Based on the fluorescence titration, the detection limit of 1eCu2þ for CN
was calculated to be 5.7108Musing 3s/K60 (Fig. S4). In particular,isosbestic points at 307 and 430 nm (Fig. 7b). The second change is
that the absorption peak at 380 nm decreased obviously, whereas
a new prominent band at 440 nmwas developed with well-defined
isosbestic points at 400 and 464 nm (Fig. 7c). The two-step change
of the absorption bands is well consistent with that of the fluorescent
titration