137174-84-6Relevant academic research and scientific papers
Molecular and supramolecular control of the work function of an inorganic electrode with self-assembled monolayer of umbrella-shaped fullerene derivatives
Lacher, Sebastian,Matsuo, Yutaka,Nakamura, Eiichi
, p. 16997 - 17004 (2011)
The surface properties of inorganic substrates can be altered by coating with organic molecules, which may result in the improvement of the properties suitable for electronic or biological applications. This article reports a systematic experimental study on the influence of the molecular and supramolecular properties of umbrella-shaped penta(organo)[60]fullerene derivatives, and on the work function and the water contact angle of indium-tin oxide (ITO) and gold surfaces. We could relate these macroscopic characteristics to single-molecular level properties, such as ionization potential and molecular dipole. The results led us to conclude that the formation of a SAM of a polar compound generates an electronic field through intermolecular interaction of the molecular charges, and this field makes the overall dipole of the SAM much smaller than the one expected from the simple sum of the dipoles of all molecules in the SAM. This effect, which was called depolarization and previously discussed theoretically, is now quantitatively probed by experiments. The important physical properties in surface science such as work function, ionization potential, and water contact angles have been mutually correlated at the level of molecular structures and molecular orientations on the substrate surface. We also found that the SAMs on ITO and gold operate under the same principle except that the "push-back" effect operates specifically for gold. The study also illustrates the ability of the photoelectron yield spectroscopy technique to rapidly measure the work function of a SAM-covered substrate and the ionization potential value of a molecule on the surface.
Enhanced dielectric properties of sol-gel-BaTiO3/P(VDF-HFP) composite films without surface functionalization
Ehrhardt, Claudia,Fettkenhauer, Christian,Glenneberg, Jens,Münchgesang, Wolfram,Leipner, Hartmut S.,Wagner, Gerald,Diestelhorst, Martin,Pientschke, Christoph,Beige, Horst,Ebbinghaus, Stefan G.
, p. 40321 - 40329 (2014)
Barium titanate/poly(vinylidenfluoride-co-hexafluoropropylene) (BTO/P(VDF-HFP)) nanocomposite films were prepared by spin coating and their dielectric properties were investigated. Ferroelectric BaTiO3was prepared by a low temperature sol-gel soft-chemistry method leading to spherical nanoparticles with a high degree of surface hydroxyl groups. Phosphonic acids and/or additional dispersant are typically used to cover the surface of hydrophilic oxide particles in order to improve the compatibility between the particles and the hydrophobic polymer. The effect of such surface modifications was studied using 2,3,4,5,6-pentafluorobenzyl phosphonic acid and additionally the dispersant BYK-W 9010 as surfactants. Against expectation, the use of pure sol-gel barium titanate led to the lowest particle agglomeration in the composite suspension and the best film quality resulting in a large enhancement of the relative permittivity by a factor of 10 compared to pure P(VDF-HFP). For this simple biphasic system without any further components a very high relative permittivity εrof 57 was obtained at 1 kHz for a 50 vol% BaTiO3/P(VDF-HFP) composite. The εrvalues further increase at lower frequencies. These findings show that for the BTO nanoparticles, prepared by the sol-gel synthesis, no surface coating is required to obtain good dielectric properties, allowing for a considerable simplification of the preparation technique. This journal is
A solution-based approach to composite dielectric films of surface functionalized CaCu3Ti4O12 and P(VDF-HFP)
Ehrhardt, Claudia,Fettkenhauer, Christian,Glenneberg, Jens,Muenchgesang, Wolfram,Leipner, Hartmut S.,Diestelhorst, Martin,Lemm, Sebastian,Beige, Horst,Ebbinghaus, Stefan G.
, p. 2266 - 2274 (2014/02/14)
High permittivity CaCu3Ti4O12/ poly(vinylidenefluoride-co-hexafluoropropylene) P(VDF-HFP) nanocomposites were investigated as dielectrics for film capacitors. CaCu3Ti 4O12 was synthesized by two different soft-chemistry methods, namely, decomposition of a citrate precursor and a recently developed lactate precursor to identify a preferable route to nanometer scale spherical particles with an increased interfacial area. A ball-milling step was applied to break particle agglomerates and to enhance particle distribution in the composite films. To improve the wetting of the CaCu3Ti 4O12 oxide particles and the polymer, a variety of surfactants, e.g. carbonic acid, silane, sulfonic acid and phosphonic acid were investigated. A successful oxide surface functionalization was achieved by 2,3,4,5,6-pentafluorobenzyl phosphonic acid, leading to stable bonds and good structural compatibility between the surfactant and the highly fluorinated polymer matrix. The films were prepared from composite dispersions by a spin-coating technique and can be formed out of powders from both precursors, but the citrate method is preferable due to milder synthesis conditions and improved film homogeneity. The use of ball-milled powders as the oxide component results in homogeneous particle distributions even near to the percolation threshold. In addition, such fine-ground particles lead to homogeneous film thickness and decreased film roughness. Dielectric measurements at different frequencies revealed an enhancement in the relative permittivity by a factor of 5 compared to the pure polymer while the dielectric losses remained very low.
