NiO has been analyzed by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) analysis, and X-ray photoelectron spectroscopy (XPS) for bulk-scale and nanosized polycrystalline samples. XAFS indicates that the 5-and 25-nm NiO materials show bulk-like structural properties, with the exception of a lattice contraction, relative to the bulk material, and exhibit the anticipated decrease in average coordination numbers typically observed for nanoparticle systems. Carefully calibrated high-resolution XRD measurements confirm the lattice contraction for the nanoparticles. XPS also indicates the surface of NiO is comparable across the size scale for both binding energies and characteristic Ni 2p satellite structure. Detailed examination of the Ni 2p and O 1s regions reveals that hydroxylation upon prolonged exposure to the ambient causes a noticeable change in the Ni 2p peak shape that could be misinterpreted as an artifact of particle size.

Rock-salt NiO and Ni0.7Zn0.3O nanoparticles were investigated by x-ray diffraction, atomic-force microscopy, and magnetic measurements. Nanoparticle diameters varied from 8 to 30 nm depending on reaction conditions. There are two main magnetization contributions, the field-induced spin canting of the antiferromagnetic sublattices and the magnetization rotation caused by uncompensated spins interacting with the magnetic field. The former is a bulk effect, modified by the presence of Zn, whereas the latter is a nanoscale effect that increases with decreasing particle size. The relative contributions of the two effects depend on particle size with a critical size of about 18 nm resulting in bulklike behavior.

X-ray photoelectron spectra were obtained for a series of M-TiO 2 samples in which transition metal ions are directly attached to the surface of anatase TiO 2 nanocrystals. The samples were prepared using CrCl 3 .nH 2 O, MnCl 2 .nH 2 O, FeCl 2 .nH 2 O, CoCl 2 .nH 2 O, NiCl 2 .nH 2 O, and CuCl 2 .nH 2 O as metal sources. We observed spontaneous air oxidation of the metal for the Mn-TiO 2 and Fe-TiO 2 samples as indicated by rapid color changes. X-ray photoelectron spectroscopy (XPS) data confirms the oxidation states of the metals Cr, Co, and Ni are unchanged from the precursor, Mn and Fe are oxidized, and Cu is in a more reduced state. The reduction of Cu likely arises during the XPS experimenta phenomenon well-documented in the literature; whereas UV-visible data of the Cu-TiO 2 dispersions are consistent with Cu 2+ .

Ruthenium nanocrystals were prepared upon decomposition of Ru 3 (CO) 12 at high temperature in the presence of alkylamine stabilizers. The reaction produced a dark brown colloid that was processed with toluene/ethanol as solvent/nonsolvent pair. The materials were characterized using high resolution electron microscopy and powder X-ray diffraction. The Ru nanocrystals were single crystals with a hcp structure, and displayed regular facets. At lower temperatures nucleation was followed by attachment to yield mesoscale polycrystalline branched ruthenium structures.