187 research outputs found
Analyzing the frequency shift of physiadsorbed CO2 in metal organic framework materials
Combining first-principles density functional theory simulations with IR and
Raman experiments, we determine the frequency shift of vibrational modes of CO2
when physiadsorbed in the iso-structural metal organic framework materials
Mg-MOF74 and Zn-MOF74. Surprisingly, we find that the resulting change in shift
is rather different for these two systems and we elucidate possible reasons. We
explicitly consider three factors responsible for the frequency shift through
physiabsorption, namely (i) the change in the molecule length, (ii) the
asymmetric distortion of the CO molecule, and (iii) the direct influence of
the metal center. The influence of each factor is evaluated separately through
different geometry considerations, providing a fundamental understanding of the
frequency shifts observed experimentally.Comment: 9 pages, 4 figure
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Metalloporphyrin-based MOFs: First Cobalt Based TPPS-bipy Coordination Network
Poster presentado en el congreso: Third International Conference on Multifunctional, Hybrid and Nanomaterials (3-7 March 2013, Sorrento, Italy)Supramolecular entities based on self-assembly of metalloporphyrins are paradigmatic examples of the great efficiency of the nanodevices used by natural systems in photosynthesis, oxygen transport, electron transfer and catalysis. Thus, porphyrin catalysts are well-known to be highly efficient in many catalytic reactions and, during the last years, a great effort has been devoted to the immobilization of distinct types of catalysts on solids.
In this sense, recent strategy consists of the immobilization of catalysts in MOFs (metal-organic frameworks). In our group we have started exploring the possibility of using metalloporphyrins both as structural units in MOFs and catalyst, in the same compound.Ministerio de Ciencia e Innovación (MAT2010-15375) y Gobierno Vasco (Basque University System Research Groups, IT-177-07
Co-doping Strategy for Developing Perovskite Oxides as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction
A synergistic co-doping strategy is proposed to identify a series of BaCo0.9–xFexSn0.1O3–δ perovskites with tunable electrocatalytic activity for the oxygen evolution reaction (OER). Simply through tailoring the relative concentrations of less OER-active tin and iron dopants, a cubic perovskite structure (BaCo0.7Fe0.2Sn0.1O3–δ) is stabilized, showing intrinsic OER activity >1 order of magnitude larger than IrO2 and a Tafel slope of 69 mV dec−1
Proteins Identified from Saliva and Salivary Glands of the Chinese Gall Aphid Schlechtendalia chinensis
Aphid saliva plays an essential role in the interaction between aphids and
their host plants. Several aphid salivary proteins have been identified but
none from galling aphids. Here the salivary proteins from the Chinese gall
aphid are analyzed, Schlechtendalia chinensis, via an LC-MS/MS analysis.
A total of 31 proteins are identified directly from saliva collected via an
artificial diet, and 141 proteins are identified from extracts derived from
dissected salivary glands. Among these identified proteins, 17 are found in
both collected saliva and dissected salivary glands. In comparison with
salivary proteins from ten other free-living Hemipterans, the most striking
feature of the salivary protein from S. chinensis is the existence of high
proportion of proteins with binding activity, including DNA-, protein-, ATP-,
and iron-binding proteins. These proteins maybe involved in gall formation.
These results provide a framework for future research to elucidate the
molecular basis for gall induction by galling aphids
Hot probe measurements on neutron irradiated, isotope enriched ZnO nanorods
We report on neutron transmutation doping (NTD) of isotopically (64Zn) enriched ZnO nanorods to produce material with holes as the majority mobile carrier. Nanorods of ZnO enriched with 64Zn were synthesised and the abundance of 64Zn in these samples is ∼ 71%, compared to the natural abundance of ∼ 49 %. The enriched material was irradiated with thermal neutrons which converts some 64Zn to 65Zn. The 65Zn decays to 65Cu with a half-life of 244 days and the Cu can act as an acceptor dopant. After 690 days, a hot probe technique was used to determine the majority charge carriers in non-irradiated and neutron irradiated nanorod samples. Non-irradiated samples were measured to be to have electrons as the majority mobile carrier and the irradiated samples were measured to have holes as the majority mobile carrier
Infrared optical absorbance of intersubband transitions in GaN/AlGaN multiple quantum well structures
Intersubband transitions in Si-doped molecular beam epitaxygrown GaN/AlGaN multiple quantum wells on c-plane sapphire were investigated using the Fourier-transform infrared optical absorption technique. Several GaN quantum well samples were grown with either AlGaN bulk or GaN/AlGaN short period superlattice barriers. The measurements were made in a waveguide configuration utilizing a facet polished at 45° to the c plane. The integrated area of the intersubband transitions in several waveguides cut from different location of the wafer was measured, from which we estimated the two-dimensional electron gas density (σ). The measured values of σ are about two orders of magnitude larger than the Si doping level of ∼8×1017 cm−3, which is consistent with the polarization effects, particularly considering the large number of GaN/AlGaN interfaces. The internal quantum efficiency of the intersubband transitions was estimated to be on the order of 40% for samples with superlattice barriers
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