Cobalt oxide nanomaterials prepared by CVD as negative electrodes in lithium batteries

III Encuentro sobre Nanociencia y Nanotecnología de Investigadores y Tecnólogos Andaluce

Growth of NiO thin films in the presence of water vapor: insights from experiments and theory

NiO-based thin films and nanomaterials are promising candidates for a variety of end-uses, encompassing photo- and electrocatalysts, solar cells, displays, and sensors. This widespread attention has strongly fueled the interest in the fabrication of tailored systems featuring modular chemico-physical properties as a function of the required application. In this study, a single-step chemical vapor deposition (CVD) route for the preparation of pure and fluorine-doped NiO films is presented. Growth experiments were performed under water vapor-containing oxygen atmospheres from a series of Ni(II) β-diketonate–diamine molecular precursors featuring a different fluorination degree of the ligand side chain. A comprehensive experimental and theoretical investigation yielded valuable insights into the growth mechanism, with particular regard to the dependence of the system electronic properties on fluorine doping and content, and to the role exerted by water vapor in the reaction atmosphere. In fact, the interactions of water with the diketonate ligands contribute to weaken Ni–O bonds, favoring precursor activation. The obtainment of F-doped NiO systems from fluorinated derivatives and the simplicity of our process make the adopted strategy a valuable tool to control the system characteristics for a variety of eventual functional applications

A LCAO-LDF study of Bronsted acids chemisorption on ZnO(0001)

The local density functional theory coupled to the molecular cluster approach has been used to study the chemisorption of Bronsted acids (H2O, H2S, HCN, CH3OH and CH3SH) on the ZnO(0001) polar surface. Geometrical parameters and vibrational frequencies for selected species molecularly and dissociatively chemisorbed have been computed. The agreement with literature experimental data, when available, has been found to be good. The nature of the interaction between the conjugate base of the examined Bronsted acids and the Lewis acid site available on the surface has been elucidated, confirming its leading role in determining the actual relative acidity scale obtained by titration displacement reactions. The strength of this interaction follows the order OH(-)approximate to CN- > CH3O- > SH- > CH3S-

g-C3N4-based materials functionalized with Au, Ag, and Au-Ag: An XPS study

In the present contribution, x-ray photoelectron spectroscopy was used to characterize the surface composition and elemental chemical states of graphitic carbon nitride (g-C3N4) materials decorated with highly dispersed noble metals (Au, Ag, or Au + Ag). Samples were prepared through electrophoretic deposition of g-C3N4 on fluorine-doped tin oxide substrates and annealed at 500 ? in Ar. The resulting systems were subsequently functionalized by radio frequency-sputtering and finally annealed again under an Ar atmosphere. Material's structural and morphological characterization revealed an intimate contact of the introduced noble metals with the underlying g-C3N4 matrix. Survey spectra as well as detailed scans for C 1s, N 1s, O 1s, Au 4f, Ag 3d, and Sn 3d regions are presented and critically discussed. The obtained results evidence the presence of highly defective carbon nitride matrices functionalized by low-sized Au nanoaggregates, atomically dispersed Ag, or partially alloyed Au-Ag core/shell nanoparticles