TV-holography in artwork diagnostics

TV-holography can hold a great potential in non-destructive diagnostics of the state of conservation and preservation of artworks. Its use in revealing debonds, cracks, voids, delaminations or residual stress in both ancient paintings on wooden panels, statuaries and mural supports has been proven. The method is easy to apply and very functional for the basic objectives of conservation; its compactness enables detection of microdisplacements even in non laboratory environments. Measurements in field of microcracks and subsurface detachments on ancient frescoes and panel paintings are reported.     

An XPS investigation on glucose oxidase and Ni/Al hydrotalcite interaction

In this work, a Ni/Al hydrotalcite (HT) was used as glucose oxidase (GOx) immobilizer. Small‐area and angle‐resolved X‐ray photoelectron spectra were recorded on HTs electrosynthesized on Pt in the absence and in the presence of GOx, and compared with those obtained for a Pt surface, modified with the electrosynthesized HT, on which a drop of GOx solution was deposited. The simultaneous electrodeposition of HT + GOx resulted in a compact deposit, thicker than the XPS sampling depth (>10 nm), that is not homogeneous in the lateral and in‐depth composition. The presence of GOx can be deduced comparing the N1s spectra of HT and HT + GOx: in the latter, the N1s component at 400 eV binding energy (BE) is predominant whilst, depending on the analyzed point, a small or no contribution from the component at 407.2 eV, due to nitrate, is revealed. Angle‐resolved XPS provides evidence on the in‐depth composition of anions, cations and GOx. The results highlight the crucial role played by nickel in GOx immobilization. On the basis of the results, it can be suggested that enzyme activity is unevenly distributed and is localized in small areas, where Ni concentration is higher. Copyright © 2010 John Wiley & Sons, Ltd.     

Monitoring of water quality in South Paris district by clustering and SIMCA classification

With the aim of obtaining a monitoring tool to assess the quality of water, a multivariate statistical procedure based on cluster analysis (CA) coupled with soft independent modelling class analogy (SIMCA) algorithm, providing an effective classification method, is proposed. The experimental data set, carried out throughout the year 2004, was composed of analytical parameters from 68 water sources in a vast southwest area of Paris. Nine variables carrying the most useful information were selected and investigated (nitrate, sulphate, chloride, turbidity, conductivity, hardness, alkalinity, coliforms and Escherichia coli). Principal component analysis provided considerable data reduction, gathering in the first two principal components the majority of information representing about 92.2% of the total variance. CA grouped samples belonging to different sites, distinctly correlating them with chemical variables, and a classification model was built by SIMCA. This model was optimised and validated and then applied to a new data matrix, consisting of the parameters measured during the year 2005 from the same objects, providing a fast and accurate classification of all the samples. The most of the examined sources appeared unchanged during the 2-year period, but five sources resulted distributed in different classes, due to statistical significant changes of some characteristic analytical parameters.     

Unexpected Carbon–Carbon Bond Cleavage in the Reactions of the Pentagonal Bipyramidal Cluster Fe3(CO)6(μ-CO)2[μ3-η4-{RCC(Et)C(Et)CR}] with Styrene. Synthesis and X-ray Structure of Fe3(CO)6[μ3-η4-{EtC2CR}]2 (R = CH3(=CH2))

The thermal reactions of 2-methyl-1-hexen-3-yne [CH₃CH₂C≡CC(=CH₂)CH₃, metey] with Fe₃(CO)₁₂ have been studied: cluster opening or fragmentation and alkyne dimerization occur. Main products are the open triangular isomers [Fe₃(CO)₆(μ-CO)₂{CH₃(=CH₂)CC(Et)C(Et)C(=CH₂)CH₃}] (complex 3a) and [Fe₃(CO)₆(μ-CO)₂{C(Et)CCH₃(=CH₂)C(Et)CCH₃(=CH₂)}] (complex 3b). The structure and isomerism of the complexes has been confirmed by X-ray studies. The minor products of the reaction have been characterized by spectroscopic techniques. An attempt at exploiting the reactivity of the “free” C=C bonds of the coordinated ene-yne was made: complex 3a was reacted with styrene under thermal conditions. Unexpectedly considerable yields of the closed triangular cluster [Fe₃(CO)₆{EtC₂C(=CH₂)CH₃}₂] (complex 5) have been obtained. This behaviour had not been previously observed. The unprecedented structure of complex 5 has been confirmed with an X-ray study.     

