Laurent Lisnard

Investigation of the photoinduced magnetization of copper octacyanomolybdates nanoparticles by X-ray magnetic circular dichroism

Through an extensive set of SQUID magnetic measurements, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism, we have determined the nature of the metastable photomagnetic phase in the cyano-bridged 3D network Cs(2)Cu(7)[Mo(CN)(8)](4). The photomagnetic effect is induced by the photoconversion of Mo(IV) ions in low spin (LS) configuration (S = 0) into Mo(IV) ions in high spin (HS) configuration (S = 1). The magnetic and spectroscopic measurements fully support the LS to HS conversion, whereas the previously invoked charge transfer mechanism Mo(IV) + Cu(II) ⇒ Mo(V) + Cu(I) can be completely ruled out.

Synergy in Photomagnetic/Ferromagnetic Sub-50 nm Core-Multishell Nanoparticles

Based on nickel hexacyanidochromate and cobalt hexacyanidoferrate Prussian blue analogues, two series of photomagnetic/ferromagnetic sub-50 nm core multishell coordination nanoparticles have been synthesized in a surfactant-free one-pot multistep procedure with good control over the dispersity (10% standard deviation) and good agreement with the targeted size at each step. The composition and the valence state of each shell have been probed by different techniques that have revealed the predominance of Co(II)-NC-Fe(III) pairs in a series synthesized without alkali while Co(III)-NC-Fe(II) photoswitchable pairs have been successfully obtained in the photoactive coordination nanoparticles by control of Cs(+) insertion. When compared, the photoinduced behavior of the latter compound is in good agreement with that of the model one. Exchange coupling favors a uniform reversal of the magnetization of the heterostructured nanoparticles, with a large magnetization brought by a soft ferromagnetic shell and a large coercivity due to a harder photomagnetic shell. Moreover, a persistent increase of the photoinduced magnetization is observed for the first time up to the ordering temperature (60 K) of the ferromagnetic component because of a unique synergy.

Design of silica-coated microcapsules for bioencapsulation

Alginate-based microcapsules are coated with silica, providing enhanced mechanical resistance, protein diffusion and allowing enzyme immobilization.

Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes.

Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest—and more attractive—systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [CoII(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination—without nanoparticle aggregation and without complex dissociation—of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude.

A tetranuclear oxomolybdenum(V) complex with bridging squarate ligands, [MoV4O8(OH)2(H2O)2(C4O4)2]2−

Abstract The new tetranuclear polyoxomolybdate(V) ion [MoV4O8(OH)2(H2O)2(C4O4)2]2− has been obtained in one step by the reaction of sodium molybdate, hydrazine and squaric acid in water and crystallized as a potassium salt. The structure has been solved by single-crystal X-ray diffraction showing the location of the hydroxo and water molecule ligands.

Synthesis and structure of the first dinuclear lanthanide oxalato complexes [{MoV2O4(C2O4)2(H2O)2}2{(Ln2(H2O)4)2(C2O4)}]·7H2O (Ln=La3+,Ce3+)

Abstract Reaction between the [MoV2O4(H2O)2(C2O4)2]2− anion and Ln III ( Ln = La , Ce ) in water affords the isostructural neutral complexes [{MoV2O4(C2O4)2(H2O)2}2{(Ln2(H2O)4)2(C2O4)}]. The structures have been solved by single-crystal X-ray diffraction and consist in a heteronuclear six-membered ring encapsulating an oxalate anion which connects the two rare earth cations. The formation of these complexes implies a partial decomposition of the precursor due to the high affinity of lanthanide toward oxalate in water which prevents the formation of analogous compounds with heavier rare earth cations in aqueous media.

Link between Affinity and Cu(II) Binding Sites to Amyloid-β Peptides Evaluated by a New Water-Soluble UV–Visible Ratiometric Dye with a Moderate Cu(II) Affinity

Being able to easily determine the Cu(II) affinity for biomolecules of moderate affinity is important. Such biomolecules include amyloidogenic peptides, such as the well-known amyloid-β peptide involved in Alzheimers disease. Here, we report the synthesis of a new water-soluble ratiometric Cu(II) dye with a moderate affinity (109 M-1 at pH 7.1) and the characterizations of the Cu(II) corresponding complex by X-ray crystallography, EPR, and XAS spectroscopic methods. UV-vis competition was performed on the Aβ peptide as well as on a wide series of modified peptides, leading to an affinity value of 1.6 × 109 M-1 at pH 7.1 for the Aβ peptide and to a coordination model for the Cu(II) site within the Aβ peptide that agrees with the one mostly accepted currently.