Electronic states and phases of KxC60 from photoemission and X-ray absorption spectroscopy

HIGH-resolution photoemission and soft X-ray absorption spectroscopies have provided valuable information on the electronic structure near the Fermi energy in the superconducting copper oxide compounds 1-4, helping to constrain the possible mechanisms of superconductivity. Here we describe the application of these techniques to K(x)C60, found recently to be superconducting below 19.3 K for x almost-equal-to 3 (refs 5-7). The photoemission and absorption spectra as a function of x can be fitted by a linear combination of data from just three phases, C60, K3C60, and K6C60, indicating that there is phase separation in our samples. The photoemission spectra clearly show a well defined Fermi edge in the K3C60 phase with a density of states of 5.2 x 10(-3) electrons eV-1 angstrom-3 and an occupied-band width of 1.2 eV, suggesting that this phase may be a weakly coupled BCS-like (conventional) superconductor. The C1s absorption spectra show large non-rigid-band shifts between the three phases with half and complete filling, in the K3C60 and K6C60 phases respectively, of the conduction band formed from the lowest unoccupied molecular orbital of C60. These observations clearly demonstrate that the conduction band has C 2p character. The non-rigid-band shift coupled with the anomalous occupied-band width implies that there is significant mixing of the electronic states of K and C60 in the superconducting phase

Hollow Sodium Tungsten Bronze (Na0.15WO3) Nanospheres: Preparation, Characterization, and Their Adsorption Properties

We report herein a facile method for the preparation of sodium tungsten bronzes hollow nanospheres using hydrogen gas bubbles as reactant for chemical reduction of tungstate to tungsten and as template for the formation of hollow nanospheres at the same time. The chemical composition and the crystalline state of the as-prepared hollow Na0.15WO3nanospheres were characterized complementarily, and the hollow structure formation mechanism was proposed. The hollow Na0.15WO3nanospheres showed large Brunauer–Emment–Teller specific area (33.8 m2 g−1), strong resistance to acids, and excellent ability to remove organic molecules such as dye and proteins from aqueous solutions. These illustrate that the hollow nanospheres of Na0.15WO3should be a useful adsorbent

Measurement of w-InN/h-BN Heterojunction Band Offsets by X-Ray Photoemission Spectroscopy

X-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) of the w-InN/h-BN heterojunction. We find that it is a type-II heterojunction with the VBO being −0.30 ± 0.09 eV and the corresponding conduction band offset (CBO) being 4.99 ± 0.09 eV. The accurate determination of VBO and CBO is important for designing the w-InN/h-BN-based electronic devices

A shared role for RBF1 and dCAP-D3 in the regulation of transcription with consequences for innate immunity

Previously, we discovered a conserved interaction between RB proteins and the Condensin II protein CAP-D3 that is important for ensuring uniform chromatin condensation during mitotic prophase. The Drosophila melanogaster homologs RBF1 and dCAP-D3 co-localize on non-dividing polytene chromatin, suggesting the existence of a shared, non-mitotic role for these two proteins. Here, we show that the absence of RBF1 and dCAP-D3 alters the expression of many of the same genes in larvae and adult flies. Strikingly, most of the genes affected by the loss of RBF1 and dCAP-D3 are not classic cell cycle genes but are developmentally regulated genes with tissue-specific functions and these genes tend to be located in gene clusters. Our data reveal that RBF1 and dCAP-D3 are needed in fat body cells to activate transcription of clusters of antimicrobial peptide (AMP) genes. AMPs are important for innate immunity, and loss of either dCAP-D3 or RBF1 regulation results in a decrease in the ability to clear bacteria. Interestingly, in the adult fat body, RBF1 and dCAP-D3 bind to regions flanking an AMP gene cluster both prior to and following bacterial infection. These results describe a novel, non-mitotic role for the RBF1 and dCAP-D3 proteins in activation of the Drosophila immune system and suggest dCAP-D3 has an important role at specific subsets of RBF1-dependent genes

Partial spectral weights of disordered Cu-Au alloys

We present valence band photoemission spectra of polycrystalline CuxAu1-x (x = 0.10, 0.25, 0.50, 0.75, 0.90) disordered binary alloys taken with variable incident-photon energies using synchrotron radiation. Taking advantage of the Cooper minimum phenomenon of the Au 5d band and taking proper account of the photoionization matrix element, we obtain experimental partial spectral weights for the alloys determined from the measured ratio of Au 5d and Cu 3d photoionization cross sections. We find that the Au partial density of states in dilute Au alloys is very strongly hybridized with the Cu host band and its bandwidth is not much reduced, contrary to the conclusion of some earlier work which claimed that the Au states have a greatly narrowed bandwidth due to the band repulsion between different d bands. Our finding is consistent with recent theoretical results. The lattice relaxation effect on the electronic structures of Cu-Au alloys is also investigated using ultraviolet photoemission spectroscopy. Compared with the bandwidths of ordered alloys which do not suffer lattice relaxation, those of disordered alloys are reduced by a small amount, which can be interpreted as the result of both the total volume change and the lattice relaxation effects, whose magnitudes are comparable.open1110sciescopu