The confinement effect on the activity of Au NPs in polyol oxidation

We demonstrate a confinement effect where gold nanoparticles trapped within N-functionalized carbon nanofibers (N-CNFs) are more active for polyol oxidation and promote selectivity towards di-acid products, whereas AuNPs trapped on the surface produce as a major by-product the one derived from C-C cleavage. The behaviour of NPs confined inside the N-CNF channels can be attributed to a different, possibly multiple, coordination of glycerol on the active site

Dexamethasone intravitreal implant in previously treated patients with diabetic macular edema : Subgroup analysis of the MEAD study

Background: Dexamethasone intravitreal implant 0.7 mg (DEX 0.7) was approved for treatment of diabetic macular edema (DME) after demonstration of its efficacy and safety in the MEAD registration trials. We performed subgroup analysis of MEAD study results to evaluate the efficacy and safety of DEX 0.7 treatment in patients with previously treated DME. Methods: Three-year, randomized, sham-controlled phase 3 study in patients with DME, best-corrected visual acuity (BCVA) of 34.68 Early Treatment Diabetic Retinopathy Study letters (20/200.20/50 Snellen equivalent), and central retinal thickness (CRT) 65300 \u3bcm measured by time-domain optical coherence tomography. Patients were randomized to 1 of 2 doses of DEX (0.7 mg or 0.35 mg), or to sham procedure, with retreatment no more than every 6 months. The primary endpoint was 6515-letter gain in BCVA at study end. Average change in BCVA and CRT from baseline during the study (area-under-the-curve approach) and adverse events were also evaluated. The present subgroup analysis evaluated outcomes in patients randomized to DEX 0.7 (marketed dose) or sham based on prior treatment for DME at study entry. Results: Baseline characteristics of previously treated DEX 0.7 (n = 247) and sham (n=261) patients were similar. In the previously treated subgroup, mean number of treatments over 3 years was 4.1 for DEX 0.7 and 3.2 for sham, 21.5 % of DEX 0.7 patients versus 11.1 % of sham had 6515-letter BCVA gain from baseline at study end (P = 0.002), mean average BCVA change from baseline was +3.2 letters with DEX 0.7 versus +1.5 letters with sham (P = 0.024), and mean average CRT change from baseline was -126.1 \u3bcm with DEX 0.7 versus -39.0 \u3bcm with sham(P < 0.001). Cataract-related adverse events were reported in 70.3 % of baseline phakic patients in the previously treated DEX 0.7 subgroup; vision gains were restored following cataract surgery. Conclusions: DEX 0.7 significantly improved visual and anatomic outcomes in patients with DME previously treated with laser, intravitreal anti-vascular endothelial growth factor, intravitreal triamcinolone acetonide, or a combination of these therapies. The safety profile of DEX 0.7 in previously treated patients was similar to its safety profile in the total study population

Selective oxidation of glycerol under acidic conditions using gold catalysts

Herein, we report progress towards eliminating the need for a base while maintaining high activity and selectivity for the aqueous-phase oxidation of glycerol.We have discovered that by using the right alloy nanoparticle and support material, we are able to prepare an active and durable catalyst that is highly selective towards the formation of oxidized C3 molecules from glycerol under acidic conditions. This discovery is significant because previous investigations of Pd and Pt catalysts at pH 2\u20134 reported that the main products derived from these catalysts under acidic conditions are C1 and C2 molecules produced from C C bond scissio

Bismuth as a modifier of Au\u2013Pd catalyst : enhancing selectivity in alcohol oxidation by suppressing parallel reaction

Bi has been widely employed as a modifier for Pd and Pt based catalyst mainly in order to improve selectivity. We found that when Bi was added to the bimetallic system AuPd, the effect on activity in alcohol oxidation mainly depends on the amount of Bi regardless its position, being negligible when Bi was 0.1 wt% and detectably negative when the amount was increased to 3 wt%. However, the selectivity of the reactions notably varied only when Bi was deposited on the surface of metal nanoparticles suppressing parallel reaction in both benzyl alcohol and glycerol oxidation. After a careful characterization of all the catalysts and additional catalytic tests, we concluded that the Bi influence on the activity of the catalysts could be ascribed to electronic effect whereas the one on selectivity mainly to a geometric modification. moreover, the Bi-modified AuPd/AC catalyst showed possible application in the production of tartronic acid, a useful intermediate, from glycerol

Pd-modified Au on carbon as an effective and durable catalyst for the direct oxidation of HMF to 2,5-furandicarboxylic acid

Mixed noblility: We show that the modification of a gold/carbon catalyst with platinum or palladium produces stable and recyclable catalysts for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA): the support and nanoparticle chemistry directly mediate the selective oxidation of terminal hydroxyl groups in bio-derived HMF. This finding is a significant advance over current conversion technology because of the technological importance of FDCA

Au on nanosized NiO: a cooperative effect between Au and nano NiO in the base-free alcohol oxidation

Nanosized NiO has been synthesized and used as a support for polyvinyl alcohol-protected Au nanoparticles. This catalytic system exhibits an extraordinary performance in the base-free liquid phase oxidation of alcohols compared to the same Au supported on a commercial, micrometersized NiO. This enhancement in activity cannot be solely attributed to the improved basic properties of the support. A cooperative effect between Au nanoparticles and nanosized NiO is envisaged

Ru supported on micro and mesoporous carbons as catalysts for biomass-derived molecules hydrogenation

Supported ruthenium based materials are active for the catalytic hydrogenation of biomass-derived molecules. However, such catalysts still have problems regarding deactivation coming from Ru leaching and particles aggregation. In this work we demonstrate that spatial restriction on metal nanoparticles limits aggregation and eliminates performance losses upon subsequent testing. We synthesized and compared Ru supported on activated (Ru/AC) or mesoporous carbon (Ru/MC). Electron tomography characterization showed preferential Ru location depending on the material porosity; Ru nanoparticles were located inside mesoporous carbon pores and showed narrower size distribution. In catalytic reactions, Ru/MC reached the complete conversion of levulinic acid with the 96% selectivity to \u3b3-valerolactone while it converted 74% of glycerol compared to the 34% showed by Ru/AC. The Ru/AC materials deactivated after 1 catalytic cycle, however the Ru/MC maintained constant activity for multiple catalytic cycles

NiO as a peculiar support for metal nanoparticles in polyols oxidation

The peculiar influence of a NiO support was studied by preparing gold catalysts supported on NiO1 12x\u2013TiO2 x mixed oxides. PVA protected Au nanoparticles showed high activity when supported on NiO for the selective oxidation of glycerol and ethane-1,2-diol. A detailed characterization of the resulting Au catalysts revealed a preferential deposition of the metal nanoparticles on the NiO phase. However, the activity of Au on NiO1 12x\u2013TiO2 x decreased with respect to pure NiO and the selectivity evolved with changes in the support