Near-IR (NIR) emitting semiconducting polymer dots (Pdots) with ultrabright fluorescence have been prepared for specific cellular targeting. A series of π-conjugated polymers were synthesized to form water dispersible multicomponent Pdots by an ultrasonication-assisted co-precipitation method. By optimizing cascade energy transfer in Pdots, high-intensity NIR fluorescence (Φ= 0.32) with tunable excitations, large absorption–emission separation (up ...