Sorbonne-Univ./CNRS

Laboratoire de chimie de la matière condensée de Paris
Tour 44-43 / 4ème étage
Case courrier 174
4, Place Jussieu
75005 PARIS
France

Dr. François RIBOT

Directeur(trice) de Recherche
NANO

francois.ribot(@-Code a retirer pour éviter le SPAM-)sorbonne-universite.fr
bureau 34-44-418

François Ribot was born in 1962. He graduated from Ecole Supérieure de Physique et Chimie Industrielle (ESPCI) in 1986. He then received his PhD in inorganic chemistry in 1990 from Pierre et Marie Curie University (UPMC), now part of Sorbonne University. His work, performed under the supervision of Pr. C. Sanchez and financed by Rhone-Poulenc Company, dealt with the sol-gel process of yttrium(III) and cerium(IV) oxides. During his PhD, he spent 16 months as a research associate in the group of Pr. Egon Matijevic at Clarkson University (Potsdam, NY, USA), working on the synthesis of uniform sub-micronic mixed colloids of yttrium(III) and copper(II) compounds. He joined the CNRS in 1990 and has been working since at the Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP-UMR 7574). In 2010, F. Ribot obtained his habilitation to lead research from Pierre et Marie Curie University (UPMC). He co-authored more than 100 peer reviewed papers.

His research deals with the chemistry of materials. He has contributed to the fields of sol-gel by studying the role of complexing ligands on the reactivity of various metals alkoxydes. He then worked on hybrid organic-inorganic materials and more particularly on those designed by the nanobulding blocks approach from organotin oxo-clusters. He also collaborated with industrial partners on the nanotexturation of hybrid coatings and the controlled precipitation of cerium(IV) phosphates. Over the last years, he shifted his research focus toward gold nanoparticles with two main topics: the synthesis of N-heterocyclic carbene stabilized gold nanoparticles and the in-situ study of their functionalization.

NMR spectroscopy constitutes an important tool in his researches and he developed strategies based on diffusion ordered spectroscopy (DOSY) experiments to study the interface of various nano-objects, ranging from molecularly defined oxo-clusters to nanoparticles, in solution or in suspension.

Last update 2020/01/07

  • Alexandre Porcheron, « Coordination complexes grafted on plasmonic nanoparticles », Sorbonne Université, started October 2018 – financed by ANR COCOsMEN, PhD adviser, co-supervised with L. Fensterbank.
  • Victoire Asila, « N-heterocyclic carbene-stabilized gold nanoclusters », Sorbonne Université, started October 2018 – financed by ED397, co-supervised with C. Chanéac (PhD adviser).
  • Laura Hippolyte, « New syntheses of N-heterocyclic carbene-stabilized gold nanoparticles », UPMC, 26/11/2018 – financed by Labex MiChem, ED 397 and Labex Matisse, PhD adviser, co-supervised with L. Fensterbank.
  • Perrot Alexandre, « Sol-gel coatings incorporating active mesostructured particles obtained by spray drying for aeronautical aluminum alloys protection against corrosion », UPMC, 2/6/2015 – financed by ANR AERO2, PhD adviser, co-supervised with L. Nicole.
  • Ben Sassi Hanen, « Probing, in suspension, the ligands on the surface of gold nanoparticles by DOSY NMR », UPMC, 28/2/2013 – financed by MESR, PhD adviser.
  • Letailleur Alban, « Pattering of hybrid silica coatings by nanoimprint : applications to light extractions », UPMC, 15/3/2012 – financed by Saint-Gobain Recherche, co-supervised with C. Boissière and C. Sanchez (PhD adviser).
  • Monget Julie, « Hybrid sol-gel coating for the corrosion protection of aeronautical aluminium alloys », UPMC, 14/12/2010 – financed by EADS-IW, co-supervised with L. Nicole and C. Sanchez (PhD adviser).
  • Nazaraly Micaela, « Control of structure, morphology and size of cerium(IV) phosphate particles », UPMC, 24/10/2006 – financed by Rhodia, co-supervised with C. Chanéac and J.-P. Jolivet (PhD adviser).
  • De Monredon Sophie, « Organosilanes/precipited silica interaction from hydroalcoolic to aqueous medium », UPMC, 7/12/2004 – financed by Rhodia, co-supervised with C. Bonhomme and F. Babonneau (PhD adviser).
  • Eychenne-Baron Christophe, « New syntheses of the macrocation {(BuSn)12O14(OH)6}2+: use as nanobrick for the synthesis. of hybrid materials », UPMC, 11/5/2001 – financed by MRT, co-supervised with C. Sanchez (PhD adviser).
  • Banse Frédéric, « Hydrolysis-condensation of monorganotin trialkoxides: synthesis of hybrid organic-inorganic systems », UPMC, 20/10/1995 – financed by MRT, co-supervised with C. Sanchez (PhD adviser).

