Chemical vapor functionalization: a continuous production process for functionalized ZnO nanoparticles

The continuous functionalization of nanoparticles in the gas-phase directly after their generation, chemical vapor functionalization, is studied with ZnO and 1-hexanol as a model system using two reactors in series. In the first reactor ZnO nanoparticles are synthesized in the gas-phase from diethylzinc and oxygen at 1,073 K with grain sizes of 13 nm as determined by Rietveld refinement of X-ray diffractograms. The second reactor, connected at the exit of the first reactor and kept at lower temperatures (573, 673, and 773 K), is used as a functionalization chamber. At the connection point of the two reactors, the vapor of 1-hexanol is injected to react with the surface of ZnO nanoparticles in the gas phase. The process has been analyzed by quadrupole mass spectrometry to obtain information about optimal conditions for functionalization. Dynamic light scattering data show that the functionalized particles have substantially improved colloidal dispersibility with hydrodynamic diameters of 60 nm. Diffuse reflectance fourier transform infrared spectra and ¹H nuclear magnetic resonance spectra are consistent with 1-hexanol adsorbed at the particle surface acting as a functionalizing agent. The agglomerate size is substantially reduced owing to chemical vapor functionalization.     

Blocked-micropores,surface functionalized,bio-compatible and silica-coated iron oxide nanocomposites as advanced MRI contrast agent

Quasi-critical fluctuations occur close to critical points or close to continuous phase transitions. In three-dimensional systems, precision tuning is required to access the fluctuation regime. Lowering the dimensionality enhances the parameter space for quasi-critical fluctuations considerably. This enables one to make use of novel properties emerging in fluctuating systems, such as giant susceptibilities, Casimir forces or novel quasi-particle interactions. Examples are discussed ranging from simple metal–adsorbate systems to unconventional superconductivity in iron-based superconductors.     

Aluminum-doped ZnO nanoparticles: gas-phase synthesis and dopant location

Printed electronics, as an extension to conventional electronics, has grown considerably for decades. At this moment, therefore, tracing the development of this technology up to the present will provide researchers and R&D planners with better understanding of the technology’s evolving characteristics and insights for further R&D directions. This paper carries out two bibliographic analyses to study the technology development life cycle and the technological knowledge within the area of printed electronics. First, we fit a growth curve to yearly patent registration data, thereby calculating several indicators, including the current technological maturity ratio, the number of potential future patents and the expected remaining life. Second, we identify the core and brokering technology classes within the overall technology network of printed electronics by combining patent co-classification analysis and social network analysis. As a result, we could obtain some findings from the inventional point of view; the technological development of printed electronics has entered the maturity stage, and the expected remaining life was 8.5 years as of the beginning of 2013. In addition, we identified several technology areas that have the high importance to act as both core and brokering technologies, apparatus for metal working, anti-inductive structures, and electronic circuit control systems.     

A new probe for local structure: Paramagnetic hyperfine structure in Nd3+ Mössbauer spectra

The⁴I_9/2 ground state of Nd³⁺ (4f³) is split by a crystal field of lower than cubic symmetry into five Kramer doublets. The magnetic hyperfine interactions can be calculated by using an effective magnetic hyperfine tensor Ã, which is obtained from the linear combination coefficients of the ground state doublet eigenvector. The hyperfine tensor à and the line shape depend strongly on the local structure of the system. Nondiagonal magnetic hyperfine interactions produce nonadiabatic relaxation. Corresponding lineshapes are calculated by means of the Clauser-Blume model and the eigenvalue treatment of superoperators. We found for Nd³⁺ in the investigated laser phosphate glass a network-forming function consistent with aC _3h orD _3h point symmetry.     

