Heat Capacity Study of Monolayer Propane on Graphite

Lee, M.-A.; Alkhafaji, M. T.; Migone, Aldo

doi:10.1021/la962017u

Cited by 6 publications

(6 citation statements)

References 28 publications

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“…These weak interactions allow the influence of weak adsorbate−adsorbate interactions to be expressed and investigated. These adsorbed layers have been studied using several approaches including calorimetry, − adsorption isotherms, − X-ray and neutron scattering, − NMR, microscopy, and simulation studies . An overview of various systems and techniques used to study these physisorbed layers can be found in reviews published recently. , …”

Section: Introductionmentioning

confidence: 99%

Crystalline Structures of Alkylamide Monolayers Adsorbed on the Surface of Graphite

Bhinde¹,

Clarke²,

Phillips³

et al. 2010

Langmuir

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Synchrotron X-ray and neutron diffraction have been used to determine the two-dimensional crystalline structures of alkylamides adsorbed on graphite at submonolayer coverage. The calculated structures show that the plane of the carbon backbone of the amide molecules is parallel to the graphite substrate. The molecules form hydrogen-bonded dimers, and adjacent dimers form additional hydrogen bonds yielding extended chains. By presenting data from a number of members of the homologous series, we have identified that these chains pack in different arrangements depending on the number of carbons in the amide molecule. The amide monolayers are found to be very stable relative to other closely related alkyl species, a feature which is attributed to the extensive hydrogen bonding present in these systems. The characteristics of the hydrogen bonds have been determined and are found to be in close agreement with those present in the bulk materials.

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Section: Introductionmentioning

confidence: 99%

Crystalline Structures of Alkylamide Monolayers Adsorbed on the Surface of Graphite

Bhinde¹,

Clarke²,

Phillips³

et al. 2010

Langmuir

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“…We, and others, have previously observed the formation of solid adsorbed monolayers for a wide variety of hydrocarbon and alkyl adsorbates (including the normal alkanes, cyclic alkanes, alkenes, alcohols, carboxylic acids, and amines) using a combination of STM, ,− NMR, , X-ray and neutron scattering, − calorimetry − measurements, and molecular dynamics simulations. − …”

Section: Introductionmentioning

confidence: 99%

“…There are STM reports of alkyl molecules adsorbed in a vertical orientation on graphite, specifically carboxylic acid salts. 11 We, and others, have previously observed the formation of solid adsorbed monolayers for a wide variety of hydrocarbon and alkyl adsorbates (including the normal alkanes, cyclic alkanes, alkenes, alcohols, carboxylic acids, and amines) using a combination of STM, 5,[12][13][14][15][16][17][18] NMR, 19,20 scattering, [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] calorimetry [37][38][39][40][41][42][43][44][45][46] measurements, and molecular dynamics simulations. [47][48][49][50] In this work, we present a differential scanning calorimetry (DSC) study of the solid monolayer formation of alkyl amides adsorbed onto graphite from the liquid and from liquid mixtures for a wide range of alkyl chain lengths, with unsaturation, and for different isomers and their mixtures.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Investigation of the Adsorption of Amides on Graphite from Their Liquids and Binary Mixtures

Arnold¹,

Clarke²

2008

Langmuir

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We report a thermodynamic investigation of the adsorption of saturated and unsaturated (cis- and trans-) alkyl amides onto the surface of graphite from their pure liquids and from binary mixtures. We identify the formation of solid monolayers of the amides at temperatures when the bulk materials are liquid. The extent of this presolidification is much more extensive than other related materials, indicating that these amide layers are significantly more stable. The monolayer stability is found to be greatest for saturated amides. In addition, the stability of unsaturated amides is extremely sensitive to the location of the double bonds in the alkyl chain of the molecules, and trans isomers are found to be more stable than cis. We also address the preferential adsorption and mixing behavior of amide mixtures and amides mixed with other species coadsorbed onto graphite from binary solution. The results indicate that the amide molecules appear to be adsorbed with their principal axis parallel to the graphite surface and that amides are found to be strongly preferentially adsorbed with respect to alkanes. Interestingly the amides appear to mix rather better than might have been expected. There is also evidence of a number of other transitions in the adsorbates.

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“…Additional insight can be gained by considering earlier thermodynamic studies of ethane and propane films on graphite. − It has been suggested that ethane exhibits an ordered liquid phase on graphite up to 95 K. Studies by Migone et al reveal that monolayer propane films have thermodynamic signatures consistent with an ordered fluid phase. Thus, it is quite possible that the abrupt stepwise increase in adsorption curves upon bilayer formation observed here for ethane and propane signals the formation of an ordered (second layer) fluid.…”

Section: Resultsmentioning

confidence: 99%

“…Extensive literature exists on atomic and molecular adsorption on the surface of graphite. A subset of this work has focused on the interaction of alkanes on the basal plane of graphite using heat capacity and diffraction measurements. − In contrast, studies of adsorption on hBN are less substantial. Nearly four decades ago, Bockel et al published a limited set of adsorption isotherms of methane on hBN between 77 and 90 K. On the basis of these measurements, they proposed a 2D critical temperature of ∼77 K. Several years later, Tessier and Larher extended the adsorption studies of Bockel et al to lower temperatures and to include deuterated-methane on hBN.…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Volumetric Adsorption and Molecular Dynamics of then-Alkanes on the Surface of Hexagonal Boron Nitride

Strange

Larese

2018

J. Phys. Chem. C

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High-resolution, volumetric adsorption isotherm measurements of methane through octane on hexagonal boron nitride (hBN) were performed in the vicinity of their bulk triple-point temperatures. It is observed that the adsorption behavior can be classified into three regimes depending on the molecular geometry and chain length; i.e., quasispherical, cigarlike, and rodlike. The film growth is observed to change from six discrete steps, i.e., layer-by-layer like, to two discrete steps, i.e., incomplete wetting as the molecular length increases. The heat of adsorption and differential entropy and enthalpy were calculated from these isotherm data for monolayer, bilayer, and where possible, thicker films. It is found that the monolayer heat of adsorption exhibits a smooth increase with increasing chain length. Molecular dynamics simulations were performed to provide complementary microscopic insight into the adsorption properties of these alkanes on hBN. Concentration profiles (C(z)) normal to the hBN surface plane calculated using these modeling studies reveal that with increasing chain length, there is less stratification of individual layers. The simulations also clearly show that at the highest temperatures, interlayer traffic increases. The resulting fluidlike upper layers are found to stabilize the solid layer closest to the surface such that it melts near or above the bulk triple point.

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Heat Capacity Study of Monolayer Propane on Graphite

Cited by 6 publications

References 28 publications

Crystalline Structures of Alkylamide Monolayers Adsorbed on the Surface of Graphite

Crystalline Structures of Alkylamide Monolayers Adsorbed on the Surface of Graphite

Thermodynamic Investigation of the Adsorption of Amides on Graphite from Their Liquids and Binary Mixtures

High-Resolution Volumetric Adsorption and Molecular Dynamics of then-Alkanes on the Surface of Hexagonal Boron Nitride

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