Quenching and enhancement of single-molecule fluorescence under metallic and dielectric tips

We report on fluorescence experiments by apertureless near-field optical mi croscopy. We develop a simple model that demonstrates the importance of non -radiative transfer and that takes into account the dependence of non-radia tive transfer on tip geometry. This process is in competition with field en hancement and it is a key process to understand the observed fluorescence e nhancement factors. The analysis of the different factors involved in the g lobal fluorescence enhancement or quenching leads to new strategies to reac h resolution down to a few nanometers by apertureless fluorescence microsco py.