Rhodamine-based fluorescent polyacrylic nanoparticles: A highly selective and sensitive chemosensor for Fe (II) and Fe (III) cations in water

Fe2+ and specially Fe3+ are important in our daily life and their deficiency or excess amounts may cause serious disorders and infectious diseases. Most of their existing fluorescent sensors consist of small molecules and may operate in organic media with prolonged response time and inadequate detection limit which restrict their widespread applications. Fluorescent poly(methyl methacrylate-co-glycidyl methacrylate) nanoparticles bearing Rhodamine B ethylenediamine acrylate (RhAcL-3) were prepared through semi-continues emulsion polymerization. Chemical structure of the prepared RhAcL-3 polyacrylic nanoparticles with smooth spherical morphology, average particle size of 46 nm and narrow size distribution (polydispersity index of 0.09) were completely characterized by FTIR, H-1 NMR, UV-Vis, SEM and DLS techniques. Water dispersion of RhAcL-3 nanoparticles demonstrated an immediate and apparent color change together with enhancement in fluorescence emission at 590 nm after addition of Fe2+ and Fe3+ ions up to 2 and 2.2-folds, respectively. This was attributed to chelation of these ions to spirolactam moiety in Rhodamine B to consequate open-ring amide form. It was found that the presence of some other metal cations had no interference on the above affinity and sensing role. Linear dynamic detection range (4-320 mu M) and detection limit of RhAcL-3 sensor toward Fe2+ and Fe3+ were estimated 2.63 and 2.5 mu M, respectively. The results suggest that these prepared nanoparticles could be utilized as colorimetric and fluorescent sensor with instant responsivity, wide linear detection range, high sensitivity and low detection limit for Fe2+ and Fe3+ ions in future advances and applications.