Far-red/near-infrared fluorescent conjugated polymer nanoparticles with size-dependent chirality and cell imaging applications

A novel chiral conjugated polymer is developed and used for the preparation of conjugated polymer nanoparticles (CPNs) with particle sizes ranging from 80 to 190 nm. The size-dependent optical properties of chiral CPNs are fully studied and it was found that the nanoparticles exhibited a prominent red shift both in UV-vis and fluorescence emission with increasing diameters. The circular dichroism (CD) spectra and anisotropy r values of the CPNs display size-tunable chirality features, which can be attributed to the nature of the aggregates as nanoparticles grow. Meanwhile, the obtained CPNs can serve as efficient far-red/near-infrared (FR/NIR) fluorescent probes with low cytotoxicity and high photostability for HeLa cell imaging.