9 research outputs found
Multicore Iron Oxide Mesocrystals Stabilized by a Poly(phenylenepyridyl) Dendron and Dendrimer: Role of the Dendron/Dendrimer Self-Assembly
We report the formation of multicore iron oxide mesocrystals using the thermal decomposition of iron acetyl acetonate in the presence of the multifunctional and rigid poly(phenylenepyridyl) dendron and dendrimer. We thoroughly analyze the influence of capping molecules of two different architectures and demonstrate for the first time that dendron/dendrimer self-assembly leads to multicore morphologies. Single-crystalline ordering in multicore NPs leads to cooperative magnetic behavior: mesocrystals exhibit ambient blocking temperatures, allowing subtle control over magnetic properties using a minor temperature change
Cap. 12 L'imposta sulle società
La giustificazione dell'imposta sulle società. Un primo aspetto da chiarire con riguardo dell'imposta sulle società ruota attorno all'ampo dibattito sui motivi che ne giustificano l'introduzione. Perchè esiste l'imposta sulle società
Functionalization of Monodisperse Iron Oxide NPs and Their Properties as Magnetically Recoverable Catalysts
Here we report the functionalization of monodisperse
iron oxide
nanoparticles (NPs) with commercially available functional acids containing
multiple double bonds such as linolenic (LLA) and linoleic (LEA) acids
or pyridine moieties such as 6-methylpyridine-2-carboxylic acid, isonicotinic
acid, 3-hydroxypicolinic acid, and 6-(1-piperidinyl)pyridine-3-carboxlic
acid (PPCA). Both double bonds and pyridine groups can be reacted
with noble metal compounds to form catalytically active species in
the exterior of magnetic NPs, thus making them promising magnetically
recoverable catalysts. We determined that both LLA and LEA stabilize
magnetic iron oxide NPs, allowing the formation of π-complexes
with bis(acetonitrile)dichloropalladium(II) in the NP shells. In both
cases, this leads to the formation of NP aggregates because of interparticle
complexation. In the case of pyridine-containing ligands, only PPCA
with two N-containing rings is able to provide NP stabilization and
functionalization whereas other pyridine-containing acids did now
allow sufficient steric stabilization. The interaction of PPCA-based
particles with Pd acetate also leads to aggregation because of interparticle
interactions, but the aggregates that are formed are much smaller.
Nevertheless, the catalytic properties in the selective hydrogenation
of dimethylethynylcarbinol (DMEC) to dimethylvinylcarbinol were the
best for the catalyst based on LLA, demonstrating that the NP aggregates
in all cases are penetrable for DMEC. Easy magnetic separation of
this catalyst from the reaction solution makes it promising as a magnetically
recoverable catalyst
Multicore Iron Oxide Mesocrystals Stabilized by a Poly(phenylenepyridyl) Dendron and Dendrimer: Role of the Dendron/Dendrimer Self-Assembly
We report the formation of multicore
iron oxide mesocrystals using
the thermal decomposition of iron acetyl acetonate in the presence
of the multifunctional and rigid poly(phenylenepyridyl) dendron and
dendrimer. We thoroughly analyze the influence of capping molecules
of two different architectures and demonstrate for the first time
that dendron/dendrimer self-assembly leads to multicore morphologies.
Single-crystalline ordering in multicore NPs leads to cooperative
magnetic behavior: mesocrystals exhibit ambient blocking temperatures,
allowing subtle control over magnetic properties using a minor temperature
change
Multicore Iron Oxide Mesocrystals Stabilized by a Poly(phenylenepyridyl) Dendron and Dendrimer: Role of the Dendron/Dendrimer Self-Assembly
We report the formation of multicore
iron oxide mesocrystals using
the thermal decomposition of iron acetyl acetonate in the presence
of the multifunctional and rigid poly(phenylenepyridyl) dendron and
dendrimer. We thoroughly analyze the influence of capping molecules
of two different architectures and demonstrate for the first time
that dendron/dendrimer self-assembly leads to multicore morphologies.
Single-crystalline ordering in multicore NPs leads to cooperative
magnetic behavior: mesocrystals exhibit ambient blocking temperatures,
allowing subtle control over magnetic properties using a minor temperature
change
Zinc-Containing Magnetic Oxides Stabilized by a Polymer: One Phase or Two?
Here
we developed a new family of Zn-containing magnetic oxides
of different structures by thermal decomposition of Zn(acac)<sub>2</sub> in the reaction solution of preformed magnetite nanoparticles (NPs)
stabilized by polyphenylquinoxaline. Upon an increase of the Zn(acac)<sub>2</sub> loading from 0.15 to 0.40 mmol (vs 1 mmol of Fe(acac)<sub>3</sub>), the Zn content increases, and the Zn-containing magnetic
oxide NPs preserve a spinel structure of magnetite and an initial,
predominantly multicore NP morphology. X-ray photoelectron spectroscopy
(XPS) of these samples revealed that the surface of iron oxide NPs
is enriched with Zn, although Zn species were also found deep under
the iron oxide NP surface. For all the samples, XPS also demonstrates
the atom ratio of Fe<sup>3+</sup>/Fe<sup>2+</sup> = 2:1, perfectly
matching Fe<sub>3</sub>O<sub>4</sub>, but not ZnFe<sub>2</sub>O<sub>4</sub>, where Fe<sup>2+</sup> ions are replaced with Zn<sup>2+</sup>. The combination of XPS with other physicochemical methods allowed
us to propose that ZnO forms an ultrathin amorphous layer on the surface
of iron oxide NPs and also diffuses inside the magnetite crystals.
At higher Zn(acac)<sub>2</sub> loading, cubic ZnO nanocrystals coexist
with magnetite NPs, indicating a homogeneous nucleation of the former.
The catalytic testing in syngas conversion to methanol demonstrated
outstanding catalytic properties of Zn-containing magnetic oxides,
whose activities are dependent on the Zn loading. Repeat experiments
carried out with the best catalyst after magnetic separation showed
remarkable catalyst stability even after five consecutive catalytic
runs
Polyphenylenepyridyl Dendrons with Functional Periphery and Focal Points: Syntheses and Applications
For
the first time we report syntheses of a family of functional
polyphenylenepyridyl dendrons with different generations and structures
such as focal groups, periphery, and a combination of phenylene and
pyridyl moieties in the dendron interior using a Diels–Alder
approach and a divergent method. The dendron structure and composition
were confirmed using NMR spectroscopy, MALDI-TOF mass spectrometry,
FTIR, and elemental analysis. As a proof of concept that these dendrons
can be successfully used for the development of nanocomposites, synthesis
of iron oxide nanoparticles was carried out in the presence of thermally
stable dendrons as capping molecules followed by formation of Pd NPs
in the dendron shells. This resulted in magnetically recoverable catalysts
exhibiting exceptional performance in selective hydrogenation of dimethylethynylcarbinol
(DMEC) to dimethylvinylcarbinol (DMVC)