1-Methyl Naphthalene Reorientation at the Air−Liquid Interface upon Water Saturation Studied by Vibrational Broad Bandwidth Sum Frequency Generation Spectroscopy

Hommel, Eva; Allen, Heather C.

doi:10.1021/jp027830e

Cited by 16 publications

(21 citation statements)

References 62 publications

(125 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…No specific trends emerge in Figures and that distinguish chain length or branching, but we note that 1-methylnaphthalene (light blue, MN) lies below the prediction based on its high surface tension in Figure . This molecule, composed of two fused aromatic rings (Figure c), is observed to preferentially stack in a plane perpendicular to the surface. , It is intriguing to speculate that He atoms can pass more easily through gaps between the rigid rings than in spaces between flexible alkyl chains. This interfacial packing should be lost in the DO/SQ/MN mixture as the long-chain alkanes intermix with MN and because MN is depleted from the surface region.…”

Section: Discussionmentioning

confidence: 99%

Probing Gas–Liquid Interfacial Dynamics by Helium Evaporation from Hydrocarbon Liquids and Jet Fuels

et al. 2015

View full text Add to dashboard Cite

We have monitored the speeds of evaporating helium atoms dissolved in liquid octane, isooctane, 1-methylnaphthalene, dodecane, squalane, ethylene glycol, and two jet fuels. In all cases, the average kinetic energies of the evaporating He atoms exceed the Maxwellian value of 2RT. The energies roughly track solvent surface tensions; this correlation may reflect the tighter packing and attractions of interfacial solvent molecules that restrict the gaps through which He atoms escape. Mixtures of dodecane, squalane, and 1-methylnaphthalene generate He evaporation energies that lie between the pure liquid values. We find, however, that He atoms evaporate from pure 1-methylnaphthalene with kinetic energies lower than expected based on its high surface tension, perhaps because the sideways packing of the aromatic rings provides more direct channels for the escaping He atoms. Additionally, He evaporates from two complex fuel mixtures, Jet A and JP-8, with nearly identical energies, implying that the extra additives in JP-8 do not segregate to the surface in ways that alter the dynamics of evaporation. ■ INTRODUCTIONHelium atom scattering is an enormously powerful tool to elucidate the surface structure and surface vibrations of crystalline solids, organic monolayers, and even polymer films. 1−5 The diffraction features that make this technique so useful are unfortunately lost for room-temperature liquids because of long-range disorder and extensive thermal motions that promote energy transfer between the He and surface atoms. However, it may still be possible to glean insights into interfacial motions and packing by replacing He atom scattering with He atom evaporation from liquids. 6 We continue our studies here by measuring the energy distributions of He atoms evaporating from a wide range of linear and branched hydrocarbon liquids, including mixtures, jet fuels, and ethylene glycol (as a model for a deicing additive). The experiments are performed by dissolving He atoms into each liquid, injecting the liquids into a vacuum as microjets, 7,8 and monitoring the velocities of the evaporating He atoms.The evaporation of He atoms dissolved in hydrocarbons, alcohols, and salty water appears to be special: these small and weakly attractive atoms evaporate at speeds that are faster than predicted by a Maxwell−Boltzmann (MB) distribution. This behavior stands in contrast to larger and more polarizable species such as Ar, N 2 , O 2 , H 2 O, CO 2 , HCl, and HNO 3 , which evaporate with flux-weighted average energies of 2RT liq consistent with a MB energy distribution for a liquid at temperature T liq . 6,9 We recently found that the He speed distributions depend on the nature of the solvent molecules, with average kinetic energies ranging from 1.14 × 2RT liq for He evaporation from dodecane to 1.7 × 2RT liq from a 7.5 M LiBr/ H 2 O solution. 6 Detailed balancing of the incoming and outgoing fluxes implies that He atoms must preferentially dissolve at higher kinetic energies as well. 10 In this timereversed picture, the attractive...

show abstract

Section: Discussionmentioning

confidence: 99%

Probing Gas–Liquid Interfacial Dynamics by Helium Evaporation from Hydrocarbon Liquids and Jet Fuels

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Later, Shen and co-workers used SFG to study the neat methanol liquid interface, and in 1993, they reported the first SFG spectrum of the pure water interface . Currently, SFG is the only technique capable of selectively producing vibrational spectra of neat liquid interfaces, liquid/air solution interfaces, or buried liquid/liquid interfaces. ,− …”

Section: Sum Frequency Generationmentioning

confidence: 99%

“…16 Currently, SFG is the only technique capable of selectively producing vibrational spectra of neat liquid interfaces, liquid/air solution interfaces, or buried liquid/liquid interfaces. 1,[17][18][19][20][21][22] The basis for SFG is as follows. When a light beam impinges on a surface, it induces a polarization by exerting a force on the valence electrons.…”

Section: Sum Frequency Generationmentioning

confidence: 99%

Vibrational Spectroscopic Studies of Aqueous Interfaces: Salts, Acids, Bases, and Nanodrops

Gopalakrishnan¹,

Liu²,

Allen³

et al. 2006

Chem. Rev.

Self Cite

418

520

View full text Add to dashboard Cite

show abstract

“…The first factor might be investigated in greater detail with atomistic simulations and surface sensitive spectroscopy (33), whereas a number of new experimental methods are available to probe dynamics at the surface of glasses (25,34). Structure at liquid surfaces is an active area of study (35,36), and our results indicate that physical vapor deposition might be a useful tool in this endeavor.…”

mentioning

confidence: 92%

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

Dalal

Walters

Lyubimov

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

197

351

View full text Add to dashboard Cite

Physical vapor deposition is commonly used to prepare organic glasses that serve as the active layers in light-emitting diodes, photovoltaics, and other devices. Recent work has shown that orienting the molecules in such organic semiconductors can significantly enhance device performance. We apply a high-throughput characterization scheme to investigate the effect of the substrate temperature (T substrate ) on glasses of three organic molecules used as semiconductors. The optical and material properties are evaluated with spectroscopic ellipsometry. We find that molecular orientation in these glasses is continuously tunable and controlled by T substrate /T g , where T g is the glass transition temperature. All three molecules can produce highly anisotropic glasses; the dependence of molecular orientation upon substrate temperature is remarkably similar and nearly independent of molecular length. All three compounds form "stable glasses" with high density and thermal stability, and have properties similar to stable glasses prepared from model glass formers. Simulations reproduce the experimental trends and explain molecular orientation in the deposited glasses in terms of the surface properties of the equilibrium liquid. By showing that organic semiconductors form stable glasses, these results provide an avenue for systematic performance optimization of active layers in organic electronics.glasses | organic semiconductors | molecular orientation | physical vapor deposition | high-throughput characterization

show abstract

1-Methyl Naphthalene Reorientation at the Air−Liquid Interface upon Water Saturation Studied by Vibrational Broad Bandwidth Sum Frequency Generation Spectroscopy

Cited by 16 publications

References 62 publications

Probing Gas–Liquid Interfacial Dynamics by Helium Evaporation from Hydrocarbon Liquids and Jet Fuels

Probing Gas–Liquid Interfacial Dynamics by Helium Evaporation from Hydrocarbon Liquids and Jet Fuels

Vibrational Spectroscopic Studies of Aqueous Interfaces: Salts, Acids, Bases, and Nanodrops

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

Contact Info

Product

Resources

About