Preparation, characterisation and application of europium(III) chelate-dyed polystyrene–acrylic acid nanoparticle labels

Preparation, characterisation and application of europium(III) chelate-incorporated polystyrene–acrylic acid (AAc) nanoparticle labels featuring diverse AAc proportions is described. Emulsion copolymerisation of styrene and AAc was used to synthesise uniform-sized nanoparticles, approximately 50 nm in diameter. The structural, fluorescence and functional properties of the nanoparticles were characterised to obtain the optimal polymer composition of particulate labels. The AAc content had only a delicate effect on the fluorescence of the chelate and structural characteristics of the particles. The fluorescence spectra or lifetime of the incorporated europium(III) chelate were not notably affected, and all the particles were analogous in size, had monomodal size distributions and good colloidal stability. However, the AAc content affected strongly on the stability of the incorporated dye and functionality of the labels. Nanoparticles having up to 5.4 mass% of AAc were stable and applicable in high-sensitivity assays, where low detection limit and variation were achieved. The nanoparticles possessing 7.2 or 11.5 mass% of AAc lost remarkably the dye content during storage influencing their usability as labels in assays. Overall, the characterisation and employment results achieved evidenced the importance of the structural composition of nanoparticles, moreover, the knowledge of the effects of structural changes is utilisable in the development of improved nanoparticle labels and assay applications.