Raman spectroscopy investigation of magnesium oxide nanoparticles.

We investigate Raman spectra (100 cm to 3900 cm) of magnesium oxide nanoparticles with nominal sizes of 10 nm, 20 nm, 40 nm, 50 nm, and 300 nm. The crystal structure of MgO prohibits first-order modes and yet, there are numerous reports of relatively intense peaks throughout the literature. Raman signals at approximately 278 cm and 445 cm that were attributed to MgO nanoparticles by previous authors are shown to belong to layers of Mg(OH) formed on the surface of MgO nanoparticles.

In Operando Photoswitching of Cu Oxidation States in Cu-Based Plasmonic Heterogeneous Photocatalysis for Efficient H Evolution.

Metal nanoparticles (NP) supported on TiO are known to be efficient photocatalysts for solar-to-chemical energy conversion. While TiO decorated with copper NPs has the potential to become an attractive system, the poor oxidative stability of Cu severely limits its applicability. In this work, we demonstrate that, when Cu NPs supported on TiO nanobelts (NBs) are engaged in the photocatalytic generation of H from water under light illumination, Cu is not only oxidized in CuO but also dissolved under the form of Cu/Cu ions, leading to a continuous reconstruction of nanoparticles via Ostwald ripening.