmonic biosensor based on hundreds of individual gold nanorods with single-molecule sensitivity that are simultaneously monitored in real-time within a dark-field microscopy setup. The approach allows for the statistical analysis of single-molecule interactions without requiring any labeling of the analyte. We study an antibody-antigen interaction and find that the waiting-time distribution is concentration-dependent and obeys Poisson statistics.