Here we describe single-particle imaging studies conducted on the conjugated polyelecrolyte poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene] (MPS-PPV) supported on SiO2 nanoparticles. The particles are subjected to a time-programmed sequence involving addition and removal of different additives, including excited-triplet-state quenchers and scavengers of singlet oxygen as well as ground-state oxygen. Our studies show that these additives enhance the emission intensity and photostability of the nanoparticles and may further repair photodamaged conjugated polymer. The ability to monitor the emission from individual particles along multiple cycles under a range of conditions provides a mechanistic insight into the action of these additives.