Epitaxy and chainlength dependent strain in self-assembled monolayers

Fenter, Paul; Eberhardt, A.; Liang, K. S.; Eisenberger, P.

doi:10.1063/1.473281

Cited by 137 publications

(191 citation statements)

References 34 publications

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“…The measurements also reiterate the importance of secondary structure in macromolecular activity. SAM structure and packing, which are strongly influenced by chain length (39,40), have a strong control on calcite nucleation. A recent molecular dynamics analysis suggests these effects may be related to the degree of symmetry in interactions between SAM monomers and its impact on SAM order, highlighting once again the importance of cooperativity in both SAM-crystal-binding and templatedirected nucleation (35).…”

Section: Significancementioning

confidence: 99%

Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies

Hamm

Giuffre

Han

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

136

173

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The physical basis for how macromolecules regulate the onset of mineral formation in calcifying tissues is not well established. A popular conceptual model assumes the organic matrix provides a stereochemical match during cooperative organization of solute ions. In contrast, another uses simple binding assays to identify good promoters of nucleation. Here, we reconcile these two views and provide a mechanistic explanation for template-directed nucleation by correlating heterogeneous nucleation barriers with crystal-substrate-binding free energies. We first measure the kinetics of calcite nucleation onto model substrates that present different functional group chemistries (carboxyl, thiol, phosphate, and hydroxyl) and conformations (C11 and C16 chain lengths). We find rates are substrate-specific and obey predictions of classical nucleation theory at supersaturations that extend above the solubility of amorphous calcium carbonate. Analysis of the kinetic data shows the thermodynamic barrier to nucleation is reduced by minimizing the interfacial free energy of the system, γ. We then use dynamic force spectroscopy to independently measure calcitesubstrate-binding free energies, ΔG b . Moreover, we show that within the classical theory of nucleation, γ and ΔG b should be linearly related. The results bear out this prediction and demonstrate that low-energy barriers to nucleation correlate with strong crystal-substrate binding. This relationship is general to all functional group chemistries and conformations. These findings provide a physical model that reconciles the long-standing concept of templated nucleation through stereochemical matching with the conventional wisdom that good binders are good nucleators. The alternative perspectives become internally consistent when viewed through the lens of crystal-substrate binding.B iological systems are unique in their ability to organize minerals into functional materials with complex patterns and architectures. A substantial body of evidence suggests specialized macromolecules, particularly proteins (1, 2) and carbohydrates (3, 4), provide preferential sites for nucleation to direct the placement, timing, and orientation of crystals (5), both intra-and extracellular. Within the biomineralization community, the conventional view of biologically directed nucleation is that macromolecular matrices present an interfacial match to the crystal lattice that assists in forming the crystal nucleus. This cooperative view of directed nucleation is rooted in the collective action of multiple residues that guide the organization of ions into a configuration defining the energetic minimum for the system. A series of in vitro observations have reinforced this picture by showing that highly ordered organic monolayers can control the location and orientation of calcite crystals precipitated from solution (6). In this approach, good templates are revealed through a direct functional assay, i.e., nucleation. Over the years, this view of mineralization, both in the context of natural stru...

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Section: Significancementioning

confidence: 99%

Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies

Hamm

Giuffre

Han

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

136

173

View full text Add to dashboard Cite

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“…This tilt angle (α) is found to be 30°with respect to the surface normal toward the nearest neighbor direction. Fenter et al demonstrated a systematic dependence of the tilt structure (tilt angle and direction) with the chain length, which is explained as due to the change in intralayer interaction strength [23]. The twist angle β (which defines the rotation of the carbon chain backbone about the chain axis with respect to the plane defined by the chain axis and the surface normal) for the long-chain alkanethiol is found to be ~52°, which implies that Au-S-C bond angle is nearly 120°, close to the optimum value for the sp 2 hybridized sulfur atoms.…”

Section: Adsorption and Structure Of Samsmentioning

confidence: 99%

Structure and dynamics of monolayers on planar and cluster surfaces

Pradeep

Sandhyarani

2002

Pure and Applied Chemistry

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Organized molecular assemblies have been one of the intensely pursued areas of contemporary chemistry. Among the various methodologies used to make organized monolayer structures, self-assembled monolayers (SAMs) have been attractive to many materials chemists owing to the simplicity of the preparative method and high stability. Advances in various techniques and their application in the study of SAMs have significantly improved our understanding of these molecular systems. These studies have been further intensified since the successful preparation of stable metal clusters protected with monolayers. This article reviews the structure, temperature-induced phase transitions, and associated dynamics of monolayers, principally in the context of our own work in this area. Alkanethiols on Au (111) and Ag(111) are taken as archetypal systems to discuss the properties of 2D SAMs; studies from our laboratory have been on evaporated thin films. Alkanethiols on Au and Ag cluster surfaces are taken as examples of 3D SAMs. Although our principal focus will be on alkanethiols, we will touch upon a few other adsorbate systems as well.

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“…This tilt angle ðÞ is found to be 308 with respect to the surface normal towards the nearest-neighbour direction. Fenter et al demonstrated a systematic dependence of the tilt structure (tilt angle and tilt direction) on the chain length, explained as being due to the change in intralayer interaction strength [108]. The twist angle (defines the rotation of the alkyl carbon backbone about the chain axis with respect to the plane defined by the chain axis and the surface normal) for the long-chain alkanethiol is found to be $528, which implies that Au-S-C bond angle is nearly 1208, close to the optimum value for the sp 2 -hybridized sulphur atoms.…”

Section: Structure Of Sams: An Overall Viewmentioning

confidence: 99%