Surface energy transfer (SET) is a dipole-surface energy transfer process involving a metallic surface and a molecular dipole. [1]
The SET rate follows the inverse of the fourth power of the distance [2]
where
The energy transfer efficiency also follows a similar form
Due to the fourth power dependence SET can cover a distance more than 15 nm, which is almost twice the efficiency of FRET. [3] Theoretically predicted in 1978 by Chance et al. it was proved experimentally in 2000s by different workers. [4]
The efficiency of SET as nanoruler has been used in live cells. [5]
Gold nano particles are frequently used in these studies as the nanoparticle surface.[ citation needed]