Last update 2020/01/05

  • Nathalie Bridonneau, « Synthesis of N-heterocyclic carbene-stabilized gold nanoparticles », 1/9/2016-31/8/2017, ATER UPMC.
  • Anne Soleilhavoup, « Probing, by multinuclear NMR, the integrity and mobility of organotin oxo-clusters inserted in lipidic membranes », 5/1/2015-29/2/2016, ANR MEMINT.
  • Baradari Hiva, « Mineral and hybrid additives for Portland cement », 15/2/2012-31/8/2013, financed by Chryso.
  • Becuwe Matthieu, « Portland cement based hybrid materials », 1/9/2010-31/8/2011, financed by Chryso.
  • Van Lokeren Luk, « Pulsed field gradient based NMR methodology to probe, in suspension, the affinity of an organic ligand for nanoparticles surface », 1/9/2009-29/2/2012, ANR EVALON (ANR-08-NANO-026).
  • Van der Beek David, « New hybrid organic-inorganic liquid crystals based on nano building units », 2/11/2005-15/7/2007, EU(FP6-Marie Curie Mobility Actions) HYBRIDLICRYST.
  • Martinez-Ferrero Eugenia, « New tin(IV) based-nanobricks for hybrid materials », 1/10/2003-31/1/2005, EU(FP5-HP) NBB-Hybrids.
  • Armelao Lidia, « Sol-process prepared tin oxide », 1/4/1995-31/3/1996, grant from the University of Padova (Italy).
  • Kehr Gerald, « Monoorganotin based hybrid systems », 3/4/1995-2/2/1996, EU(FP3-HCM) CHRX940610.

Last update 2020/01/05

Last update 2020/01/07

last update 2020/07/09

The macrocation {(RSn)12O14(OH)6}2+

Its oxo-metallic framework, as determined by single crystal X-ray diffraction on several compounds, correspond to a quasi spherical cage made of an equal number of six-coordinated tin atoms (SnH) and five-coordinated tin atoms (SnP) linked by µ3-O and µ2-OH bridges. This framework, which is perfectly stable in solution, gives a distinct 119Sn-{1H} NMR signature, composed of two signals (one for each coordination) and four coupling constants in line with the different connection paths. One positive charge is located at each pole formed by the six-coordinated tin atoms and the µ2-OH bridges (Inorg. Chem. 1995, 34, 6371-6379 ; Organometallics 2000, 19, 1940-1949 ; J. Mater. Chem. 2005, 15, 3973-3978).

Various organizations of {(BuSn)12O14(OH)6}2+ encountered in the solid state.

In {(BuSn)12O14(OH)6}(O2PPh2)2(H2O)2, chains are formed by bridging diphenylphosphinate anions (unpublished result).
In {(BuSn)12O14(OH)6}(pTS)2(C4H8O2)2, the chains, formed by bridging p-toluenesulfonate anions, are assembled in plane by dioxane molecules, which interact with five-coordinated tin atoms (Organometallics 2000, 19, 1940-1949).
In {(BuSn)12O14(OH)6}(CHAPS)2, the chains, formed by a complex set of electrostatic contacts between the 3-cyclohexylamino-1-propanesulfonate anions and the µ2-OH groups of the macrocation, are assembled in planes through hydrogen bonds involving the amino and the sulfonate groups (unpublished result).
In {(BuSn)12O14(OH)6}(AMPS)2, -NH•••O=C(R)-NH•••O=C(R)- hydrogen bonds yield right and left helices, which are assembled in a 3D framework by a complex set of electrostatic contacts between the 2-acrylamido-2-methyl-1-propanesulfonate anions and the µ2-OH of the macrocation (J. Mater. Chem. 2005, 15, 3973-3978).

