Biomimetic Thin-Film Synthesis

Rieke, Peter C.; Tarasevich, Barbara J.; Bentjen, Susan B.; Fryxell, Glen E.; Campbell, Allison A.

doi:10.1021/bk-1992-0499.ch006

Cited by 14 publications

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“…It appears, though, that the orientational effect was less strong than that which can be achieved in the Langmuir monolayer studies where the ligands are presented in a two-dimensional lattice. − ,, However, direct comparison is not fully valid at this point because we have not quantified the density of the immobilized NTA. Toward the further study of the influence of functional group stereochemistry it is clear that the next step would be to both increase the number of ligand interactions per surface bound unit (i.e., immobilize face-specific oligomers or polymers) as well as increase the density of units, perhaps by employing self-assembled films. , …”

Section: Discussionmentioning

confidence: 99%

“…Crystal nucleation and growth at organic interfaces often have an important role in biological mineralization and may also be involved in some geological cementation processes. Recently, crystal growth at synthetic organic interfaces has become an active area of research because of the relevance to understanding biomineralization − as well as the more practical objectives of novel processing of thin films − and substance purification. , Model studies of crystallization at interfaces such as Langmuir monolayers suggest that control of crystallization by organic interfaces is affected by both the ability of the organic template to mimic the lattice of a two-dimensional face as well as the stereochemistry and orientation of the functional groups at the interface. − ,, It is unclear which of these factors will be more important in a particular surface−crystal growth system. In this study we examined patterns of crystal growth at well-defined interfaces in which there is no attempt to mimic a crystal lattice, but for which it is possible to systematically vary the functional groups that are present.…”

Section: Introductionmentioning

confidence: 99%

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Modified Calcite Deposition Due to Ultrathin Organic Films on Silicon Substrates

1996

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In order to study the effect of organic surface chemistry on calcite nucleation, attachment, and growth, calcium carbonate was precipitated in the presence of various ultrathin-film organosilane-modified silicon wafers. The chemistry of the aminosilane surfaces was systematically changed by the coupling of various acidic molecules, without creating a geometric lattice of acidic functional groups. Optical microscopy, scanning electron microscopy with image analysis, and X-ray scattering were employed to characterize crystallite density and orientation normal to the surface. Calcite grown on amino-modified surfaces was produced with the equilibrium rhombohedral habit and had the 〈104〉 orientation. Surfaces of the silicon oxide, carboxylate, iminodiacetate, or phosphoramidate tended to favor the orientation of surface crystals along 〈001〉 or near the 〈001〉 axes of the crystal. Primarily this is a result of the affinity of the surface for cations, but functional-group-mediated ion ordering and/or stereochemical matching is also suggested by the much greater amount of crystal nucleation on the long-chain carboxylates when compared to shortchain carboxylates. Coupling of nitrilotriacetic acid (NTA) favored appearance of 〈110〉, 〈113〉, and 〈116〉 oriented crystals when compared to the other acid surfaces. Growth of calcite with relatively larger {110} faces was observed when the microcrystals were synthesized in the presence of freely soluble NTA. Appearance of these faces is a result of a relatively suppressed growth rate due to face-specific adsorption on the growing crystallites. Similarly, the enhancement of specific crystal surface binding by the substrate bound NTA is probably the mechanism influencing orientation of surface microcrystals. Two common structural features of the {110}, {113}, and {116} faces are the tilt of the carbonate plane at large angles from the face and the same angle of rotation of the carbonates about their 3-fold symmetry axes. That angle may enhance the ability of two NTA carboxylates to simultaneously occupy carbonate sites of these calcite faces. The fact that crystallite density and orientation are influenced by submonolayers of functional groups attests to the importance of electrostatic and stereochemical recognition of certain crystal faces even without matching of the geometric lattice.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modified Calcite Deposition Due to Ultrathin Organic Films on Silicon Substrates

