▎ 摘　　要

We present a low background, highly selective and amplified fluorescent sensor for potassium ions using graphene oxide (GO) and a cationic conjugated polymer (CCP). This method takes advantage of the phenomenon that the addition of CCP cannot release the dye labeled guanine-rich DNA from the GO surface, and the conformational switch of the guanine-rich DNA from random coil to G-quadruplex induced by the target.