67 research outputs found
Using Cognitive Coaching to Build School Leadership Capacity: A Case Study in Alberta
The impact of Cognitive Coaching included as part of the Leader2Leader (L2L)Leadership Pilot Program for beginning principals in Alberta, Canada, was evaluated in the present study. Fifteen qualified principals (coaches) and 23 new principals completed the L2L Pilot Program that took place over 18 months. Questionnaires for coaches and new principals were used to obtain reactions to the Cognitive Coaching component. The findings suggest that the L2L Leadership Program can help develop a network of reflective, self-reliant school principals. Recommendations for improving the Cognitive Coaching component of the L2L Leadership Program are provided
Electronic structures of B-2p and C-2p of boron-doped diamond film by soft X-ray absorption and emission spectroscopy
X-ray absorption (XAS) and emission (XES) spectroscopy near B-K and C-K edges
have been performed on metallic (~1at%B, B-diamond) and semiconducting
(~0.1at%B and N, BN-diamond) doped-diamond films. Both B-K XAS and XES spectra
shows metallic partial density of state (PDOS) with the Fermi energy of 185.3
eV, and there is no apparent boron-concentration dependence in contrast to the
different electric property. In C-K XAS spectrum of B-diamond, the impurity
state ascribed to boron is clearly observed near the Fermi level. The Fermi
energy is found to be almost same with the top of the valence band of non-doped
diamond, E_V, 283.9 eV. C-K XAS of BN-diamond shows both the B-induced shallow
level and N-induced deep-and-broad levels as the in-gap states, in which the
shallow level is in good agreement with the activation energy (E_a=0.37 eV)
estimated from the temperature dependence of the conductivity, namely the
change in C-2p PDOS of impurity-induced metallization is directly observed. The
electric property of this diamond is mainly ascribed to the electronic
structure of C-2p near the Fermi level. The observed XES spectra are compared
with the DVX-alpha cluster calculation. The DVX-alpha result supports the
strong hybridization between B-2p and C-2p observed in XAS and XES spectra, and
suggests that the small amount of borons (<1at%) in diamond occupy the
substitutional site rather than interstitial site.Comment: submitted to Phys. Rev. B, 5 pages and 5 figure
Carbon States in Carbon-Encapsulated Nickel Nanoparticles Studied by Means of X-Ray Absorption, Emission, and Photoelectron Spectroscopies
Electronic structure of nickel nanoparticles encapsulated in carbon was
characterized by photoelectron, X-ray absorption, and X-ray emission
spectroscopies. Experimental spectra are compared with the density of states
calculated in the frame of the density functional theory. The carbon shell of
Ni nanoparticles has been found to be multilayer graphene with significant
(about 6%) amount of Stone--Wales defects. Results of the experiments evidence
protection of the metallic nanoparticles from the environmental degradation by
providing a barrier against oxidation at least for two years. Exposure in air
for 2 years leads to oxidation only of the carbon shell of Ni@C nanoparticles
with coverage of functional groups.Comment: 16 pages, 6 figures, accepted in J. Phys. Chem.
Nitrogen-Functionalized Graphene Nanoflakes (GNFs:N): Tunable Photoluminescence and Electronic Structures
This study investigates the strong photoluminescence (PL) and X-ray excited
optical luminescence observed in nitrogen-functionalized 2D graphene nanoflakes
(GNFs:N), which arise from the significantly enhanced density of states in the
region of {\pi} states and the gap between {\pi} and {\pi}* states. The
increase in the number of the sp2 clusters in the form of pyridine-like N-C,
graphite-N-like, and the C=O bonding and the resonant energy transfer from the
N and O atoms to the sp2 clusters were found to be responsible for the blue
shift and the enhancement of the main PL emission feature. The enhanced PL is
strongly related to the induced changes of the electronic structures and
bonding properties, which were revealed by the X-ray absorption near-edge
structure, X-ray emission spectroscopy, and resonance inelastic X-ray
scattering. The study demonstrates that PL emission can be tailored through
appropriate tuning of the nitrogen and oxygen contents in GNFs and pave the way
for new optoelectronic devices.Comment: 8 pages, 6 figures (including toc figure
Change of Structural Behaviors of Organo-Silane Exposed Graphene Nanoflakes
[[abstract]]The electronic structures of graphene nanoflakes (GNFs) exposed to an organo-silane precursor [tetramethylsilane, TMS, Si(CH3)4] were studied using electron field emission (EFE), Raman spectroscopy, X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES), and first-principles calculation. The results of XANES, XPS, and Raman spectroscopy indicate that the silyl radical strong covalent bonds were formed in GNFs, which induced local structural relaxations and enhanced sp3 hybridization. Comparison of calculated electronic structure, XANES, and XES spectra of Sitreated GNFs suggests that the Si atom substitutes one 3-fold coordinated C atom in a given graphene layer and relaxes outward to form sp3 bonding with another C atom in the adjacent graphene layer. The EFE measurements show an increase in the turn-on electric field with the increase of the Si content, which suggests an enhancement of the nonmetallic sp3 bonding[[journaltype]]國外[[incitationindex]]SCI[[booktype]]紙本[[countrycodes]]US
The Effect of Thermal Reduction on the Photoluminescence and Electronic Structures of Graphene Oxides
[[abstract]]Electronic structures of graphene oxide (GO) and hydro-thermally reduced graphene oxides (rGOs)processed at low temperatures (120–1806C) were studied using X-ray absorption near-edge structure XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). C K-edge XANES spectra of rGOs reveal that thermal reduction restores C 5 C sp2 bonds and removes some of the oxygen and hydroxyl groups of GO, which initiates the evolution of carbonaceous species. The combination of C K-edge XANES and Ka XES spectra shows that the overlapping p and p* orbitals in rGOs and GO are similar to that of highly ordered pyrolytic graphite (HOPG), which has no band-gap. C Ka RIXS spectra provide evidence that thermal reduction changes the density of states (DOSs) that is generated in the p-region and/or in the gap between the p and p* levels of the GO and rGOs. Two-dimensional C Ka RIXS mapping of the heavy reduction of rGOs further confirms that the residual oxygen and/or oxygen-containing functional groups modify the p and s features, which are dispersed by the photon excitation energy. The dispersion behavior near the K point is approximately linear and differs from the parabolic-like dispersion observed in HOPG.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[ispeerreviewed]]Y[[booktype]]電子版[[countrycodes]]GB
Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and EmissionSpectroscopy Study
Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements
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