Specific In Vivo Staining of Astrocytes in the Whole Brain after Intravenous Injection of Sulforhodamine Dyes

Fluorescent staining of astrocytes without damaging or interfering with normal brain functions is essential for intravital microscopy studies. Current methods involved either transgenic mice or local intracerebral injection of sulforhodamine 101. Transgenic rat models rarely exist, and in mice, a backcross with GFAP transgenic mice may be difficult. Local injections of fluorescent dyes are invasive. Here, we propose a non-invasive, specific and ubiquitous method to stain astrocytes in vivo. This method is based on iv injection of sulforhodamine dyes and is applicable on rats and mice from postnatal age to adulthood. The astrocytes staining obtained after iv injection was maintained for nearly half a day and showed no adverse reaction on astrocytic calcium signals or electroencephalographic recordings in vivo. The high contrast of the staining facilitates the image processing and allows to quantify 3D morphological parameters of the astrocytes and to characterize their network. Our method may become a reference for in vivo staining of the whole astrocytes population in animal models of neurological disorders

Oxidation Reactions Catalyzed by Atomically Well-Defined Gold Clusters

International @ MATERIAUX+CLA:ATU:ADMInternational audienceSub-2 nm gold clusters have attracted more attention since atomically well-defined and monodisperse thiolate capped ones have been successfully isolated. These clusters, with Aun(SR)m formula, are formed by a precise number n of gold atoms comprised between ~10 and few hundred and stabilized by m thiolate molecules. In this communication we investigate the influence of gold atoms number, the type of ligand at the surface and also the support effect on different aerobic oxidation reactions. More importantly, we pointed out that while still being functionalized; gold nanoclusters are active and highly selective in epoxidation of trans-stilbene

Atomically well-defined gold clusters: Oxidation reactions catalized by ultra-small gold core

International @ MATERIAUX+CLA:ATU:ADMInternational audienceRecently, atomically well defined thiolate-capped gold nanoclusters (denoted Aun(SR)m with (10,10) < (n,m) < (333,79)) have been successfully isolated and few structures have been solved. Thus, these monodispersed functionalized clusters, with precise atomic positions and gold core less than 2 nm, hold promises as a new generation of catalysts. More importantly, these nanoclusters permit in-depth studies on the subtle correlation of the structure, core diameter, thiolate ligands effect and electronic state of gold nanoparticles with their catalytic activity. New clusters made of 4-aminothiophenol (HSPhNH2) have been isolated, such as Au25(SPhNH2)17, and fully characterized by mass spectrometry, X-ray diffraction and XPS.3 Moreover these clusters exhibit absorption bands related to their molecular state. Those clusters have then be used to investigate in aerobic oxidations reactions and compared to the Au25(SC2H4Ph)18 cluster, having the same Au core but different thiolate ligand. They have been deposited on silica supports (hydrophobic 16 nm-SiO2 nanoparticles and SBA-15 mesoporous silica) and by properly selecting the support to maximize clusters/support interactions, it was possible to prepare materials with ultra-small gold particles (<2nm, fig. 1) and very narrow size distribution. We investigated the catalytic properties in aerobic oxidations of these sub-2 nm gold catalysts in (i) the aerobic epoxidation of trans-stilbene and (ii), the oxidative dehydrogenation of benzyl alcohol. By comparing the results for the different supported gold clusters, we pointed out that while still being functionalized, gold nanoclusters exhibit a good catalytic activity for the trans-stilbene epoxidation and that this catalytic activity is linked to the presence of the thiolate moiety.4 For the benzyl acohol oxidation, we showed that the presence of ligands is inhibiting the catalytic activity. This ligand effect observed with functionalized gold clusters makes possible to tune the overall catalytic selectivity and specificity to have chimio specific reactions on multi-modal sites. We showed here that thiolated gold nanoclusters compounds hold great interests and promises as a new class of catalysts thanks to their well-defined structure and to the ligands effect over the catalysis. [1] Qian et al., Acc. Chem. Res., 2012, 45, 1470 [2] R. Jin et al., Chem. Eur. J., 2011, 17, 6584. [3] C. Lavenn et al., Nanoscale, 2012, 4, 7334. [4] C. Lavenn et al., Cat. Tod., Accepte

