The scanning electron microscope (SEM) image of pure TiO2
nano particles synthesized by sol–gel method with a pH value of 2
is shown Fig. 3(a). The TiO2 nano particles have aggregated together
to form nano clusters. These nano clusters will affect the photo catalytic
behavior of TiO2 as a photo anode material in DSSC. Hence,
capping agent is needed to minimize this aggregation. The SEM
image of natural dye mixed TiO2 is shown in Fig. 3(b). The mixing
of natural dye during synthesis has yielded uniform adsorption of
dye molecules on TiO2 and prevents the formation of nano clusters.
The morphology of TiO2 has improved as nearly spherical particles
due to the adsorption of the dye rich in betanin. So, the betanin rich
natural dye takes an additional role of a capping agent. The average
crystalline size of TiO2 nano particles is 32 nm and it well agrees
with the value obtained from PXRD.