PNNL

Abstract

Photoswitchable nanoparticles that exhibit fluorescence on-off properties enable an array of innovative applications. The fluorescence on-off switching allows accurate determination of the molecular emitter down to nanometer-resolution; this offers a break-through of the diffraction-limit barrier. Using photo-actuated unimolecular logical switching attained reconstruction (PULSAR) nanoscopy, we have revealed the structures of nanoparticles selfassemblies at the nanoscale. Moreover, the fluorescence-off state of the photoswitching dyes do not absorb at wavelength of the fluorescence excitation. As a result, almost all the interfering fluorophores can be photobleached by the fluorescence excitation light while preserving the photoswitching dyes in the non-absorbing off states. Finally, no current techniques can determine the locations of the photoswitching dyes inside the nanoparticles. PULSAR nanoscopy offers the unique advantage to reveal the photoswitching events, thus the dye location, in the hydrophobic cores of particles.