Single-molecule biosensing
We develop next-generation biosensing principles based on plasmonic nanoparticles and photonic crystals, and bound-states in the continuum (BIC). We work on label-free (direct) assays that convert molecular binding to a resonance shift that is caused by local changes in refractive index. Secondly, we develop sandwich and competition assays based on plasmon-enhanced fluorescence. Plasmon-enhanced single-molecule fluorescence enables single-molecule detection at high concentrations and on short timescales. We develop these principles toward highly sensitive, specific, and continuous biosensors for monitoring in the environment, industrial processes, and healthcare.
Plasmon-molecule coupling
We investigate the coupling between single molecules and plasmons under optical excitation. This coupling modifies the properties of the molecule (e.g. enhancement of fluorescence) but also the properties of the plasmon (e.g. wavelength shifts and broadening). We use these mechanisms to enhance single-molecule signals and achieve biosensors with a high sensitivity, specificity, and signal-to-noise ratio. These studies include both numerical simulations (e.g. BEM or FDTD) and single-molecule experiments. Detailed understanding of signal-generation mechanisms enables us to achieve single-molecule detection at very high (micromolar) concentrations and on very short (microsecond) timescales.
Super-resolution microscopy
We use super-resolution microscopy for the visualization of nanoscale materials and particle-based biosensors. We develop protocols to synthesize and functionalize both polymeric and nanophotonic materials with biomolecules. After synthesis and/or functionalization we quantify the result using super-resolution microscopy (e.g. DNA-PAINT or STED). This enables the visualization of the number and distribution of functional groups at the single-molecule level, while the use of solvatochromic dyes enables the nanoscale imaging of polarity. The super-resolution microscopy toolbox therefore serves as a novel method to quantify the surface chemistry of nanomaterials on the nanoscale.