Figure3 Electron density difference between the S0 and
S1
(a)C23-1 and (b)C23-4
The probe C23 could detect HSA and SO2 simultaneously
due to the different fluorescence signal while binding with them.
Michael addition reaction between probe C23 and SO2(HSO3-1) could saturate the rotational
bonds in the C23 and stabilize the conformation which led to the strong
fluorescence signal within the blue channel. To understand this
mechanism, the conformation and electron excitation process of CS (C23
combined with HSO3-1) were analyzed
using the same methods which were used for C23 before. The stable
conformations of CS structure were reduced to two (CS-1 and CS-2 shown
in Figure4). It can be clearly seen that due to the steric hindrance
effect of HSO3 group, the rotational C-C bonds between
the two rings in the probe were saturated and no longer rotated. This
Michael addition reaction cut off the non-radiative pathway and led to
the blue fluorescence signal within the electron excitation process of
CS.