Tunable physics through coordination chemistry: formation on oxide surface of Ti and Al chelates with 3-hydroxyflavone capable of electron injection and light emission.

The optoelectronic features of 3-hydroxyflavone (3HF) self-assembled on the surface of an n-type semiconducting metal oxide (TiO2) and an insulator (Al2O3) are herein investigated. 3HF molecules use the coordinatively unsaturated metal ions present on the oxide surface to form metal complexes, which exhibit different behaviors upon light irradiation, depending on the nature of the metal ion. Specifically, we show that the photoluminescence of the surface species can be modulated according to the chemical properties of the complex (i.e. the binding metal ion), resulting in solid-state emitters in a high quantum yield (about 15%). Furthermore, photoinduced charge injection can be promoted or inhibited, providing a multifunctional hybrid system.

Galvanic Replacement Reaction as a Route to Prepare Nanoporous Aluminum for UV Plasmonics.

There is a growing interest in extending plasmonics applications into the ultraviolet region of the electromagnetic spectrum. Noble metals are commonly used in plasmonic, but their intrinsic optical properties limit their use above 350 nm. Aluminum is probably the most suitable material for UV plasmonics, and in this work we fabricated substrates of nanoporous aluminum starting from an alloy of Al2Mg3. The porous metal is obtained by means of a galvanic replacement reaction. Such nanoporous metal can be exploited to achieve a plasmonic material suitable for enhanced UV Raman spectroscopy and fluorescence. Thanks to the large surface to volume ratio, this material represents a powerful platform for promoting interaction between plasmonic substrates and molecules in the UV.

Kinetic effects of alcohol addition on the anodic behavior of silicon in acid fluoride media.

The anodic dissolution of silicon in acid solutions of ammonium fluoride is investigated in aqueous and water-alcohol media by rotating disk voltammetry and impedance spectroscopy. The voltammograms recorded in water-alcohol media show, in comparison to water, the following effects: an increase of the dissolution currents measured at pH>2 and an opposite effect at pH<2; a distortion of the curve, with a relative increase of the characteristic currents in the region of low applied potentials, indicating easier dissolution of the "wet" oxide forming under those conditions; a shift of the maximum of the current-pH curves from about pH 3 in water to about pH 4 in 50% ethanol v/v. Analysis of impedance data at pH values 4-5 in water and water-ethanol media show similar dependence on potential for the parameters Chf (high-frequency capacitance) and RhfI (Rhf is a high-frequency resistance and I is the steady state current), suggesting the formation of oxide films with similar properties. The marked differences of anodic behavior in the two types of media are discussed and explained in terms of the effects of alcohol addition on the speciation equilibria of hydrofluoric acid and on the kinetic rate constants of dissolution of the surface oxide layer.