Bright and photo-stable luminescent nanoparticles held great potential for bioimaging, long-term molecular tracking. Rare-earth-doped upconversion nanoparticles (UCNPs) have been recently discovered with unique properties for Stimulated Emission Depletion (STED) super-resolution microscopy imaging. However, this system strictly requires optical alignment of concentric excitation and depletion beams, resulting in cost, stability, and complicity of the system. Taking the advantage of intermediate state saturation in UCNPs, emission saturation nanoscopy has been developed as a simplified modality by using a single doughnut excitation beam. In this work, we report that the emission saturation curve of fluorescence probes can modulate the performance of multi-photon emission saturation nanoscopy. With the precise synthesis of UCNPs, we demonstrate the resolution of this new imaging approach can be improved with five parameters, including emission band, activator doping, excitation power, sensitizer doping, core-shell. This approach opens a new strategy to a simple solution for super-resolution imaging and single molecule tracking at low cost, suggesting a large scope for materials science community to improve the performance of emission saturation nanoscopy.
We present a study of the trapping properties of Au nanorods of different aspect ratios in an optical tweezers and comparison with other characterization techniques like transmission electron microscope (TEM) imaging and dynamic light scattering (DLS). This study provides information on the dynamics and orientation of Au nanorods inside an optical trap based on a time study of their localised surface plasmon resonance (LSPR) features. The results indicate that the orientation of the Au nanorods trapped in our optical tweezers varies with time and LSPR spectra can provide information on the angle of the nanorod with respect to the direction of propagation of the trapping laser.
We present a novel method for spatial mapping of the luminescent properties of single optically trapped semiconductor
nanowires by combing dynamic optical tweezers with micro-photoluminescence. The technique involves the use of a
spatial light modulator (SLM) to control the axial position of the trapping focus relative to the excitation source and
collection optics. When a nanowire is held in this arrangement, scanning the axial position of the trapping beam enables
different sections of the nanowire axis to be probed. In this context we consider the axial resolution of the luminescence
mapping and optimization of the nanowire trapping by spherical aberration correction.
We report on the dynamics of micro-photoluminescence of single InP semiconductor nanowires trapped in a gradient
force optical tweezers. Nanowires studied were of zinc blende, wurtzite or mixed phase crystal poly-types and ranged in
length from one to ten micrometers. Our results show that the band-edge emission from trapped nanowires exhibits a
quenching of the initial intensity with a characteristic time scale of a few seconds and an associated spectral red shift is
also observed in the mixed phase nanowires.