A hexaazatriphenylene (HAT) derivative, naphtho [2,3-h]naphtho[2 0 ,3':7,8]quinoxalino[2,3-a]naphtho [2 0 ,3 0 :7,8]quinoxalino [2,3-c] 10,15,20,25, was synthesized, characterized, and found to have novel properties in being selective toward the detection of copper (Cu 2+ ) ions. The capability of NQH to be employed as a colorimetric, chemo-fluorescence and electrochemical sensor for the detection of Cu 2+ was demonstrated by performing UV-Vis absorbance, fluorescence intensity, and cyclic voltammetry (CV) measurements. The interaction between NQH and Cu 2+ was initially observed with an obvious color change from yellow to brown upon the addition of Cu 2+ ions to NQH.The interaction was also confirmed by UV-Vis absorbance, fluorescence intensity, and mass spectroscopy (MS/MS) measurements. UV absorbance, fluorescence and CV of NQH toward Cu 2+ showed good linearity with a detection limit of 3.32 mM, 2.20 mM and 0.78 mM, respectively, which are lower than the toxicity levels of copper in drinking water (20-30 mM) set by the U.S. Environmental Protection Agency (EPA) and World Health Organization (WHO). A 1 : 2 stoichiometry complexation between NQH and Cu 2+ was confirmed by Job's plot and MS/MS. In addition, the selectivity and sensitivity of the NQH compound towards Cu 2+ ions were further confirmed by performing CV on a screen printed flexible and planar electrochemical sensor.
Monitoring changes in optical properties of NQH upon exposure to Cu 2+The selectivity and the sensitivity of the NQH compound towards different heavy metals was investigated by using UV-Vis absorbance spectroscopy. Initially, UV-Vis absorption spectra of NQH was recorded in the presence of 100 mM concentration of metal ions including Cu 2+ , Co 2+ , Ni 2+ , Fe 2+ , Fe 3+ , Li 1+ , Pb 2+ , and Hg 2+ in aqueous media (Fig. 4(a)). An absorbance peak at $435 nm was observed for the NQH compound. No color change as well as no shi in peak was observed in the presence Fig. 2 (a) 1 H-NMR and (b) 13 C-NMR spectra of NQH.This journal is