Time-resolved x-ray excited optical luminescence (XEOL) and x-ray absorption near edge structures have been employed to study the origin of the multicolor luminescence from SnO2 nanoribbons. The authors find that the yellow-green luminescence has a long lifetime while the blue luminescence a short one. The luminescence is attributed to the radiative decay of trapped electrons in oxygen vacancies just below the conduction band and electrons in the conduction band to intrinsic surface states in the band gap.

ZnO nanostructures, including single-crystal nanowires, nanoneedles, nanoflowers, and tubular whiskers, have been fabricated at a modestly low temperature of 550 degrees C via the oxidation of metallic Zn powder without a metal catalyst. Specific ZnO nanostructures can be obtained at a specific temperature zone in the furnace depending on the temperature and the pressure of oxygen. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) studies show that ZnO nanostructures thus prepared are single crystals with a wurtzite structure. X-ray excited optical luminescence (XEOL) from the ZnO nanostructures show noticeable morphology-dependent luminescence. Specifically, ZnO nanowires of around 15 nm in diameter emit the strongest green light. The morphology of these nanostructures, their XEOL, and the implication of the results will be discussed.

A collective order of spin and charge degrees of freedom into stripes has been predicted to be a possible ground state of hole-doped Cuo 2 planes, which are the building blocks of hightemperature superconductors. In fact, stripe-like spin and charge order has been observed in various layered cuprate systems. For the prototypical high-temperature superconductor La 2 − x sr x Cuo 4 , no charge-stripe signal has been found so far, but several indications for a proximity to their formation. Here we report the observation of a pronounced charge-stripe signal in the near surface region of 12-percent doped La 2 − x sr x Cuo 4 . We conclude that this compound is sufficiently close to charge stripe formation that small perturbations or reduced dimensionality near the surface can stabilize this order. our finding of different phases in the bulk and near the surface of La 2 − x sr x Cuo 4 should be relevant for the interpretation of data from surface-sensitive probes, which are widely used for La 2 − x sr x Cuo 4 and similar systems.