Photophysics and Biophysical Applications of Upconverting Nanoparticles

Abstract

Upconverting nanoparticles (UCNPs) such as NaYF4:Yb3+,Er3+ convert near-infrared (NIR) photons to visible photons (red and green). Because of their optical properties, UCNPs have attracted for use in various biological applications such as bioimaging and biosensor. UCNPs do not exhibit photobleaching, photoblinking, and cytotoxicity. UCNPs enable long-term and real-time single-particle tracking (SPT) in living cells due to the photostability and low cytotoxicity of UCNPs. This thesis research covers three research topics; (1) photophysical mechanisms of photon upconversion in NaYF4:Yb3+,Er3+ nanoparticles, (2) multiplexed three-dimensional (3D) tracking of UCNPs, (3) intracellular transport dynamics of endosomal vesicles containing UCNPs. In conclusions, (1) the red emission pathway of NaYF4:Yb3+,Er3+ nanoparticles is revealed by stimulated emission depletion, (2) high-throughput multiplexed 3D SPT of UCNPs is performed by MATLAB code, (3) the anomalous dynamics of UCNP vesicles in living cells is quantitatively explained and predicted by a multimode motor protein multiplexes model.