Papers by Claude Pasquier
Inorganic Chemistry, 2015
Control of band filling or doping of molecular (semi)conductors can be performed by substitutiona... more Control of band filling or doping of molecular (semi)conductors can be performed by substitutional insertion of molecules with a similar shape but a different electron count, with one more or one less electron. This strategy has been explored here within the semiconducting, single-component, radical gold dithiolene complex [AuOC4] bearing para-butoxyphenyl substituents. Alloying with the corresponding neutral nickel dithiolene complex [NiOC4] lacking one electron afforded a complete isostructural series [NiOC4]1-x[AuOC4]x, spanning the whole composition range from x = 0 to x = 1 by 0.1 increments, further characterized by X-ray diffraction and EDX analyses. Magnetic susceptibility data confirm the antiferromagnetic interactions between neighboring radical gold dithiolene complexes. The electrical conductivity increases exponentially with the x gold fraction, while the activation energy remains constant in the more conducting, gold-rich samples. This behavior is tentatively assigned to the tunneling barriers of variable width (with x) but of constant height, separating more conducting gold-rich segments. Comparison of redox potentials for the 1e(-) oxidation and reduction of both [NiOC4] and [AuOC4] dithiolene complexes indicates that the [NiOC4] nickel complex does not act as a dopant for the radical [AuOC4] complex.
Surface Science, 1992
ABSTRACT The 2D electron gas of a GaAs/GaAlAs heterojunction is confined to a small island by mea... more ABSTRACT The 2D electron gas of a GaAs/GaAlAs heterojunction is confined to a small island by means of Schottky gates. Two gates provide adjustable tunnel barriers and a central gate controls the electron number of the island. Conductance oscillations, periodic with the electron number, are observed in the Coulomb blockade regime with negligible energy level spacing. At low temperature, the blockade of the conductance by the island is shown to be limited by the quantum process of co-tunneling.
New Journal of Chemistry, 2007
Nanowires of molecule-based charge-transfer salts are prepared using two different processing tec... more Nanowires of molecule-based charge-transfer salts are prepared using two different processing techniques. Isolated [TTF][TCNQ] nanowires are grown by a simple adsorption in organic solution method on stainless steel conversion coatings, used as substrates. They are characterized by Raman spectroscopy and current-voltage measurements. Nanowire films of Per 2 [Au(mnt) 2 ] and (EDT-TTFVO) 4 (FeCl 4 ) 2 are electrodeposited on (001)-oriented silicon wafers, used as anodes.
Journal of the Physical Society of Japan, 2008
We have studied the onset temperature of the superconductivity T onset c of the organic supercond... more We have studied the onset temperature of the superconductivity T onset c of the organic superconductor (TMTSF) 2 ClO 4 , by precisely controlling the direction of the magnetic field H. We compare the results of two samples with nearly the same onset temperature but with different scattering relaxation time τ. We revealed a complicated interplay of a variety of pair-breaking effects and mechanisms that overcome these pair-breaking effects. In low fields, the linear temperature dependences of the onset curves in the H-T phase diagrams are governed by the orbital pair-breaking effect. The dips in the in-plane field-angle φ dependence of T onset c , which were only observed in the long-τ sample, provides definitive evidence that the field-induced dimensional crossover enhances the superconductivity if the field direction is more than about 19-degrees away from the a axis. In the high-field regime for H a, the upturn of the onset curve for the long-τ sample indicates a new superconducting state that overcomes the Pauli pair-breaking effect but is easily suppressed by impurity scatterings. The Pauli effect is also overcome for H b ′ by a realization of another state for which the maximum of T onset c (φ) occurs in a direction different from the crystalline axes. The effect on T onset c of tilting the applied field out of the conductive plane suggests that the Pauli effect plays a significant role in determining T onset c . The most plausible explanation of these results is that (TMTSF) 2 ClO 4 is a singlet superconductor and exhibits Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states in high fields.
Journal of Solid State Chemistry, 2012
The motley family of polar compounds (MV)[M(X 5 À x X 0
Inorganic Chemistry, 2003
Free Radical Research, 1991
Bovine Cu Zn SOD was used during an 8 year period as an antiinflammatory drug in 26 patients with... more Bovine Cu Zn SOD was used during an 8 year period as an antiinflammatory drug in 26 patients with severe Crohn's disease (CDAI 300) usually after failure of corticotherapy or when this drug was discontinued because of side effects or infection. This was a phase II trial during which doses routes of administration and concomitant therapies were progressively modified. We obtained 73% good short term responses (judged upon CDAI and anatomic healing) and 82% positive results on long term evolution (the criteria were: i CDAI lower than 100 in between relapses, ii complete healing or notable improvement of lesions, iii no surgery needed, iv return to work. The acceptability was excellent with the free enzyme. Since the above described experience, published in Free Radical Biology and Medicine (1989, 7: 145-151), we used always the same treatment schedule (SOD 8 mg/day associated with Desferroxamine--500 mg subcutaneous every 2 days). The follow-up during the 87-89 period showed that 12 are in good health without any relapse, 9 experienced one or more relapses, and showed good responses upon resumption of treatment, 5 failed to respond to treatment, all part of the initial group on which SOD treatment had already failed, and among whom 3 were lost for follow-up before 1987, and two others took up another SOD treatment which also failed. 3 new patients (2 females, 1 male) were treated since then, and all 3 had positive results (one with disappearance of ileocoecal mass). The efficacy of SOD as an antiinflammatory drug in Crohn's disease needs to be confirmed by controlled trials.
