The catalytic oxidation of methane was studied over palladium supported on nanocrystalline ceria. Three palladium weight loadings (1, 5, and 10 wt%) were tested after calcining at 500 °C, at 280 °C and after no calcination at all. For the 5 and 10 wt% loadings, the 280 °C-calcined and non-calcined catalysts exhibit enhanced activity after several heating and cooling cycles. Calcining these same catalysts at 500 °C results in a systematic decline in activity. For all pretreatments the 1 wt% Pd catalyst exhibits decreasing activity. For the 5 and 10 wt% Pd loadings, the non-calcined catalysts are more active than the 280 °C-calcined catalysts, which are more active than the 500 °C-calcined catalysts. For the 1 wt% Pd catalyst, the opposite is true. The catalyst activity improves as the Pd loading is increased.

We investigate nanostructures that are formed when dendrimers act as hosts. Poly(amidoamine) (PAMAM) dendrimers can be used as templates for inorganic nanocrystals, both in aqueous solution1-3 and in a polymeric matrix4. SANS, SAXS and TEM are used to characterize the resulting hybrid structures. Different inorganic colloids like noble metal and cadmium sulfide colloids are studied1,2. With increasing dendrimer generation, we observe a transition from low molecular colloid stabilizing to an effective polymer templating in terms of a “host-guest nanoscale synthesis”. For these higher generation dendrimers, inorganic colloids are formed inside single dendrimer molecules and the size of the nanocrystal can precisely be controlled by the dendrimer generation (“fixed loading law”). Hydrophobically modified dendrimers in organic solvent represent a further, different kind of host system that we have investigated using scattering methods5.

Ferrofluids containing superparamagnetic Fe3O4 nanoparticles have been prepared by a controlled co-precipitation method.The aggregation of the particles was prevented by using a polymeric starch network as a coating agent. Structural and magnetic measurements reveal a particle size of around 6 nm, with a clear evidence of a uniform particle coating. The ferrofluids have been used as a contrast agent for MR imaging in biological tissue.

We report a straightforward, non-aqueous solvothermal method for the production of nanoscale gallium nitride structures. Nanoparticles with spherical and rod-like morphologies are produced via in situ gallium azide precursor synthesis and decomposition in superheated toluene or THF. The solution reaction between gallium chloride and sodium azide produces an insoluble azide precursor that is then solvothermally decomposed to GaN at temperatures below 260 °C. The resulting products are poorly crystalline but thermally stable and crystallize to hexagonal GaN upon annealing at 750 °C. Product morphologies include spherical particles (ca. 50 nm) and nanorods. Upon annealing, the nanoparticles coalesce into larger organized crystalline structures with hexagonal facets.

Simulations of dopant pair-state distributions are presented for zincblende nanocrystals with different radii and for different dopant fractions. The probability of finding at least one pair-state and the concentration of pair-states were calculated on the basis of a statistical average of 105 simulations per crystal size and dopant concentration. The distribution of nanocrystal lattice positions over the surface and the bulk of the crystal is computed. A mathematical description of the distributions, valid in any crystal lattice, is discussed. This removes the need for further simulations.

Dendrimer nanocomposites (DNC) are hybrid nanoparticles formed by the dispersion and immobilization of guest atoms or small clusters in dendrimer matrices. They have a great potential in biomedical applications due to their controlled composition, predetermined size, shape and surface functionalities. In this work, nanocomposites of gold and poly(amidoamine) dendrimers {Au(0)n-PAMAM} have been selected to demonstrate this nanoparticle based concept. {Au(0)n-PAMAM} gold dendrimer nanocomposites with a well-defined size have been synthesized and imaged by TEM both in vitro and in vivo. Dendrimer nanocomposites have also the potential to be used as drug delivery vehicles either utilizing bioactive guests or incorporating radioactive isotopes. Radioactive dendrimer nanocomposites, e.g. {198-Au}, can be delivered to the tumor either by means of injecting the active nanoparticles directly into the tumor microvasculature or by intravenous injection. Both specific or non-specific targeting can be utilized in this process to achieve appropriate transfer.

We present a novel synthesis technique to grow bulk quantities of semiconductor nanowires at temperatures less than 500 °C. Gallium is used as the liquid medium in a mechanism similar to vapor-liquid-solid (VLS). We demonstrated this low temperature technique with silicon and carbon nanowires. Gallium exhibits extremely low solubility for several elemental semiconductors. This property enables nucleation and growth of nanometer scale wires from large sized gallium droplets (>1 μm) eliminating the need for creation of quantum sized metal droplets.

