[Show abstract][Hide abstract] ABSTRACT: Ultrasmall gold nanoparticles (Au UNPs) represent a unique class of nanomaterials making them very attractive for certain applications. Herein, we developed an organometallic approach to the synthesis of Au UNPs stabilized with the C18H37-NHC ligand by the solvent free thermolysis of [RMIM][Au(C6F5)2] (1) or [Au(C6F5)(RNHC)] (3) (with R = C18H37-), by controlling the reactivity of pentafluorophenyl ligands as deprotonating or reductive elimination agents; Au UNPs can be achieved by solvent free thermolysis. Pentafluorophenyl Au(I) complexes 1 and 3 are synthesized from the corresponding ionic and neutral precursors. The presence of long alkyl chain imidazolium or carbene species in the complexes makes them to behave as isotropic liquids at moderate temperatures. The use of multinuclear NMR allows the description of the mechanism of formation of the UNPs as well as the surface state of the UNPs.
[Show abstract][Hide abstract] ABSTRACT: Correction for ‘Investigation of the local environment of iodate in hydroxyapatite by combination of X-ray absorption spectroscopy and DFT modeling’ by Danielle Laurencin et al., RSC Adv., 2014, 4, 14700–14707.
[Show abstract][Hide abstract] ABSTRACT: Boronate ligands [R–B(OH)3–] have recently started to attract attention for the elaboration of coordination polymer networks. Here, three new crystalline structures involving butyl- and octylboronate ligands are described: Sr[Bu–B(OH)3]2, Ca[Oct–B(OH)3]2 and Sr[Oct–B(OH)3]2 (Bu = C4H9, Oct = C8H17). All were obtained as microcrystalline powders, and their structures were solved by synchrotron powder X-ray diffraction. IR and multinuclear (13C, 11B, 43Ca, 87Sr and 1H) solid-state NMR characterizations were performed on the materials. Computational models of the new Sr[Bu–B(OH)3]2 phase and the previously reported Sr[Ph–B(OH)3]2·H2O structure were then developed. The IR O–H stretching modes and NMR parameters were calculated for these models and are discussed in view of the experimental spectra. This work confirms the importance of computational studies on boronate phases to determine the nature of the H-bond network within the materials and to better understand their spectroscopic signatures.
Berichte der deutschen chemischen Gesellschaft 09/2014; · 2.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: TiO2/conjugated polymers are promising materials in solar energy conversion where efficient photo-induced charge transfers are required. Here, a 'grafting-from' approach for the synthesis of TiO2 nanoparticles supported with conjugated polymer brushes is presented. Poly(3-hexylthiophene) (P3HT), a benchmark material for organic electronics, was selectively grown from TiO2 nanoparticles by Surface-Initiated Kumada Catalyst-Transfer Polycondensation (SI-KCTP). The grafting of the polymer onto the surface of the TiO2 nanoparticles by this method was demonstrated by 1H and 13C solid-state NMR, XPS (X-ray photoelectron spectrometry), thermogravimetric analysis (TGA), Transmission Electron Microscopy (TEM) and UV-Visible spectroscopy. Sedimentation tests in THF revealed improved dispersion stability for the TiO2@P3HT hybrid material. Films were produced by solvent casting and the quality of the dispersion of the modified TiO2 nanoparticles was evaluated by Atomic Force Microscopy (AFM). The dispersion of the P3HT-coated TiO2 NPs in the P3HT matrix was found to be homogeneous and the fibrillar structure of the P3HT matrix was maintained which is favourable for charge transport. Fluorescence quenching measurements on these hybrids materials in CHCl3 indicated improved photo-induced electron transfer efficiency. All in all, better physicochemical properties for P3HT/TiO2 hybrid material were reached via surface-initiated "grafted from" approach compared to the "grafting onto" approach.
Langmuir : the ACS journal of surfaces and colloids. 09/2014;
[Show abstract][Hide abstract] ABSTRACT: A new method for the functionalization of detonation nanodiamonds (DNDs) is proposed, based on the surface modification with phosphonic dichloride derivatives. DNDs were first modified by phenylphosphonic dichloride and the grafting modes and hydrolytic stability were investigated using 1H, 13C and 31P solid state NMR spectroscopy, Fourier transform infrared spectroscopy, as well as elemental analysis. Then, in order to illustrate the possibilities offered by this method, DNDs functionalized by mesityl imidazolium groups were obtained by post-modification of DNDs modified by 12-bromododecylphosphonic dichloride. The oxidative thermal stability of the functionalized DNDs was investigated using thermogravimetric analysis.
