The synchrotron x-ray absorption near edge structures (XANES) technique was used in conjunction with first-principles calculations to characterize Al-doped ZnO films. Standard characterizations revealed that the amount of carrier concentration and mobility depend on the growth conditions, i.e. H 2 ðor O 2 Þ=Ar gas ratio and Al concentration. First-principles calculations showed that Al energetically prefers to substitute on the Zn site, forming a donor Al Zn , over being an interstitial (Al i ). The measured Al K-edge XANES spectra are in good agreement with the simulated spectra of Al Zn , indicating that the majority of Al atoms are substituting for Zn. The reduction in carrier concentration or mobility in some samples can be attributed to the Al Zn -V Zn and 2Al Zn -V Zn complex formations that have similar XANES features. In addition, XANES of some samples showed additional features that are the indication of some -Al 2 O 3 or nAl Zn -O i formation, explaining their poorer conductivity.

A combination of X-ray absorption spectroscopy (XAS) measurements and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations has been applied to elucidate detailed information on the hydration structures of Ca(2+) and Cl(-). The XAS spectra (extended X-ray absorption fine structure, EXAFS, and X-ray absorption near-edge structure, XANES) measured from aqueous CaCl(2) solution were analyzed and compared to those generated from snapshots of QM/MM MD simulations of Ca(2+) and Cl(-) in water. With regard to this scheme, the simulated QM/MM-EXAFS and QM/MM-XANES spectra, which correspond to the local structure and geometrical arrangement of the hydrated Ca(2+) and Cl(-) at molecular level show good agreement with the experimentally observed EXAFS and XANES spectra. From the analyses of the simulated QM/MM-EXAFS spectra, the hydration numbers for Ca(2+) and Cl(-) were found to be 7.1 +/- 0.7 and 5.1 +/- 1.3, respectively, compared to the corresponding values of 6.9 +/- 0.7 and 6.0 +/- 1.7 derived from the measured EXAFS data. In particular for XANES results, it is found that ensemble averages derived from the QM/MM MD simulations can provide reliable QM/MM-XANES spectra, which are strongly related to the shape of the experimental XANES spectra. Since there is no direct way to convert the measured XANES spectrum into details relating to geometrical arrangement of the hydrated ions, it is demonstrated that such a combined technique of XAS experiments and QM/MM MD simulations is well-suited for the structural verification of aqueous ionic solutions.

NiAl 2 O 4 , CuAl 2 O 4 , and ZnAl 2 O 4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine (DEA) as a fuel. The effects of calcination temperature on structure, crystallinity, morphology, and optical properties of MAl 2 O 4 (M = Ni, Cu, Zn) have been investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) spectroscopy. The XRD and FT-IR results confirm the formation of single-phase spinel structure of NiAl 2 O 4 , CuAl 2 O 4 , and ZnAl 2 O 4 at 1200, 1000, and 600 ℃, respectively. The direct band gap of these aluminate spinels, calculated from UV-DRS spectra using the Kubelka-Munk function, is found to increase with calcination temperature. The PL spectra demonstrate that NiAl 2 O 4 gives the highest blue emission intensity, while CuAl 2 O 4 and ZnAl 2 O 4 exhibit a very strong violet emission. During fluorescence process, the ZnAl 2 O 4 emits visible light in only violet and blue regions, while NiAl 2 O 4 and CuAl 2 O 4 emissions extend to the green region. It seems therefore that the transition metal type and intrinsic defects in these aluminate powders are responsible for these phenomena.