Optical and electronic characterization of the band structure of blue methylene and rhodamine 6G-doped TiO2 sol–gel nanofilms

• Published in: Microelectronics 2005-03, Vol.36 (3-6), p.570-573
• Main Authors: Tomás, S.A., Palomino, R., Lozada, R., da Silva, E.F., de Vasconcelos, E.A., de Azevedo, W.M., Persson, C., Pepe, I., David, D.G.F., Ferreira da Silva, A.
• Format: Article
• Language: English
• Subjects: Band structure; behavior; Optical; Sol–gel
• ISSN: 1879-2391; 0026-2692; 1879-2391
• DOI: 10.1016/j.mejo.2005.02.093

The optical properties and the band structure of TiO2 sol–gel thin films prepared by the sol–gel process and doped with methylene blue or rhodamine were studied by absorption, excitation and emission spectroscopy. The absorption spectra show two absorption bands, around 2.3eV and above 3.0eV suggesting that besides the excitation bands observed in rhodamine at 2.3eV an efficient energy transfer occurs between the TiO2 conduction band and the molecular rhodamine excited states, yielding a strong emission band at 600nm, while for methylene blue a strong hypsochromic shift of the absorption bands is observed. The optical absorption and band gap energy for the phase rutile of TiO2 films were calculated with a LDA+U/FPLAPW method, and a comparison of this calculation with experimental data of TiO2 films prepared by undoped sol–gel and sputtering is performed.