We demonstrate a hierarchical self-assembly approach to the fabrication of planned nanostructures of colloidal gold particles on silicon, comprising the initial assembly of a molecular template pattern with terminal amino functionality, which then guides the surface assembly and site specific anchoring of gold nanoparticles from a colloidal solution. Well defined amino-terminated templates are obtained via a chemical functionalization process whereby highly ordered bilayer nanopatterns produced by constructive nanolithography (Maoz, R.; Frydman, E.; Cohen, S. R.; Sagiv, J. Adv. Mater. 2000, 12, 725−731) are in-situ modified to generate the top amine functions. This novel approach offers promising performance in terms of the precision, reproducibility, and structural robustness needed for the advancement of a reliable bottom-up nanofabrication methodology.

Planned nanopatterns of [Au 55 (Ph 2 PC 6 H 4 SO 3 Na) 12 Cl 6 ] clusters are generated on smooth silicon surfaces using a "bottom-up" fabrication methodology based on the selective self-assembly of the gold clusters on purpose-designed organic template patterns themselves fabricated via a hierarchical layer-by-layer self-assembly strategy. The patterns are laterally defined by constructive nanolithography, a novel surface patterning process utilizing conductive AFM tips as nanoelectrochemical "pens", with which nanoscale chemical information is inscribed in a nondestructive manner (in the form of a localized chemical transformation) on the top surface of a highly ordered organosilane monolayer self-assembled on silicon. Development of the initial tip-imprinted information is achieved via further self-assembly and chemical derivatization steps. This generic all-chemical approach offers attractive options for the advancement of nanofabrication capabilities that might have real impact on future technologies.

This paper provides a convenient and simple method for fabricating a self-organized two-dimensional (2D) array of gold nanoparticles on a silicon substrate. The silicon substrate, modified with an aminopropyltriethoxylsilane(APTES) monolayer, was first exposed to a gold colloidal suspension to deposit the gold particles and form a submonolayer of gold nanoparticles. This was followed by treatment with an alkanethiol solution, and then this randomly scattered submonolayer of nanosized gold particles on the silicon substrate was organized into small patches of 2D nanoparticle aggregates. Finally an alcohol solvent was used to drive these small patches of gold nanoparticle aggregates to self-organize together and form continuous ordered arrays on the silicon surface. The SEM images of the samples show that ordered two-dimensional arrays of gold nanoparticles are formed over a very large area and that the nanoparticles are highly organized and formed hexagonally closed packed structured arrays. This highly organized structure of gold nanoparticles can be reproduced over a large area by these effective procedures. Therefore, it is believed such procedures hold promise as an advanced new approach to construct ordered mesoscopic structural materials or for the controlled self-assembly of nanoparticles and could provide the possibility of detecting the collective physical properties of the ensemble.

This paper reports on the surface modification of plastic microfluidic channels to prepare different biomolecule micropatterns using ultraviolet (UV) photografting methods. The linkage chemistry is based upon UV photopolymerization of acryl monomers to generate thin films (0.01-6 microm) chemically linked to the organic backbone of the plastic surface. The commodity thermoplastic, cyclic olefin copolymer (COC) was selected to build microfluidic chips because of its significant UV transparency and easiness for microfabrication by molding techniques. Once the polyacrylic films were grafted on the COC surface using photomasks, micropatterns of proteins, DNA, and biotinlated conjugates were readily obtained by surface chemical reactions in one or two subsequent steps. The thickness of the photografted films can be tuned from several nanometers up to several micrometers, depending on the reaction conditions. The micropatterned films can be prepared inside the microfluidic channel (on-chip) or on open COC surfaces (off-chip) with densities of functional groups about 10(-7) mol/cm2. Characterization of these films was performed by attenuated-total-reflectance IR spectroscopy, fluorescence microscopy, profilometry, atomic force microscopy, and electrokinetic methods.

Monolayer self-assembly (MSA) was discovered owing to the spectacular liquid repellency (lyophobicity) characteristic of typical self-assembling monolayers of long tail amphiphiles, which facilitates a straightforward visualization of the MSA process without the need of any sophisticated analytical equipment. It is this remarkable property that allows precise control of the self-assembly of discrete, well-defined monolayers, and it was the alternation of lyophobicity and lyophilicity (liquid affinity) in a system of monolayer-forming bifunctional organosilanes that allowed the extension of the principle of MSA to the layer-by-layer self-assembly of planed multilayers. On this basis, the possibility of generating at will patterned monolayer surfaces with lyophobic and lyophilic regions paves the way to the engineering of molecular templates for site-defined deposition of materials on a surface via either precise MSA or wetting-driven self-assembly (WDSA), namely, the selective retention of a liquid repelled by the lyophobic regions of the pattern on its lyophilic sites. Highly ordered organosilane monolayer and thicker layer-by-layer assembled structures are shown to be ideally suited for this purpose. Examples are given of novel WDSA and MSA processes, such as guided deposition by WDSA on lyophobic-lyophilic monolayer and bilayer template patterns at elevated temperatures, from melts and solutions that solidify upon cooling to the ambient temperature, and the possible extension of constructive nanolithography to thicker layer-by-layer assembled films, which paves the way to three-dimensional (3D) template patterns made of readily available monofunctional n-alkyl silanes only. It is further shown how WDSA may contribute to MSA on nanoscale template features as well as how combined MSA and WDSA modes of surface assembly may lead to composite surface architectures exhibiting rather surprising new properties. Finally, a critical evaluation is offered of the scope, advantages, and limitations of MSA and WDSA in the bottom-up fabrication of surface structures on variable length scales from nano to macro.