title: Improved Langmuir-Blodgett titanate films via in situ exfoliation study and optimization of deposition parameters.
abstract: The exfoliation and deposition of large (10-100 μm) Ti0.87O2 and small (0.1-1 μm) Ti0.91O2 nanosheets from lepidocrocite-type protonated titanates was investigated for getting high quality films. Exfoliation was carried out with different tetra-alkyl ammonium ions (TAA(+)) and varying TAA(+)/H(+) ratios, and the colloidal solutions were characterized by small-angle X-ray scattering (SAXS) and ultraviolet-visible (UV-vis) spectroscopy. Using Langmuir-Blodgett deposition the titanate nanosheets were directly transferred onto a Si substrate. The resulting films were characterized by atomic force microscopy (AFM).The results indicate that the H1.07Ti1.73O4 titanate exfoliated at very low ratios of TAA(+)/H(+); no lower threshold for exfoliation was observed for the TAA(+) concentration. Nanosheets exfoliated at very low ratios of TAA(+)/H(+) typically showed a small size and porous surface. Subsequent exfoliation of the remaining layered titanate particles yielded much higher quality nanosheets. The optimized deposition parameters for Langmuir-Blodgett films suggest that the surface pressure is a key parameter to control the coverage of the film. The bulk concentration of nanosheets was found to be a less important deposition parameter in the LB deposition process. It only influenced whether the desired surface pressure could be reached at a given maximum degree of compression.
authors.affiliation: MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Huiyu
authors.initials: H
authors.lastname: Yuan
authors.forename: Roy
authors.initials: R
authors.lastname: Lubbers
authors.forename: Rogier
authors.initials: R
authors.lastname: Besselink
authors.forename: Maarten
authors.initials: M
authors.lastname: Nijland
authors.forename: Johan E
authors.initials: JE
authors.lastname: Ten Elshof