Temperature Response of Rhodamine B-Doped Latex Particles. From Solution to Single Particles.

Nanoparticle-based temperature imaging is an emerging field of advanced applications. Herein, the sensitivity of the fluorescence of rhodamine B-doped latex nanoparticles toward temperature is described. Submicrometer size latex particles were prepared by a surfactant-free emulsion polymerization method that allowed a simple and inexpensive way to incorporate rhodamine B into the nanoparticles. Also, rhodamine B-coated latex nanoparticles dispersed in water were prepared in order to address the effect of the dye location in the nanoparticles on their temperature dependence. A better linearity of the temperature dependence emission of the rhodamine B-embedded latex particles, as compared to that of free rhodamine B dyes or rhodamine B-coated latex particles, is observed. Temperature-dependent fluorescence measurements by fluorescent confocal microscopy on individual rhodamine B-embedded latex particles were found similar to those obtained for fluorescent latex nanoparticles in solution, indicating that these nanoparticles could be good candidates to probe thermal processes as nanothermometers.

Formation of a covalent bond between a polyoxometalate and silica covered by SiH moieties.

Dehydroxylated silica was modified by grafting reaction of SiHMe2 groups. The resulting material was fully characterized by various methods including infrared and one- and two-dimensional solid-state NMR. This material can further react with dehydrated polyoxometalates (POMs), leading to the formation of a covalent POM-silica bond. In the case of H4PVMo11O40, hydrogen released during the grafting reaction reduces the POM. This leads to the formation of two surface species, which can be reoxidized in presence of oxygen. In the case of H3PW12O40, no reduction is observed. In both cases, (29)Si solid-state NMR shows that the POM-silica bond is covalent, contrary to what was observed in homogeneous conditions.

How do physical-chemical parameters influence the catalytic hydrogenation of 1,3-cyclohexadiene in ionic liquids?

The catalytic hydrogenation of 1,3-cyclohexadiene using [Rh(COD)(PPh(3))(2)]NTf(2) (COD = 1,5-cyclooctadiene) was performed in two ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(1)C(4)Im][NTf(2)]. It is observed that the reaction is twice as fast in [C(1)C(4)Im][NTf(2)] than in [C(1)C(1)C(4)Im][NTf(2)]. To explain the difference in reactivity, molecular interactions and the microscopic structure of ionic liquid +1,3-cyclohexadiene mixtures were studied by NMR and titration calorimetry experiments, and by molecular simulation in the liquid phase. Diffusivity and viscosity measurements allowed the characterization of mass transport in the reaction media. We could conclude that the diffusivity of 1,3-cyclohexadiene is 1.9 times higher in [C(1)C(4)Im][NTf(2)] than in [C(1)C(1)C(4)Im][NTf(2)] and that this difference could explain the lower reactivity observed in [C(1)C(1)C(4)Im][NTf(2)].

Unexpected, spontaneous and selective formation of colloidal Pt3Sn nanoparticles using organometallic Pt and Sn complexes.

The facile and selective synthesis of small crystalline Pt(3)Sn alloy nanoparticles was performed at room temperature under H(2), using a colloidal approach without the use of extra-stabilizing ligands. The Pt(3)Sn alloy was found to be obtained spontaneously as the unique phase regardless of the number of tin equivalents introduced.

Interaction between the pi-system of toluene and the imidazolium ring of ionic liquids: a combined NMR and molecular simulation study.

The solute-solvent interactions and the site-site distances between toluene and ionic liquids (ILs) 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [BMMIm][NTf2] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIm][NTf2] at various molar ratios were determined by NMR experiments (1D NMR, rotating-frame Overhauser effect spectroscopy (ROESY)) and by molecular simulation using an atomistic force field. The difference in behavior of toluene in these ILs has been related to the presence of H-bonding between the C2-H and the anion in [BMIm][NTf2] generating a stronger association (>20 kJ.mol-1) than in the case of [BMMIm][NTf2]. Consequently, toluene cannot cleave this H-bond in [BMIm][NTf2] which remains in large aggregates of ionic pairs. However, toluene penetrates the less strongly bonded network of [BMMIm][NTf2] and interacts with [BMMIm] cations.