Poly(2-cinnamoylethyl methacrylate)-block-poly(acrylic acid) (PCEMA-b-PAA) nanospheres are soluble in water. The lightly cross-linked PCEMA cores of these nanospheres can uptake perylene, a polycyclic aromatic hydrocarbon (PAH), from water. Reported are the rate of perylene incorporation into the nanosphere cores and the coefficient of perylene partition between the cores and water. Also the nanospheres were shown to precipitate completely with the addition of sufficient divalent cations such as Ca2+ and redisperse with EDTA. which complexes with Ca2+. These nanospheres should be useful in concentrating PAHs present in trace amounts in water for chemical analysis or in the reclamation of waters contaminated by PAHs.