Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/35813
Title: Surface modification of NaYF4:Yb,Er upconversion nanoparticles for bio-application
Authors: QIAN LIPENG
Keywords: Upconversion, Nanocomposites, Core/shell, Silica, Gold, Photothermal
Issue Date: 17-Jul-2012
Source: QIAN LIPENG (2012-07-17). Surface modification of NaYF4:Yb,Er upconversion nanoparticles for bio-application. ScholarBank@NUS Repository.
Abstract: Motivated by using NaYF4:Yb,Er upconversion nanoparticles as potential bio-probe for cell imaging and thermal therapy, this thesis studies the surface modification of these NaYF4:Yb,Er nanoparticles by undoped NaYF4 shell, amorphous silica and Au nanoparticles. NaYF4:Yb,Er nanoparticles with a particle size of 11.1 ? 1.3 nm were synthesized by a thermal decomposition method. The NaYF4:Yb,Er / NaYF4 (core/shell) nanoparticles obtained by the same synthesis method showed that an undoped NaYF4 shell significantly enhanced the emission intensity by 15 times. Amorphous silica shells were coated on NaYF4:Yb,Er nanoparticles via a reverse micro-emulsion method. The thickness of silica shell was ~ 8 nm. Silica, though providing a good barrier to the non-radiative relaxation between the upconversion nanoparticles and the environments, did not enhance the emission intensity of upconversion nanoparticles. Gold decorated NaYF4:Yb,Er / NaYF4 / silica (core/shell/shell) upconversion nanocomposites (70-80 nm) were further synthesized using chloroauric acid in a one-step reverse micro-emulsion method. These nanocomposites demonstrated strong photothermal effect and cancer cells destruction efficiency. Up to 67.5 % of cancer cells incubated with nanocomposites were destroyed after 20 min irradiation with 980 nm continuous wave laser. The nanocomposites demonstrated potential for simultaneous imaging and efficient photothermal cancer therapy.
URI: http://scholarbank.nus.edu.sg/handle/10635/35813
Appears in Collections:Ph.D Theses (Open)

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