A highly sensitive hydrogen peroxide probe that takes advantage of the amplified fluorescence quenching of conjugated polymers has been developed. The cationic conjugated polymer, poly(9,9-bis(6'-N,N,N-trimethylammonium-hexyl) fluorene phenylene) (PFP-NMe3+) and peroxyfluor-1 with boronate protecting groups (Fl-BB) are used to detect H2O2 optically. Without the addition of H2O2, the absence of electrostatic interactions between the cationic PFP-NMe3+ and the neutral Fl-BB keeps the Fl-BB well separated from the PFP-NMe3+, and no fluorescence quenching of the PFP-NMC3+ occurs. In the presence of H2O2, the formation of the anionic quencher, fluorescein, by specific reaction of the Fl-BB with H2O2 results in strong electrostatic interactions between the PFP-NMe3+ and the fluorescein, and therefore efficient fluorescence quenching of the PFPNMe3+ occurs. The absorption of fluorescein overlaps the emission of PFP-NMe3+, which encourages fluorescence resonance energy transfer (FRET) from the PFP-NMe3+ to the fluorescein. The H2O2 probe has very good sensitivity, with a detection range of 15 to 600 nM. Since glucose oxidase (GOx) can specifically catalyze the oxidation of beta-D-(+)-glucose to generate H2O2, glucose detection is also realized with the H2O2 probe as the signal transducer.