Photo-physical Behaviors and Biological application of Upconverting Nanoparticles (NaYF4:Yb3+, Er3+)

Abstract

Lanthanide-doped upconverting nanoparticles (UCNPs) have been regarded as the proper probes in the bio-imaging field due to their intrinsic optical properties such as high photo-stability with non-bleaching and non-blinking. Especially, upconversion process in UCNP, which emits visible wavelength under near-infrared (NIR) excitation, have great advantages for the bio-imaging field because of the deeper penetration depth of NIR. Additionally, low cytotoxicity of UCNPs has been attracted interests in cellular research field. Therefore, UCNPs provide the new breakthrough for the biological application due to their unique optical properties. However, the photo-physical mechanism and the origin of optical properties of these nanoparticles, especially NaYF4:Yb3+, Er3+, have been controversial and studied. Here, this thesis covers three research topics about new photo-physical properties of NaYF4:Yb3+, Er3+ upconverting nanoparticles and biological application: (1) The depletion of red emission of NaYF4:Yb3+, Er3+ nanoparticles by using 1540-nm depletion laser, (2) the stochastic photon emission of non-blinking NaYF4:Yb3+, Er3+ nanoparticles and (3) the suppression of active transport of vesicles along the microtubule direction in neurodegenerative-like cell.