A nano sensor for sensitive and selective detection of Cu based on fluorescein: Cell imaging and drinking water analysis.

A fluorescein-based nano probe was designed and synthesized for ultra-sensitive detection of Cu in aqueous solution. The formation of fluorescent organic nanoparticles confirmed by using particle size analysis and scanning electron microscopy. UV-Vis. absorption and fluorescence spectroscopy displays excellent photophysical properties of prepared nanoparticles as compared to parent molecule i.e. N-(3',6'-dihydroxy-3-oxo-3,3a-dihydrospiro[isoindole-1,9'-xanthene]-2(7aH)-yl)-1-naphthamide (FNH) in acetone. A series of 18 metal ion was examined with FNH nanoparticles (FNHNPs) to examine the change in fluorescence response. Pleasingly, only copper ion (Cu) shows selective and sensitive fluorescence enhancement effect, which discussed on chelation-enhanced fluorescence phenomenon. Other competing metal ions does not affect the FNHNPs fluorescence enhancement induced by Cu ion. The excited state complexation through chelation-enhanced fluorescence of FNHNPs was further supported by UV-Vis. absorption and fluorescence decay titration of FNHNPs with and without the addition of Cu. The present investigation approach serves extremely low detection limit of 1.62 ng/mL (0.024 μM) for Cu in aqueous solution. In addition, benefit of present study includes practical application for the quantitative estimation of Cu in drinking water sample and intracellular cell imaging for Cu.