Figure 5.

(a) Responsive probe L forms an excimer complex with Cu²⁺ that “turns-on” fluorescence at 430 nm. (b) Emission spectra of non-responsive cassette 2P (10 μM) and responsive probe L (4 μM) mixed with different concentrations of Cu²⁺ (0−2 μM). The 1 mM of Cu²⁺ stock solution was prepared by dissolving CuSO₄·5H₂O in methanol at room temperature. Emission spectra was acquired 24 h after sample preparation to ensure the sample is at equilibrim. λ_ex = 380 nm. (c) Plot of fluorescence intensity ratio (F₄₃₀/F₇₁₀) versus [Cu²⁺]. Error bars represent standard deviation for triplicate experiments.