Fluorescence-emission control of single CdSe nanocrystals using gold-modified AFM tips

The fluorescence emission of single CdSe nanocrystals was investigated using gold-modified atomic force microscope (AFM )tips technique. Luminescent CdSe/ZnS nanocrystals were prepared using solution of Cd stearate and trioctylphosphineselenide. Silicon nitride AFM tips were amino functionalized with 3-mercaptopropyltriethoxysilane and incubated with a suspension of gold nanoparticles. The dependence of the nanocrystal luminescence on the distance of the AFM tip was measured by analysis of fluorescence-intensity measurements at several z distances between the tip and a single CdSe nanocrystal using total-internal reflection fluorescence microscopy (TIRFM) and atomic force microscopy technique. It was observed that gold particles quench the nanocrystal emission. Result shows that nanocrystals are excited by the evanescent field emanating from a totally reflecting laser beam and exhibit fluorescence emission.