The UV–vis absorption spectra of compressed TiO2 NP thin films with various thicknesses. Samples A to F have a photoanode thickness of 12.7, 14.2, 25.0, 26.6, 35.3, and 55.2 μm, respectively, with dye adsorption. Sample D' is the TiO2 NP thin film of 26.6 μm in thickness (the same as sample D) but without dye adsorption.
Tsai et al. Nanoscale Research Letters 2013 8:459 doi:10.1186/1556-276X-8-459