Audrey Moores

The plasmon band in noble metal nanoparticles: an introduction to theory and applications

Noble metal nanoparticles chemistry is a domain in rapid expansion, as those objects lead to interesting applications in the fields of catalysis, biosensing, electronics and optics. Because of their structure, intermediate between that of molecules and of bulk material, they enable to bridge the gap between molecular chemistry and surface science. In particular, their optical properties, known since antiquity, have already shown a part of their potential and further major discoveries can reasonably be expected. Their most insightful optical properties rely on a strong absorption in the visible spectrum, called the plasmon band, that colloidal solutions of gold, silver or copper feature. Herein we wish to present a comprehensible overview of the fundamentals of the theories explaining the phenomenon dedicated to chemists seeking an introduction to those features. We will also give a brief review of the recently published body of relevant literature with reference to the aforementioned theory.

Fe3O4 nanoparticles: a robust and magnetically recoverable catalyst for three-component coupling of aldehyde, alkyne and amine

A robust, safe and magnetically recoverable Fe3O4 nanoparticle catalyzed three-component coupling of aldehyde, alkyne, and amine (A3-coupling) was developed. A diverse range of propargylamines were obtained in moderate to high yield under mild conditions in air. The separation and reuse of the magnetic Fe3O4 nanoparticles were very simple, effective and economical.

Cellulose nanocrystallites as an efficient support for nanoparticles of palladium: application for catalytic hydrogenation and Heck coupling under mild conditions

We report herein the synthesis of a new hybrid material, PdNPs@CNCs consisting of monodisperse Pd nanoparticles (PdNPs) evenly deposited onto colloidal cellulose nanocrystallites (CNCs). This material proved an active catalyst for the hydrogenation reaction of phenol to cyclohexanone in water as a solvent, at room temperature, under 4 bar of dihydrogen. Moreover, the catalyst perfomed well in the Heck coupling of styrene and iodobenzene in a hydro-organic mixture. CNCs constitute a highly crystalline, ordered and yet accessible green material easily obtained from wood pulp. This work demonstrates the possibility of using colloidal CNCs as an efficient support for catalysis.

Magnetic copper–iron nanoparticles as simple heterogeneous catalysts for the azide–alkyne click reaction in water

The development of a novel bimetallic copper–iron nanoparticle synthesis provides a recoverable heterogeneous catalyst for the azide–alkyne “click” reaction in water. The nanoparticles catalyze the production of a diverse range of triazoles, while separation and reuse proved to be easy.

Bare magnetic nanoparticles: sustainable synthesis and applications in catalytic organic transformations

Magnetic nanoparticles have become increasingly attractive in the field of catalysis over the last decade as they combine interesting reactivity with an easy, economical and environmentally benign mode of recovery. Early strategies focused on the use of such nanoparticles as a vehicle for supporting other catalytic nanomaterials or molecules to facilitate recovery. More recently, research has shown that bare magnetic nanoparticles may serve the dual role of a catalyst and a magnetically recoverable entity. At the same time, emerging sustainability concepts emphasize the utility of earth abundant and less toxic resources, especially iron. Herein, we review the recent progress made in the assembly of such systems and their direct application in catalysis. Examples of such bare nanoparticles include iron oxide (Fe2O3 and Fe3O4), metal ferrites (MFe2O4, M = Cu, Co and Ni), Fe(0), Co(0), Ni(0), and multi-component nanoparticles. Features such as reactivity, recoverability and leaching are discussed in a critical fashion.

Review: nanocelluloses as versatile supports for metal nanoparticles and their applications in catalysis

Nanocelluloses, derived from the biopolymer cellulose, are a class of sustainable functional nanomaterials featuring exciting properties. They have been extensively researched as key components in the design of super capacitors, pH-responsive reversible flocculants, aerogels, sensors, pharmaceuticals, chiral materials and catalysts. This review will focus on the applications of nanocelluloses in catalysis. The first part illustrates their use as support, stabilizer and/or reducing agent in the synthesis of various metal nanoparticle. Subsequently, the applications of these metal-hybrid nanocellulose composites in catalysis are reviewed. Finally, catalysis involving nanocelluloses, without the use of metal nanoparticles, is reviewed.

Cellulose Nanocrystals as Chiral Inducers: Enantioselective Catalysis and Transmission Electron Microscopy 3D Characterization

Cellulose nanocrystals (CNCs), derived from cellulose, provide us with an opportunity to devise more sustainable solutions to current technological challenges. Enantioselective catalysis, especially heterogeneous, is the preferred method for the synthesis of pure chiral molecules in the fine chemical industries. Cellulose has been long sought as a chiral inducer in enantioselective catalysis. We report herein an unprecedentedly high enantiomeric excess (ee) for Pd patches deposited onto CNCs used as catalysts for the hydrogenation of prochiral ketones in water at room temperature and 4 bar H2. Our system, where CNCs acted as support and sole chiral source, achieved an ee of 65% with 100% conversions. Cryo-electron microscopy, high-resolution transmission electron microscopy, and tomography were used for the first time to study the 3D structure of a metal functionalized CNC hybrid. It established the presence of sub-nanometer-thick Pd patches at the surface of CNCs and provided insight into the chiral induction mechanism.

Iron-iron oxide core–shell nanoparticles are active and magnetically recyclable olefin and alkyne hydrogenation catalysts in protic and aqueous media

We report for the first time the use of iron-iron oxide core-shell nanoparticles for the hydrogenation of olefins and alkynes under mild conditions in ethanol and in an aqueous medium. This catalyst proves robust towards the presence of oxidants, such as oxygen and water, is magnetically recoverable and shows selectivity towards the less activated double bonds.

Catalysed low temperature H2 release from nitrogen heterocycles

In an experimental and computational study, nitrogen- and oxygen-containing heterocycles were compared with carbocycles as liquid substrates for hydrogen release with heterogeneous catalysts. Heteroatom substitution, particularly by nitrogen, favours low temperature H2 release; indoline was fully dehydrogenated in less than 30 min with Pd/C at 110 °C.

Highly efficient iron(0) nanoparticle-catalyzed hydrogenation in water in flow

Highly efficient catalytic hydrogenations are achieved by using amphiphilic polymer-stabilized Fe(0) nanoparticle (Fe NP) catalysts in ethanol or water in a flow reactor. Alkenes, alkynes, aromatic imines and aldehydes were hydrogenated nearly quantitatively in most cases. Aliphatic amines and aldehydes, ketone, ester, arene, nitro, and aryl halide functionalities are not affected, which provides an interesting chemoselectivity. The Fe NPs used in this system are stabilized and protected by an amphiphilic polymer resin, providing a unique system that combines long-term stability and high activity. The NPs were characterized by TEM of microtomed resin, which established that iron remains in the zero-valent form despite exposure to water and oxygen. The amphiphilic resin-supported Fe(0) nanoparticles in water and in flow provide a novel, robust, cheap and environmentally benign catalyst system for chemoselective hydrogenations.