Antonio Currao

Encapsulated Lanthanides as Luminescent Materials

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Water splitting with silver chloride photoanodes and amorphous silicon solar cells

A thin silver chloride layer deposited on a conducting support photocatalyzes the oxidation of water to O(2) in the presence of a small excess of silver ions in solution. The light sensitivity in the visible part of the spectrum is due to self-sensitization caused by reduced silver species. Anodic polarization reoxidizes the reduced silver species. To test its water splitting capability, AgCl photoanodes as well as gold colloid modified AgCl photoanodes were combined with an amorphous silicon solar cell. The AgCl layer was employed in the anodic part of a setup for photoelectrochemical water splitting consisting of two separate compartments connected through a salt bridge. A platinum electrode and an amorphous silicon solar cell were used in the cathodic part. Illumination of the AgCl photoanode and the amorphous Si solar cell led to photoelectrochemical water splitting to O(2) and H(2). For AgCl photoanodes modified with gold colloids an increased photocurrent, and consequently a higher O(2) and H(2) production, were observed.

Zeolite A and zeolite L monolayers modified with AgCl as photocatalyst for water oxidation to O2

The appealing features of zeolite A and zeolite L tempted us to prepare zeolite monolayers on conducting surfaces like gold coated glass and gold foil. For the preparation of the monolayers, cubic crystals of zeolite A, disc-shaped and cylindrical crystals of zeolite L were used. The zeolites were linked to the gold surface by means of a thiolalkoxysilane as molecular linker. Afterwards, the monolayers were used as back support for AgCl, a photocatalyst used in water oxidation and water splitting experiments. All AgCl photoanodes modified with a zeolite monolayer on the back showed an increased water oxidation capability.

Gold and silver metal nanoparticle-modified AgCl photocatalyst for water oxidation to O2

Nanostructured AgCl layer acts as photocatalyst for water oxidation in the presence of a small excess of Ag+ in solution. The photoactivity of AgCl extends from the UV into the visible light region due to self-sensitization, caused by the formation of silver species during the photoreaction. Anodic polarization reoxidizes the produced silver species. Experiments were carried out with spherical gold as well as spherical and prismatic silver nanoparticle modified AgCl layers. We observed that traces of these nanoparticles greatly influenced the photoelectrochemical activity. With spherical gold nanoparticle modification, the O2 production and the photocurrent increased by a factor of about 3, as compared to layers without gold colloids. Also spherical and prismatic silver nanoparticles led to an increased O2 production and photocurrent.

Structural studies of the hydrido-bridged iridium gold complexes ‘IrHm{CH3C(CH2PPh2)3}{Au(PR3)}n’

Abstract The X-ray crystal structure of [{(triphos)H (3− x ) Ir}(μ-H) x {Au(PR 3 )}][PF 6 ] (triphos=CH 3 C(CH 2 PPh 2 ) 3 , x =2) shows that the gold atom builds two almost equal IrHAu bridges with the he ‘IrH 3 (triphos)’ building block. The IrHAu bridging parameters are typical of three-center-two-electron interactions. The X-ray crystal structure of [{(triphos)H (3− y ) Ir}(μ-H) y {Au(PR 3 )} 2 ][PF 6 ] 2 shows that each gold atom builds two Ir(μ 2 -H)Au bridges with the three hydrides of the ‘IrH 3 (triphos)’ building block; one Ir(μ 3 -H)Au 2 bridge is also present ( y =3). The relative positions of the Ir, H, Au and P atoms show that typical three-center-two-electron interactions predominate in this compound, in which there is no direct AuAu bonding. The neutron diffraction structure of [{(triphos)Ir}(μ-H) 2 {Au(PPh 3 )} 3 ][PF 6 ] 2 confirms the earlier hypothesis that only two of the three IrAu edges are associated with a hydride with formation of Ir(μ 2 -H)Au bridges. The presence or absence of the latter ligand changes the IrAu distance only marginally, in contrast to the general trend in hydride clusters. It is shown that the formation of a ‘classical’ cluster in this set of compounds requires a quadrimetallic unit and the two additional electrons generated by loss of a proton from an IrH bond in the trication [{(triphos)Ir (μ 2 -H) 3 {Au(PR 3 )} 3 } 3+ .

Ba4Ti12O27: Rietveld refinement using X-ray powder diffraction data

The title compound is a new mixed-valence barium titanate (Ba II 4 Ti III 2 Ti IV 10 O 27 ). A refinement using X-ray powder data was carried out using the Rietveld method, with the lattice parameters and atomic sites of the isostructural compound Ba 4 Al 2 Ti 10 O 27 as a starting model.

The AgCl photoanode for photoelectrochemical water splitting

Solar energy is the greatest potential source of renewable energy known to human kind and is still largely untapped. The quest to find an efficient means of converting it to a clean and storable fuel remains elusive and is the goal of artificial photosynthesis: the solar splitting of water in O 2 and H 2 in a man-made system. Our approach to water splitting is based on a photoelectrochemical cell with two semiconductor-liquid junctions, where AgCl acts as the photoanode for O 2 production along with the photocathodic materials p-GalnP 2 and a silicon solar cell for H 2 production. We report light-assisted water splitting with this system, under UV/Vis illumination from aqueous solution, at good yields and without degradation of the photocatalysts.

Zeolite A and ZK-4

The synthesis of zeolite A and ZK-4 crystals of high purity and well-defined morphology is described. Three procedures are detailed, leading to cubic crystals of zeolite A with chamfered edges (average size 3–5 µm), cubic crystals of ZK-4 with sharp edges (average size 1–2 µm), and nano-sized cubic crystals of zeolite A with slightly rounded edges (size ≤ 1 µm).