Papers by ANDRE MAISONNAT
Chemischer Informationsdienst, Jan 22, 1980
Journal of Organometallic Chemistry, Feb 1, 2002
ABSTRACT Decomposition of the organometallic precursor [Zn(C6H11)2] in wet anisole leads to the f... more ABSTRACT Decomposition of the organometallic precursor [Zn(C6H11)2] in wet anisole leads to the formation of monodisperse spherical Zn particles of 6 nm mean diameter. High resolution electron microscopy (HRTEM) indicates the crystalline nature of these particles and photoelectron studies (XPS) are consistent with the presence of both zinc and zinc oxide. In the presence of polyvinylpyrolidone (PVP), the decomposition leads to well dispersed nanoparticles for which HRTEM studies evidenced the presence of hexagonal zinc (0) surrounded by a thin layer of hexagonal zinc oxide of wurtzite type. The thermal oxidation of these zinc nanoparticles yields well-crystallized nanoparticles of ZnO without coalescence or size change. An X-ray diffraction pattern shows that the powder consists of pure hexagonal wurtzite-type phase.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 8, 2009
Metal oxides such as tin oxide (SnO 2) are widely used for gas sensing applications, particularly... more Metal oxides such as tin oxide (SnO 2) are widely used for gas sensing applications, particularly in environmental applications. The change in the resistance of the sensing layer is the detection principle of the gas sensors. The variations of the resistance are due to the charge transfers resulting from the chemical reactions which occur at the surface of the tin dioxide sensitive layer. In this work, a multiscale approach is developed in order to model interactions of SnO 2 with various gases, such as CO and CO 2. Ab initio calculations are systematically used to identify and characterize, at the atomic scale, the chemical reactions occurring at the surface of the sensitive layer of the sensor. Structures and activation energies associated to surface reactions, and charge transfers characteristics of each surface species, are determined. To simulate the sensors behaviour on a wider scale, a mesoscopic model based on the ab initio results and a chemical rate theory technique is developed. This model gives the temporal evolution of the sensors response as a function of external parameters. This methodology, combining ab initio calculations and mesoscopic model, leads to a better understanding of the macroscopic gas sensor behaviour. We identify the SnO 2 reduction by CO, the catalytic oxidation mechanism of CO involving successive reduction and reoxidation of the oxide layer and the tricky detection of CO 2 gas as a function of external parameters like humidity.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 8, 2009
Because of environmental and safety concerns, there is a large need of gas sensing devices. Semic... more Because of environmental and safety concerns, there is a large need of gas sensing devices. Semiconductor metal oxides, like tin dioxide, are widely used for such applications. In these devices, the gas detection is usually performed by measuring conductivity variations of the oxide sensing layer. Indeed, gas adsorption and surface chemical reactions result in formal electron transfers, modifying the number of charge carriers. In this work, we have performed DFT calculations to characterize different chemical reactions involved in the detection of CO and CO2 by SnO2: CO and CO2 adsorption, SnO2 reduction by CO and its re-oxidation by O2, and the formation of carbonates in the case of CO2. In each case, we have calculated the reaction energy and its activation barrier but also the resulting charge transfer in order to evaluate the sensor electrical response. We find that CO detection is easy thanks to low barrier exothermic reactions and large associated charge transfers. In particular, SnO2 reduction results in the formation of surface oxygen vacancies that formally behave as two electrons in the conduction band. On the other hand, CO2 detection is troublesome due to weakly exothermic reactions and ten times smaller charge transfers. Finally, we study the influence of H2O on the reaction mechanisms and the charge transfers in order to evaluate its interfering capabilities.
HAL (Le Centre pour la Communication Scientifique Directe), Dec 7, 2005
His research interests include microtechnology, analogue IC for Microsystems, instrumentation, el... more His research interests include microtechnology, analogue IC for Microsystems, instrumentation, electrical modelling and design of MEMS.