1996

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“…Through use of mixed monolayers the properties can be varied in a continuous manner from one type to another. We have been interested in these surfaces for fundamental studies of wetting and adhesion, lithography, heterogeneous nucleation, and growth of minerals and therefore have been exploring synthetic reactions on these surfaces. − The clean and efficient installation and manipulation of a wide variety of functional groups are of paramount importance for these studies to be quantitatively meaningful. Of equal importance is the ability to install these functionalities with systematically varied loading densities that are predictable and accurately known.…”

Section: Introductionmentioning

confidence: 99%

Nucleophilic Displacements in Mixed Self-Assembled Monolayers

et al. 1996

Self Cite

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Synthetic elaboration of self-assembled monolayers (SAMs) provides a powerful method for the preparation of smooth, ordered surfaces with carefully controlled functionality. Chemically rugged siloxane-based SAMs have been employed as a foundation for the preparation of a variety of functionalized surfaces. Nucleophilic displacements are described between halide-terminated SAMs and anionic nucleophiles (e.g. azide, thiocyanate, thiolate). Problems were encountered due to the steric congestion surrounding the terminal bromomethylene carbon. The concept of trajectory control is applied to these displacement reactions. In addition, reactions between ester-terminated SAMs and neutral nucleophiles (e.g. amines, hydrazine, hydroxylamine) are described. Evidence is presented suggesting that a modest amount of cross-linking (i.e. imide formation) takes place in the amidation reactions, while reaction stoichiometry indicates that cross-linking is virtually complete for the bifunctional nucleophiles. These synthetic elaborations were also carried out on mixed monolayers to create functionalized SAMs with systematically varied loading densities. Linear correlation (or lack thereof) of elemental composition to predicted functional composition is used to provide an estimation of reaction efficiency.

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“…An alternative solution approach for depositing ceramic oxide, hydroxide, and oxyhydroxide films of controlled thickness at low temperatures is the ''biomimetic'' synthesis technique. [2][3][4][5] This deposition technique was first demonstrated on chemically modified plastic surfaces 2 and, later, on organic self-assembled monolayers on silicon; 3 this deposition approach has two important characteristics; 4 (i) control of solution conditions, including ionic concentrations (supersaturation levels), pH, and temperature, and (ii) the use of functionalized interfaces to promote mineralization at the substrate surface. The functionalized surfaces are believed to be analogous to nucleation proteins in biological systems in regard to providing energetically favorable interfaces for heterogeneous nucleation and growth of inorganic films from supersaturated solutions.…”

Section: Introductionmentioning

confidence: 99%

Titanium Oxide Thin Films on Organic Interfaces through Biomimetic Processing

Baskaran

Song

Liu

et al. 1998

Journal of the American Ceramic Society

114

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Titanium oxide (TiO 2 ) thin films have been deposited on silicon, glass, and plastic substrates by destabilization of an aqueous titanium lactate solution at low temperatures (<100°C). The process uses a commercially available, lowcost precursor and is simple to perform; it involves only control of pH in aqueous, chelated titanium solutions. With this solution technique, high deposition rates (>50 nm/min), film thickness (>100 nm), and excellent film uniformity have been obtained. Uniform coatings can be applied on complex-shaped polymeric substrates and porous membranes. Films can be formed on both sulfonated and untreated polymeric surfaces. As-deposited films on plastic substrates consist of amorphous, hydrated TiO 2 . On sulfonated self-assembled monolayers on silicon substrates, nanocrystalline TiO 2 films have been formed. The deposited films exhibit strong ultraviolet (UV) absorption with excellent transmission in the visible wavelength range, which indicates that the coatings may be useful as protective UV blockers for polymeric materials.

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Biomimetic Thin-Film Synthesis

Cited by 14 publications

References 0 publications

Modified Calcite Deposition Due to Ultrathin Organic Films on Silicon Substrates

Modified Calcite Deposition Due to Ultrathin Organic Films on Silicon Substrates

Nucleophilic Displacements in Mixed Self-Assembled Monolayers

Titanium Oxide Thin Films on Organic Interfaces through Biomimetic Processing

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