Two classical conjugated polymers, poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), commonly used in organic optoelectronic devices are endowed with a new function for radical sensing. The synergetic effect between MEH-PPV and PFO nanoparticles (NPs) plays an important role in the detection of hydroxyl radicals and sulfate anion radicals. When exposed to free radicals, MEH-PPV NPs are subjected to attack by the radicals and undergo molecular structure changes. Thus, a strong-polarity shell can be formed on the radical treated MEH-PPV NPs. When such radical treated MEH-PPV NPs come into close contact with PFO NPs, a new phenomenon whereby PFO alters its fluorescence emission intensity of the 0–2 transition relative to the 0–0 transition band is observed. The relative intensity ratio of these two transition bands can serve as an index for the hydroxyl radical concentration. Therefore, radical detection can be realized by measuring the solid state fluorescence, which is highly desired in off-site laboratory determination since solid samples are more convenient for storage and transport than solutions. Our results can open a way for the application of conjugated polymer nanoparticles in chemical/biological sensing.
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