Mukherjee, Smita and Das, Pradip Sekhar and Choudhuri, Madhumita and Datta, Alokmay and Ghosh, Jiten and Saha, Biswajit and Koshmak, Konstantin and Nannarone, Stefano and Mukhopadhyay, Anoop Kumar (2017) Tuning the Band Gap in Titanium Dioxide Thin Films by Surfactant-Mediated Confinement and Patterning of Gold Nanoparticles. Journal of Physical Chemistry C, 121 (39). pp. 21311-21323. ISSN 1932-7447

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Au nanoparticle (NP)-decorated titanium dioxide (TiO2) thin films (Au-TO), prepared by a unique surfactant-assisted 2D self-assembling technique of Au NP layering onto a titanium dioxide matrix (TO) with molecular level control, in conjunction with a classic sol-gel route, showed a significant decrease in the optical band gap (Delta E-g = similar to 0.6 eV) of Au-TO films compared to the conventional sol-gel-prepared pristine counterpart. Strong dependence on surfactant type and deposition temperature of the 2D Au NP layer was observed upon a band gap decrease of the films. Unlike spin-coated Au NP overlayers on TiO2, which resulted in Au NP agglomeration, in this modified inverted Langmuir-Schaefer (MILS) technique, the organic surfactant induced 2D patterned confinement of Au NP layers on TiO2, causing an increase in the active surface area of the Au NP-TiO2 interface. Results of X-ray diffraction and near-edge X-ray absorption fine structure spectroscopy indicated changes in crystal structure as well as in electronic states at the O k absorption edge for Au NP-surfactant patterned films, changes being maximum for films showing a maximum band gap decrease. A temperature evolution of morphology of Au-TO films and their Au NP-surfactant monolayer counterpart at the air-water interface, by ellipsometric imaging and Brewster angle microscopy, respectively, revealed that Au NP patterning was induced by surfactant and varied with the temperature of the Au NP-surfactant monolayer, the band gap decrease being closely associated with a change in the active Au NP-TiO2 surface area. The maximum band gap decrease was observed for Au-TO films having tree- or finger-like 2D Au NP patterns, clearly indicating that an increase in active Au-TiO2 surface area causes enhancement in structural changes and hence a greater band gap decrease of the system. Results demonstrate the potential of the MILS technique of surfactant-aided Au NP-patterned confinement in semiconducting oxides, in band gap engineering of the latter.

Item Type: Article
Subjects: Engineering Materials
Depositing User: Bidhan Chaudhuri
Date Deposited: 29 Jan 2018 11:53
Last Modified: 29 Jan 2018 11:53

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