Fluorescein-labeled starch maleate nanoparticles as sensitive fluorescent sensing probes for metal ions

Fluorescein 5(6)-isothiocyanate starch maleate (FISM) nanoparticles were prepared by covalently attached fluorescein 5(6)-isothiocyanate (FITC) with starch maleate. FISM nanoparticles with a mean particle size of 87 nm were formed via self-assembly upon precipitation in ethanolic solution. FISM nanoparticles were strongly fluorescent with maximum emission wavelength of 518 nm. The fluorescence of FISM nanoparticles can be quenched by silver (Ag+) and lead (Pb2+) ions in a concentration dependent manner. We have demonstrated the first use of FISM nanoparticles as cheap and effective fluorescent sensing probes for Ag+ and Pb2+ ions with detection limits as low as 2.55 x 10(-5) M and 3.64 x 10(-5) M, respectively.