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AFM/XPS Analysis of the Growth and Architecture of Oriented Molecular Monolayer by Spin Cast Process and Its Cross-Linking Induced by Hyperthermal Hydrogen. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12126233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We used atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) to comprehensively study the growth and the cross-linking of dotriacontane (C32H66) nanofilms that were deposited on a silicon wafer by the spin-coating process. It was found that the molecular structure of the nanofilms changed with C32H66 concentration at the given spin speed, of which a monolayer of oriented C32H66 molecules, formed at lower deposition concentrations, was composed of a perpendicular orientation state with the molecular long-chain axis perpendicular to the substrate surface and a parallel orientation state, while the perpendicular state was essentially dominant when the nanofilm was formed at higher deposition concentrations. The shortening of the first perpendicular layer in AFM topography could be attributed to the mixing of both parallel and perpendicular lamellas in the first layer. XPS analysis indicated that the average thickness of the layer almost linearly increased with the C32H66 concentration. The monolayer of C32H66 film could be cross-linked by a hyperthermal hydrogen-induced cross-linking (HHIC) at a few eV via kinetic collision to cleave C-H bonds. The water contact angle measurement of extensive HHIC on C32H66 nanofilms disclosed that the static contact angle decreased with the treatment time (or fluence) and saturated after full cross-linking of the film.
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Díaz D, Nickel O, Moraga N, Catalán RE, Retamal MJ, Zelada H, Cisternas M, Meißner R, Huber P, Corrales TP, Volkmann UG. How water wets and self-hydrophilizes nanopatterns of physisorbed hydrocarbons. J Colloid Interface Sci 2021; 606:57-66. [PMID: 34388573 DOI: 10.1016/j.jcis.2021.07.121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 07/22/2021] [Accepted: 07/23/2021] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS Weakly bound, physisorbed hydrocarbons could in principle provide a similar water-repellency as obtained by chemisorption of strongly bound hydrophobic molecules at surfaces. EXPERIMENTS Here we present experiments and computer simulations on the wetting behaviour of water on molecularly thin, self-assembled alkane carpets of dotriacontane (n-C32H66 or C32) physisorbed on the hydrophilic native oxide layer of silicon surfaces during dip-coating from a binary alkane solution. By changing the dip-coating velocity we control the initial C32 surface coverage and achieve distinct film morphologies, encompassing homogeneous coatings with self-organised nanopatterns that range from dendritic nano-islands to stripes. FINDINGS These patterns exhibit a good water wettability even though the carpets are initially prepared with a high coverage of hydrophobic alkane molecules. Using in-liquid atomic force microscopy, along with molecular dynamics simulations, we trace this to a rearrangement of the alkane layers upon contact with water. This restructuring is correlated to the morphology of the C32 coatings, i.e. their fractal dimension. Water molecules displace to a large extent the first adsorbed alkane monolayer and thereby reduce the hydrophobic C32 surface coverage. Thus, our experiments evidence that water molecules can very effectively hydrophilize initially hydrophobic surfaces that consist of weakly bound hydrocarbon carpets.
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Affiliation(s)
- Diego Díaz
- Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile; Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Ole Nickel
- Hamburg University of Technology, Institute of Polymers and Composites, 21073 Hamburg, Germany
| | - Nicolás Moraga
- Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| | - Rodrigo E Catalán
- Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| | - María José Retamal
- Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| | - Hugo Zelada
- Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| | - Marcelo Cisternas
- Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| | - Robert Meißner
- Hamburg University of Technology, Institute of Polymers and Composites, 21073 Hamburg, Germany; Helmholtz-Zentrum Hereon, Institute of Surface Science, 21494 Geesthacht, Germany
| | - Patrick Huber
- Hamburg University of Technology, Institute for Materials and X-Ray Physics, 21073 Hamburg, Germany; Deutsches Elektronen-Synchrotron DESY, Centre for X-Ray and Nano Science CXNS, 22603 Hamburg, Germany; University of Hamburg, Centre for Hybrid Nanostructures CHyN, 22607 Hamburg, Germany.
| | - Tomas P Corrales
- Departamento de Física, Universidad Técnica Federico Santa María, Valparaiso 2390123, Chile.
| | - Ulrich G Volkmann
- Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile; Centro de Investigación en Nanotecnología y Materiales Avanzados (CIEN-UC), Pontificia Universidad Católica de Chile, Santiago 7820436, Chile.
