Adriana Mignani

Synthesis Route to Supported Gold Nanoparticle Layered Double Hydroxides as Efficient Catalysts in the Electrooxidation of Methanol

This work describes a new one-step method for the preparation of AuNP/LDH nanocomposites via the polyol route. The novelty of this facile, simple synthesis is the absence of additional reactants such as reductive agents or stabilizer, which gives the possibility to obtain phase-pure systems free of undesiderable effect. The AuNP formation is confirmed by SEM, TEM, PXRD, and XAS; moreover, the electrochemical characterization is also reported. The electrocatalytic behavior of AuNP/LDH nanocomposites has been investigated with respect to the oxidation of methanol in basic media and compared with that of pristine NiAl-Ac. The 4-fold highest catalytic efficiency observed with AuNP/LDH nanocomposites suggests the presence of a synergic effect between Ni and AuNP sites. The combination of these experimental findings with the low-cost synthesis procedure paves the way for the exploitation of the presented nanocomposites materials as catalysts for methanol fuel cells.

Mild fabrication of silica-silver nanocomposites as active platforms for environmental remediation

Herein we report a new, simple, low cost and one step way to obtain silica-supported silver nanoparticles (AgNPs) on commercial polyethyleneimine-functionalized silica beads (SiO2-PEI) under mild experimental conditions. The novel AgNPs/(SiO2-PEI) material has been thoroughly analyzed using FE-SEM, BET, XRD, XPS and XE-AES analysis. The reduction of Methylene Blue (MB) to Leuco Methylene Blue (LMB) in the presence of NaBH4 was chosen for testing the catalytic properties of AgNPs/(SiO2-PEI) towards dyes decoloration. Moreover, the prepared supported nanocatalyst was also found to exhibit excellent catalytic activity towards decoloration of some azo dyes such as E110 and E122.

Fluoroalkylsilanes with Embedded Functional Groups as Building Blocks for Environmentally Safer Self-Assembled Monolayers

The fabrication of silane-based fluorinated self-assembled monolayers (FSAMs) on indium tin oxide (ITO, a transparent electrode) was carried out making use of the following fluoroalkylsilanes (FAS): 2,2,3,3,4,4,5,5,6,6,6-undecafluoro-N-[3-(trimethoxysilyl)propyl]hexanamide (1; R(F) = C5F11) and 1,1,2,2,3,3,4,4,4-nonafluoro-N-[3-(trimethoxysilyl)propyl]butane-1-sulfonamide (2; R(F) = C4F9), containing an embedded amide and a sulfonamide group, respectively, between the short perfluoroalkyl chain (R(F) with C < 6) and the syloxanic moiety. The obtained FSAM-modified/ITO systems were characterized by X-ray photoelectron spectroscopy (XPS), contact angle (CA), surface energy measurements, and electrochemical impedance spectroscopy (EIS) and compared to ITO modified with a 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltriethoxysilane (3; R(F) = C6F13), with the perfluoroalkyl group linked to the syloxanic moiety through a simple hydrocarbon chain. The results obtained show that the presence of the -NHCO- and -NHSO2- groups have a different mode of action and, with the former, despite the short perfluoroalkyl chain, the ITO-1 system presents a CA (Θ(water )= 113.5°) and surface energy (γl = 14.0 mJ m(-2)) typical of amphiphobic materials. These properties can be exploited in a variety of applications, such as self-cleaning, anti-fouling, and anti-fingerprint coatings, and in advanced microelectronic components.

Functionalization of silica through thiol-yne radical chemistry: a catalytic system based on gold nanoparticles supported on amino-sulfide-branched silica

This work proposes a preparation route to heterogeneous catalysts based on gold nanoparticles (AuNPs) supported on chemically modified silica. More specifically, the latter is functionalized with amino-sulfide branches (Au-SiO2@AeThio) through a thiol-yne radical coupling performed between cysteamine hydrochloride and an alkynyl-substituted triethoxysilane, followed by co-condensation with tetraethoxysilane (TEOS). The target procedure, involving only a gold precursor without any need of additional reducing and/or stabilizing agents, is straightforward, controllable, reproducible, and particularly appealing from a “green” point of view. The supported AuNPs, with an average diameter of 10 nm, possess a remarkable catalytic activity (specific rate constants of the order of 10−2 s−1 mgcat−1) in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride (NaBH4) in aqueous media. The higher performances with respect to previous literature work, along with the possibility of successfully recycling the catalyst, shows the developed materials as attractive functional platforms.

Structural and electronic studies of metal hexacyanoferrates based cathodes for Li rechargeable batteries

Operando XANES and EXAFS spectra on the newly prepared Fe hexacyanocobaltate active material for positive electrodes in lithium batteries have been recorded at the XAFS beamline of Elettra using a suitable in situ cell. In this way, it was possible to follow in detail the main structural and electronic changes during the charge and discharge processes of the battery. The use of a chemometric approach for data analysis is also underlined.

Hydrogen Adsorption Properties of Carbon Nanotubes and Platinum Nanoparticles from a New Ammonium-Ethylimidazolium Chloroplatinate Salt.

Self-supporting membranes built entirely of carbon nanotubes have been prepared by wet methods and characterized by Raman spectroscopy. The membranes are used as supports for the electrodeposition of Pt nanoparticles without the use of additional additives and/or stabilizers. The Pt precursor is an ad hoc synthesized ammonium-ethylimidazolium chloroplatinate(IV) salt, [NH3 (CH2 )2 MIM)][PtCl6 ]. The Pt complex was characterized using NMR spectroscopy, XRD, ESI-MS, and FTIR spectroscopy. The interaction between the Pt-carbon nanotubes nanocomposites and hydrogen is analyzed using electrochemical and quartz microbalance measurements under near-ambient conditions. The contribution of the Pt phase to the hydrogen adsorption on nanotube is found and explained by a kinetic model that takes into account a spillover event. Such a phenomenon may be exploited conveniently for catalysis and electrocatalysis applications in which the hybrid systems could act as a hydrogen transfer agent in specific hydrogenation reactions.