Carbon-hydrogen stretching modes and the structure of n-alkyl chains. 2. Long, all-trans chains

MacPhail, Richard A.; Strauss, Herbert L.; Snyder, Robert; Elliger, Carl A.

doi:10.1021/j150647a002

Cited by 734 publications

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“…The IR-active CH 2 stretch frequencies are sensitive to the local intermolecular interactions and thus serve as the primary indicator of chain order. 46,47 For C18SH on p-Pt, the observed ν a (CH 2 ) frequency (2917 cm -1 ) is characteristic of an ordered, all-trans chain and is essentially the same as those reported in a previous study of SAMs on plasma-cleaned Pt, 5 indicating a similarly high degree of crystalline order. For all monolayers on p-Pt the ν s (CH 2 ) and ν a (CH 2 ) features are strongly suppressed compared to the CH 3 features (Figure 3).…”

Section: Monolayer Thickness Stoichiometry and Molecularsupporting

confidence: 81%

Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

et al. 2006

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We have studied the formation of self-assembled monolayers (SAMs) of n-alkanethiols on platinum thin films using X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and contact angle (CA) measurements. Specifically, SAMs of 1-hexanethiol, 1-dodecanethiol, and 1-octadecanethiol were grown on polycrystalline Pt films, and the effects of Pt surface preparation, deposition conditions, and solvent treatments on the initial quality and stability of the monolayer in air were investigated. The SAMs prepared under ambient conditions on piranha-cleaned and UV/ozone-cleaned substrates were compared to monolayers formed on template-stripped Pt in an inert atmosphere. We found that alkanethiols deposited from 1 mM ethanolic solutions on piranha-cleaned Pt formed densely packed monolayers in which alkyl chains were oriented close to the surface normal. Stored in the laboratory ambient, these monolayers were unchanged over about 1 week but were largely oxidized in about 1 month. No evidence was found of molecules being weakly bound within the monolayer or having undergone C-S bond scission; however, three distinct sulfur states were observed for all samples in the XPS of the S 2p region. The lowest-and highest-binding-energy components are assigned to alkylthiolate and partially oxidized alkylthiolate species, respectively. The remaining S 2p component (approximately one-third of the sulfur layer), intermediate in binding energy between the other two components, is attributed to a chemisorbed species with a S binding configuration distinct from the majority alkylthiolate: for example, S bound to Pt bound to O, S with a different Pt coordination number, or S in an adsorbed disulfide.

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Section: Monolayer Thickness Stoichiometry and Molecularsupporting

confidence: 81%

Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

et al. 2006

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“…The absorption bands of methylene and methyl groups are well separated from other characteristic group frequencies. Therefore, they are widely investigated [12,[109][110][111][112][113][114]. However, most lipid and protein molecules contain a large number of these groups making assignments to a particular molecular structure difficult.…”

Section: Role Of Isotopic Substitution In Biomolecules In a Complex Bmentioning

confidence: 99%

Application of Polarization Modulation Infrared Reflection Absorption Spectrosocpy Under Electrochemical Control for Structural Studies of Biomimetic Assemblies

Brand

2015

Zeitschrift Für Physikalische Chemie

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An ideal bioanalytical method would allow carrying out sensitive, selective, reproducible, fast, and in situ chemical measurements of the composition, structure and function of complex biological systems. Physical chemistry possesses advanced structure analyzing techniques which are suitable to solve, at a sub-molecular level, the structure of biomolecules. However, the prerequisite of the presence of the electrolyte solution limits the number of applicable structure analyzing techniques. Infrared spectroscopy is one of the most powerful analytical techniques used to identify the structure of biomolecules, monitor structural changes under various experimental environments and physical states. In addition, infrared reflection absorption spectroscopy (IRRAS) has been successfully applied to study supramolecular films at the solid|liquid interface. Assemblies of biomolecules belong to a particularly demanding because they bring specific for the maintenance of their functions experimental requirements which have to be taken into account planning in situ spectroelectrochemical experiments. In this paper potnential of in situ IRRAS under electrochemical control for studies of structural changes in assemblies of biomolecules such as lipid bilayers and protein films is described. Studies of different classes of biomolecules bring certain experimetnal conditions concerning the electrolyte composition, pH value, temperature or chemical nature of the solid support, which have to be fulfilled. Obviously, these conditons may significantly restrict the applicability of the in situ PM IRRAS. The selection of the solid substrate with required optical and electrical properties, the optical window and the electrolyte composition have to be adapted to the needs of biomolecules. Adjustement of experimetnal conditions as well as possibilites of the enlargement of the in situ PM IRRAS for studies of biomimetic assemblies is reviewed in this paper. Furthermore, experimetnal resutls reporting potenial driven changes in models of cell membranes and protein films are reviewed. Pioneering studies aiminig at the determination of structural changes in lipid membranes exposed to physiological electric fields and interacting simultaneously with protiens are described.