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Liu Y, Yang DQ, Nie HY, Lau WM, Yang J. Study of a hydrogen-bombardment process for molecular cross-linking within thin films. J Chem Phys 2011; 134:074704. [DOI: 10.1063/1.3554430] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Diama A, Matthies B, Herwig KW, Hansen FY, Criswell L, Mo H, Bai M, Taub H. Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation. J Chem Phys 2009; 131:084707. [PMID: 19725621 DOI: 10.1063/1.3212095] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present evidence from neutron diffraction measurements and molecular dynamics (MD) simulations of three different monolayer phases of the intermediate-length alkanes tetracosane (n-C(24)H(50) denoted as C24) and dotriacontane (n-C(32)H(66) denoted as C32) adsorbed on a graphite basal-plane surface. Our measurements indicate that the two monolayer films differ principally in the transition temperatures between phases. At the lowest temperatures, both C24 and C32 form a crystalline monolayer phase with a rectangular-centered (RC) structure. The two sublattices of the RC structure each consists of parallel rows of molecules in their all-trans conformation aligned with their long axis parallel to the surface and forming so-called lamellas of width approximately equal to the all-trans length of the molecule. The RC structure is uniaxially commensurate with the graphite surface in its [110] direction such that the distance between molecular rows in a lamella is 4.26 A=sqrt[3a(g)], where a(g)=2.46 A is the lattice constant of the graphite basal plane. Molecules in adjacent rows of a lamella alternate in orientation between the carbon skeletal plane being parallel and perpendicular to the graphite surface. Upon heating, the crystalline monolayers transform to a "smectic" phase in which the inter-row spacing within a lamella expands by approximately 10% and the molecules are predominantly oriented with the carbon skeletal plane parallel to the graphite surface. In the smectic phase, the MD simulations show evidence of broadening of the lamella boundaries as a result of molecules diffusing parallel to their long axis. At still higher temperatures, they indicate that the introduction of gauche defects into the alkane chains drives a melting transition to a monolayer fluid phase as reported previously.
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Affiliation(s)
- A Diama
- Department of Physics and Astronomy and the University of Missouri Research Reactor, University of Missouri, Columbia, Missouri 65211, USA
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Tanaka K, Ishikawa K, Nozaki K, Urakami N, Yamamoto T. Structures of Multilayered Thin Films of Long-Chain Molecules: X-ray Scattering Study. Polym J 2008. [DOI: 10.1295/polymj.pj2007230] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Explanation and correction of false step heights in amplitude modulation atomic force microscopy measurements on alkane films. Ultramicroscopy 2008; 108:946-52. [DOI: 10.1016/j.ultramic.2008.03.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Revised: 03/07/2008] [Accepted: 03/26/2008] [Indexed: 11/23/2022]
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Yamamoto T, Nozaki K, Yamaguchi A, Urakami N. Molecular simulation of crystallization in n-alkane ultrathin films: Effects of film thickness and substrate attraction. J Chem Phys 2007; 127:154704. [DOI: 10.1063/1.2781390] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Trogisch S, Simpson MJ, Taub H, Volkmann UG, Pino M, Hansen FY. Atomic force microscopy measurements of topography and friction on dotriacontane films adsorbed on a SiO2 surface. J Chem Phys 2005; 123:154703. [PMID: 16252965 DOI: 10.1063/1.2060707] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report comprehensive atomic force microscopy (AFM) measurements at room temperature of the nanoscale topography and lateral friction on the surface of thin solid films of an intermediate-length normal alkane, dotriacontane (n-C32H66), adsorbed onto a SiO2 surface. Our topographic and frictional images, recorded simultaneously in the contact mode, reveal a multilayer structure in which one to two layers of molecules adsorb adjacent to the SiO2 surface oriented with their long axis parallel to the interface followed by partial layers of molecules oriented perpendicular to the surface. The thicknesses of the parallel and perpendicular layers that we measured with the AFM agree with those inferred from previous x-ray specular reflectivity measurements on similarly prepared samples. We also observe bulk dotriacontane particles and, in contrast with our previous measurements, are able to determine their location. Above a minimum size, the bulk particles are separated from islands of perpendicularly oriented molecules by regions of exposed parallel layers that most likely extend underneath the particles. We find that the lateral friction is sensitive to the molecular orientation in the underlying crystalline film and can be used effectively with topographic measurements to resolve uncertainties in the film structure. We measure the same lateral friction on top of the bulk particles as on the perpendicular layers, a value that is about 2.5 times smaller than on a parallel layer. Scans on top of parallel layers indicate a constant height but reveal domains having different sublevels of friction. We explain this by the domains having different azimuthal orientations of the molecules.
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Affiliation(s)
- S Trogisch
- Department of Physics and Astronomy and University of Missouri Research Reactor, University of Missouri-Columbia, Columbia, Missouri 65211, USA
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