Stefano Caporali

Formation of ZnSe on Ag(111) by electrochemical atomic layer epitaxy

ZnSe is an ideal candidate for optoelectronic devices. However, modern technology is quite demanding as to the quality of materials employed. The electrochemical atomic layer epitaxy (ECALE) method ensures good atomic-level control of thin film formation, as it is based on the alternated deposition of atomic layers of the elements making up the compound. The electrochemical conditions necessary to form ZnSe deposits of up to 35 Zn layers and 35 Se layers on Ag(111) by ECALE are described here. The 1:1 stoichiometric ratio of Zn to Se suggests that ZnSe is formed. A miniaturized electrochemical cell is also described.

SERS, XPS, and DFT Study of Adenine Adsorption on Silver and Gold Surfaces

The adsorption of adenine on silver and gold surfaces has been investigated combining density functional theory calculations with surface-enhanced Raman scattering and angle-resolved X-ray photoelectron spectroscopy measurements, obtaining useful insight into the orientation and interaction of the nucleobase with the metal surfaces.

An unusual common ion effect promotes dissolution of metal salts in room-temperature ionic liquids: a strategy to obtain ionic liquids having organic–inorganic mixed cations

A simple strategy has been reported to prepare new ionic liquids with binary systems of organic–inorganic cations exploiting the common ion effect, i.e. dissolving metal salts with organic or inorganic anions (bistriflylimide or nitrate) in ionic liquids bearing the same anions. The resulting concentrated solutions of metal cations in ionic environments, which may have great potential for electrochemical processes, have been characterized by X-Ray photoelectron spectroscopy (XPS) and electrospray ionization mass spectrometry (ESI-MS)

Interface properties of ionic liquids containing metal ions: features and potentialities

Interfaces and surfaces are the regions where important events happen: catalysis, molecular recognition, charge transfer, polymerization, and many other critical processes take place at the boundary between one medium and another. In this article we discuss the interface (liquid/air) properties of ionic liquids (ILs) containing dissolved metal ions with the aim to show the possibility to use metal salts to transform ILs and their surfaces into engineered liquid supports to apply in material sciences, separation procedures or to use as optical devices.

Coordination Environment of Highly Concentrated Solutions of Cu(II) in Ionic Liquids through a Multidisciplinary Approach

The coordination environment around Cu(II) in highly concentrated solutions of copper(II) salts (CuCl(2) and Cu(Tf(2)N)(2)) in two pure ionic liquids bearing the same anion, namely, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf(2)N]) and 1-butyl-3-methylimidazolium chloride ([bmim]Cl), is investigated by X-ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, EPR spectroscopy and DFT calculations. Moreover, the electrochemical behavior of these mixtures is studied. Whereas reversible reduction of Cu(II) to copper metal can be observed in the 1:1 [bmim][Tf(2)N]:Cu(Tf(2)N)(2) solution, 2:1 and 1:1 [bmim]Cl:CuCl(2) mixtures showed one-electron reduction of Cu(II) to Cu(I) with formation of a permanent deposit of CuCl. XPS, UV/Vis and EPR spectra as well as DFT calculations suggest the formation in [bmim]Cl of dynamic coordination complexes arising from the interaction between CuCl(2) and [bmim](+)Cl(-). The two long-lived situations are probably trigonal and deformed tetrahedral copper(II) chloride coordination complexes ([CuCl(3)](-) and [CuCl(4)](2-), respectively).

Water-Soluble, 1,3,5-Triaza-7-phosphaadamantane-Stabilized Palladium Nanoparticles and their Application in Biphasic Catalytic Hydrogenations at Room Temperature

Water‐dispersible Pd nanoparticles stabilized by the hydrophilic cage‐like aminophosphine ligand 1,3,5‐triaza‐7‐phosphaadamantane and its N‐methyl derivative were synthesized and fully characterized in the colloidal state by TEM, and NMR and UV spectroscopy and in the solid state by X‐ray photoelectron spectroscopy and powder XRD. The three different nanoparticles obtained showed a narrow distribution range with average core sizes of 2.8, 3.2, and 3.5 nm. The activity of some of these Pd nanoparticles as catalysts in the biphasic hydrogenation of organic substrates under mild conditions has been tested, and good results and excellent reusability (up to nine catalytic runs) were obtained.