Dalton Transactions, 2008
The electrocrystallization of o-dimethyl-tetrathiafulvalene in the presence of halide anions affo... more The electrocrystallization of o-dimethyl-tetrathiafulvalene in the presence of halide anions affords 2 : 1 salts formulated as [o-DMTTF] 2 X, (X = Cl, Br, I). The three salts are isomorphous, crystallizing in the tetragonal system, space group I42d, with the halide anion on the −4 site and the o-DMTTF molecule along a two-fold axis, forming strictly uniform stacks along c, and is further stabilized by C-H · · · X hydrogen bonds. Detailed physical investigations were performed on the bromide salt. It exhibits a metallic behaviour down to T MI = 50 K, while application of pressure moves the metal insulator transition to 39 K at 7.9 kbar. Band-structure calculations indicate a strong one-dimensional character, also confirmed by the anisotropy ratio of the conductivity, r // /r ⊥ = 500, as determined by two independent methods (four-contact, low-frequency transport measurements and analysis of the anisotropy of the Dysonian EPR line). The singular temperature dependence of the g tensor and the EPR line width at the phase transition suggests charge ordering.
Chemistry of Materials, 2009
Organic-inorganic hybrid systems have absorbed more and more attention of material chemists in th... more Organic-inorganic hybrid systems have absorbed more and more attention of material chemists in the past decade due to the opportunity to combine distinctive properties of both components in one material. In fields of extensively studied halometalate hybrids, compounds based on Sn(II), Pb(II), Sb(III), and Bi(III) ions have demonstrated special attraction for device applications due to their electronic 1,2 or optical 3 properties as well as their room-temperature processability. 4 The inherent structural characteristic of these elements of groups 14 and 15 is their ns 2 electronic lone pair which can be more or less stereochemically active. An obvious trend is that the coordination geometry of the metal ion is a slightly distorted octahedron, revealing a rather weak lone pair stereoactivity, 5 and this trend becomes the rule when the radii of metal centers and halide atoms increase (i.e., M = Pb, Bi, X = I). 6 However, the degree of distortion of a specific MX 6 octahedron depends on its coordination environment and partly on the nature of organic cations also. For instance, by rationally changing the nature of cations, the inorganic networks of a series of 1D SnI 3 anion-based hybrids can be tuned from face-shared regular octahedra to edge-shared square-based pyramids. 7 Furthermore, the lone pair of M(II) or M(III) centers has a key role in the collective properties of materials: for instance, its stereochemical inactivity in hybrid perovskites, which are materials based on corner-shared M(II)X 6 octahedra, is corraleted to low band gaps and improved conductivities, 1,8-10 while its stereochemical activity favors the formation of acentric materials that can display peculiar optical 3 or ferroelectric properties. 11 Among all of the halogenometalate anions M (III) X n (n-3)-(M=Bi, Sb and X=I, Br), most of them are clusters, while 1D infinite networks, typically MX 4 and MX 5 2-, are comparatively rare. The MX 5 chains exist as two isomers, where octahedra are either cis-connected (common) or trans-connected (rare). The trans-MX 5 chain, which is also known in hybrids of Pb(II) or Sn(II), can be considered as the m = 1 member of the AE110ae-oriented hybrid perovskite family. In the [NH 2 C(I)dNH 2 ]ASnI 5 system, depending on the nature of A, the trans-SnI 5 chain can be either regular (stereochemically inactive lone pair, A = formamidinium) 13 or adopts alternation of short and long Sn-I distances along the chain (stereochemically active lone pair, A = iodoformamidinium). In this communication, we report the synthesis, X-ray single crystal structures, and electrical and dielectric properties of (MV)BiBr 5 , where MV 2þ is the methylviologen dication, a well-known electron acceptor which has been frequently incorporated into salts with charge transfer property. Herein, we will show that MV 2þ stabilizes unprecedented regular BiBr 5 chains of trans-connected octahedra at room temperature (β-phase) and that the Bi 3þ electronic lone pair is sterochemically activated when crystals were cooled down below -30°C, leading to the acentric R-phase. The stereochemical activation of the lone pair is correlated with an increase of the band gap, as determined from conductivity measurements and, interestingly, with the transfer from a para-to a ferroelectric phase.
The Journal of Physical Chemistry C, 2010
ABSTRACT Enhanced photocatalytic properties of oriented films of rutile nanorods have previously ... more ABSTRACT Enhanced photocatalytic properties of oriented films of rutile nanorods have previously been observed when the polarization of UV light is parallel to the rutile c axis. To reach a better understanding of this effect, we report here an investigation, in the dark and under UV-light irradiation, of the electrical resistance of aligned rutile nanorod films. In both cases, the resistance along the nanorod main ([001]) axis is 4 times smaller than that in the perpendicular directions. Moreover, the resistance decreases by an order of magnitude under UV irradiation. Furthermore, experiments were also performed with linearly polarized UV light, and we found that the film resistance is twice smaller when the UV-light polarization is parallel to the nanorods than in the perpendicular direction. These results give information about the mechanisms that control the electrical conductivity of aligned rutile nanorod films.
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Papers by Claude Pasquier