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•Overview of bottom-up synthetic strategies of Prussian blue analogs and related cyanide-bridged coordination polymers.•Synthetic template-free approaches to core shells, ...heterostructures, hollow particles and other original nanostructures.•Application fields of nanoparticles and heterostructures based on Prussian blue analogs.
This review is dedicated to the synthesis, properties and potential applications of Prussian blue analogs and other cyanide-bridged coordination polymers that have been recently investigated at the nanoscale. A wide range of nanostructures including core-shells, hollow particles and other architectures were designed with the objective of creating new and original functionalities targeting a wide range of fields such as information storage, waste water treatment, catalysis, gas storage and biomedical applications. Cyanide-bridged coordination nanoparticles have also chemical functionality and serve as precursors for the controlled design of other nanomaterials (alloys, oxides…).
This contribution reports on the state of the art of the elaboration and the application of nanoparticles (NPs) and nanohybrid/nanocomposite materials based on spin-crossover (SCO) complexes. The ...first part of this review concerns the syntheses and the characterizations of the physical properties of SCO NPs. All of the methods including homogeneous and heterogeneous media syntheses developed for the elaboration of such NPs and the associated methods used for their morphological characterization are presented. A particular attention is paid on the effects of the size reduction and the influence of the environment on the SCO properties and to specific and recent remarkable advanced physical measurements realized on a batch of NPs or on an isolated object. The second part presents the elaboration of various nanocomposite or nanohybrid materials for which SCO NPs have been associated with magnetic entities, noble metals, different fluorescent dyes, and different active polymers with the objectives to go toward specific applications based on synergistic effects between the two components.
Cette contribution rend compte de l'état de l'art sur l'élaboration et la mise en application de nanoparticules et de matériaux nanohybrides/nanocomposites à base de complexes à transition de spin. La première partie de cette revue concerne la synthèse et la caractérisation des propriétés physiques de nanoparticules à transition de spin. Toutes les méthodes, y compris les synthèses en milieux homogène et hétérogène développées pour l'élaboration de telles nanoparticules et les méthodes utilisées pour leurs caractérisations morphologiques, sont présentées. Une attention particulière est portée aux effets de la réduction de taille et de l'influence de l'environnement sur les propriétés de transition de spin et sur des mesures physiques récentes remarquables réalisées sur un lot de nanoparticules ou sur un objet unique. La deuxième partie présente l'élaboration de divers matériaux nanocomposites ou nanohybrides au sein desquels des nanoparticules à transition de spin ont été associées à des entités magnétiques, des métaux nobles, divers fluorophores et différents polymères actifs dans le but d'aller vers des applications spécifiques basées sur des effets synergétiques entre les deux composants.
► Proton exchange membrane water electrolysis has a number of advantages over the traditional water–alkaline. ► The main drawback comes from the fact that this is an expensive technology. ► The ...replacement of platinum-family catalysts and expensive solid polymer electrolyte remain challenging issues. ► Some recent advances have been made at the cathodes of PEM cells using non-precious metal electrocatalysts and are presented.
At the last COST (European Cooperation in Science and Technology) EU–US meeting held in May 2011 in Prague, one of the main questions raised was how can molecular chemistry with an emphasis on the use of non noble metal complexes contribute to water photolysis for the production of solar fuels. In general molecular chemistry can help not only in the understanding of the sequential steps of water oxidation with the design of sophisticated metal complexes but also in the catalytic reaction involving the reduction of protons to hydrogen to make a fuel. The water oxidation reaction stands as the grand challenge for molecular chemists as water has been recognised as the source of protons and electrons to be used in the synthesis of solar fuels. Based on recent advances, it seems that the development of molecular metal complexes with abundant and cheap metals holds the promises for their putative integration in functional devices for the hydrogen production reaction. However, for the majority of these metal complexes, the electrocatalytic activity towards the reduction of protons has been reported in organic solvents and only rarely in aqueous medium. Furthermore, these molecular catalysts also suffer from degradative processes upon catalytical activity in solution. Hence there is still much room for the design and preparation of molecular based catalysts capable to perform the H2 production in aqueous phase. In this review/article we give a brief overview on the state of the art on solid polymer exchange (SPE) membrane water electrolysers and their limitations regarding their widespread commercialisation, that is in part related to the expensive and rare noble metal catalysts used for both the hydrogen producing reaction and the water oxidation process. We focus herein on the recent advances made in preparing modified carbon electrodes with molecular based complexes and on their catalytic properties in heterogeneous medium. A challenging step in this research field is to couple the cathodic process to that of the water oxidation reaction. We report here on the implementation of fluroboryl dimethylglyoxime cobalt complexes supported on a carbonaceous material at the cathode of a proton exchange membrane (PEM) water electrolysers. electrocatalytic activity for the H2 production was observed with current densities in the range of 500mAcm−2 for a cell efficiency of 80% using iridium at the anode. The durability of these systems was tested for several days upon on and off polarisation without noticeable loss in activity. These results therefore lead us to think that it should be feasible to reduce the cost of actual PEM water electrolyser by replacing platinum at the cathode.
