Nanowires are created by nucleation of nanometer‐scaled noble metal particles on microtubules formed from highly ordered protein assemblies. The periodic functional groups of amino acids serve as active sites for nucleation and binding of the metallic nanoparticles to form ordered patterns of particles, which, by further particle growth, generate quasi‐continuous metal coatings (see Figure).

The synthesis of increasingly miniaturized structures using alternative techniques is strongly motivated by future applications in areas such as nanoelectronics. Highly ordered protein assemblies of tubular structure and high geometric aspect ratio are used as bioorganic templates for the bottom-up synthesis of metal nanostructures. When the biotemplate is coupled to an appropriate chemical reaction, metal is generated in situ and deposited along the backbone of the biostructure. Ag/protein structures with different morphologies are produced, from microtubules densely covered with small Ag nanoparticles to continuous Ag nanowires. Our results demonstrate the potential of bioassemblies in general for the fabrication of multidimensional structures with interesting material properties.

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The production of hydrogen by the reforming of methanol was studied in a continuously operated tubular reactor made of the nickel-based alloy Inconel 625. Experiments were performed at pressures from 25 to 45 MPa and temperatures in the range of 400−600 °C. The concentration of the aqueous feed varied from 5 to 64 wt % methanol. Residence times under reaction temperature conditions varied in the range from 3 to 100 s. The main component of the product gas is hydrogen, with smaller amounts of carbon dioxide, carbon monoxide, and methane. Methanol conversion is up to 99.9% without addition of a catalyst. Obviously, the heavy metals on the inner surface of the reactor influence the composition of the product gas and the conversion rate. Oxidation of the reactor inner surface before gasification turned out to enhance the reaction rate and to decrease the carbon monoxide concentration.

Commercial requirements for miniaturized microelectronic devices provide strong motivation for exploring the synthesis of nanoscale systems using bottom-up techniques. The manipulation of charges at the single-electron level in regularly arranged nanoparticles can be utilized to create devices, such as switches, transistors, and digital electronic circuits.[1] An interesting feature of nanoscale ring systems is the AharonovBohm effect: interference phenomena of electron wave functions observed for electrons in ring systems. [2] Up to now, the bottom-up wet-chemical synthesis of inorganic materials has provided a tool for the fabrication of a range of nanostructures, from particles to one-dimensional (1D) structures, [3,4] but these chemical techniques offer little control over the deposition of metals or metal particles as nanometer-sized ring structures, even though interesting properties are expected for such structures. The growth of inorganic materials on biomolecular templates as well as biomolecule-directed assembly of inorganic building blocks are other promising strategies for fabricating complex functional nanostructures, such as wires and ring structures. [5][6][7][8][9] For example, wild-type and genetically engineered viruses have been used to template quasi-1D magnetic [10] and semiconducting nanowires [11] as well as ring structures of Au nanoparticles. [12] In this communication, we address the template-directed deposition of metals on ring-shaped tubulin assemblies for synthesizing metal ring nanostructures. The controlled deposition of metals on polymorphic tubulin structures, as already shown for microtubules (MTs), [13] have great potential for use in future electronic components, for example, AharonovBohm rings to be used in nanoscale circuits. Tubulin is a protein that forms a,b-heterodimers that are about 8 nm in length with diameters ranging from 4 to 5 nm. Tubulin molecules exhibit chemically active surfaces with defined patterns of amino acid side chains, which provide a wide variety of active sites for derivatization, especially for nucleation, organization, and binding metal particles. Tubulin is able to self-assemble into a wide variety of polymorphs: tubules, sheets, ribbons, spirals, and rings, [14] all consisting of differently arranged protofilaments with a strict alternation of a-and b-tubulin monomers. In the presence of Ca 2+ ions, tubulin assembles in vitro into rings and spirals instead of MTs. [15,16] Unlike tubulin rings, MTs have been used as templates to generate metal nanoparticles and nanowires, [13,[17][18][19] for the mineralization of iron oxide, [20] as well as for the kinesinbased transport of synthetic cargo [21][22][23] and CdSe quantum dots.[24]We have investigated ring and spiral formation by transmission electron microscopy (TEM, Fig. 1a). TEM images of tubulin rings fixed by 0.1 % glutaric dialdehyde (GA) and negatively stained by uranyl acetate reveal an outer and inner diameter of 56.4 ± 4.0 nm and 27.1 ± 3.8 nm, respectively, corresponding to a wall thickne...

Subcritical water is a high potential green chemical for the hydrolysis of cellulose. In this study microcrystalline cellulose was treated in subcritical water to study structural changes of the cellulose residues. The alterations in particle size and appearance were studied by scanning electron microscopy (SEM) and those in the degree of polymerization (DP) and molar mass distributions by gel permeation chromatography (GPC). Further, changes in crystallinity and crystallite dimensions were quantified by wide-angle X-ray scattering and (13)C solid-state NMR. The results showed that the crystallinity remained practically unchanged throughout the treatment, whereas the size of the remaining cellulose crystallites increased. Microcrystalline cellulose underwent significant depolymerization in subcritical water. However, depolymerization leveled off at a relatively high degree of polymerization. The molar mass distributions of the residues showed a bimodal form. We infer that cellulose gets dissolved in subcritical water only after extensive depolymerization.

Monodisperse Co, Fe, and FeCo nanoparticles are prepared via thermal decomposition of metal carbonyls in the presence of aluminium alkyls, yielding air-stable magnetic metal nanoparticles after surface passivation. The particles are characterized by electron microscopy (SEM, TEM, ESI), electron spectroscopy (MIES, UPS, and XPS) and x-ray absorption spectroscopy (EXAFS). The particles are peptized by surfactants to form stable magnetic fluids in various organic media and water, exhibiting a high volume concentration and a high saturation magnetization. In view of potential biomedical applications of the particles, several procedures for surface modification are presented, including peptization by functional organic molecules, silanization, and in situ polymerization.

Electronic instruments mimicking the mammalian olfactory system are often referred to as "electronic noses" (E-noses). Thanks to recent nanotechnology breakthroughs the fabrication of mesoscopic and even nanoscopic E-noses is now feasible in the size domain where miniaturization of the microanalytical systems encounters principal limitations. Here we describe probably the simplest and yet fully functioning E-nose made of an individual single-crystal metal oxide quasi-1D nanobelt. The nanobelt was indexed with a number of electrodes in a way that each segment of the nanobelt between two electrodes defines an individual sensing elemental "receptor" of the array. The required diversity of the sensing elements is "encoded" in the nanobelt morphology via longitudinal width variations of the nanobelt realized during its growth and via functionalization of some of the segments with Pd catalyst. The proposed approach represents the combined bottom-up/top-down technologically viable route to develop robust and sensitive analytical systems scalable down to submicrometer dimensions.