Cellulose mediated conjugated polymer nanoparticles with enhanced fluorescence efficiency for bioimaging

Conjugated polymers (CPs) attract a lot of attention in sensing, imaging, and biomedical applications by taking advantage of their extraordinary characteristics. However, most of them inevitably aggregate at higher concentrations, leading to attenuated fluorescence efficiency. Herein, we report a fluorescence enhancement strategy for conjugated polymers by using cellulose as a mediator. The composite nanoparticles CMC@PFE-1-NPs are prepared based on carboxymethyl cellulose (CMC) and poly(fluorene-co-phenylene ethynylene) derivative (PFE-1) via self-assembly through electrostatic and hydrophobic interactions. This spatial confinement effectively restricts π-π stacking effects and other nonradiative channels, leading to high luminescent efficiency of isolated PFE-1. A 5-fold enhancement in fluorescence quantum yield for CMC@PFE-1-NPs is obtained compared with conjugated polymers themselves. Furthermore, the nanoparticles realize more sensitive cell imaging. Therefore, this simple and effective method provides a new way for reducing the aggregation between rigid fluorescent molecules and improving their photophysical properties and biological application.