LAUSR

Abstract 2′-Hydroxy-2,4-diaminoazobenzene (L1-OH), a fluorescence probe bearing ortho hydroxyl and amino group for the detection of Cu2+ ion was synthesized through diazo coupling reaction. The visible color change of L1-OH from yellow to pink was attributed to the coordination with Cu2+. The 1:1 binding mode of L1-OH with Cu2+ was confirmed by UV titration, Job-plot method and ethylene diamine tetraacetic acid (EDTA) chelation experiment. Meanwhile, the non-emissive L1-OH (Fluorescence quantum yield, Φ = 0.003) has transformed into fluorescent benzotriazole derivative 2-(2-hydroxy-phenyl)–2H-5-aminobenzo[d][1–3]triazole (L1-OH-BTA) (Φ = 0.27) by adding Cu2+, which was supported by the HPLC spectra and DFT calculations. L1-OH was applied for quantitative detection of Cu2+ with good linear relationship between UV absorbance, fluorescence intensity and Cu2+ concentration, and exhibited high selectivity toward Cu2+ over other metal ions (Na+, K+, Ca2+, Ag+, Pb2+, Zn2+, Mn2+, Mg2+, Ni2+, Fe2+, Fe3+, Co2+, Cd2+ and Al3+). Furthermore, the test paper dyed by L1-OH shown colorimetric detection soaking in practical water sample with Cu2+ ion (≥10 μM). The L1-OH could also be used as a fluorescent probe for monitoring Cu2+ ion in living HepG2 cells.