3.3 UV-Vis absorption spectra
Figure 5 depicts the simulated absorption spectra of the dyes after introduction of a heterocyclic ring and further introduction of an amino-ethyl-amino group. As shown in Figure 5, the absorption of MTPABT-Pyc is slightly red shifted. The presence of methyl-benzotriazole effectively reduced the LUMO+1 level, thereby reducing the energy gap of HOMO-LUMO+1 and causing the red shift in the absorption spectrum.