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Immobilization of palladium on magnetite nanoparticles has been carried out with the assistance of two differently functionalized linkers containing phosphino- or amino-terminated groups. The linkers have been anchored to the magnetite surface by means of catechol, mercapto or carboxylate groups. The nature of the resulting Pd nanoparticles deposited has been examined by HAADF-STEM images and XPS electron spectroscopy. The efficiency of the two kinds of catalysts has been checked and compared for the Suzuki–Miyaura reaction, 4-nitrophenol reduction and styrene hydrogenation. The results evidence that the nanoparticles equipped with the phosphino fragment are better catalysts than those functionalized with the amino group and, in some processes, they are among the most active catalysts reported in the literature., Postprint (published version)

The molecule 4-(diphenylphosphino) benzoic acid (dpa) anchored on the surface of magnetite nanoparticles permits the easy capture of palladium ions that are deposited on the surface of the magnetite nanoparticles after reduction with NaBH4. Unexpectedly, a significant fraction of dpa is removed in this process. Samples of Fe(3)O(4)dpa@Pdx containing different Pd loadings (x = 0.1, 0.3, 0.5 and 1.0 wt%) were prepared, and their catalytic efficiency for the Suzuki C-C coupling reaction was studied. The best catalyst was Fe(3)O(4)dpa@Pd-0.5, which gave the highest TOF published to date for the reaction of bromobenzene with phenylboronic acid in a mixture of ethanol/water (1/1). Interestingly, the same reaction carried out in water also produced excellent yields of the resulting C-C coupling product. The behaviour of other bromide aryl molecules was also investigated. The best catalytic results for the aqueous phase reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) were obtained using Fe(3)O(4)dpa@Pd-0.1. The presence of Pd SACs (single atom catalysts) seems to be responsible for this performance. In contrast, the same Fe(3)O(4)dpa@Pd-0.1 catalyst is absolutely inactive for the hydrogenation of styrene in ethanol., Peer Reviewed, Postprint (published version)

This journal is © The Royal Society of Chemistry. The molecule 4-mercaptophenyldiphenylphosphine (Sdp) has been synthesized for use as a linker to immobilize Pd nanoparticles onto the surface of magnetite nanoparticles. The high loading shown by Sdp was attributed to the presence of one only anchoring (S) atom. The treatment of the resulting nanoparticles after Pd deposition with an aqueous solution of hydrogen peroxide permitted the removal of a large fraction (70%) of Sdp. Aberration corrected high-resolution scanning transmission electron microscopy images of the final nanocomposite showed that the Pd dispersion is constituted by very small nanoparticles along with a few isolated metal atoms. The partial loss of linker protection makes the Pd nanoparticles one of the most efficient catalysts for the Suzuki-Miyaura C-C cross coupling reaction and for hydrogenation of 4-nitrophenol and styrene., Postprint (published version)

A macroporous silicon micromonolith containing ca. 40,000 regular channels of 3.3 ¿m in diameter per square millimeter has been successfully functionalized with an Au/TiO2 catalyst for CO preferential oxidation (CO-PrOx) in the presence of hydrogen. The functionalization of the silicon microchannels has been accomplished by growing a SiO2 layer on the channel walls, followed by exchange with a titanium alkoxyde precursor and decomposition into TiO2 and, finally, by anchoring carbosilanethiol dendron protected pre-formed Au nanoparticles. Catalytically active centers at the Au-TiO2 interface have been obtained by thermal activation. With this method, an excellent homogeneity and adherence of the catalytic layer over the microchannels of the macroporous silicon micromonolith has been obtained, which has been tested for CO-PrOx at 363-433 K and ¿=2 under H2/CO=0-20 (molar). The macroporous silicon micromonolith converts ca. 3 NmL of CO per minute and mL of microreactor at 433 K under H2/CO=20, suggesting that it could be particularly effective for hydrogen purification in lowtemperature microfuel cells for portable applications., Postprint (published version)

A facile strategy has been explored for loading noble metals onto the surface of ferrite nanoparticles with the assistance of phosphine-functionalized linkers. Palladium loading is shown to occur with participation of both the phosphine function and the surface hydroxyl groups. Hybrid nanoparticles containing simultaneously Pd and Au (or Rh) are obtained by successive loading of metals. Similarly, ferrite nanoparticles decorated with Pd, Au, and Rh have also been formed by using the same strategy. The catalytic properties of the new nanoparticles are evidenced in processes such as reduction of 4-nitrophenol or hydrogenation of styrene. Besides, the sequential process involving a cross-coupling reaction followed by reduction of 1-nitrobiphenyl has been successfully achieved by employing Pd/Au decorated nanoferrite particles. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., Postprint (published version)