Multicolour nanospheres fabricated byin situtransformation of metal nanostructures on the surface of polymer spheres

The optical properties of polymer nanospheres were tuned by in situ transformation of metal structures on their surfaces. Silver nanoparticles (NPs) deposited on the polystyrene nanospheres were transformed into metal hollows made of gold/silver alloy by a galvanic replacement reaction. The metal hollows made of gold/silver alloy were finally changed into solid gold nanoparticles by the additional treatment of chloroauric acid. Through the transformation process, the optical resonance peak of metal-coated polystyrene (PS) nanospheres was tuned in the 410 to 820nm region. The transformation of metal nanostructures on the surface of PS nanospheres was monitored and characterized by UV-visible-near infrared (NIR) spectroscopy and transmission electron microscopy. The described protocols should be applied to prepare the metal-coated polymer nanospheres with tunable surface plasmon resonance (from 450 to 820nm) which would be very useful for biological assays.