An investigation of a genomewide supported psychosis variant in ZNF804A and white matter integrity in the human brain

ZNF804A, a genomewide supported susceptibility gene for schizophrenia and bipolar disorder, has been associated with task-independent functional connectivity between the left and right dorsolateral prefrontal cortices. Several lines of evidence have converged on the hypothesis that this effect may be mediated by structural connectivity. We tested this hypothesis using diffusion tensor magnetic resonance imaging in three samples: one German sample of 50 healthy individuals, one Scottish sample of 83 healthy individuals and one Scottish sample of 84 unaffected relatives of bipolar patients. Voxel-based analysis and tract-based spatial statistics did not detect any fractional anisotropy (FA) differences between minor allele carriers and individuals homozygous for the major allele at rs1344706. Similarly, region-of-interest analyses and quantitative tractography of the genu of the corpus callosum revealed no significant FA differences between the genotype groups. Examination of effect sizes and confidence intervals indicated that this negative finding is very unlikely to be due to a lack of statistical power. In summary, despite using various analysis techniques in three different samples, our results were strikingly and consistently negative. These data therefore suggest that it is unlikely that the effects of genetic variation at rs1344706 on functional connectivity are mediated by structural integrity differences in large, long-range white matter fiber connections.     

The influence of sintering conditions on the phase purity of bulk EuTiO3 and Eu0.5Ba0.5TiO3 ceramics

EuTiO₃ and Eu_0.5Ba_0.5TiO₃ ceramics were synthesized using mechanochemical activation of oxide precursors and then calcined. The uniaxially as well as isostatically pressed samples were sintered in different kinds of reducing atmospheres, namely Ar?+?(7–10)%H₂, respectively, 99.99%H₂ in the case of pressureless sintering or in vacuum (enriched by CO vapors) in the case of pressure-assisted spark plasma sintering (SPS). The samples prepared by SPS contained the pyrochlore phase as the second phase. In contrast with SPS, pressureless sintered samples were phase pure, although thermodynamics calculations showed that CO atmosphere in SPS is more reducing than pure hydrogen. This is explained by short sintering times in SPS that do not allow establishment of the thermodynamic equilibrium. The proper choice of sintering temperature, time, and atmosphere enabled preparation of dense and phase pure samples of Eu _x Ba_{1? x} TiO₃ ceramics suitable for the evaluation of “true” physical properties (e.g., infrared reflectivity), or for experimental confirmation of specific functionalities proposed from theory.     

Silica-based composite and mixed-oxide nanoparticles from atmospheric pressure flame synthesis

Binary TiO₂/SiO₂ and SnO₂/SiO₂ nanoparticles have been synthesized by feeding evaporated precursor mixtures into an atmospheric pressure diffusion flame. Particles with controlled Si:Ti and Si:Sn ratios were produced at various flow rates of oxygen and the resulting powders were characterized by BET (Brunauer–Emmett–Teller) surface area analysis, XRD, TEM and Raman spectroscopy. In the Si–O–Ti system, mixed oxide composite particles exhibiting anatase segregation formed when the Si:Ti ratio exceeded 9.8:1, while at lower concentrations only mixed oxide single phase particles were found. Arrangement of the species and phases within the particles correspond to an intermediate equilibrium state at elevated temperature. This can be explained by rapid quenching of the particles in the flame and is in accordance with liquid phase solubility data of Ti in SiO₂. In contrast, only composite particles formed in the Sn–O–Si system, with SnO₂ nanoparticles predominantly found adhering to the surface of SiO₂ substrate nanoparticles. Differences in the arrangement of phases and constituents within the particles were observed at constant precursor mixture concentration and the size of the resultant segregated phase was influenced by varying the flow rate of the oxidant. The above effect is due to the variation of the residence time and quenching rate experienced by the binary oxide nanoparticles when varying the oxygen flow rate and shows the flexibility of diffusion flame aerosol reactors.     

Paramagnetic relaxation of Nd3+ in glasses from Mössbauer spectra

Glasses containing Nd₂O₃ were studied by¹⁴⁵Nd(72.5 keV) Mössbauer spectroscopy. The spectra depend strongly on the concentration of Nd³⁺ and on temperature.