Soft template synthesis of honeycomb-like ratiometric oxygen sensitive polystyrene nanospheres and their application in anti-counterfeit authentication and food packaging dynamic indication

Abstract

A new methodology to obtain honeycomb-like oxygen-sensitive polystyrene nanospheres has been developed via a facile co-precipitation procedure. Commercially available triblock copolymer Pluronic F127 was utilized as a soft template to shape polystyrene into regular spherical nanostructures. The morphology of the prepared polystyrene nanospheres could be tuned through the modification of the initial concentration of F127 or polystyrene in the aqueous phase. The oxygen indicator, platinum(II)-tetrakis(pentafluorophenyl)porphyrin (maximal emission wavelength at 648nm), and the reference fluorophore, poly(9, 9-dioctylfluorene) (maximal emission wavelength at 440nm), were selected and doped into the polystyrene nanospheres for the ratiometric detection of oxygen. The honeycomb-like oxygen-sensitive polystyrene nanospheres exhibited satisfactory ratiometric luminescence responses to O2 with high quenching efficiency and full reversibility in oxygen sensing. More importantly, the as-prepared polystyrene nanospheres displayed distinct change from red to blue when they were exposed to air from a nitrogen atmosphere. These prepared polystyrene nanospheres can potentially be used as anti-counterfeit labels in the recognition of forged items, or acted as a dynamic signage for on shelf food packaging, since many foods are kept in a vacuum or in an inert gas, such as carbon dioxide or nitrogen.