Abstract
We research the fluorescence enhancement of Rose Bengal on the different distance between Rose Bengal and Gold nanoparticle. In this experiment, we use confocal microscopy to measure the fluorescence lifetime of dye on the single Gold nanoparticle. The medium between molecular and Gold nanoparticle are polymer or TiO2 coating on the surface of Gold nanoparticle. In the polymer coating, we use Poly Styrene Sulfonate (PSS) and Poly Allyamine Hydrochloride (PAH) to coat on the 70 nm of Gold nanoparticle by the Layer by Layer method. We coat 1 to 7 layers, and the thickness are 1.1 nm to 7.3 nm, the average of thickness is 1.05 nm per layer. The fluorescence lifetime are bi-exponent decay. The lifetime of TAU1 are 34 ps to 60 ps, and the lifetime of TAU2 are 282 ps to 368 ps from 1 layer to 7 layers. In the TiO2 coating, we modify the surface of Gold nanoparticle, then add Titanium isopropoxide (TTIP) to coat 5 nm, 10 nm, 15 nm and 20 nm of thickness with different reaction time. And the fluorescence lifetime are also bi-exponent decay. The sample coating from 5 nm to 20 nm, which TAU1 are 24 ps to 120 ps, TAU2 are 241 ps to 672 ps. Finally, we use the experiment result and some reference to propose the simple kinetic mechanism. The fluorescence enhancement are decrease when the distance increase. The fluorescence enhancement of dye are limited on the medium of TiO2, because the excited of dye can decay by electron transfer.