A simple terpyridine-Zn(II) complex is shown to act as an efficient and highly selective fluorescent sensor for pyrophosphate in water at physiological pH. The sensor complex showed an unprecedented fluorescence response (∼500 fold increase) and a record nanomolar sensitivity (detectable fluorescent response at 20 nM and LOD ∼ 0.8 nM). It has successfully been used to stain and record confocal fluorescence microscopy images of HeLa cells. Moreover, the complex was found to self-assemble into a hydrogel which was subsequently used to coat disposable paper strips for easy, low-cost detection of pyrophosphate.