Solvent Effects on the Monolayer Structure of Long<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">n</mml:mi><mml:mo>−</mml:mo><mml:mi mathvariant="normal">A</mml:mi><mml:mi mathvariant="normal">l</mml:mi><mml:mi mathvariant="normal">k</mml:mi><mml:mi mathvariant="normal">a</mml:mi><mml:mi mathvariant="normal">n</mml:mi><mml:mi mathvariant="normal">e</mml:mi></mml:math>Molecules Adsorbed on Graphite

Herwig, K. W.; Matthies, B.; Taub, H.

doi:10.1103/physrevlett.75.3154

Cited by 92 publications

(85 citation statements)

References 15 publications

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“…Previous experiments with alkane adsorption on graphite ͑0001͒, 3,19 Cu͑111͒, 20 Au͑111͒, 20 Ag͑111͒, 21 and Pt͑111͒ 22 surfaces, using a wide variety of techniques, have always indicated a first layer in which the long molecular axis is parallel to the surface. In addition, molecular dynamics ͑MD͒ simulations of intermediate-length alkanes adsorbed on Au͑001͒ 23 and graphite basal plane surfaces 24 show the molecules in the first layer to be parallel to the surface.…”

Section: Discussionmentioning

confidence: 99%

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High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

Volkmann

Pino

Altamirano

et al. 2002

The Journal of Chemical Physics

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Using high-resolution ellipsometry and stray light intensity measurements, we have investigated during successive heating-cooling cycles the optical thickness and surface roughness of thin dotriacontane (n-C 32 H 66 ) films adsorbed from a heptane (n-C 7 H 16 ) solution onto SiO 2 -coated Si͑100͒ single-crystal substrates. Our results suggest a model of a solid dotriacontane film that has a phase closest to the SiO 2 surface in which the long-axis of the molecules is oriented parallel to the interface. Above this ''parallel film'' phase, a solid monolayer adsorbs in which the molecules are oriented perpendicular to the interface. At still higher coverages and at temperatures below the bulk melting point at T b ϭ341 K, solid bulk particles coexist on top of the ''perpendicular film.'' For higher temperatures in the range T b ϽTϽT s where T s ϭ345 K is the wetting temperature of the bulk phase, the coexisting bulk particles melt into droplets; and for TϾT s , a uniformly thick fluid film wets to the parallel film phase. This structure of the alkane/SiO 2 interfacial region differs qualitatively from that which occurs in the surface freezing effect at the bulk alkane fluid/vapor interface. In that case, there is again a perpendicular film phase adjacent to the air interface but no parallel film phase intervenes between it and the bulk alkane fluid. Similarities and differences between our model of the alkane/SiO 2 interface and one proposed recently will be discussed. Our ellipsometric measurements also show evidence of a crystalline-to-plastic transition in the perpendicular film phase similar to that occurring in the solid bulk particles present at higher coverages. In addition, we have performed high-resolution ellipsometry and stray-light measurements on dotriacontane films deposited from solution onto highly oriented pyrolytic graphite substrates. After film deposition, these substrates proved to be less stable in air than SiO 2 .

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Section: Discussionmentioning

confidence: 99%

“…They are also of fundamental interest as prototypes of more complex polymers. 3 The Si͑100͒ substrates are commercially available wafers widely used in the semiconductor industry. They provide large, high-quality single-crystal surfaces with few defects.…”

Section: Introductionmentioning

confidence: 99%

High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

Volkmann

Pino

Altamirano

et al. 2002

The Journal of Chemical Physics

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“…Previous experimental studies of the monolayer structure of intermediate-length alkanes have focused on high-quality solid surfaces of graphite, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Ag͑111͒, 22,23 and SiO 2 . 3,24,25 Of these systems, probably the best characterized are monolayers of C32 and C24 on high-quality graphite basal-plane surfaces that have been investigated by scanning tunneling microscopy ͑STM͒, [10][11][12][13][14] x-ray diffraction, 15 and neutron scattering.…”

Section: Introductionmentioning

confidence: 99%

“…3,24,25 Of these systems, probably the best characterized are monolayers of C32 and C24 on high-quality graphite basal-plane surfaces that have been investigated by scanning tunneling microscopy ͑STM͒, [10][11][12][13][14] x-ray diffraction, 15 and neutron scattering. [16][17][18][19][20][21] Graphite substrates also have the advantage that relatively reliable empirical atom-atom potentials are available for representing the molecule/graphite basal-plane interaction.…”

Section: Introductionmentioning

confidence: 99%

Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation

Diama

Matthies

Herwig

et al. 2009

The Journal of Chemical Physics

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We present evidence from neutron diffraction measurements and molecular dynamics ͑MD͒ simulations of three different monolayer phases of the intermediate-length alkanes tetracosane ͑n-C 24 H 50 denoted as C24͒ and dotriacontane ͑n-C 32 H 66 denoted as C32͒ 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 ͑RC͒ 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 ͓110͔ direction such that the distance between molecular rows in a lamella is 4.26 Å = ͱ 3a g , where a g = 2.46 Å 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 ϳ10% 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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“…Subsequently, structural studies of short-alkane films (n = 4, 6, and 7) have been extended to synchrotron x-ray scattering experiments on films vapour-deposited on single-crystal Ag(111) substrates in ultrahigh vacuum (UHV) [2]. There have also been neutron diffraction experiments on films of intermediate-length alkanes (n = 24 and 32) deposited both from vapour phase and from solution onto Grafoil substrates [3,4].…”

Section: Introductionmentioning

confidence: 99%

Studies of the structure and growth mode of dotriacontane films by synchrotron x-ray scattering and molecular dynamics simulations

Trogisch

Taub

et al. 2004

J. Phys.: Condens. Matter

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We report on synchrotron x-ray scattering experiments and molecular dynamics simulations of the structure and growth mode of dotriacontane (n-C 32 H 66 or C32) films adsorbed on Ag(111) and SiO 2 -coated Si(100) substrates. On the SiO 2 surface, the x-ray measurements confirm a structural model of the solid film inferred from high-resolution ellipsometry measurements in which one or two layers of C32 adsorb with the long axis of the molecule oriented parallel to the interface followed by a monolayer in which the molecules have a perpendicular orientation. At higher C32 coverages, preferentially oriented bulk particles nucleate, consistent with a Stranski-Krastanov growth mode. On the Ag(111) surface, we again observe one or two layers of the 'parallel' film but no evidence of the perpendicular monolayer before nucleation of the preferentially oriented bulk particles. We compare the experimentally observed structures with molecular dynamics simulations of a multilayer film of the homologous C24 molecule.

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Solvent Effects on the Monolayer Structure of Longn−AlkaneMolecules Adsorbed on Graphite

Cited by 92 publications

References 15 publications

High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation

Studies of the structure and growth mode of dotriacontane films by synchrotron x-ray scattering and molecular dynamics simulations

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