Atomically Well-Defined Thiolate Gold Nanoclusters for Heterogeneous Catalysis

National @ MATERIAUX+CLA:ADM:ATUInternational audienceGold nanoparticles exhibit catalytic activity in many chemical processes.1 However, fundamental investigations on the structure-catalytic activity relationships still lag behind, partly due to the polydispersity issue of gold nanoparticles. Indeed polydisperse particles obscure the interesting size-dependent catalytic activity of nanogold and preclude an in-depth understanding of the origin of this size dependence. Recently, atomically monodisperse, thiolate-capped Au nanoclusters (denoted as Aun(SR)m) have been successfully isolated and their catalytic properties have been demonstrated.2 These well-defined gold clusters hold promises as a new generation of catalysts and, more importantly, permit in-depth studies on the subtle correlation of structure and catalytic activity, since these nanoclusters are atomically well defined and some of their structures have been solved by single crystal X-ray diffraction.3 To investigate the influence of the size, the type of ligands at the surface and also the support effect, different nanoclusters have been synthesized. Here we present the synthesis of new clusters made of 4-aminothiophenol (HSPhNH2). Among them Au10(SPhNH2)9/10 and Au25(SPhNH2)17 have been isolated and fully characterized by mass spectrometry, X-ray diffraction and XPS.4 Moreover these clusters exhibit characteristic absorption behaviors related to their molecular state. Catalytic activity for oxidation of alkene derivatives of these colloidal or supported clusters were investigated and compared to commonly used Aun(SCH2CH2Ph)m nanoclusters or bared nanoparticles. (1) Hashmi, A. S. K.; Hutchings, G. J. Angew. Chem.-Int. Edit. 2006, 45, 7896. (2) Jin, R. C.; Zhu, Y.; Qian, H. Chem. Eur. J. 2011, 17, 6584. (3) Zhu, Y.; Qian, H. F.; Zhu, M. Z.; Jin, R. C. Adv. Mater. 2010, 22, 1915. (4) Lavenn, C.; Albrieux, Bergeret, G.; F.; Chiriac, R., Delichčre P.; Tuel, A.; Demessence, A. Nanoscale , 2012, 4, 7334

Atomically Well Defined Thiolate Gold Nanoclusters for Heterogeneous Catalysis

International @ MATERIAUX+CLA:ATU:ADMInternational audienceGold nanoparticles, less than 5 nm, exhibit a catalytic activity in many chemical processes. However polydisperse particles obscure the interesting size-dependent catalytic activity of nanogold. Recently, atomically well defined thiolate-capped Au nanoclusters (denoted as Aun(SR)m) have been successfully isolated and their catalytic properties have been demonstrated. These monodispersed functionalized clusters, with gold core between less than 1 nm and more than 2 nm, hold promises as a new generation of catalysts. More importantly, these nanoclusters permit in-depth studies on the subtle correlation of structure and catalytic activity, since they are well defined and their crystallographic structures start to be solved. To investigate the influence of the size, the type of ligands at the surface and also the support effect, different nanoclusters have been synthesized. New clusters made of 4-aminothiophenol (HSPhNH2) have been synthesized, such as Au25(SPhNH2)17, and fully characterized by mass spectrometry, X-ray diffraction and XPS. Moreover these clusters exhibit absorption bands related to their molecular state. Catalytic activity for oxidation of alkene and alcohol derivatives of these colloidal or supported clusters were investigated and compared to the commonly used Aun(SCH2CH2Ph)m nanoclusters. At the opposite of the bare gold nanoparticles, the presence of the ligands around the clusters leads to a much better selectivity of the product

