In this work, gold nanocap-polystyrene particle (PSP) conjugates have been prepared using thermal deposition of gold flux onto PSP particle pre-coated on glass substrate, followed by the lift-up and separation into acetonitrile solvent under sonication. The hollow gold nanocaps were obtained after the PSPs were dissolved with dichloromethane. When the nanocaps were covalently modified with phenyl derivatives in diazonium salt form, the optical absorptions were found as red- or blue-shift, which was probably due to the changing of the electron density of the nanocap surface by the surface-bound electron donating or electron withdrawing functional groups.