Sn12(μ3-O)6(μ2-O)2(μ2-OH)4(μ2-OEt)10(OEt)18(HOEt)4

Its centrosymmetric oxo-metallic framework and the location of the ethoxy groups have been first determined by single crystal X-ray diffraction. Then, with advanced multinuclear solution state NMR experiments, such as 1H-119Sn HSQC, four bridging hydroxy groups (µ2-OH) have been localized. Finally, a closer look at the O•••O distances has identified four pseudo bidentate « EtOH•••OEt » bridging groups. This tin oxo-cluster is perfectly stable in solution (Inorg. Chem. 2008, 47, 5831-5840).

Last update 2020/01/05

Strategies to functionalise and assemble the macrocation {(RSn)12O14(OH)6}2+

In the nano building block (NBB) approach to hybrid materials from the oxo-cluster {(RSn)12O14(OH)6}2+, several functionalization and assembling strategies have been explored. They mainly vary by the method use to introduce the functional groups amenable to link the clusters (eg. by polymerization) or to react with a complementary NBB. A first one uses the strong and covalent Sn-C(sp3) bond. A second one takes advantage of the positive charge localized at each pole of this NBB (New J. Chem. 1995, 19, 1145-1153; J. Sol-Gel Sci. Tech. 1997, 8, 529-533; Comm. Inorg. Chem. 1999, 20, 327-371; Chem. Mater. 2001, 13, 3061-3083; Adv. Mater. 2002, 14, 1496-1499; J. Mater. Chem. 2005, 15, 3973-3978; Polym. Chem. 2014, 5, 4474-4479; Macromolecules 2014, 47, 4266-4287).

Last update 2020/01/05

Coordination complexes grafted on metallic nanoparticles: toward synergy

ANR COCOsMEN

N-heterocyclic carbene-stabilized gold nanoparticles

N-heterocyclic carbenes (NHC), which form strong and covalent bonds with various metals, constitute a rich class of caping ligands, more and more studied in the field of nanoparticles. We proposed a simple and straightforward synthesis of NHC-stabilized gold nanoparticles from (benz)imidazolium-AuX4 complexes and NaBH4 only. The method allows size tuning, from 3 to 6 nm, by adding (benz)imidazolium bromide. Changing the reducing agent to tBuNH2BH3 shifts the size range to ca. 6-12 nm. A one pot protocol was also reported from AuCl, (benz)imidazolium bromides and NaBH4, thereby delivering an even more straightforward way of producing NHC-capped gold nanoparticles. In addition, X-ray photoelectron spectroscopy (XPS) unambiguously evidenced, on the nanoparticles, the covalent bond formed between the NHC and the surface gold atoms (Dalton Trans. 2018, 47, 6850-6859).

Quantified binding scale of competing ligands on the surface of thiols stabilized gold nanoparticles

Partially exchanging the surface ligands is a convenient way to modulate the properties of nanoparticles. However, the surface composition at equilibrium usually does not match the solution composition. For thiols stabilized gold nanoparticles, the concentrations of the initial and new ligands, in their free and grafted forms, can be monitored by 1H NMR. The constant K, which rules the partition of both ligands between the solution and the surface, can be determined from the equilibrium concentrations. K depends on the pair of ligands and on the particles size (ACS Nano 2015, 9, 7572-7582; Small 2017, 13, 1604028).

Last update 2020/01/05

Pulsed Field Gradient NMR basis

Pulsed field gradient (PFG) NMR spectroscopy or DOSY (Diffusion Ordered SpectroscopY) is a way of measuring diffusion coefficient for each component in a solution. The method is based on a series of spin echo or stimulated spin echo experiments, in which the gradient strength is increased. According to the equation derived by Stejskal and Tanner in 1965, the signal intensities depend on the diffusion coefficient and on parameters related to the studied nucleus (gyromagnetic ratio) or set by the experimenter (gradient strength, diffusion delay and gradient pulses length). Data can be processed in several ways. For instance, plotting the logarithm of the echo intensity versus the square of the gradient strength for each chemical signal yields, in simple cases, straight lines, the slopes of which are proportional to the diffusion coefficients. Alternatively, a global processing of the data can yield 2D DOSY maps where one axis corresponds to the usual NMR spectroscopic dimension and the other one to a dimension along which species are spread according to their diffusion behavior. In the example presented, two types of TOPO (trioctylphosphine oxide) molecules can be differentiated by their diffusion: those anchored on the surface of CdSe quantum dots and those free in solution.

