Rhodamine based organic nanoparticles for sensing of Fe3+ with high selectivity in aqueous medium: Application to iron supplement analysis

• Synthesis of rhodamine based receptor and formation of organic nanoparticles N1.
• Fluorescence enhancement due to ring opening of spirolactam ring after interaction with Fe3+.
• Highly sensitive and selective “OFF–ON” sensing of Fe3+ in aqueous medium.
• Application in iron supplement analysis.

A rhodamine-based “ON–OFF” fluorescent probe was designed on the bases of modulation in structure between spirocyclic (non-fluorescent) and ring-open (fluorescent) forms of rhodamine dye. The sensing behavior toward metal ions was investigated with fluorescence spectroscopy. The dye has been processed into nanoaggregates through reprecipitation method. Nanoaggregates N1 show high sensitivity and selectivity toward Fe3+ in aqueous medium with detection limit of 9.2 nM, whereas other ions including Li+, Na+, K+, Mg2+, Ca2+, Sr2+, Ba2+, Cr3+, Mn2+, Co2+, Cu2+, Zn2+, Ag+, Cd2+, Pb2+, Hg2+ and Cs+ showed no such spectral change, which constituted a Fe3+ selective fluorescent chemosensor. Further, the practical utility of sensor has been evaluated for analysis of Fe3+ content in iron supplement tablets available in local market.

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