Atomically Well Defined Thiolate Gold Nanoclusters for Heterogeneous Catalysis

International @ MATERIAUX+CLA:ATU:ADMInternational audienceGold nanoparticles exhibit a catalytic activity in many chemical processes.1 Most of the reactions are size-dependant, i. e. the specific activity depends on the average gold particle size. Generally, the activity increases when the particle size decreases, with a marked increase below 5 nm, which strongly supports the role of surface gold atoms in the reactions. But for sub-2 nm particles, the origin of the catalytic power is still unclear and under intense debate. Fundamental investigations on the structure-catalytic activity relationships still lag behind, partly due to the polydispersity issue of gold nanoparticles. Indeed, polydisperse particles obscure the interesting size-dependent catalytic activity of nanogold and preclude an in-depth understanding of the origin of this size dependence. Recently, atomically well defined thiolate-capped Au nanoclusters (denoted as Aun(SR)m) have been successfully isolated and their catalytic properties have been demonstrated.2 These monodispersed functionalized clusters, with gold core between less than 1 nm and more than 2 nm, hold promises as a new generation of catalysts. More importantly, these nanoclusters permit in-depth studies on the subtle correlation of structure and catalytic activity, since they are well defined and their crystallographic structures start to be solved.3 To investigate the influence of the size, the type of ligands at the surface and also the support effect, different nanoclusters have been synthesized. New clusters made of 4-aminothiophenol (HSPhNH2) have been synthesized, such as Au25(SPhNH2)17, and fully characterized by mass spectrometry, X-ray diffraction and XPS.4 Moreover these clusters exhibit absorption bands and paramagnetic behaviour related to their molecular state. Catalytic activity for oxidation of alkene and alcohol derivatives of these colloidal or supported clusters were investigated and compared to the commonly used Aun(SCH2CH2Ph)m nanoclusters. At the opposite of the bare gold nanoparticles, the presence of the ligands around the clusters leads to a much better selectivity of the product. (1) Hashmi, A. S. K.; Hutchings, G. J. Angew. Chem.-Int. Edit. 2006, 45, 7896. (2) Jin, R. C.; Zhu, Y.; Qian, H. Chem. Eur. J. 2011, 17, 6584. (3) Zhu, Y.; Qian, H. F.; Zhu, M. Z.; Jin, R. C. Adv. Mater. 2010, 22, 1915. (4) Lavenn, C.; Albrieux, F.; Bergeret, G.; Chiriac, R.; Delichčre, P.; Tuel, A.; Demessence, A. Nanoscale DOI: 10.1039/C2NR32367B

Synthesis, characterization and optical properties of an amino-functionalized gold thiolate cluster: Au-10(SPh-pNH(2))(10)

MATERIAUX+CLA:ATU:ADMResearch interest in ultra small gold thiolate clusters has been rising in recent years for the challenges they offer to bring together properties of nanoscience and well-defined materials from molecular chemistry. Here, a new atomically well-defined Au-10 gold nanocluster surrounded by ten 4-aminothiophenolate ligands is reported. Its synthesis followed the similar conditions reported for the elaboration of Au-144(SR)(60), but because the reactivity of thiophenol ligands is different from alkanethiol derivates, smaller Au-10 clusters were formed. Different techniques, such as ESI-MS, elemental analysis, XRD, TGA, XPS and UV-vis-NIR experiments, have been carried out to determine the Au-10(SPh-pNH(2))(10) formula. Photo-emission experiment has been done and reveals that the Au-10 clusters are weakly luminescent as opposed to the amino-based ultra-small gold clusters. This observation points out that the emission of gold thiolate clusters is highly dependent on both the structure of the gold core and the type of the ligands at the surface. In addition, ultra-small amino-functionalized clusters offer the opportunity for extended work on self-assembling networks or deposition on substrates for nanotechnologies or catalytic applications. (C) 2013 Elsevier Inc. All rights reserved

Ion Trajectory Simulations in a High-Pressure Cylindrical Ion Trap

International audienc

mu-Nitrido diiron octaethylporphyrin complex: synthesis and properties

BIOVERT:RAFFINAGE+EKU:PAF:ASOmu-nitrido diiron porphyrin complex (OEPFe)(2)N (OEP = octaethylporphyrinato dianion) was synthesized by the treatment of (OEPFe)Cl with hydrazoic acid followed by the thermal decomposition of formed (OEPFe)N-3 complex. The (OEPFe)(2)N complex was investigated by UV-vis, IR, HR ESI-TOF MS and EPR spectroscopic methods. EXAFS study indicated a very short Fe-Fe distance of 3.30 angstrom in this dimer compared with 3.48 angstrom distance between iron sites in the related mu-nitrido diiron complex on the tetraphenylporphyrin platform. This difference can be explained by the steric hindrance exerted by phenyl substituents in the latter. The spectral properties of the (OEPFe)(2)N complex are discussed. The catalytic properties of (OEPFe)(2)N were evaluated in the oxidation of cyclohexene and cyclohexane

How Does an Acidic Support Affect the Hydrotreatment of a Gas Oil with High Nitrogen Content?

SSCI-VIDE+ECI2D+CGEInternational audience--