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“…71−81 Spectral bands in the region from 3200 to 3000 cm −1 are attributed to the coupled aromatic ring C−H stretching vibrations of the imidazolium hydrogen atoms, while those between 3000 and 2850 cm −1 can be assigned to the aliphatic C−H stretches of the CH 2 and CH 3 groups of the ethyl chain and of the CH 3 group bonded directly to the [C 2 MIM + ] ring. [71][72][73][74][75][76][77][78]81 4 ] thin films to water vapor in the sealed ATR cell at different levels of RH at 295 K. After each RH adjustment, spectra were collected until the band intensities stopped changing to ensure that equilibrium was attained. It typically took ∼20 min for the system to equilibrate.…”

Section: ■ Introductionmentioning

confidence: 99%

Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

et al. 2012

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Understanding the interactions of humid air with ionic liquids (ILs) is critical for predicting how their physicochemical properties are affected by water. Using experimental and theoretical techniques, water vapor's interaction with aerosolized nanoparticles and thin films of [C 2 MIM][Cl] and [C 2 MIM][BF 4 ] was studied. Solutions were electrosprayed to produce dry particles. Particles' hygroscopic growth was quantified using tandem nanodifferential mobility analysis as a function of relative humidity (RH). This is the first report of the interaction of water with aerosolized IL nanoparticles. The particles' small size allows true IL−water vapor equilibrium achieved quickly. Growth curves for both ILs show steady water uptake with increasing RH. Water vapor uptake by IL thin films was also examined using ATR-FTIR spectroscopy. . They represent a large class of molecules that have unique and widely tunable physical and chemical properties. 1−3 For example, there is a significant interest in the use of ILs in green chemistry, 2,4,5 due to their negligible vapor pressure at room temperature, 6 and for many other applications including solvents in synthesis and catalysis, 1,6 chemical extraction, 1,2,5 and fuel cells. 7 Physical properties such as conductivity, viscosity, density, and surface tension of ILs are known to depend on the presence of water, both adsorbed and absorbed. 3,8 Water is ubiquitous in the environment, and hygroscopic ILs such as those with imidazolium-based cations can uptake significant amounts of water vapor from ambient air, which alters their physical and chemical properties. 1,3 Thus, quantification of water uptake by hygroscopic ILs and understanding how the presence of water affects the nature of the ion−ion and ion−water interactions are critical for use of ILs in future applications. 8−14 Numerous experimental and theoretical studies have investigated the interaction of imidazolium-based ILs with water. 3,8−35 It is understood that both the cation and the anion have an effect on how ILs interact with water, with the anion having a stronger effect. 3,17,19 Early experimental work by Seddon et al. investigated the miscibility of water with ILs containing 1-nalkyl-3-methylimidazolium ([C n MIM + ], n = number of carbons on the linear alkyl chain) cations and various anions at room temperature. 3 It was determined that, regardless of the alkyl chain length, all halide anions were fully soluble in water and all hexafluorophosphate ([PF 6 − ]) anions were insoluble. 3 However, alkyl chain length did have an effect on water miscibility of [C n MIM + ]-based ILs with tetrafluoroborate ([BF 4 − ]) anions; for chain lengths of n = 2 or 4, the ILs were fully miscible, but for n > 4, the ILs formed biphasic systems. 3 Cammarata et al. performed early attenuated total reflection (ATR) infrared (IR) studies on the molecular states of water

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Carbon-hydrogen stretching modes and the structure of n-alkyl chains. 2. Long, all-trans chains

Cited by 734 publications

References 0 publications

Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

Application of Polarization Modulation Infrared Reflection Absorption Spectrosocpy Under Electrochemical Control for Structural Studies of Biomimetic Assemblies

Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

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