Organosilane Chemical Gradients: Progress, Properties, and Promise

Collinson, Maryanne M.; Higgins, Daniel A.

doi:10.1021/acs.langmuir.7b02259

Cited by 17 publications

(21 citation statements)

References 121 publications

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“…Due to the versatility associated with the sol–gel route, materials with very different physical and chemical properties can be made. 1 In the present work, the base layer provides a uniform surface for attachment of the reactive silanol groups particularly for substrates that lack such reactive groups; 13 it can also be used to provide additional functionality to the surface. 20 Aligned gradients are formed when the individual gradients in amine and thiol are in the same direction, and opposed gradients are formed when the individual gradients run in opposite directions.…”

Section: Resultsmentioning

confidence: 99%

“…A multicomponent gradient surface is one where two or more functional groups are spatially distributed in an increasing or decreasing fashion along the length of a substrate. 1 − 6 As described in several reviews, gradient materials can be prepared in different ways that include self-assembly, dip coating, cross diffusion, electrochemical deposition, microfluidic mixing, and immersion. 1 − 6 Silane, polymer, and thiol chemistry have all been used to make these materials on a variety of surfaces including siloxane surfaces, electrodes, polymeric scaffolds, hydrogels, and even monoliths.…”

Section: Introductionmentioning

confidence: 99%

“… 1 − 6 As described in several reviews, gradient materials can be prepared in different ways that include self-assembly, dip coating, cross diffusion, electrochemical deposition, microfluidic mixing, and immersion. 1 − 6 Silane, polymer, and thiol chemistry have all been used to make these materials on a variety of surfaces including siloxane surfaces, electrodes, polymeric scaffolds, hydrogels, and even monoliths. 1 − 6 The close proximity of the different functional groups allows for specific interactions to take place between them and/or a reagent in solution.…”

Section: Introductionmentioning

confidence: 99%

“… 1 − 6 Silane, polymer, and thiol chemistry have all been used to make these materials on a variety of surfaces including siloxane surfaces, electrodes, polymeric scaffolds, hydrogels, and even monoliths. 1 − 6 The close proximity of the different functional groups allows for specific interactions to take place between them and/or a reagent in solution. These interactions are critical in many fields of science including separation science, 7 , 8 catalysis, 9 − 11 and imprinted materials, 12 and they are thus important to study and understand.…”

Section: Introductionmentioning

confidence: 99%

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On the Importance of Silane Infusion Order on the Microscopic and Macroscopic Properties of Multifunctional Charge Gradients

et al. 2020

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Four multicomponent charge gradients containing acidic and basic functionalities were prepared via sol–gel processes and the controlled-rate infusion (CRI) method to more clearly understand how preparation conditions influence macroscopic properties. CRI is used to form gradients by infusing reactive alkoxysilanes into a glass vial housing a vertically oriented modified silicon wafer. The concentration and time of infusion of the silane solutions were kept constant. Only the sequence of infusion of the silane solutions was changed. The first set of samples was prepared by initially infusing a solution containing 3-aminopropyltriethoxysilane (APTES) followed by a mercaptopropyltrimethoxysilane (MPTMS) solution. The individual gradients were formed either in an aligned or opposed fashion with respect to the initial gradient. The second set of samples was prepared by infusing the MPTMS solution first followed by the APTES solution, again in either an aligned or opposed fashion. To create charge gradients (NH 3 + , SO 3 – ), the samples were immersed into H 2 O 2 . The extent of modification, the degree of protonation of the amine, and the thicknesses of the individual layers were examined by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. The wettability of the individual gradients was assessed via static contact angle measurements. The results demonstrate the importance of infusion order and how it influences the macroscopic and microscopic properties of gradient surfaces including the surface concentration, packing density, degree of protonation, and ultimately wettability. When the gradient materials are prepared via infusion of the APTES sol first, it results in increased deposition of both the amine and thiol groups as evidenced by XPS. Interestingly, the total thickness evaluated from ellipsometry was independent of the infusion order for the aligned gradients, indicative of significant differences in the film density. For the opposed gradients, however, the infusion of APTES first leads to a significantly thicker composite film. Furthermore, it also leads to a more pronounced gradient in the protonation of the amine, which introduces a very different surface wettability. The use of aminosilanes provides a viable approach to create gradient surfaces with different functional group distributions. These studies demonstrate that the controlled placement of functional groups on a surface can provide a new route to prepare gradient materials with improved performance.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the Importance of Silane Infusion Order on the Microscopic and Macroscopic Properties of Multifunctional Charge Gradients

et al. 2020

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“…Constructive CRI (i.e., adding ligands to a substrate) is a costefficient and straightforward method to produce multicomponent chemical gradients on silica supports, by exposing one end of a substrate longer than another to a hydrolyzed organosilane solution. [17][18][19][20][21]31,32 Adaption of constructive CRI to a particle packed column that is suitable for LC, however, has not been attainable until now. Compared to planar substrates and monolithic columns, the time-dependent modication of a traditional LC packed column in situ is much more challenging, not only because of the increased back pressure required for infusion into a packed column, but also because of the high surface area and microporosity of the silica powder.…”

Section: Fabrication Of Stationary Phase Gradient Columnsmentioning

confidence: 99%

In situ silanization for continuous stationary phase gradients on particle packed LC columns

et al. 2019

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Creating Directionality in Nanoporous Carbon Materials: Adjustable Combinations of Structural and Chemical Gradients

Bahner

Klinkenberg

Frisch

et al. 2019

Adv Funct Materials

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The properties of porous materials benefit from hierarchical porosity. A less noted element of hierarchy is the occurrence of directionality in functional gradient materials. A sharp boundary is replaced by a transition from one feature to the next. The number of cases known for porous materials with either structural or chemical gradients is small. A method capable of generating combinations of structural and chemical gradients in one material does not exist. Such a method is presented with a focus on silver and nitrogen containing carbon materials because of the potential of this system for electrocatalytic CO2 reduction. A structural gradient results from controlled separation using ultracentrifugation of a binary mixture of template particles in a resorcinol–formaldehyde (RF) sol as carbon precursor. A new level of complexity can be reached, if the surfaces of the template particles are chemically modified. Although the template is removed during carbonization, the modification (Ag, N) becomes integrated into the material. Understanding how modified and unmodified large and small particles sediment in the RF sol enables almost infinite variability of combinations: chemically graded but structurally homogeneous materials and vice versa. Ultimately, a material containing one structural gradient and two chemical gradients with opposing directions is introduced.

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Organosilane Chemical Gradients: Progress, Properties, and Promise

Cited by 17 publications

References 121 publications

On the Importance of Silane Infusion Order on the Microscopic and Macroscopic Properties of Multifunctional Charge Gradients

On the Importance of Silane Infusion Order on the Microscopic and Macroscopic Properties of Multifunctional Charge Gradients

In situ silanization for continuous stationary phase gradients on particle packed LC columns

Creating Directionality in Nanoporous Carbon Materials: Adjustable Combinations of Structural and Chemical Gradients

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