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| 2. |
- Tomas, S. A., et al.
(författare)
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Optical and electronic characterization of the band structure of blue methylene and rhodamine 6G-doped TiO2 sol-gel nanofilms
- 2005
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0026-2692. ; 36:3-6, s. 570-573
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties and the band structure of TiO2 sol-gel thin films prepared by the sot-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 2.3 eV and above 3.0 eV suggesting that besides the excitation bands observed in rhodamine at 2.3 eV an efficient energy transfer occurs between the TiO2 conduction band and the molecular rhodamine excited states, yielding a strong emission band at 600 nm, 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.
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| 3. |
- Avendano, Esteban, et al.
(författare)
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Coloration Mechanism in Proton-Intercalated Electrochromic Hydrated NiOy and Ni1-xVxOy Thin Films
- 2009
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 156:8, s. p132-p138
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Tidskriftsartikel (refereegranskat)abstract
- Electrochromic (EC) films of nickel oxide, with and without vanadium, were prepared by reactive dc magnetron sputtering. They were characterized by electrochemical and optical measurements and studied by X-ray photoelectron spectroscopy (PES) using synchrotron radiation. The films were analyzed under as-deposited conditions and after bleaching/coloration by insertion/extraction of protons from a basic solution and ensuing charge stabilization. Optical measurements were consistent with a coloration process due to charge-transfer transitions from Ni2+ to Ni3+ states. The PES measurements showed a higher concentration of Ni3+ in the colored films. Moreover, two peaks were present in the O 1s spectra of the bleached film and pointed to contributions of Ni(OH)(2) and NiO. The changes in the O 1s spectra upon coloration treatment indicate the presence of Ni2O3 in the colored film and necessitated an extension of the conventional model for the mechanism of EC coloration. The model involves not only proton extraction from nickel hydroxide to form nickel oxyhydroxide but also participation of NiO in the coloration process to form Ni2O3.
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