A nano sensor for sensitive and selective detection of Cu²⁺ based on fluorescein: Cell imaging and drinking water analysis

A fluorescein-based nano probe was designed and synthesized for ultra-sensitive detection of Cu²⁺ 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 (Cu²⁺) 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 Cu²⁺ 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 Cu²⁺. The present investigation approach serves extremely low detection limit of 1.62 ng/mL (0.024 μM) for Cu²⁺ in aqueous solution. In addition, benefit of present study includes practical application for the quantitative estimation of Cu²⁺ in drinking water sample and intracellular cell imaging for Cu²⁺.