Fig. 9. Excitation (dashed line) and emission (solid line) spectra of Eu-doped cit-cAp samples prepared with different Eu³⁺ doping concentrations at 96 h suspended in water at 25 °C and pH = 7.0. Slit-widths_exc/em = 5/5 nm, t_d = 0.120 μs and t_g = 5 ms.