Vapor phase processing: a novel approach for fabricating functional hybrid materials.

Materials science is nowadays facing challenges in optimizing properties of materials which are needed for numerous technological applications and include, but are not limited to, mechanics, electronics, optics, etc. The key issue is that for emerging applications materials are needed which incorporate certain properties from polymers or biopolymers and metals or ceramics at the same time, thus fabrication of functional hybrid materials becomes inevitable. Routes for the synthesis of functional hybrid materials can be manifold. Among the explored routes vapor phase processing is a rather novel approach which opts for compatibility with many existing industrial processes. This topical review summarizes the most important approaches and achievements in the synthesis of functional hybrid materials through vapor phase routes with the goal to fabricate suitable hybrid materials for future mechanical, electronic, optical or biomedical applications. Most of the approaches rely on atomic layer deposition (ALD) and techniques related to this process, including molecular layer deposition (MLD) and vapor phase infiltration (VPI), or variations of chemical vapor deposition (CVD). The thus fabricated hybrid materials or nanocomposites often show exceptional physical or chemical properties, which result from synergies of the hybridized materials families. Even though the research in this field is still in its infancy, the initial results encourage further development and promise great application potential in a large variety of applications fields such as flexible electronics, energy conversion or storage, functional textile, and many more.

Semi-artificial and bioactive ferroxidase with nanoparticles as the active sites.

Light-chain apoferritin lacks ferroxidase activity, which can be supplemented with Pt-nanoparticles. The hybrid bioinorganic nanoparticle outperforms its heavy-chain pendant in terms of ferroxidase activity, mineralization ability and inhibition resistance. Being active in a cellular environment it regulates the iron homeostasis.

Multilayer Fresnel zone plate for soft X-ray microscopy resolves sub-39nm structures.

Best resolutions in X-ray focusing are obtained to date by using diffractive lenses called Fresnel zone plates (FZPs). Their further improvement is nevertheless hindered by fundamental limitations in the employed manufacturing techniques. Here, we show a novel method to fabricate FZPs based on multilayer deposition with atomic layer deposition (ALD) and subsequent sectioning with focused ion beam (FIB). For the first time a multilayer FZP working in the soft X-ray range was prepared and could achieve the best resolution obtained so far for multilayer FZPs by resolving features below 39nm in size in a scanning soft X-ray microscope. The new technique presents high potential for high resolution microscopy in both the soft and hard X-ray range.

Binding the tobacco mosaic virus to inorganic surfaces.

We studied the adsorption behavior and surface chemistry of the tobacco mosaic virus (TMV) on well-defined metal and insulator surfaces. TMV serves as a tubular supramolecular model system with precisely known surface termination. We show that if the surface chemistry of the substrate and the pH-dependent chemistry of the molecular surface match, for example, by hydrogen bonding, a strong adsorption occurs, and lateral movement is impeded. Due to the immobilization, the virion can be imaged by atomic force microscopy (AFM) in contact mode. We also used self-assembled monolayers with an acyl chloride group to induce covalent bonding via ester formation. Noncontact AFM proved that TMV keeps its cylindrical cross section only under weak adsorption conditions, that is, on hydrophobic surfaces, while on hydrophilic substrates a deformation occurs to maximize the number of interacting chemical groups.

Increasing Cooperation in Prisoner's Dilemmas by Establishing a Precedent of Efficiency in Coordination Games.

Coordination games have multiple Nash equilibria (i.e., sets of strategies which are best responses to one another). In weak-link coordination games players choose a number 1-7. Their payoff is increasing in the minimum number (or weakest link) and decreasing in the difference between their number and the minimum. Choosing 7 is an efficient equilibrium because it gives everybody a higher payoff than any other coordinated choice. Higher-payoff equilibria are riskier, however, so the game expresses the tradeoff between group efficiency and personal risk present in many social and organizational settings. We tested whether choosing efficiently in a weak-link game increases cooperative play in a subsequent prisoner's dilemma (PD) game. This cross-game transfer resembles the transfer of cooperative norms in small firms (which are more like coordination games than PDs) as firms grow larger and become like PDs. In two experiments, if a group of players share a history of playing the weak-link game efficiently, that efficiency precedent can transfer to a subsequent PD game, improving the level of cooperativeness. The effect of transfer is much larger in magnitude (increasing cooperation from 15-30% to 71%) than the effects of most variables in previous PD studies. However, the transfer effect depends on descriptive similarity of strategies in the two games, since it largely disappears when the strategies are numbered differently in the weak-link game and the PD. Copyright 2000 Academic Press.