[Show abstract][Hide abstract] ABSTRACT: In this contribution, the latest developments in solid state NMR are presented in the field of organic–inorganic (O/I) materials (or hybrid materials). Such materials involve mineral and organic (including polymeric and biological) components, and can exhibit complex O/I interfaces. Hybrids are currently a major topic of research in nanoscience, and solid state NMR is obviously a pertinent spectroscopic tool of investigation. Its versatility allows the detailed description of the structure and texture of such complex materials. The article is divided in two main parts: in the first one, recent NMR methodological/instrumental developments are presented in connection with hybrid materials. In the second part, an exhaustive overview of the major classes of O/I materials and their NMR characterization is presented.
Progress in Nuclear Magnetic Resonance Spectroscopy 02/2014; 77:1–48. · 6.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The reaction of gold nanoparticles with benzimididazol-2-ylidene ligands leads to the formation of well-defined bis-carbene gold(i) complexes, as shown by characterization techniques such as powder XRD and solid state NMR.
[Show abstract][Hide abstract] ABSTRACT: Mechanical resilience of bone tissue decreases with age. The ability to comprehensively probe and understand bone properties could help alleviate this problem. One important aspect of bone quality which has recently been made evident is the presence of dilatational bands formed by osteocalcin (OC) and osteopontin (OPN), which contribute to fracture toughness. However, experimental evidence of the structural role of these two proteins at the organic-mineral interface in bone is still needed. Solid state nuclear magnetic resonance (SSNMR) is emerging as a useful technique in probing molecular level aspects of bone. Here, we present the first SSNMR study of bone tissue from genetically modified mice lacking OC and/or OPN. Probing the mineral phase, the organic matrix and their interface revealed that despite the absence of OC and OPN, the organic matrix and mineral were well preserved, and the overall exposure of collagen to hydroxyapatite (HA) nanoparticles was hardly affected. However, the proximity to HA surface was slightly increased for a number bone components including less abundant amino acids like lysine, suggesting that this is how the tissue compensates for the lack of OC and OPN. Taken together, the NMR data supports the recently proposed model, in which the contribution of OC - OPN to fracture toughness is related to their presence at the extrafibrillar organic-mineral interfaces, where they reinforce the network of mineralized fibrils and form dilatational bands. In effort towards understanding further the structural role of individual amino acids of low abundance in bone, we then explored the possibility of specific 13C enrichment of mouse bone, and report the first SSNMR spectra of 97% 13C lysine-enriched tissues. Results show that such isotopic enrichment allows valuable molecular-level structural information to be extracted, and sheds light on post-translational modifications undergone by specific amino acids in vivo.
[Show abstract][Hide abstract] ABSTRACT: Phosphonic acids are increasingly being used for controlling surface and interface properties in hybrid or composite materials, (opto)electronic devices and in the synthesis of nanomaterials. In this perspective article, a concise survey of phosphonate coupling molecules is first presented, including details on their coordination chemistry, their use in the surface modification of inorganic substrates with self-assembled monolayers, and the analytical techniques available to characterize their environment in nanomaterials. Then, some of their recent applications in the development of organic electronic devices, photovoltaic cells, biomaterials, biosensors, supported catalysts and sorbents, corrosion inhibitors, and nanostructured composite materials, are presented. In the last part of the article, a brief overview of recent progress in the use of phosphonate ligands for the preparation of molecular nanomaterials like metal organic frameworks and functionalized polyoxometalates is given.
[Show abstract][Hide abstract] ABSTRACT: A 1D-microporous 3D calcium tetracarboxylate MOF has been solvothermally prepared and its structure solved from single crystal data. It exhibits coordinatively unsaturated Ca(2+) Lewis acid sites able to trap and deliver nitric oxide at a biological level.
Chemical Communications 05/2013; · 6.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Surface phosphorylation of nanodiamond was performed by reaction with phosphoryl chloride in dichloromethane. Depending on the reaction conditions, P contents of up to 1.66 mmol/g were reached. Phosphorylation dramatically enhanced the thermal stability of nanodiamond under oxidizing conditions, shifting the oxidation temperature by up to 190 °C and dividing the oxidation rate by a factor of up to 160. The nature of the grafted phosphate species and their evolution during thermal treatment was followed using solid-state NMR.