Hydrogen Atoms Location in Os<Subscript>3</Subscript>(μ-H)(CO)<Subscript>9</Subscript>(μ<Subscript>3</Subscript>, η<Superscript>2</Superscript>-C<Subscript>2</Subscript>H) from Accurate X-Ray Data at 100 K

Abstract  

The structure of the complex Os₃(μ-H)(CO)₉(μ₃, η²-C₂H) has been determined using X-ray data collected at low temperature (100 K); all hydrogen atoms have been located. The asymmetric unit is formed by two molecules joined through hydrogen bonds involving the hydrogen atoms of C₂H moiety and the oxygen atoms of carbonyl groups. The complex crystallizes in the monoclinic space group P2₁/c with a = 12.94040(2), b = 15.4705(2), c = 16.0164(2) ?, β = 106.0860(10)°, and V = 3,080.85(7) ?³, Z = 8. A molecule is formed by a triangular Os₃ cluster, with metal atoms bearing terminal CO groups. The acetylenic residual is formally π-bonded to two Os atoms in a perpendicular mode and σ-linked to the third Os atom. A bridging hydride atom completes the coordination.     

Glyphosate and glufosinate detection at electrogenerated NiAl-LDH thin films

An amperometric sensor based on Ni_1−xAl_x(OH)₂NO_3x·nH₂O layered double hydroxide (LDH) has been developed for the electrochemical analysis in one step of two herbicides: glyphosate (N-(phosphonomethyl)glycine, Glyp) and glufosinate ((DL-homoalanine-4-yl)-methylphosphinic acid, Gluf). NiAl-LDH was prepared by coprecipitation or by electrodeposition at the Pt electrode surface. Inorganic films were fully characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. Adsorption isotherms of Glyp onto this inorganic lamellar material have been established. Electrocatalytic oxidation of Glyp and Gluf is possible at the Ni³⁺ centres of the structure. The electrochemical responses of the NiAl-LDH modified electrode were obtained by cyclic voltammetry and chronoamperometry at 0.49 V/SCE as a function of herbicide concentration in 0.1 M NaOH solution. The electrocatalytic response showed a linear dependence on the Glyp concentration ranging between 0.01 and 0.9 mM with a detection limit of 1 μM and sensitivity 287 mA/M cm². The sensitivity found for Gluf was lower (178 mA/M cm²).     

Reactions of Ru3(CO)12 with 2-pentynal-diethyl-acetal. The crystal structure of Ru2(CO)6[μ-η-{EtC2C(H)(OEt)2}CO{EtC2C(H)(OEt)2}] and its reactivity towards tetraethyl-orthosilicate

The title compound has been obtained in considerable yield by reacting Ru₃(CO)₁₂ with 2-pentynal-diethyl-acetal [CH₃CH₂CCC(H)(OEt)₂] (PDA) in hydrocarbon solvents. The X-ray analysis shows that the title complex belongs to the well known family of the flyover derivatives. Some X-ray structural studies have been reported, many years ago, on di-iron flyover complexes; in contrast only a few examples of diruthenium derivatives have been structurally characterized.The complex contains ethoxy-groups which could potentially undergo hydrolysis in the presence of tetraethyl-orthosilicate (TEOS) in the presence of catalysts. Reactions of complex Ru₂(CO)₆[μ-η⁴-{EtC₂C(H)(OEt)₂}CO{EtC₂C(H)(OEt)₂}] with TEOS in the presence of HCl or of NaF (as catalysts) have been attempted. An inorganic-organometallic sol-gel material containing the skeleton of the complex has been obtained and characterized with IR-Raman, XRD on powders and SEM microscopy.