Monolayer assemblies on silicon surfaces are of interest for a number of technological reasons. Here, we present a novel, two-step strategy for assembly formation directly on silicon surfaces. In the first step, a H-terminated Si(100) or Si(111) surface reacts with Cl2 to give a Cl-capped surface. In the second step, the Cl-Si surface is immersed in an alcohol/isooctane solution for monolayer formation via Si-O linkages, with the removal of surface Cl likely in the form of HCl. This reaction mechanism is confirmed by X-ray photoelectron spectroscopy. X-ray reflectivity measurement shows that the thickness of the monolayer film is close to molecular dimension and the density is about 85% of that in crystalline paraffine. Fourier transform infrared spectroscopy and water contact angle measurements suggest that the alkyl chains within the monolayer possess, to a limited degree, conformational order. Atomic force microscopy image with molecular lattice resolution shows intermolecular distance corresponding to close packing of alkyl chains. The monolayer coatings show both chemical and mechanical stability. The possible mechanism for monolayer assembly formation on covalent Si surfaces is discussed.

A strategy has been developed for the grafting of poly(ethylene glycol) (PEG) monolayers onto the atomically flat Si(111) surface. This process involves the direct interaction of the HO-functional group on PEG with a chlorine-terminated silicon surface. The resulting monolayers show exceptional flatness, with mean roughness on the angstrom scale. Film thickness is determined by ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy. Results for different molecular weights reveal that the grafted PEG molecules are in a brushlike configuration at low molecular weight (MW = 200, 300) and a more coil-like configuration at higher molecular weight (MW = 1000, 2000). The surface density of grafted PEG molecules is significantly higher than those reported in the literature and decreases with increasing molecular weight, from 92% at MW = 300 to 35% at MW = 2000. Both the brushlike and the coil-like configurations show excellent properties of protein resistance.

We report the detection of 10–30 parts-per-trillion levels of pentaerythritol tetranitrate and hexahydro-1,3,5-triazine within 20 s of exposure to a silicon microcantilever with its gold surface modified with a self-assembled monolayer of 4-mercaptobenzoic acid. These measurements correspond to a limit of detection of a few fg.

Stable and reproducible spontaneous self-ignition and self-supporting combustion have been achieved at room temperature by exposing nanometer-sized catalytic particles to methanol/air or ethanol/air gas mixtures. Without any external ignition, structurally supported platinum nanoparticles instantaneously react with the gas mixtures. The reaction releases heat and produces CO 2 and water. Such reactions starting at ambient temperature have reached both high (>600°C) and low (a few tenths of a degree above room temperature) reaction temperatures. The reaction is controlled by varying the fuel/air mixture. Catalytic activity could be dramatically changed by reducing particle size and changing particle morphology.Catalysis is a well-known process in which a catalyst aids in the attainment of chemical equilibrium by reducing the free energy of transition-complex formation in a reaction pathway. Catalytic reactions have very wide and vitally important applications in the chemical, petroleum, energy, and automobile industries as well as in many other fields. 1 Normally, however, heterogeneous catalysts are not sufficiently active at room temperature and require external heat for ignition (generally, reaction temperatures are >200°C); the preheating requirement for a catalytic reaction can be very costly for industrial applications. 2 The search for catalysts that are sufficiently active at room temperature and that are also able to rapidly convert large amount of reactants has a long history. 3 Here we report a method to achieve spontaneous self-ignition and selfsupporting combustion of alcohols at room temperature by using nanometer-sized catalytic particles and no source of external ignition.Energy stored in the form of chemical bonds (i.e., gasoline or methanol) is most often converted to thermal energy first rather than directly to other forms of energy such as mechanical or electrical energy. Conventionally, such energy conversion occurs at high temperature, and external ignition generally is required to initiate the combustion or burning process. Modern internal combustion engines (ICEs) were designed on the basis of the Carnot cycle and built by taking advantage of such energy conversion processes in which sophisticated and complex ignition systems govern the performance and quality of the engine. Such ignition processes require an external energy source (such as a battery) and other supporting systems (such as a controller) that greatly increase the complexity of each system and potentially reduce the energy utilization efficiency. On average, the efficiency of an ICE is ∼21%; in contrast, an advanced fuel cell converts chemical energy directly to electrical energy and can yield higher energy conversion efficiency (∼51%). 4 Nevertheless, temperatures of a few hundred degrees are typically required to carry out such reactions, while heat-related energy losses represent ∼20% of total energy produced. However, high reaction temperatures may not be an absolutely necessary step in energy conversion processes. New de...