Structure, reactivity and microrheology in self-assembled monolayers

Garrell, Robin L.; Chadwick, Janice E.

doi:10.1016/0927-7757(94)02869-9

Cited by 16 publications

(14 citation statements)

References 21 publications

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“…We find evidence for limited desorption as disulfides for aryl thiols, but no oxidation products. In contrast, because alkane thiols are less resistant to oxidation, desorption as sulfinate or sulfonate cannot be ruled out in our previous work.…”

Section: Discussionmentioning

confidence: 76%

“…The most extensively studied monolayer assemblies on Au are those spontaneously formed from long-chain alkanethiol or disulfide solutions . Although these self-assembled monolayers (SAMs) are the most comprehensively studied monolayer films due to their high degree of structural order, recent interest has developed in organosulfur monolayers that are bound to Au via an aromatic moiety. − It appears that the thiolate headgroup of alkanethiol SAMs is prone to oxidation under ambient conditions, resulting in the formation of sulfinates and sulfonates . These oxidized monolayers have compromised structural stability because they are no longer chemisorbed and can be washed away. , It has been suggested that when the mercapto group is directly attached to an aryl, the thiolate is less prone to oxidation under ambient conditions …”

Section: Introductionmentioning

confidence: 99%

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Self-Assembled Monolayers of an Aryl Thiol: Formation, Stability, and Exchange of Adsorbed 2-Naphthalenethiol and Bis(2-naphthyl) Disulfide on Au

Kolega

Schlenoff

1998

Langmuir

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The adsorption of 2-naphthalenethiol and bis(2-naphthyl) disulfide onto bulk Au has been indirectly quantified from the adsorbate solution by liquid chromatography. A study of the kinetics of monolayer formation and exchange of these adsorbants has been carried out. Using chromatographic retention times and diode array spectroscopy, the products of desorption and exchange have been identified directly. For both aryl-derived monolayers, desorption in pure solvent yields bis(2-naphthyl) disulfide. Exchange of both aryl monolayers with decanethiol is observed, with 2-naphthalenethiol as the sole product, suggesting that exchange involves proton transfer at the Au surface rather than monolayer desorption followed by addition. Exchange of the aryl monolayers with didecyl disulfide is much slower and yields decyl 2-naphthyl disulfide. A comparison of the coverage of the aryl monolayers obtained by chromatography has been made with voltammetric reductive desorption. Confirmation of reductive thiolate desorption by voltammetry is obtained by in situ ultraviolet−visible spectroscopy. Thiolate oxidation of the polycyclic aromatic monolayers under aerobic conditions was not observed. Estimates of the free energies of adsorption for aliphatic and aromatic thiols provide similar values, indicating no strong preference by Au for either type of thiol. Similar conclusions are reached concerning the respective disulfides.

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Section: Discussionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Self-Assembled Monolayers of an Aryl Thiol: Formation, Stability, and Exchange of Adsorbed 2-Naphthalenethiol and Bis(2-naphthyl) Disulfide on Au

Kolega

Schlenoff

1998

Langmuir

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“…Finally, the stability of thiophenol (TP) SAMs on Ag was briefly investigated. Garrell and co-workers have reported that monolayers formed from aromatic thiols on Au are significantly more robust and less prone to air and electrochemical oxidation than alkanethiol SAMs. ,, Raman spectra for TP SAMs before and after O 3 exposure are shown in Figure . The ca.…”

Section: Resultsmentioning

confidence: 99%

Air Stability of Alkanethiol Self-Assembled Monolayers on Silver and Gold Surfaces

1998

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Surface Raman spectroscopy, electrochemistry, and X-ray photoelectron spectroscopy have been used to study the effects of air exposure on the stability of self-assembled monolayers (SAMs) formed from alkanethiols on mechanically polished, smooth Ag and Au surfaces. Raman spectra exhibit oxidized sulfur modes after only hours of air exposure. X-ray photoelectron spectroscopy of the S 2p region provides additional evidence for sulfur oxidation. Cyclic voltammetry of Ru(NH3)6 3+ indicates that oxidized alkanethiol SAMs retain blocking characteristics toward electron transfer, even after exposure of the oxidized SAM-surface to a solubilizing solvent. Control experiments suggest ozone as the primary oxidant in ambient laboratory air which causes rapid oxidation of the thiolate moiety. These results have important ramifications for the general use of SAMs in many proposed applications.

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“…The shear parameter set was determined from the best-Ðt values of G@ and GA using eqn. ( 4)È (8). The coating thickness necessary for an unambiguous determination of the shear modulus was calculated from the absolute frequency shift at [50 ¡C (after coating) using eqn.…”

Section: Extraction Of Shear Parametersmentioning

confidence: 99%