Preparation of small size palladium nanoparticles by picosecond laser ablation and control of metal concentration in the colloid

We assessed a method for the preparation of small, highly stable and unprotected Pd nanoparticles by picosecond laser ablation in 2-propanol. The nanoparticles can be extracted from 2-propanol by centrifugation and redispersed in water, where a strongly negative ζ-potential assures long term stability. The proposed procedure permits reduction of particle size down to 1.6nm and optimization of the Pd(0):Pd(II) ratio which, in the best cases, was of the order of 6:1. The increase of this ratio with ablation times has been correlated to the high temperature conversion of PdO to metallic Pd by a simple theoretical model. A study of the relationship between colloid absorption at 400nm and Pd concentration permitted the role of PdO in the determination of the UV-vis spectra to be clarified and the limits of the Mie theory for the evaluation of colloid concentration to be established. The absorption at 400nm can be used as a fast method to estimate the Pd content in the colloids, provided that a calibration of the ablation process is preliminarily performed.

Carbon supported Rh nanoparticles for the production of hydrogen and chemicals by the electroreforming of biomass-derived alcohols

Electroreforming is a low energy cost technology that combines the production of valuable chemicals from biomass-derived alcohols with the evolution of clean hydrogen at low temperature and atmospheric pressure. The selectivity for the desired chemicals is governed by the nature of the anode catalyst. Here we report the synthesis and characterization of a carbon supported nanostructured Rh electrocatalyst. The Rh nanoparticles are shown to be highly dispersed (2.2 nm) and a complete electrochemical study is reported. This Rh/C catalyst exhibits high activity for alcohol electrooxidation (e.g. 5700 A gRh for EG at 80 °C) and when employed with an anion exchange membrane and Pt/C cathode in an electroreformer produces high volumes of hydrogen at low electrical energy input (e.g. 500 mA cm−2 at 0.7 Vcell and Ecost = 9.6 kW h kgH2−1). A complete analysis of the alcohol oxidation products from several renewable alcohols (ethanol, ethylene glycol, glycerol and 1,2-propandiol) shows a selectivity in the formation of valuable chemicals such as lactate and glycolate.

SERS and DFT study of copper surfaces coated with corrosion inhibitor

Summary Azole derivatives are common inhibitors of copper corrosion due to the chemical adsorption occurring on the metal surface that gives rise to a protective film. In particular, 1,2,4-triazole performs comparable to benzotriazole, which is much more widely used, but is by no means an environmentally friendly agent. In this study, we have analyzed the adsorption of 1,2,4-triazole on copper by taking advantage of the surface-enhanced Raman scattering (SERS) effect, which highlights the vibrational features of organic ligand monolayers adhering to rough surfaces of some metals such as gold, silver and copper. To ensure the necessary SERS activation, a roughening procedure was implemented on the copper substrates, resulting in nanoscale surface structures, as evidenced by microscopic investigation. To obtain sufficient information on the molecule–metal interaction and the formation of an anticorrosive thin film, the SERS spectra were interpreted with the aid of theoretical calculations based on the density functional theory (DFT) approach.

Energy-selective neutron imaging for morphological and phase analysis of iron–nickel meteorites

We propose energy-selective neutron imaging as a new and non-destructive method to investigate rare metallic meteorites. It is based on attenuation of a neutron beam of limited spectral distribution in a sample depending on the elemental composition and crystalline structure. Radiography and tomography allow obtaining the presence, morphology and orientation information in the bulk of mineral inclusions, oxide crust and crystalline structure. Its usage in classification and meteor formation studies would be of great value.