Hydrogen is the ideal means of energy storage for transportation and conversion of energy in a comprehensive clean-energy concept. However, appropriate storage facilities, both for stationary and for mobile applications, are complicated, because of the very low boiling point of hydrogen (20.4 K at 1 atm) and its low density in the gaseous state (90 g/m3). Furthermore, the storage of hydrogen in liquid or gaseous form imposes safety problems, in particular for mobile applications, e.g. the future zero-emission vehicle. Metal hydrides are a safe alternative for H-storage and, in addition, have a high volumetric energy density that is about 60% higher than that of liquid hydrogen. Mg hydride has a high storage capacity by weight and is therefore favoured for automotive applications. However, so far light metal hydrides have not been considered competitive because of their rather sluggish sorption kinetics. Filling a tank could take several hours. Moreover, the hydrogen desorption temperature of about 300 °C is rather high for most applications. A breakthrough in hydrogen storage technology was achieved by preparing nanocrystalline hydrides using high-energy ball milling. These new materials show very fast aband desorption kinetics within few minutes, thus qualifying lightweight Mg-based hydrides for storage application. In this paper recent detailed results on the sorption behaviour of nanocrystalline Mg and Mg-based alloys are presented. In a following research effort the sorption kinetics of nanocrystalline Mg has been further enhanced by catalyst additions. Furthermore, different transition metals have been added to Mg to achieve a thermodynamic destabilisation of the hydride, thus lowering the desorption temperatures to about 230 °C. The newly developed materials are currently being tested in prototype storage tanks.

This study evaluated the affects of 2 different solutions, e. g. deionized water and Hanks' Balanced Salt Solution (HBSS), on nanohardness and elastic modulus of dentin and enamel from human third molars at storage times of 0, 1, 7, 14 and 28 days using a modified AFM (Triboscope). The pH values of the solutions were monitored throughout the test periods. Storing the specimens in deionized water resulted in a large decrease of mechanical properties, e.g. the reduced elastic modulus of dentin decreased from 24.0 ±1.5 GPa to 21.0 ±1.6, 8.6 ±1.1 and 5.2 ±1.1 GPa for storage times of 1, 7 and 14 days, respectively. Mechanical properties of dentin and enamel dropped by more than 12% after one day and more than 50% after a week when stored in deionized water. The observed changes in mechanical response were attributed to a superficial demineralization process during storage. In contrast, storing teeth in HBSS did not significantly alter the mechanical properties of dentin or enamel over the time studied.

Three arguments are considered as main for peculiarity of nano-sized materials properties. An unusual and unique combination of properties can be feasible in ultra dispersed (nano-) materials, for examples, high hardness and superplasticity. Some examples of ultra dispersed materials applications working out by Atomic Energy Industry program are following.

Nanophase Ce-Cu-O powder has been synthesised via co-precipitation approach, whereas computer-assisted thermodynamic modelling was used to predict the optimum experimental criteria. The properties of Ce-Cu-O composite (10 mol% CuO) have been extensively investigated by a variety of techniques. The obtained materials show different morphology compared to other doped ceria salts, with uniform distribution of Ce and Cu throughout the powder. Detailed XRD study does not show the formation of solid solution and the composites consist of two separate metal oxides. X-ray absorption spectroscopy study shows a variation of the existence of Cu and Ce in several oxidation states. Copper oxide seems to exist evenly distributed along the surfaces and boundaries of the crystal grains of CeO2 on the nanoscale. The temperature-programmed reduction indicated that Ce-Cu-O composite has an enhanced oxygen storage capacity compared to CeO2 or pure copper oxide.

ZnFe2O4 nanoparticles were prepared by hydrothermal reduction approach. A considerable amount of α-Fe2O3 was segregated in the as-synthesized sample, which diffused into the tetrahedral and octahedral sites of the ZnFe2O4 spinel structure with increasing the annealing temperature. The introduction of Fe3+ into the tetrahedral positions was observed by Mössbauer spectra. Magnetization measurements showed an unusual ferrimagnetic behavior of the ZnFe2O4 phase, even at room temperature, confirming the introduction of Fe3+ into the tetrahedral sites of the spinel structure. Catalytic activity measured in the oxidative dehydrogenation of 1-butene reaction increased with increasing annealing temperature, indicating that those interactions of Fe3+ in tetrahedral and octahedral positions also promotes the activity and selectivity to butadiene formation.

We report a means of directly controlling DNA dehybridization by radio frequency magnetic field coupling to a nanometer scale antenna covalently linked to the DNA. The method of control relies on induction heating of an Au nanocrystal, which raises the temperature of a biomolecule to which it is covalently bound, while leaving surrounding molecules relatively unaffected. Because heat dissipation in biomolecules in solution is rapid(<50 picoseconds[1]) this switching is reversible. This technique is specific, reversible, and non-optical. Since it can be used in solution, it has the potential to be extended to systems in vivo. The ability to differentially control local temperature forms the basis of control of properties such as hybridization and enzyme activity, and has the potential of controlling many biological processes.

