Formation and characterization of a highly ordered and well-anchored alkylsilane monolayer on mica by self-assembly

Kessel, Carl R.; Granick, Steve

doi:10.1021/la00051a020

Cited by 237 publications

(174 citation statements)

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“…After that, they were rendered hydrophobic by allowing hydrolyzed OTE to selfassemble from a dilute hydrocarbon solution. The technique for monolayer self-assembly was described previously, 20 except that the oven-baking step was omitted. The advancing contact angle of water was approximately 95°.…”

Section: Methodsmentioning

confidence: 99%

Surface Diffusion of Poly(ethylene glycol)

et al. 2002

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We report direct measurement of the center-of-mass diffusion coefficient, D, of uncharged flexible linear chains adsorbed at the solid-liquid interface at dilute surface coverage. We find D ∼ N -3/2 (N is degree of polymerization) when N was varied by more than an order of magnitude (N ) 48, 113, 244, 456, and 693) and the scatter of the data was low. The experimental system was poly(ethylene glycol), PEG, adsorbed from dilute aqueous solution onto a self-assembled hydrophobic monolayer, condensed octadecyltriethoxysilane. The method of measurement was fluorescence correlation spectroscopy of a rhodamine green derivative dye that was end-attached to one sole end of the adsorbed PEG chains. The observed scaling implies the diffusion time τ ∼ N 3 if Rg ∼ N 3/4 as expected for a chain in good solvent in two dimensions (Rg is the radius of gyration), but a variety of other theoretical approaches to describe the dynamical scaling are also plausible. The multiplicity of plausible dynamical transport scenarios is compounded by the fact that polymer diffusion is sensitive to chain conformation on the surface which is not directly observable. Various theoretical scenarios are explored, and the need for new experiments, theory, and computer simulation studies to allow definitive interpretation of this observation of simple and clean fractional power law scaling is emphasized.

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Section: Methodsmentioning

confidence: 99%

Surface Diffusion of Poly(ethylene glycol)

et al. 2002

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“…Octadecyltrichlorosilane is highly susceptible to hydrolysis and pre-crosslinking. If care is not taken to exclude water until the appropriate time, a three-dimensional network ("gelslug") can settle on a substrate (Wood and Shatma, 1994;Kessel and Granick, 1991). The use of surfaces with a large degree of functionality can mask the gelslug, but this is not the case for montmorillonite.…”

Section: Thermal Analysismentioning

confidence: 99%

“…In fact, Giaquinta et al (1997) have tested this method to encapsulate uranium in different oxidation states for environmental remediation purposes. This encapsulating methodology is similar to the self-assembled monolayer technique that has been developed for formation of well-ordered monolayers on a variety of functional surfaces, such as silicon dioxide (Wasserman et al, 1989;Maoz and Sagiv, 1987), gold (Nuzzo et al, 1987;Porter et al, 1987), alumina (A1-lara and Nuzzo, 1985;Ogawa et al, 1985), and mica (Kessel and Granick, 1991).…”

Section: Surface-area Measurementsmentioning

confidence: 99%

“…Various methods have been employed to increase the number of surface-OH groups on mica (which is nearly devoid of active surface sites), which act as anchoring points for additional surface-OH groups. For example, increased coverage by silanes on mica was attained by (1) pre-treatment with water and hydrochloric acid for octadecyltrichlorosilane (C18H37SIC13) coverage (Carson and Granick, 1990), (2) prehydrolysis of alkyltrialkoxysilanes followed by monolayer self-assembly (Kessel and Granick, 1991), (3) pretreatment with water vapor plasma (Parker et aL, 1989(Parker et aL, , 1990, and (4) a combination of (2) and (3) (Wood and Sharma, 1994). The objective of the acid pre-treatment is to remove octahedral cations, each of which leaves behind two additional Si-OH groups (RausellColom and Serratosa, 1987).…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Montmorillonite Surfaces After Modification by Organosilane

Song

Sandı́

2001

Clays and clay miner.

