A novel Förster resonance energy transfer (FRET) fluorescence "off-on" system based on the highly specific, sensitive and effective C-C bond cleavage of certain dihydropyridine derivatives was reported for real-time quantitative imaging of nitric oxide (NO). 1,4-Dihydropyridine was synthesized as a novel linker which could connect customized fluorophores and their corresponding quenchers. The s...