Mixed alkanethiol monolayers on gold surfaces: Wetting and stability studies

Ulman, Abraham; Evans, Stephen D.; Shnidman, Yitzhak; Sharma, Ram V.; Eilers, James E.

doi:10.1016/0001-8686(92)80060-b

Cited by 54 publications

(56 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, contact angles measured on rough surfaces are found to be larger than those measured on smooth, and chemically identical, surfaces [25]. It is also important to note that the contact angle estimated from wicking measurements represents an advancing contact angle, and it is commonly accepted [17,[26][27][28] that this angle on a heterogeneous surface is related to regions with lower-energy components.…”

Section: Resultsmentioning

confidence: 99%

Factors influencing contact angle measurements on wood particles by column wicking

Wålinder

Gardner

1999

Journal of Adhesion Science and Technology

View full text Add to dashboard Cite

The present work focuses on a capillary rise technique, referred to here as column wicking, for determining contact angles on wood particles. The liquid front rise versus time for different probe liquids has been measured for extracted and non-extracted spruce wood particles packed into glass columns. Wood is a porous, heterogeneous, and hygroscopic material. The sorption process of certain polar liquids in the wood substance, i.e. bulk sorption, is exothermic and causes swelling. This bulk sorption process and the resulting release of heat are observed as a distinct temperature increase within the columns during the wicking of water, formamide, and methanol. No temperature increase is observed for ethylene glycol, diiodomethane, and hexane. In some cases, the increase in temperature is observed in advance of the moving visible liquid front line. This may indicate that vapor is moving in advance of the liquid front, resulting in bulk sorption and the corresponding release of heat. An apparent non-linearity is observed when the square of the capillary rise is plotted versus time, mainly for water, formamide, and methanol. This non-linearity is strongly dependent on the probe liquid used and the variation in wood particle size. For the wicking of water, the bulk sorption, and hence the swelling of the wood particles, seems to appear instantaneously at the wetting front line, but for formamide and methanol a time delay is observed. The bulk sorption and resulting swelling of the wood particles strongly influence the determination of the effective interstitial pore radius between the particles, and thus the determination of contact angles by use of the Washburn equation.

show abstract

Section: Resultsmentioning

confidence: 99%

Factors influencing contact angle measurements on wood particles by column wicking

Wålinder

Gardner

1999

Journal of Adhesion Science and Technology

View full text Add to dashboard Cite

show abstract

“…3,4 Since most macroscopic interfacial phenomena, including adhesion, wetting, and friction are determined primarily by the properties of the outer ~5-10 Å surface molecular groups, 27 such SAMs may serve as models for polymer surfaces. However, while SAMs of thiolates on Au(111) have been used extensively as model systems for the studies of wetting, 28 they have been used only recently for systematic adhesion studies.…”

Section: Acid-base Interactionsmentioning

confidence: 99%

Adhesion studies using contact mechanics

Ulman¹,

Choi²,

Shnidman³

et al. 2000

Israel Journal of Chemistry

Self Cite

View full text Add to dashboard Cite

We report adhesion studies using the JKR contact mechanics method and poly(dimethylsiloxane) (PDMS) cross‐linked networks. When such networks are extracted, interdigitation of tethered chains into extraction zones at the network‐network interface results in a significant enhancement of adhesion. When these networks come into contact with a silicon oxide surface, an increase in adhesion hysteresis is observed in the order of increasing molecular weight between crosslinks, with a scaling factor of 1/2. Subjecting the system to maximum load for 30 min before unloading results in a scaling factor of 1/3, probably due to molecular weight dependent network relaxation rates. PDMS cross‐link networks form H‐bonds with surface Si–OH groups that result in significant and time‐dependent adhesion increase. Systematic studies of interfacial H‐bonding and its effect on adhesion have been carried out using self‐assembled monolayer (SAM) surfaces. An increase in adhesion strength was observed in the order of increasing acidity of surface OH protons [Au/S(CH2)11OH < Au/S(C6H4)2OH < Au/S(CH2)15COOH < Au/S(CH2)11PO(OH)2]. When surface OH concentration was controlled, the strength of adhesion was found to be proportional to the number of surface OH groups, with nonlinear relationship, probably due to the collective nature of H‐bonding between the PDMS chain and surface OH groups. Isotope effect studies confirmed the formation of interfacial H‐bonding.

show abstract

“…41,42 By introducing different terminal functional groups of the alkane thiols, the (macroscopic or microscopic) surface wettability, adhesion processes, and interfacial chemical properties can be modified. 43,44,45,46,47 Importantly, the surface wettability can be tailored in a continuous manner by adjusting the surface composition of the mixed SAMs. 40,41,48 In principle, an arbitrary composition of SAMs can be achieved by exposing the substrate in an adsorbate mixture solution with a defined concentration ratio.…”

Section: Introductionmentioning

confidence: 99%

“…In general, SAMs of alkanethiols and disulfides have been extensively studied as model organic films with well-defined chemical and structural properties. , Via the introduction of different terminal functional groups of the alkanethiols, the (macroscopic or microscopic) surface wettability, adhesion processes, and interfacial chemical properties can be modified. − Importantly, the surface wettability can be tailored in a continuous manner by adjusting the surface composition of the mixed SAMs. ,, In principle, an arbitrary composition of SAMs can be achieved by exposing the substrate in an adsorbate mixture solution with a defined concentration ratio. However, because of the kinetic control of the composition of the resulting binary SAM, which results in the preferential adsorption of one of the components, ,− the surface composition often differs markedly from the solution composition and must be experimentally determined.…”

Section: Introductionmentioning

confidence: 99%

Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles

2016

View full text Add to dashboard Cite

The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired in situ on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili-Gee model suggests that the binary SAMs do not segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8-10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties.

show abstract

Mixed alkanethiol monolayers on gold surfaces: Wetting and stability studies

Cited by 54 publications

References 59 publications

Factors influencing contact angle measurements on wood particles by column wicking

Factors influencing contact angle measurements on wood particles by column wicking

Adhesion studies using contact mechanics

Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles

Contact Info

Product

Resources

About