2-Hydroxy-naphthalene hydrazone based dual-functional chemosensor for ultrasensitive colorimetric detection of Cu2+ and highly selective fluorescence sensing and bioimaging of Al3+

Abstract

2-Hydroxy-naphthalene hydrazone based probe HNP demonstrated high selectivity towards sensing of Cu2+ and Al3+ in colorimetric and fluorimetric methods respectively. HNP can be used as “naked-eye” sensor based on the change of its color from very light yellow to bright yellow (for Cu2+) and colorless (for Al3+). The colorimetric detection mechanism for Cu2+ involved enhancement in internal charge transfer (ICT). In the detection of Al3+ through fluorescence, combined effect of ICT and excited-state intramolecular proton transfer (ESIPT) played major role. Job’s plots based on UV–vis (Cu2+) and fluorescence (Al3+) data along with mass spectral study indicated 1:1 metal to HNP stoichiometry. The binding of the probe HNP with Al3+ and Cu2+ was found chemically reversible on addition of EDTA. Binding mode of the probe with the metal ions was proposed based on spectroscopic data and density functional theory (DFT). Moreover, effect of pH and response time was also determined. The probe was found useful for in vivo detection and imaging of Al3+ in MDA-MB-231 cells. Paper strips of the probe were made and used for naked eye detection of Cu2+ and Al3+. The probe was also used in the construction of logic gate for detection of Al3+.