We describe the fabrication of a patterned, hydrophobic silicon substrate that can pin a water droplet despite its large contact angle. Arrays of nm tips in silicon were fabricated by reactive ion etching using polymer masks defined by photolithography. A droplet sitting on one class of these substrates did not fall even after the substrate was turned upside-down. The production allows the fabrication of large arrays of tips with a one-step simple etching process, along with silanization, to achieve a substrate with both very large contact and tilting angles.

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.

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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 ...

Electrical resistivity and Hall effect measurements of pellets compacted from fullerene-like WS 2 nanoparticles (IF-WS 2 ) and bulk 2H-WS 2 powder were carried out using the van der Pauw method over a wide temperature range. In addition IF-WS 2 pellets were annealed at elevated temperatures under vacuum in a specially designed system. Arrhenius plots for the conductivities of the WS 2 samples (2H, IF and IF+annealing) exhibit marked uprise of ∂ ln (s T -1 )/∂T -1 with temperature. The resistivity of the nonannealed IF-WS 2 pellets is higher by 2 -8 orders of magnitude than that of 2H-WS 2 pellets, whereas the resistivity of the annealed IF pellets is higher than that of the non-annealed ones. Hall Effect measurements at 300 K show p-type conductivity and similar carrier concentration for both types of materials. The carrier mobility of 2H-WS 2 platelets is found to be in the range of the reported values. However, IF-WS 2 pellets have shown an unusually low mobility for a semiconducting material. The experimental data was found to be in a good agreement with a model used for analyzing the conductivity of polycrystalline semiconductors, which takes into consideration fluctuations of the barrier heights among the different nanoparticles as well as within a single nanoparticle boundary.