DEVELOPING CORE-SHELL UPCONVERSION NANOPARTICLES FOR OPTICAL ENCODING

Abstract

UPCONVERSION NANOPARTICLES (UCNPS) EMIT UV OR VISIBLE LIGHT UNDER NEAR INFRA-RED (NIR) EXCITATIONS, THEREBY POSSESSING A LARGE ANTI-STOKES SHIFT PROPERTY. PLUS THEIR EXCELLENT PHOTO- AND CHEMICAL STABILITY, AND SHARP EMISSION BANDS, UCNPS ARE ADVANTAGEOUS FOR OPTICAL ENCODING. FABRICATING CORE-SHELL STRUCTURED UCNPS PROVIDES A PROMISING STRATEGY TO TUNE AND ENHANCE THEIR UPCONVERTING LUMINESCENCE. HOWEVER, THE ENERGY TRANSFER BETWEEN CORE AND SHELL WERE RARELY STUDIED. MOREOVER, THIS STRATEGY WAS LIMITED BY THE DIFFICULTY OF COATING EXTREMELY THICK SHELL ONTO BIG CORE UCNPS. IN THIS THESIS, THE ENERGY TRANSFER IN THE CORE-SHELL UCNPS WERE STUDIED SYSTEMATICALLY, THESE INFORMATION WERE UTILIZED TO FABRICATE UCNPS WITH ENHANCED AND TUNEABLE LUMINESCENCE BY FINE ARRANGING THE IONS IN THE CORE-SHELL STRUCTURE. A STRATEGY OF COATING THICK SHELL BY LUTETIUM DOPING WAS ALSO DEVELOPED, PROVIDING MORE FREEDOM FOR ENGINEERING CORE-SHELL UCNPS WITH MULTIPLE LAYERS AND DESIRED THICKNESS. THESE UCN