A transition from a normal Hall-Petch relationship to an abnormal one is observed at a grain size of approximately 18.5 nm for nano-RuAl. Several models each representing a controlling factor have been employed to rationalize the transition mechanism. The grain sizes corresponding to the dislocation pile-ups lower bound [2] in grain interior are much smaller than the observed transition grain size and no apparent transition grain size has been derived from the grain size dependence of unit cell volume change [5]. While the grain sizes corresponding to the transition of strain rate according to Coble creep [1] and to the significant triple junction volume fraction [3, 4] (1 %) are well consistent with the observed transition grain size. The overall results indicate that the transition of H-P relationship is dominated by the weakening effect of grain boundaries and triple junctions.

This paper reports the observation of HgTe precipitate formation and its subsequent evolution in a PbTe semiconductor matrix containing 4 mol. % HgTe (PbTe-4HgTe) produced by a controlled precipitation process. The controlled precipitation process is being developed as a new way to produce a large number of quality semiconductor nanocrystals more simply than the conventional methods. Characterization of the HgTe precipitates resulting from application of controlled precipitation to the PbTe-4HgTe alloy system provides evidence that this method is effective in generating nanocrystals. Transmission electron microscopy of the processed alloys reveals that HgTe precipitates are extremely small in size, maintain a coherent interface, and experience a unique shape evolution with aging.

Ultrafine cobalt particles in AlMCM41 silica tubes have been synthesized by ion exchange and the reduction with sodium borohydride. The role of this stable host matrix of AlMCM41 silica is to prevent agglomeration of the magnetic particles attached to the walls of AlMCM41 silica pores. The size of the host pores naturally limits the particle dimensions and thus improves their size distribution. Both magnetic susceptibility measurements and transmission electron microscopy (TEM) show a narrow distribution size of the nanoparticles. Well controlled insertion of the magnetic material to the host channel excludes formation of bulk particles outside the host material grains, which was confirmed by the TEM studies. X-ray diffraction data did not show peaks corresponding to a crystalline cobalt, but this maybe due to small size of particles and their relatively small volume fraction. The content of Co in the AlMCM41 host was measured using both magnetic measurements and elemental analysis.

We have previously described the synthesis of a family of molecular ‘squares’ based on octahedral Re(I) coordination of difunctional bridging ligands. The size and chemical composition of the square cavity is highly tunable, and the inorganic cyclophanes are being actively studied in catalytic, separations, and sensing applications. Electrochemical techniques have been primary methods for characterization of the transport properties of thin films of the nanostructured materials. For example, cyclic voltammetry and rotating disk electrode voltammetry experiments have revealed size-selective permeation by redox probes, where the size cutoff is determined by the internal square dimensions. We have more recently begun to employ scanning electrochemical microscopy to spatially image micropatterned electrodes containing these thin film materials, simultaneously allowing us to obtain permeability data and topographical information. This paper describes data obtained by employing porphyrin-based molecular squares that feature chemically tailored cavities.

Nanometer-sized bismuth has successfully been prepared using a high-temperature organic reducing system by presence of proper capping/stabilizing agents. Self-assembly of bismuth was, at the first time, obtained using size-selected nanoparticles (15nm in size). Various synthetic conditions, which may significantly affect the formation of self-assembled nanocrystalline bismuth, have been optimized and discussed in this paper. The as-prepared nanocrystallites exist in a single rhombohedral phase with high crystallinity, and oxidation problem has been efficiently overcome within limited period by employing this method.

A novel surface modification process is presented, which creates a macroscopically smooth and a nanoscopically rough surface on an austenitic stainless steel. The chemical structure of the oxide layer is changed due to the acid treatment, whereas the thickness is not increased. An altered chromiumoxide content in the passive layer connected with a high bonding strength to the substrate material suggests the use of these wet chemically modified steels in biomedical applications.

Electrical properties of icosahedral phases (I-phase) that precipitated in Zr65Al7.5Cu7.5Ni10M10 (M=Ag, Pd), Zr65Al7.5Cu1.25Ni10M5 (M=Ag, Pd), Zr65Pd25Ni10 and Zr70Pd20Ni10 metallic glasses have been investigated. In-situ resistivity change with increasing temperature was measured at a heating rate of 0.67 K/s from room temperature. I-phase transformation was occurred in the supercooled liquid phase for Zr-Al-Cu-Ni-M glasses, followed by the crystallization to stable Zr2Ni- and Zr2Cu-type crystals. Ternary glasses exhibited the I-phase crystallization from the glass solid phase and subsequently the transformation of I-phase to crystal phases like Zr2Ni and Zr2Pd. The resistivity of I-phase decreased together with advancing I-phase precipitation, about 2 % compared to the resistivity of the supercooled liquid phase, for typical Zr65Al7.5Cu7.5Ni10Ag10 glass. On the other hand, Zr70Pd20Ni10 glass showed the resistivity increment of about 5 % just after completing I-phase crystallization. Low temperature conductivity of Zr65Al7.5Cu7.5Ni10Ag10 and Zr70Pd20Ni10 glasses and I-phases may be explained by the weak localization model of conduction electron in the range from about 20 K to room temperature.