Showing papers in "Langmuir in 1988"

Additive and nonadditive surface tension components and the interpretation of contact angles

Abstract: It is demonstrated that, while the Lifshitz-van der Waals (rLW) and the polar, Lewis acid-base (rAB) surface tension components are additive, the Lewis acid-base electron-acceptor (7') and electron-donor (y-) surface tension parameters (which on account of the intrinsic asymmetry of their interactions are connected in a more complex manner) are not additive. Contact angle data cannot, in general, be correlated with a single surface tension property. The relation between contact angles and the three controlling parameters ybw, yg, and 7s of a polar solid, S, cannot be established by means of one single equation. These three unknowns can, however, be determined by means of contact angle measurements with three different liquids L (of which two must be polar and H-bonding), which are completely characterized as to their respective rkw, yL+, and y i parameters by using a modified Young-Good-GirifalcoFowkes equation 3 times. In view of these considerations. recent claims to have proven the applicability of a single "equation of state" are shown to be spurious.

Structures of self-assembled monolayer films of organosulfur compounds adsorbed on gold single crystals: electron diffraction studies

Abstract: : Transmission electron microscopy and diffraction have been used to study the packing arrangements of docosyl thiol (RSH), didocosyl sulfide (RSR), and didocosyl disulfide (RSSR) on gold single crystal foils. The specimens include gold films in (100) and (111) orientations. Docosyl thiol and didocosyl disulfide adsorbed on (111) faces assemble in coincidence lattice structures yielding hexagonal overlayers c(7 x 7) in which the short interchain distance indicates freely rotating methylene chains. On a (100) surface both alkyl groups exhibit an in-plane structure consisting of a base-centered square array in which the interchain distance implies a hindered chain movement. We have presented evidence that substrate crystallography does control the packing of monolayer alkyl sulfides adsorbed from the solution phase.

Monolayer Films Prepared by the Spontaneous Self-Assembly of Symmetrical and Unsymmetrical Dialkyl Sulfides from Solution onto Gold Substrates: Structure, Properties, and Reactivity of Constituent Functional Groups

Abstract: : Exposure of evaporated gold films supported on silicon wafers to solutions of dialkyl sulfides (R(CH2)m-S-(CH2)n-R'; R and R'=CH3 or CO2H) or alkyl thiols (R(CH2)nSH, R=CO2H or CH3) in methanol or ethanol results in rapid formation of a monolayer of the organosulfer compound adsorbed onto the gold. The resulting films have been characterized using a number of techniques, including X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IRS), ellipsometry, and wetting. These self-assembled, supported organic monolayer films are systems that can be used to study problems in the physical-organic chemistry and materials science of organic surfaces, especially the relation between the molecular-level structure of the film constituents and the macroscopic properties of the assembled monolayers. Keywords: Thin film, Monolayer, Surface spectroscopy, electronic materials

Surface Raman spectroscopy of a number of cyclic aromatic molecules adsorbed on silver: selection rules and molecular reorientation

Abstract: Etude par spectrometrie SERS de l'adsorption de plusieurs composes aromatiques (derive benzenique, pyrazine, pyridine) sur l'argent. Interpretation des variations dans les spectres par une reorientation moleculaire a la surface

General patterns of the phase behavior of mixtures of water, nonpolar solvents, amphiphiles, and electrolytes. 2

Abstract: Determination des diagrammes de phase pour les systemes eau-NaCl-agent de surface non ionique

Preparation and properties of monodispersed colloidal particles of lanthanide compounds. 2. Cerium(IV)

Abstract: Preparation d'une suspension colloidale d'oxyde de cerium. Determination des proprietes optiques et des proprietes de surface d'une telle suspension

Wetting of functionalized polyethylene film having ionizable organic acids and bases at the polymer-water interface: relations between functional group polarity, extent of ionization, and contact angle with water

Abstract: : This paper examines the wetting by water of low density polyethylene film modified at the polymer water (air) interface by introduction of polar organic functional groups (carboxylic acids, amines, and others). Water/polymer contact angles were determined for each of these interfaces; for interfaces containing acidic or basic functional groups, the contact angle was determined as a function of the pH. The observed contact angle was related to the hydrophilicity of these functional groups: as the hydrophilicity (as measured by Hansch pi parameters) increased up to a certain point, the contact angle decreased. Beyond that point, increased hydrophilicity had little additional influence on the contact angle. The result is interpreted in terms of water adsorbed on the polar interfacial functional groups: extensive hydration of interfacial groups having large negative pi parameters moderates their effective hydrophilicity. Keywords: Polyethylene, Wettability, Ionization, Acids, Bases, Monolayers, Gold.

Adsorption and decomposition of aliphatic alcohols on titania

Abstract: Etude, par thermodesorption, de l'adsorption puis de la decomposition chimique du methanol, ethanol, propanol-1 et propanol-2 sur le dioxyde de titane

In-plane structure of underpotentially deposited copper on gold(111) determined by surface EXAFS

Abstract: Presentation des spectres de SEXAFS en incidence rasante de la couche de Cu deposee de facon electrochimique sur une electrode Au(111) immergee en solution sous potentiel controle. Les rayons X sont polarises parallelement a la surface d'or. Analyse de la fonction de distribution radiale

Light scattering from simulated smoke agglomerates

Abstract: Etude de la croissance des agglomerats de fumee par une technique de simulation par ordinateur. Mesure par diffusion de lumiere, de la concentration, de la dimension fractale et de la taille des agregats

Langmuir-blodgett films of an enzyme-lipid complex for sensor membranes

Abstract: Preparation de couches monomoleculaires de glucose oxydase, deposees sur une electrode de platine

Study of viscoelasticity of soluble monolayers using analysis of propagation of excited capillary waves

Abstract: Etude par propagation d'ondes capillaires, de la viscoelasticite superficielle des couches monomoleculaires de bromure de dodecyltrimethylammonium

Direct observation of the surfaces of small metal crystallites: rhodium supported on TiO2

Abstract: Utilisation de la microscopie electronique a transmission pour la detection de couches subnanometriques importantes du point de vue catalytique

An efficient method for the determination of interfacial tensions from drop profiles

Abstract: Determination de la tension interfaciale entre deux liquides par la methode de la goutte pendante et de la goutte sessile

Pathways for carboxylic acid decomposition on titania

Abstract: Etude de l'adsorption puis de la decomposition chimique de l'acide formique, acetique et propionique sur le dioxyde de titane

Fluorescence enhancement from Langmuir-Blodgett monolayers on silver island films

Abstract: guishing high and low Si/Al ratio zeolites and may be important in studies of zeolites that are chemically or physically altered. ence Foundation under Grant CHE 8204417 is gratefully acknowledged. We thank Professor T. L. Barr, Professor J. Vedrine, Dr. C. D. Wagner, Dr. J. M. Stencel, and Dr. T. D. Debies for helpful discussions and for their comments and suggestions concerning this manuscript. Acknowledgment. The support of the National Sci-