UV–Vis spectra of dyes
PL dyes have an intense absorption maximum at approximately 464 nm as shown in Fig. 1, known as Soret band. The second spectra peak of the PL dyes found at wavelengths 660 nm and similar to the Q bands of chlorophyllins [4]. The addition of benzoic acid to the PL dyes has minor effect to the absorption spectra of the PL dyes revealing that the optical properties of PL dyes are almost the same. In addition, the absorption spectra peak of N719 dye is at a wavelength of 518 nm. Meanwhile, Fig. 2 shows that there are differences in the ability of the dye to adsorb onto the TiO2 semiconducting layer for 24 h resulting in a change in the intensity of the absorption spectra. The Soret and Q bands are not seen in the spectra of the dyes on TiO2 showing that the dyes have formed good bonding with TiO2 surfaces.