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Title: Surface modification of NaYF4:Yb,Er upconversion nanoparticles for bio-application
Keywords: Upconversion, Nanocomposites, Core/shell, Silica, Gold, Photothermal
Issue Date: 17-Jul-2012
Citation: 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.
Appears in Collections:Ph.D Theses (Open)

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