The collective magnetic behavior of photoswitchable 11 nm cyanide-bridged nanoparticles based of the Prussian blue analogue CsCoFe were investigated when embedded in two different matrices with ...different concentrations. The effect of the intensity of light irradiation was studied in the less concentrated sample. Magnetization studies and alternating magnetic susceptibility data are consistent with a collective magnetic behavior due to interparticle dipolar magnetic interaction for the two compounds, even though the objects have a size that place them in the superparamagnetic regime.
The local symmetry and local magnetic properties of 6 nm‐sized, bimetallic, cyanide‐bridged CsNiCr(CN)6 coordination nanoparticles 1 and 8 nm‐sized, trimetallic, CsNiCr(CN)6@CsCoCr(CN)6 core–shell ...nanoparticles 2 were studied by X‐ray absorption spectroscopy (XAS) and X‐ray magnetic circular dichroism (XMCD). The measurements were performed at the NiII, CoII, and CrIII L2,3 edges. This study revealed the presence of distorted NiII sites located on the particle surface of 1 that account for the uniaxial magnetic anisotropy observed by SQUID measurements. For the core–shell particles, a combination of the exchange anisotropy between the core and the shell and the pronounced anisotropy of the CoII ions is the origin of the large increase in coercive field from 120 to 890 Oe on going from 1 to 2. In addition, XMCD allows the relative orientation of the magnetic moments throughout the core–shell particles to be determined. While for the bimetallic particles of 1, alignment of the magnetic moments of CrIII ions with those of NiII ions leads to uniform magnetization, in the core–shell particles 2 the magnetic moments of the isotropic CrIII follow those of CoII ions in the shell and those of NiII ions in the core, and this leads to nonuniform magnetization in the whole nanoobject, mainly due to the large difference in local anisotropy between the CoII ions belonging to the surface and the NiII ions in the core.
Two different NiII environments in 6 nm‐sized, bimetallic, CsNiCr(CN)6 nanoparticles and 8 nm‐sized, trimetallic, CsNiCr(CN)6@CsCoCr(CN)6 core–shell nanoparticles were revealed by X‐ray magnetic circular dichroism (XMCD). The experimental XMCD spectrum could be reproduced by ligand‐field multiplet calculations assuming NiII(NC)6 and NiII(NC)6−x(OH2)x coordination spheres with Oh and D4h symmetry, respectively (see figure).
Negatively charged nanocrystals of the magnetic coordination network CsNiCr(CN)(6) were prepared in water through a seed-mediated growth with a few atomic layers accuracy and final sizes tailored ...from 6 to 30 nm. A lower limit of the magnetic single-domain critical size was determined to be around 15 nm possessing a blocking temperature above 20 K.
A number of tools exist to guide the monitoring and evaluation of science, technology, engineering and mathematics (STEM) education and outreach programmes. Fewer tools exist for evaluating astronomy ...outreach programmes. In this paper we try to overcome this limitation by presenting a monitoring and evaluation framework developed for the International Astronomical Union's Office of Astronomy for Development (OAD). The mandate of the OAD is to stimulate sustainable development at an international level and to expand astronomy education and outreach globally. The broad assumptions of this programme are that astronomy has the potential to contribute to human development by means of the transferable nature of its science discoveries, as well as its potential to activate feelings of wonderment, inspiration and awareness of the universe. As a result, the programme potentially embodies a far broader mix of outcomes than conventionally considered in STEM evaluation approaches. Towards this aim, we operationalise our monitoring and evaluation approach by first outlining programme theories for three key OAD programmes: a programme for universities and research, another one for schools, and one for public outreach. We then identify outcomes, indicators and measures for each one of these programmes. We conclude with suggestions for evaluating the global impact of astronomy for development.
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