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Abstract--X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), surface area measurements, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to examine the surface properties of organosilane-modified smectite-type aluminosilicate clays. Organic modified clays derived from the reactions of montmorillonite (containing 93-95% montmorillonite from a bentonite, <1% quartz, and 4-6% opal CT) with octadecyltrichlorosilane (C~sH37SiCI3) and octadecyltrimethoxysilane [CIsH37Si(OMe)3] are highly hydrophobic. Surface loadings of the modified clays depend on the organosilane and the solvent, and they range from 10 to 25 wt. %. The organic species are probably adsorbed to the outer surfaces and bound to the edges of the clay via condensation with edge-OH groups.Encapsulation of montmorillonite with CIsH37SiC13 and ClgH37Si(OMe)3 resulted in a hydrophobic coating that acts like a "cage" around the clay particles to limit diffusion. Basal spacings of the organic modified claysoremain at --15 A upon heating to 400~ in N2, whereas those of unmodified clays collapse to --10 A. A considerable reduction in surface area (by 75-90%) for organic modified clays is observed, which is consistent with the existence of a surface coating. The solvent used can affect the amount of organic silane coated on the clay particles, whereas the difference between the products prepared using C18H37SIC13 and ClsH37Si(OMe)3 in the same solvent is relatively small. The carbon and oxygen K-edge NEXAFS spectroscopy of the modified montmorillonite surfaces showed that surface coatings on the outside of the clay particles exist. The encapsulating system may allow for economical remediation and storage of hazardous materials.

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“…15 The degree of the introduction was evaluated by the contact angle of water; values from 90° to 105 were obtained, depending on the period of the treatment.…”

Section: Methodsmentioning

confidence: 99%

Simultaneous Measurement System for an Adsorbed Substance on a Glass Slab Optical Waveguide and a Dissolved Substance in Liquid-Phase by Visible Absorption Spectrometryt

et al. 1995

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A slab optical waveguide (SOWG) is an element which can transmit light through a thin layer with a minimum attenuation of the light power. Since the refractive index of the thin layer (guiding layer) is higher than those of the outer atmosphere, typically air and a solvent, and of the substrate of the SOWG (Fig. 1), incident light is transmitted through the guiding layer based on total reflection. When the SOWG is applied to spectroscopic measurements, an evanescent wave from the SOWG surface is used for exciting an analyte. Thus, only the surface phenomena of the SOWG can be observed. Moreover, the guiding layer is so thin that the number of reflections often becomes more than one hundred per 1 cm, which results in a remarkable enhancement of the sensitivity. Recently, the SOWG has often been applied to analytical chemistry, e.g., opto-chemical sensorsl-4, opto-biosensors5-', and highly sensitive spectroscopic measurements of a thin film and its surface.g-11We have also been applying the glass SOWG to an absorption detector of flow analysis to detect trace amounts of several dyes and iron(II).12-14 These analytes were adsorbed onto the SOWG and detected by this method. In principle, the SOWG absorption detector is sensitive to an adsorbed chromophore onto the SOWG surface, while it is almost insensitive to a dissolved substance in solution. Thus, the sample matrix scarcely interferes with the SOWG measurements. Moreover, the SOWG detector showed a fairly high sensitivity for those analytes, i, e., several-times better than conventional spectrophotometry with a 0.5 ml of sample. In these studies, however, only less than 1% of the analytes was adsorbed onto the SOWG surface. Hence, further improvements in the sensitivity could be achieved if greater adsorption of analytes could be achieved. For such purpose, it is necessary to understand the adsorption mechanism of analytes onto the glass surface. In this study, we developed a simultaneous measurement system for both an adsorbed substance onto the SOWG surface and a dissolved substance in a flow cell by visible absorption spectrometry. This system was applied to a study of the adsorption behavior of Methylene Blue (MB) onto the SOWG surface.

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Formation and characterization of a highly ordered and well-anchored alkylsilane monolayer on mica by self-assembly

Cited by 237 publications

References 1 publication

Surface Diffusion of Poly(ethylene glycol)

Surface Diffusion of Poly(ethylene glycol)

Characterization of Montmorillonite Surfaces After Modification by Organosilane

Simultaneous Measurement System for an Adsorbed Substance on a Glass Slab Optical Waveguide and a Dissolved Substance in Liquid-Phase by Visible Absorption Spectrometryt

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