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Different Ti-Si catalysts, viz. TiO 2 supported on amorphous SiO 2 or Si-MCM-41, TiO 2 -SiO 2 xerogels, and Ti zeolites (TS-1 and Ti-beta), were compared in terms of activity and selectivity for the direct conversion of methyl lactate to lactide in the gas phase. Except for Ti-beta, all catalysts exhibit a high lactide selectivity of 88−92% at conversions below 50%. From DR UV−vis spectroscopy, it is evidenced that the catalytic activity of tetrahedral TiO 4 sites is higher than those of polymerized TiO 5 or the octahedral TiO 6 counterparts, irrespective of the catalyst structure, an analysis supported by ToF-SIMS measurements. A kinetic analysis shows that the catalytic activity is proportional to the number of vacant sites on the catalyst surface. Thus, the activity increase observed for tetrahedral TiO 4 sites may be attributed to an increased number of vacant sites (e.g., two for TiO 4 , zero for TiO 6 ). Lactide productivity thus highly benefits from an increased dispersion of Ti sites on the catalyst surface and could be increased by a factor of 2.5 (up to 10 g LD g cat −1 h −1 ) when TiO 2 is dispersed on a Si-MCM-41 support, with higher surface areas in comparison to amorphous SiO 2 gels.

Poly(ethylene glycol) (PEG) films are known to be protein‐repelling and to reduce biofilms attachment. We use a simple, easy to set up, versatile atmospheric pressure radiofrequency plasma to deposit plasma‐polymerized poly(ethylene glycol) films onto polyvinylfluoride (PVF) and gold surfaces, using liquid or gaseous tetraglyme (CH3O(CH2CH2O)4CH3) as precursor. The chemical composition of the films was studied using infrared reflection absorption spectroscopy, X‐ray photoelectron spectroscopy and secondary ions mass spectroscopy. Bovine Serum Albumin adsorption has revealed good biocompatible properties that are correlated to the surface composition.

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The advantages and drawbacks of using either monatomic or buckminsterfullerene primary ions for metal-assisted secondary ion mass spectrometry (MetA-SIMS) are investigated using a series of organic samples including additive molecules, polyolefins, and small peptides. Gold deposition is mostly performed by sputter-coating, and in some cases, the results are compared to those of thermal evaporation (already used in a previous article: Delcorte, A.; Médard, N.; Bertrand, P. Anal. Chem. 2002, 74, 4955). The microstructure of the gold-covered sample surfaces is assessed by scanning and transmission electron microscopies. The merits of the different sets of experimental conditions are established via the analysis of fragment and parent-like ion yields. For most of the analyzed samples, the highest yields of fragment and parent-like ions are already reached with the sole use of C60+ projectiles. Metallization of the sample does not lead to a significant additional enhancement. For polyethylene and polypropylene, however, gold metallization associated with Ga+/In+ projectiles appears to be the only way to observe large cationized, sample-specific chain segments (m/z approximately 1000-2000). A detailed study of the polypropylene mass spectra as a function of gold coverage shows that the dynamics of yield enhancement by metal nanoparticles is strongly dependent on the choice of the projectile, e.g., a pronounced increase with Ga+ and a slow decay with C60+. The cases of Irganox 1010, a polymer antioxidant, and leucine enkephalin, a small peptide, allow us to investigate the specific influence of the experimental conditions on the emission of parent(like) ions such as M+, (M + Na)+, and (M + Au)+. The results show a dependence on both the type of sample and the considered secondary ion. Using theoretical and experimental arguments, the discussion identifies some of the mechanisms underlying the general trends observed in the results. Guidelines concerning the choice of the experimental conditions for MetA-SIMS are provided.