Chemistry of Materials. 05/2013; 25(10):2051–2055.
[Show abstract][Hide abstract] ABSTRACT: Multinuclear solid state NMR (including Ca-43 NMR), in combination with DFT calculations, is applied to the study of the crystal structure of whewellite, CaC2O4 center dot H2O. This particular hydrated calcium oxalate is of paramount importance as it corresponds to a major phase present in urinary stones. Ca-43 MAS NMR experiments and GIPAW calculations were performed in order to further refine neutron diffraction data. The sensitivity of Ca-43 NMR as a structural probe is demonstrated. This is the first step for the full description of calcium oxalates at the DFT level and the characterization of interfaces between these biomineral phases and organic phases.
[Show abstract][Hide abstract] ABSTRACT: Boronic acids (R-B(OH)(2) ) are a family of molecules that have found a large number of applications in materials science. In contrast, boronate anions (R-B(OH)(3) (-) ) have hardly been used so far for the preparation of novel materials. Here, a new crystalline phase involving a boronate ligand is described, Ca[C(4) H(9) -B(OH)(3) ](2) , which is then used as a basis for the establishment of the spectroscopic signatures of boronates in the solid state. The phase was characterized by IR and multinuclear solid-state NMR spectroscopy ((1) H, (13) C, (11) B and (43) Ca), and then modeled by periodic DFT calculations. Anharmonic OH vibration frequencies were calculated as well as NMR parameters (by using the Gauge Including Projector Augmented Wave-GIPAW-method). These data allow relationships between the geometry around the OH groups in boronates and the IR and (1) H NMR spectroscopic data to be established, which will be key to the future interpretation of the spectra of more complex organic-inorganic materials containing boronate building blocks.
Chemistry - A European Journal 12/2012; · 5.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Manipulating interfacial thermal transport is important for many technologies including nanoelectronics, solid-state lighting, energy generation and nanocomposites. Here, we demonstrate the use of a strongly bonding organic nanomolecular monolayer (NML) at model metal/dielectric interfaces to obtain up to a fourfold increase in the interfacial thermal conductance, to values as high as 430 MW m(-2) K(-1) in the copper-silica system. We also show that the approach of using an NML can be implemented to tune the interfacial thermal conductance in other materials systems. Molecular dynamics simulations indicate that the remarkable enhancement we observe is due to strong NML-dielectric and NML-metal bonds that facilitate efficient heat transfer through the NML. Our results underscore the importance of interfacial bond strength as a means to describe and control interfacial thermal transport in a variety of materials systems.
[Show abstract][Hide abstract] ABSTRACT: Natural-abundance 25Mg solid-state NMR data obtained using very high magnetic fields of 17.6, 20.0, and 30.0 T are reported for a series of magnesium phosphate compounds, some of which are of potential biomedical interest. The 25Mg NMR parameters have been calculated by using the DFT PAW and GIPAW methods, for both the experimental and DFT atomic position optimized structures. For most of the studied compounds, the geometry optimization step improves significantly the accuracy of the calculations and good correlations between experimental and calculated 25Mg chemical shifts and quadrupolar coupling constants were achieved showing that this approach can be used to obtain unambiguous assignments of the 25Mg resonances in more complex phosphate compounds. The possibility of recording natural abundance 25Mg NMR spectra in materials with very low Mg content is illustrated for a 10% Mg-substituted hydroxyapatite sample. In this case, the distribution of 25Mg quadrupolar coupling measured experimentally has been compared with values previously calculated for several structural models. The results suggest that more complex structural models must be developed to improve the understanding of the Ca/Mg substitution on the basis of 25Mg NMR data.
The Journal of Physical Chemistry C 08/2012; 116(37):19984-19995. · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr(2+) ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that (87)Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity (87)Sr solid-state NMR experiments is presented using (87)Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr-Purcell-Meiboom-Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute (87)Sr NMR parameters. Last and most importantly, (87)Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ~9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of (87)Sr NMR parameters. Finally, changes in the (87)Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed.
Journal of the American Chemical Society 06/2012; 134(30):12611-28. · 10.68 Impact Factor