Study of Dye Absorption in Carbon Nanotube-Titanium Dioxide Heterostructures

In this work, the authors present a study of dye absorption in TiO2 doped with CNTs (carbon nanotubes). Absorption decreases exponentially with the increase of CNTs in the film, while morphological characterization, conducted by SEM (scanning electron microscope) and TEM (transmission electron microscope) microscopes, suggests that this behavior is strongly related to morphological structure of grown films. For CNTs amounts greater than 1%, the authors observe the formation of CNTs clusters randomly distribute on TiO2 bulk, which strongly reduces the film porosity quenching the dye absorption. Comparison with optical properties of CNT/TiO2 filmstudied in the previous work, suggest that the best level of doping is with 0.5% of CNTs. FTIR (Fourier transform infrared spectroscopy) measurements conducted on a series of pristine and doped samples clearly indicate the absence of change in allotropic species of TiO2, while AFM (atomic force microscope) analysis indicates that the sample roughness strongly changes with doping, preventing the dye adsorption. Finally, measurements of cell efficiency indicate an increase of 5% in cells with 0.5% of CNT doping and a decrease for greater values.