F. Herbst

FTIR and XPS Study of Pt Nanoparticle Functionalization and Interaction with Alumina

Platinum nanoparticles with a mean size of 1.7 nm were synthesized by reduction in sodium acetate solution in 1,2-ethanediol. The particles were then functionalized with dodecylamine, dodecanethiol, and omega-mercapto-undecanoic acid (MUDA). Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed important variations of the particle surface state with functionalization whereas their structure differs only slightly. Platinum-to-sulfur charge transfer inferred from XPS of thiol-coated particles enabled the identification of the formation of Pt (delta+)-S (delta-) bonds. The native carbon monoxide (CO) at the surface of the particles was a very efficient probe for following the functionalization of the particles by FTIR. The red shift of nu(CO) accounts for the nature of the ligands at the surface of the particles and also for their degree of functionalization. Immobilization on alumina substrates of particles functionalized with MUDA was realized by immersion in colloidal solutions. Free molecules, isolated particles, and aggregates of particles interconnected by hydrogen bonds at the surface of alumina were evidenced by FTIR. With successive washings, the energy variation of the CO stretch of carbon monoxide and of carboxylic acid groups and the relative intensity nu(CH2)/nu(CO) showed that the free molecules are eliminated first, followed by aggregates and less-functionalized particles. Particles presenting a high degree of functionalization by MUDA remain and interact strongly with alumina.

Hairy carbon nanotube@nano-Pd heterostructures: design, characterization, and application in Suzuki C-C coupling reaction.

Poly(glycidyl methacrylate), PGMA, was prepared via ATRP in bulk solution, and its epoxy groups were further acid-hydrolyzed in order to obtain a polymer with glycerol moieties (noted POH). The POH chain end C-Br bonds were subjected to a nucleophilic attack by NaN(3), resulting in azide-terminated POH (POH-N(3)). The CNTs were modified by in-situ-generated alkynylated diazonium cations from the para-alkynylated aniline of the formulas H(2)N-C(6)H(4)-C≡C-H, yielding CNT-C(6)H(4)-C≡C-H nanotubes. The azide-functionalized polymer POH-N(3) was clicked to the alkynyl-modified CNTs giving CNT@POH hybrids, which were further subjected to an oxidation resulting in carboxylated polymer-modified CNTs (noted CNT@PCOOH). The as-designed hairy CNTs served as efficient platforms for the in-situ synthesis and massive loading of 3 nm sized palladium nanoparticles (NPs). The CNT@PCOOH@Pd heterostructures prepared so far exhibited an efficient catalytic effect in the C-C Suzuki coupling reaction and were regenerated up to four times without any significant loss of catalytic activity.

Preparation of Water-Soluble Magnetic Nanocrystals Using Aryl Diazonium Salt Chemistry

A novel and facile methodology for the in situ surface functionalization of Fe(3)O(4) nanoparticles is proposed, based on the use of aryl diazonium salts chemistry. The grafting reaction involves the formation of diazoates in a basic medium. These species are unstable and dediazonize along a homolytic pathway to give aryl radicals which further react with the Fe(3)O(4) NPs during their formation and stop their growth. Advantages of the present approach rely not only on the simplicity, rapidity, and efficiency of the procedure but also on the formation of strong Fe(3)O(4)-aryl surface bonds, highly suitable for further applications.

Size-dependent magnetic properties of CoFe2O4 nanoparticles prepared in polyol.

Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe Mössbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles.

Photosynthetic Microorganism-Mediated Synthesis of Akaganeite (β-FeOOH) Nanorods

Common Anabaena and Calothrix cyanobacteria and Klebsormidium green algae are shown to form intracellularly akaganeite beta-FeOOH nanorods of well-controlled size and unusual morphology at room temperature. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy X-ray energy dispersive spectrometry (SEM-EDS) analyses are used to investigate particle structure, size, and morphology. A mechanism involving iron-siderophore complex formation is proposed and compared with iron biomineralization in magnetotactic bacteria.

Synthesis of highly soluble polymer-coated magnetic nanoparticles using a combination of diazonium salt chemistry and the iniferter method

Polymer-coated magnetic nanoparticles were synthesized using an original and simple chemical strategy combining aryl diazonium salt chemistry and the iniferter method. This approach provides individually dispersed, highly soluble and pH-sensitive poly(methacrylic acid)-coated magnetic iron oxide nanoparticles.

Spray deposition of nanocrystalline Ni1−xZnxFe2O4 (x⩽0.6) films from polyol-mediated sol: Microstructure and magnetic properties

Static-spray deposition of a polyol-based sol, containing nanoparticles of NiZn ferrite, on a moderately heated glass support, has been used to generate crystalline thin films. The films exhibit superparamagnetic behavior with a blocking temperature, which decreases as the zinc content increases, due to their nanocrystalline character. At low temperature, the films are ferrimagnetic; the saturation magnetization and the coercivity depend markedly on both the zinc content and the microstructure.

Polyol synthesis of non-stoichiometric Mn–Zn ferrite nanocrystals: structural /microstructural characterization and catalytic application

The structure of polyol-made Mn–Zn ferrite powders was investigated by X-ray diffraction, X-ray photoelectron spectrometry and X-ray absorption spectroscopy. It was found to be a defect-spinel structure in relation with non-stoichiometry introduced by the mixed oxidation-state of Mn and Fe cations. The ionic defects were identified as cation vacancies mainly located in the octahedral sites. The microstructure of these ferrites was studied by X-ray-diffraction and transmission electron microscopy. They appear to be constituted by quasi-isotropic monodisperse nano-aggregates which consist of pseudo-single crystals. Considering their reduced size, high crystalline quality, and cation mixed valence state related to their non-stoichiometry, the produced particles appear to be particularly valuable for redox-based solid–gas catalytic reactions. They exhibit an interesting activity toward catalytic combustion of dimethyl ether.

Size tuned polyol-made Zn0.9M0.1Fe2O4 (M = Mn, Co, Ni) ferrite nanoparticles as potential heating agents for magnetic hyperthermia: from synthesis control to toxicity survey

Zn-rich substituted Zn0.9M0.1Fe2O4 (M?=?Mn, Co, Ni) ferrite nanoparticles (NPs) of about 5 and 10 nm were produced by the so-called polyol method. They were engineered for hyperthermia therapy based on their magnetic and morphological properties. Indeed, because of their comparatively low Curie temperature and reasonable magnetization, these probes may turn into useful self-regulated heating agents under suitable conditions. For such a purpose, the structure, the microstructure, the magnetic and magnetocalorimetric properties of the produced NPs as well as their in vitro cytotoxicity were investigated. Our results demonstrate that the magnetic properties of these magnetically diluted spinel ferrite particles can be largely modified by just changing their size. They also show that the about 10 nm sized manganese-based ones exhibit the highest heating power under a 700 kHz ac magnetic field and the lowest cytotoxicity on Immortalized human umbilical vascular endothelial cells (HUVEC).