First-principles calculations were employed to investigate the adsorption-induced surface stress of self-assembled alkanethiolate monolayers on a Au(111) surface as a function of the alkyl chain length. A recently developed fully nonlocal van der Waals density functional was used to accurately account for the chain-chain interactions. We found that surface charge redistribution produces compressive surface stress, while chain-chain interactions produce tensile surface stress. The stress induced by surface charge redistribution is about one order of magnitude greater than that of chain-chain interactions. We observed that the chain-chain interactions play an important role in determining the molecular configuration during adsorptions, and also contribute significantly to the induced anisotropic tensile (positive) surface stress. As the chain length increases the tensile stress increases at a rate of ∼ 0.32 (∼ 0.18) N/m for the direction perpendicular (parallel) to the chain tilt direction.

In this article, the biofunctionalization of 6H–SiC (0001) surfaces via self-assembled monolayers (SAMs) has been studied as a means to modify the in vitro biocompatibility of this semiconductor substrate with H4 (human neuroglioma) and PC12 (rat pheochromocytoma) cells. Silanization with aminopropyldiethoxymethylsilane (APDEMS) and aminopropyltriethoxysilane (APTES), which provided moderately hydrophilic surfaces, and alkylation with 1-octadecene that produced hydrophobic surfaces were used to control the 6H–SiC surface chemistry and evaluate changes in cell viability and morphology due to these surface modifications. The morphology of the cells was evaluated with atomic force microscopy. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were used to quantitatively evaluate the cell viability on the SAM-modified surfaces. In all cases, the cell proliferation was observed to improve with respect to untreated 6H–SiC surfaces, with up to a 2x increase in viability on the 1-octadecene-modified surfaces, up to 6x increase with APDEMS-modified surfaces, and up to 8x increase with APTES-modified surfaces. This proves the potential of SiC as a substrate for medical devices given the possibility to tailor its surface chemistry for specific applications.

Self-assembled nanostructures of α,ω-dihexylsexithiophene (DH6T) formed by spreading DH6T solutions onto freshly cleaved mica surface were studied by atomic force microscopy. The effects of solvent and concentration on the nanostructures of DH6T molecules were studied. Flat, well-ordered, and platelet-like domains were observed on mica surfaces after treatment with various polar solvent solutions of DH6T. These domains form a uniform film with height of 2.4 ± 0.2 nm, which is consistent with a 45° tilt in the molecular conformation of DH6T on mica surfaces. The formation mechanism of these multilayers is discussed in detail.

Recent progress in various biotechnology fields, such as microfluidics, tissue engineering, and cellular biology, has created a great demand for substrates that can undergo defined remodeling with time. As a result, the latest research on materials with dynamically controllable surface properties has led to a variety of novel smart surface designs.

The design of future molecular electronic devices requires a firm understanding of the conduction mechanisms that determine their electrical characteristics. Progress toward this goal has been hindered by complications in controlling the exact configuration and makeup of fabricated molecular junctions, thus limiting the availability of quantitative experimental data for developing cohesive theories to model and predict molecular transport. This article summarizes recent research aimed at developing well-controlled systems for comparing molecular conduction and vibrational spectra using crossed-wire and in-wire metal–molecule–metal junctions. Systematic variations in molecular structure and metal–molecule contacts show strong quantitative agreement in device properties, while spectroscopic data provide evidence that the properties are due to the molecular junction. Further investigations using these and other molecular junction test beds will provide the needed experimental data to advance fundamental understanding of molecular transport and facilitate future molecular electronics applications.

The following article is based on the presentation given by George M. Whitesides, recipient of the 2000 MRS Von Hippel Award, the Materials Research Society's highest honor, at the 2000 MRS Fall Meeting in Boston on November 29, 2000. Whitesides was cited for “bringing fundamental concepts of organic chemistry and biology into materials science and engineering, through his pioneering research on surface modification, self-assembly, and soft lithography.” The article focuses on the growing role of organic chemistry in materials science. Historically, that role has been to provide organic polymers for use in structures, films, fibers, coatings, and so on. Organic chemistry is now emerging as a crucial part of three new areas in materials science. First, it provides materials with complex functionality. Second, it is the bridge between materials science and biology/medicine. Building an interface between biological systems and electronic or optical systems requires close attention to the molecular level of that interface. Third, organic chemistry provides a sophisticated synthetic entry into nanomaterials. Organic molecules are, in fact, exquisitely fabricated nanostructures, assembled with precision on the level of individual atoms. Colloids are a related set of nanostructures, and organic chemistry contributes importantly to their preparation as well.