Size-dependent Properties of Functional PPV-based Conjugated Polymer Nanoparticles for Bioimaging.

•PPV-based conjugated nanoparticles of tunable size as bioimaging probes.•CPM-co-MDMO-PPV and MDMO-PPV NPs were constructed with a size between 50 and 20 nm.•Reducing the diameter does not affect optical properties and biocompatibility.•Lowering the size below 20 nm causes permanent changes in optical properties.•Cell uptake increases with a decreasing diameter.