Surface Functionalization of Detonation Nanodiamonds by Phosphonic Dichloride Derivatives

A new method for the functionalization of detonation nanodiamonds (DNDs) is proposed, on the basis of surface modification with phosphonic dichloride derivatives. DNDs were first modified by phenylphosphonic dichloride, and the grafting modes and hydrolytic stability under neutral conditions 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 postmodification of DNDs modified by 12-bromododecylphosphonic dichloride. The oxidative thermal stability of the functionalized DNDs was investigated using thermogravimetric analysis

Improvement of the Oxidative Stability of Nanodiamonds by Surface Phosphorylation

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

A one step non-hydrolytic sol-gel route to mesoporous Re- and Mo-based mixed oxides for olefin metathesis

<p>The simplicity of NHSG makes it attractive: multi-step procedures, expensive precursors, or reactivity modifiers are not needed.</p> <p>Poster presented at the Europacat conference September 2, 2013, Lyon, France.</p

Tuning Local Nanoparticle Arrangements in TiO₂–Polymer Nanocomposites by Grafting of Phosphonic Acids

The influence of surface modification of TiO₂ nanoparticles with phosphonic acid molecules on the structure of polymer nanocomposites has been studied by small-angle scattering and transmission electron microscopy. The grafting of phosphonic acids was done by phase transfer into chloroform, and polymer nanocomposites have been formulated by solvent casting with two polymers of slightly different hydrophobicity, PMMA and PEMA. By analyzing the shape of the scattering curves around the interparticle correlation peak, and in particular the depth of the correlation hole, information on nearest-neighbor correlations between nanoparticles is obtained. While local nanoparticle arrangements are found to be independent of the global particle volume fraction, they are controlled by the degree of hydrophobicity of the alkyl­phosphonic acid grafts with respect to hydrophobicity of the matrix. Quantitative analysis of the correlation hole thus evidences the fine-tuning of local nanocomposite structure with phosphonic acids

Simultaneous Phase Transfer and Surface Modification of TiO₂ Nanoparticles Using Alkylphosphonic Acids: Optimization and Structure of the Organosols

An original protocol of simultaneous surface modification and transfer from aqueous to organic phases of anatase TiO₂ nanoparticles (NPs) using alkylphosphonic acids (PAs) is studied. The influence of the solvent, the nature and concentration of the PA, and the size, concentration, and aggregation state of the TiO₂ NPs was investigated. Complete transfer was observed for linear alkyl chains (5, 8, 12, and 18 C atoms), even at very high sol concentrations. After transfer, the grafted NPs were characterized by ³¹P solid-state MAS NMR. The dispersion state of NPs before and after phase transfer was monitored by dynamic light scattering (DLS). Small-angle neutron scattering (SANS) was used to characterize the structure of PA-grafted NPs in the organic solvent. Using a quantitative core–shell model cross-checked under different contrast conditions, it is found that the primary particles making up the NPs are homogeneously grafted with a solvated PA-layer. The nanometric thickness of the latter is shown to increase with the length of the linear carbon chain of the PA, independent of the size of the primary TiO₂ NP. Interestingly, a reversible temperature-dependent aggregation was evidenced visually for C₁₈PA, and confirmed by DLS and SANS: heating the sample induces the breakup of aggregates, which reassemble upon cooling. Finally, in the case of NPs agglomerated by playing with the pH or the salt concentration of the sols, the phase transfer with PA is capable of redispersing the agglomerates. This new and highly versatile method of NP surface modification with PAs and simultaneous transfer is thus well suited for obtaining well-dispersed grafted NPs