Condensation product of 2-hydroxy-1-napthaldehyde and 2-aminophenol: Selective fluorescent sensor for Al3+ ion and fabrication of paper strip sensor for Al3+ ion

The condensation product of 2-hydroxy-1-napthaldehyde and 2-aminophenol (L), in 1:1 (v/v) CH3OH:H2O acts as selective fluorescent sensor for Al3+. The fluorescence intensity of L at emission wavelength 517 nm, when excited with 360 nm photons, increases on interaction with Al3+ by ca. 7-fold. Under UV lamp, L shows light yellow fluorescence on interaction with Al3+ visible to bare eyes. Metal ions – Na+, K+, Ca2+, Mg2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+do not interfere. The increase in fluorescence intensity is due to the quenching of photoinduced electron transfer (PET) process prevailing in L. The fluorescent and UV/Visible spectral data analysis showed a 1:1 complexation between L and Al3+ with logβ = 4.532 (β = binding constant) and detection limit 10−5 M. DFT and TDDFT calculations also confirm 1:1 interaction between L and Al3+. L has been successfully applied in fluorescent imaging of Al3+ in live rat L6 myoblasts cells and as paper strip fluorescent sensor for Al3+ in aqueous medium.