Figure 4.

Absorption spectra (a) and fluorescence spectra (b) of probe 5 (5 μM) in ethanol/HEPES (pH 7.4, 1/1, v/v) at 25 °C upon addition of 1 equiv of Cu²⁺ ions and other metal ions including Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Pb²⁺, Cd²⁺, and Hg²⁺ ions (excitation wavelength: 460 nm, emission wavelength: 536 nm).