Probing the ionic association on {(BuSn)12O14(OH)6}X2

The possibility to individually monitor the diffusion coefficient of multiple anionic and cationic species in mixtures allowed us to evidence ion exchange. Thus when [(BuSn)12O14(OH)6](pTS)2 (pTS=p‐toluenesulfonate) is mixed with two equivalents of [NMe4]Ph2PO2, pTS− is displaced by Ph2PO2−, even though there is no evidence of ionic dissociation. This example clearly illustrates the potential of pulsed field gradient 1H NMR spectroscopy in inorganic/organometallic chemistry, to follow preferential ion pairing in multi‐ion systems at the level of each individually charged species (Chem. Eur. J. 2004, 10, 1747-1751).

Looking at the functionalization of Ti16O16(OEt)32

The titanium oxo-cluster Ti16O16(OEt)32 can be functionalized by exchanging some of its surface ethoxy groups by other hydroxylated molecules. When the entering molecules are hydroxyl-terminated long polymers, the outcome of the exchange reaction is difficult to infer. 1H DOSY NMR shows that part of the added polymers remains free but also that part of them get grafted to the oxo-metallic core, what yields larger species with a smaller diffusion coefficient (J. Mater. Chem. 2011, 21, 4470-4475; J. Poly. Sci. A 2011, 49, 2636-2644).

Ligands interacting with sol-gel prepared nano-TiO2

Suspensions of titanium dioxide nanoparticles (~3 nm), prepared by hydrolysis-condensation of titanium tetrabutoxide in the presence of acetylacetone (AcacH), p-toluene sulfonic acid (pTSH) and n-butanol (BuOH), have been characterized by diffusion ordered NMR spectroscopy (DOSY NMR). The Acac(H), which is added in the process to act as a blocking ligand, can be found grafted (enol form) to the nanoparticles or free (enol form in equilibrium with the ketone form). The pTS(H), which is added to catalyze the hydrolysis-condensation, also interacts with the nanoparticles once they are formed. Part of the pTS(H) is strongly bound to the surface, likely through the sulfonate head group, while the other part corresponds to free pTS(H) in rapid exchange with molecules weakly interacting with the nanoparticles (Chem. Eur. J. 2007, 13, 6957-6966).

Quantitative analysis of mixtures


Pulsed Field-Gradient Spin Echo (PGSE) NMR, which associates to a spectral dimension the measure of diffusion coefficients, is a convenient technique for mixture analysis. Unfortunately, because of relaxation effects, the quantification by PGSE NMR is far from straightforward for mixtures with strong spectral overlap. By explicitly including the relaxation effects in the Stejskal and Tanner equation, meaningful fractions can be obtained from a multicomponent fit of the PGSE attenuation. This approach is illustrated with a binary mixture of polystyrenes, the 1H NMR spectra of which are perfectly identical. Fractions with error lower than 3% are obtained. The T1 and T2 values, required for this analysis, are either independently measured with conventional sequences or determined, along with the fractions and the diffusion coefficients, from the simultaneous analysis of up to 6 PGSE data sets recorded with different diffusion delays (J. Magn. Reson. 2013, 231, 46-53).

Dynamics at the cross-linking nodes in hybrid self-healing materials

Self-healing elastomers, based on electrostatic cross-linking, can be prepared from butyl acrylate and the organotin NBB {(BuSn12O14(OH)6}(AMPS)2. The dynamics at the cross-linking nodes, which is responsible of self-healing, has been evidenced by DOSY NMR on a swollen hybrid material doped with a non-functional version of the organotin NBB, {(BuSn12O14(OH)6}(pTS)2. The difference observed between the diffusion coefficient of the butyltin oxo-core, measured by 119Sn DOSY NMR, and its charge compensating anions (pTS), measured by 1H DOSY NMR, clearly reveals the exchange taking place at the cross-linking nodes (Polym. Chem. 2014, 5, 4474-4479).

Last update 2020/01/06

None for the moment

Last update 2020/08/03

Last update on 2020/08/03