Daniele Costenaro

On the Intercalation of the Iodine−Iodide Couple on Layered Double Hydroxides with Different Particle Sizes

Molecular iodine was intercalated from nonaqueous solution into microsized ZnAl-layered double hydroxide (LDH) in the iodide form, generating the I(3)(-)/I(-) redox couple into the interlayer region. Chloroform, ethanol, acetonitrile, or diethyl ether were used as solvents to dissolve the molecular iodine. The intercalation compounds were characterized by thermogravimetric analysis, X-ray powder diffraction, UV-vis spectroscopy, and scanning and transmission electron microscopy. The stability of iodine-solvent adducts and the iodine concentration affected the LDH iodine loading, and samples with I(2)/I(-) molar ratio ranging from 0.14 to 0.82 were prepared. Nanosized, well dispersible LDH, synthesized by the urea method in water-ethylene glycol media, were also prepared and successfully functionalized with the I(3)(-)/I(-) redox couple applying the conditions optimized for the micrometric systems.

Preparation of luminescent ZnO nanoparticles modified with aminopropyltriethoxy silane for optoelectronic applications

Highly luminescent ZnO nanoparticles have been synthesized through a co-precipitation method, starting from a solution of zinc acetate in methanol and precipitating the oxide phase in basic media in the presence of variable amounts of aminopropyltriethoxy silane (APTS). The adopted conditions led to the condensation between Zn-OH species and the alkoxy functionalities of the organosilane during the formation of nanoparticles (one-pot method) thus allowing covalent binding of organic functionalities on the ZnO surface. HR-TEM measurements indicated that samples synthesized with increasing concentration of APTS (from 1 to 10% of Si/Zn molar ratio) are made of ZnO nanoparticles of decreasing dimension, passing from ca. 6 nm for pure ZnO to ca. 3 nm for the ZnO functionalized with the highest organosilane loading. ZnO samples with reduced particle size showed a significant variation of the optical properties. In particular, the particle size reduction is associated with a significant modification of ZnO absorption properties, as studied by diffuse reflectance UV-Vis spectroscopy, and to an exceedingly high photoemission. The organo-modified ZnO nanopowder with the highest photoemission was successfully tested as a light-emitting layer in a new generation of LED devices thus proving that they also possess interesting electroluminescent properties.

Enhancing the open circuit voltage of dye sensitized solar cells by surface engineering of silica particles in a gel electrolyte

We prepared a quasi-solid electrolyte for dye-sensitized solar cells (DSSCs) that consist of ionic liquid and modified silica particles. Commercial bare silica F5 particles and modified silica F5 by NH2 and NH3+ groups were prepared, and fully characterized. The best photovoltaic performance was observed using the NH2 modified silica particles giving an open circuit voltage (Voc) of 815 mV, a short-circuit current (Jsc) of 11.23 mA cm−2, and a fill factor (FF) of 0.75 corresponding to an overall power conversion efficiency of 7.04% at 100 mW cm−2 AM 1.5. The modification of the silica particles by NH2 groups increases the Voc of DSSCs by around 60 mV compared to pure ionic liquid electrolyte based DSSCs.

Organo-modified ZnO nanoparticles: tuning of the optical properties for PLED device fabrication

Organo-modified ZnO nanoparticles were synthesized in basic media through a co-precipitation method, starting from a solution of zinc acetate in methanol and three different organosilane species (i.e. 3-aminopropyl-triethoxy silane, isobutyl-triethoxy silane and phenyl-triethoxy silane). Following this one-pot procedure, highly luminescent nanoparticles with organic species covalently bound on the ZnO surface were successfully obtained. The samples were studied through a multidisciplinary approach aiming to define their structural, morphological and surface properties in relation to the different organosilanes used for the ZnO preparation. Furthermore, a comparison of the optical features of the produced materials was also attained. Among the different ZnO nanoparticles, those functionalized with isobutyl groups were added to a light-emitting poly(p-phenylene vinylene) derivative copolymer (Super Yellow of the Merck Company) in order to obtain a novel composite material with enhanced emission properties. The latter was used as an active layer in the fabrication of a highly efficient Polymeric Light Emitting Diode (PLED) device.

Tungsten oxide: a catalyst worth studying for the abatement and decontamination of chemical warfare agents

Abstract Tungsten(VI) oxide, WO3, was studied and used as a heterogeneous catalyst for the liquid-phase oxidative abatement and solid-phase decontamination of simulants of chemical warfare agents, CWAs. The catalytic performance of WO3 was compared to the one of a soluble W-containing model catalyst, W(IV)-heptaisobutyl polyhedral oligomeric silsesquioxane, W-POSS. In liquid-phase abatement tests, WO3 promoted a complete degradation of the toxic agent simulant within 24 h, in the presence of aqueous hydrogen peroxide, at room temperature. In solid-phase decontamination tests, when WO3 was mixed with sodium perborate as a solid oxidant, it was also tested in the decontamination of a cotton textile support from organosulfide and organophosphonate agents (simulants of blistering and nerve CWAs, respectively), showing promising performances comparable to, or sometimes better than, a nanostructured TiO2 catalyst, taken as a reference material. The environmental impact of the WO3 catalyst was assessed on bioluminescent Photobacterium leiognathi Sh1 bacteria, over which no acute nor chronic detrimental effects were recorded. Then, when in contact with a vegetable species such as Phaseolus vulgaris L. (common bean), WO3 did not cause damage to the photosynthetic apparatus of the plant, whereas a clear inhibition of the seed germination was evidenced.