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.

Ionic transport plays a central role in key technologies relevant to energy, and information processing and storage, as well as in the implementation of biological functions in living organisms. Here, we introduce a supramolecular strategy based on the non-destructive chemical patterning of a highly ordered self-assembled monolayer that allows the reproducible fabrication of ion-conducting surface patterns (ion-conducting channels) with top -COOH functional groups precisely definable over the full range of length scales from nanometre to centimetre. The transport of a single layer of selected metal ions and the electrochemical processes related to their motion may thus be confined to predefined surface paths. As a generic solid ionic conductor that can accommodate different mobile ions in the absence of any added electrolyte, these ion-conducting channels exhibit bias-induced competitive transport of different ionic species. This approach offers unprecedented opportunities for the realization of designed ion-conducting systems with nanoscale control, beyond the inherent limitations posed by available ionic materials.

Experimental evidence is presented, demonstrating the feasibility of a surface-patterning strategy that allows stepwise electrochemical generation and subsequent in situ metallization of patterns of carboxylic acid functions on the outer surfaces of highly ordered OTS monolayers assembled on silicon or on a flexible polymeric substrate. The patterning process can be implemented serially with scanning probes, which is shown to allow nanoscale patterning, or in a parallel stamping configuration here demonstrated on micrometric length scales with granular metal film stamps sandwiched between two monolayer-coated substrates. The metal film, consisting of silver deposited by evaporation through a patterned contact mask on the surface of one of the organic monolayers, functions as both a cathode in the printing of the monolayer patterns and an anodic source of metal in their subsequent metallization. An ultrathin water layer adsorbed on the metal grains by capillary condensation from a humid atmosphere plays the double role of electrolyte and a source of oxidizing species in the pattern printing process. It is shown that control over both the direction of pattern printing and metal transfer to one of the two monolayer surfaces can be accomplished by simple switching of the polarity of the applied voltage bias. Thus, the patterned metal film functions as a consumable "floating" stamp capable of two-way (forward-backward) electrochemical transfer of both information and matter between the contacting monolayer surfaces involved in the process. This rather unusual electrochemical behavior, resembling the electrochemical switching in nanoionic devices based on the transport of ions in solid ionic-electronic conductors, is derived from the nanoscale thickness of the water layer acting as an electrolyte and the bipolar (cathodic-anodic) nature of the water-coated metal grains in the metal film. The floating stamp concept introduced in this report paves the way to a series of unprecedented capabilities in surface patterning, which are particularly relevant to nanofabrication by chemical means and the engineering of a new class of molecular nanoionic systems.

Effective control of chemistry at interfaces is of fundamental importance for the advancement of methods of surface functionalization and patterning that are at the basis of many scientific and technological applications.Aconceptually new type of interfacial chemical transformations has been discovered, confined to the contact surface between two solid materials,w hichm ay be induced by exposure to X-rays, electrons or UV light, or by the application of electrical bias. One of the reacting solids is aremovable thin film coating that acts as ar eagent/catalyst in the chemical modification of the solid surface on which it is applied. Given the diversity of thin film coatings that mayb eu sed as solid reagents/catalysts and the lateral confinement options provided by the use of irradiation masks,c onductive AFM probes or stamps,a nd electron beams in such solid-phase reactions,t his approach is suitable for precise targeting of different desired chemical modifications to predefined surface sites spanning the macroto nanoscale.Recent exploratory experiments conducted by us with the purpose of devising acomprehensive methodology of surface chemical functionalization and patterning led to the rather surprising discovery that the top CH 3 groups of highly ordered OTSmonolayers (monolayers self-assembled from n-octadecyltrichlorosilane precursor molecules,S iCl 3 À(CH 2 ) 17 À CH 3 ) [1, 2] may be quantitatively converted to COOH with full preservation of the composition and structure of the monolayer hydrocarbon core using various thin-film coatings as oxidizing reagents.T he conversion of OTSi nto OTSox (surface-oxidized OTS) is implemented upon exposure of the coated OTSm onolayer to different sources of electromag-netic radiation or electrons (see Scheme 1f or some representative examples). Reaction route (a) in Scheme 1w as discovered by accident in experiments involving electron beam (e-beam) deposition of different metals (Ag, Al, Au,Ti) on OTSm onolayers on silicon (OTS/Si) or quartz (OTS/Q) covered with 4-10 nm-thick PVA( polyvinyl alcohol) film coatings.D epositing the same metals (under identical experimental conditions) on bare OTS monolayers did not affect their composition and structure in any measurable manner, whereas using at ungsten target in the e-beam evaporator operated under conditions below the threshold evaporation of this metal was found to convert OTSinto OTSox as in the actual deposition of metals on the PVAsurface.Finally,using thermal instead of e-beam metal deposition on PVA-coated OTSm onolayers did not affect their composition and structure either.T hese observations suggested that, in the presence of as ource of oxygen (here the thin PVAc oating), the surface oxidation of OTSisinduced by the radiation that accompanies the metal evaporation in e-beam evaporators (X-rays,s econdary and scattered electrons and UV light, emitted when energetic electrons strike am etal target) [3] rather than by the metal deposition itself.T hat each of the different components of this radiation may induce ...