HAL (Le Centre pour la Communication Scientifique Directe), Sep 20, 2009
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Chemischer Informationsdienst, Jan 6, 1981
Reaction of Tetracyanoethylene with SCl 2 ; New Molecular Rearrangements.-Reaction of tetracyanoe... more Reaction of Tetracyanoethylene with SCl 2 ; New Molecular Rearrangements.-Reaction of tetracyanoethylene (I) with SCl 2 in the presence of catalytic chloride ions affords the dicyanomethylene-substituted thiadiazine derivative (II) in moderate yield. Two by-products (III) and (IV) are identified, the latter representing a novel tricyclic system. Reaction of compound (II) with excess SCl 2 is proposed to generate an N-sulfenylchloride intermediate, which cyclizes to furnish pyrrolothiadiazine (VIII). The two chlorine atoms in tricyclic compound (IV) can be replaced by secondary amines like pyrrolidine, affording mono-(VI) or dipyrrolidinyl derivatives (VII) depending on the reaction conditions used.-(KOUTENTIS, PANAYIOTIS
Journal of physics, Dec 1, 2007
Surface optical phonons in freestanding cylindrical ZnO nanoparticles surrounded by organic molec... more Surface optical phonons in freestanding cylindrical ZnO nanoparticles surrounded by organic molecules have been theoretically investigated using a dielectric continuum model and experimentally with Raman spectrometry. From a theoretical point of view, we calculate surface optical phonons in the cases of cylindrical and planar surfaces of nanoparticles. We also investigate the dispersion of these modes regarding the dielectric constant of the outer medium. By modelling the organic shell of nanoparticles with a dielectric constant and based on experimental results of Raman spectrometry, we show that we observed a top surface mode of nanoparticles.
Journal of Organometallic Chemistry, May 1, 1982
... Permissions & Reprints. Preliminary communication. Complexes du titane et du zirconiu... more ... Permissions & Reprints. Preliminary communication. Complexes du titane et du zirconium contenant les ligands cyclopentadienyldiphenylphosphine et cyclopentadienylethyldiphenyl phosphine: acces a des structures heterobimetalliques. ... Article Outline. References. References ...
Journal of Organometallic Chemistry, Apr 1, 1997
Iodide abstraction by silver salts from the complexes [{η5:η1-C5H4(CH2)2PPh2}MI2], (1, M = Rh; 2,... more Iodide abstraction by silver salts from the complexes [{η5:η1-C5H4(CH2)2PPh2}MI2], (1, M = Rh; 2, M = Ir), yields products whose structures are dependent on the coordinating ability of the anion originally associated with silver. Silver trifluoroacetate gave fully characterized disubstituted derivatives of the type [{η5:η1-C5H4(CH2)2PPh2}M(CF3COO)2], (3, M = Rh; 4, M = Ir), in which the trifluoroacetate anions are bound in a monodentate fashion. Silver hexafluorophosphate gave a dinuclear dicationic compound [{{η5:η1-C5H4(CH2)2PPh}2}Rh (μ−1)}2][PF6]2, 5, in which the metal atoms are bridged by iodide. Complex 3 crystallizes in the triclinic space group P1 with two molecules in the unit cell, with a = 8.3060(7)Å, b = 18.289(2)Å, c = 7.9724(8) Å, α=94.178(8)°, β = 106.477(8)°, γ = 93.964(7)° and V = 1153.2(2)Å3. Least squares refinement leads to conventional R values R(Fo) = 0.041 and Rw = 0.042 for 3361 reflections having 1 > 3σ(1). Complex 5 crystallizes in the monoclinic space group P21/c with two molecules of 5 and two molecules of acetone in the unit cell, the dimensions of which are a = 13.838(1)Å, b = 13.403(1)Å, c = 14.362(1)Å, β = 104.73(1)° and V = 2576.2(5)Å3. Least squares refinement leads to conventional R values R(Fo) = 0.034 and Rw = 0.040 for 2246 reflections having 1 > 2σ(1). Surprisingly, the treatment of the bis-trifluoroacetato complexes 3 and 4 with lithium triethylhydroborate yields quantitatively the ethylene metal(I) derivatives [{η5:η1-C5H4(CH2)2PPh2}M(C2H4)], (9, M = Rh; 10, M = Ir), whereas unstable polyhydride derivatives result from the reaction of the diiodo complex 1 with lithium triethylhydroborate, and from the reaction of the bis-trifluoroacetato complex 3 with sodium tetrahydroborate. The chemical or electrochemical reduction of complex 5 leads to the solvated rhedium(III) species. [{(η5:η1-C5H4(CH2)2PPh2}RhI(THF)][PF6], 6, together with a dinuclear rhodium(II) species. [{{η5:η1-C5H4(CH2)2PPh2}RhI}2], 7. The protonation of 7 with tetrafluoroboric acid affords the monocationic dinuclear complex [{{η5:η1-C5H4(CH2)2PPh2}RhI}2}H][BF4], 8, in which the added proton bridges the rhodium atoms.
