CdTe nanocrystal-polymer composite thin film without fluorescence resonance energy transfer by using polymer nanospheres as nanocrystal carriers

A series of positively charged polystyrene (PS) nanosphere emulsions were prepared by copolymerization of quaternary ammonium chloride cationic monomer with styrene via emulsifier-free emulsion polymerization. The average diameter of the nanospheres was tuned in the range of 35-100 nm by adjusting the recipe. The PS nanospheres were used as carriers of aqueous CdTe nanocrystals (NCs) by adsorbing them on the surface through static interaction. After attached to the nanospheres, NCs' stability against pH change and UV light irradiation was enhanced. The CdTe-PS composite nanospheres were blended with compatible poly (vinyl alcohol) (PVA) matrix to prepare fluorescent thin film by spin coating. CdTe-PS nanospheres had homogenous distribution in the thin film and their light scattering performance was largely reduced after solvent evaporated, as a result, the composite thin film was highly transparent. In the meantime, the immobilization effect of PS nanospheres prevented NCs from aggregation, thus they preserved original high fluorescence without fluorescence resonance energy transfer. The CdTe-PS/PVA composite solution has potential applications in light emitting devices by inkjet printing. (C) 2010 Elsevier Inc. All rights reserved.