Chemischer Informationsdienst, Feb 14, 1978
ChemInform Abstract Nach einer Literaturmethode wurde die Protonierung der Komplexe (I) durch Zug... more ChemInform Abstract Nach einer Literaturmethode wurde die Protonierung der Komplexe (I) durch Zugabe einer Lösung von konzentrierter HCl untersucht. Während bei den Verbindungen (Ia) stabile Produkte (II) als Hexafluorophosphate isoliert werden können, lassen sich die Komplexe (Ib) nach diesem Verfahren nicht protonieren. In einer Mischung aus Trifluoressigsäure und Hexafluorphosphorsäure sind die protonierten Formen von (Ib) IR-und NMR-spektroskopisch nachweisbar. Dieser Unterschied wird auf die Basizität des Liganden in trans-Stellung zu der Metall-Metall-Bindung zurückgeführt.
HAL (Le Centre pour la Communication Scientifique Directe), Sep 11, 2005
In this paper, we show the influence of short temperature variations on the transient response of... more In this paper, we show the influence of short temperature variations on the transient response of a SnO 2 nanoparticular gas sensor. By consideration of the shape and time constants of the normalized response curves, we can differentiate different gasses mixtures at a ppm level. This new method of analysis is promising to conceive a gas detector based on combination of temperature profiles and different sensitive layers.
Chemischer Informationsdienst, Jan 3, 1978
Journal de chimie physique, 1991
Journal of the Chemical Society, 1977
ABSTRACT
Organometallics, Jul 1, 1991
A new route for the preparation of the homobimetallic complex [Mo,(~-C,H,PPh2)2(CO)~l in good yie... more A new route for the preparation of the homobimetallic complex [Mo,(~-C,H,PPh2)2(CO)~l in good yield (90%) is described and its X-ray structure is reported, together with some spectroscopic data and its redox properties.
Organometallics, Nov 1, 1989
A new route for the preparation of the homobimetallic complex [Mo,(~-C,H,PPh2)2(CO)~l in good yie... more A new route for the preparation of the homobimetallic complex [Mo,(~-C,H,PPh2)2(CO)~l in good yield (90%) is described and its X-ray structure is reported, together with some spectroscopic data and its redox properties.
Organometallics, Jul 1, 1994
Physical Review B, Apr 23, 2008
Surface optical modes in cylindrical ZnO nanoparticles have been studied theoretically using a di... more Surface optical modes in cylindrical ZnO nanoparticles have been studied theoretically using a dielectric continuum model and experimentally by Raman spectrometry. Theoretically, both wave vector dispersion and outer medium dielectric constant effects have been investigated. Consequently, we attribute the intense peak at 490 cm −1 in the Raman experiment to a surface optical mode related to the top basis of the nanoparticles. We deduce that the bonding of long alkyl chain amines is likely related to the lateral surface of the nanoparticles.
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Papers by ANDRE MAISONNAT