NixPt1−x is the missing link in the series of magnetic alloy particles. We report here on the first high‐quality synthesis of this nanomaterial. Although the chemistry of the Fe, Co, and Ni compounds is usually similar, distinctive differences are found in the nucleation, growth, and shape control of the respective nanoparticles, and first magnetic measurements are presented. The image shows star‐shaped agglomerates of nanoparticles.

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Colloidally prepared metal nanoparticles are gaining attention for catalytic applications because of the advanced possibilities to tailor particle size and shape, which are often important factors governing activity and selectivity. In the case of bimetallic catalysts, composition is usually difficult to control by traditional techniques, but by colloidal chemistry the relative portions of the metals in the nanoparticles can be exactly predefined. This approach not only offers the advantage of controlling structure and composition but also allows very high particle loadings. Colloidal nanoparticles with well-defined size and shape have a strong tendency to self-organize into well-ordered and close-packed 2D arrangements.[1, 2] Thus, it can be expected that depositing colloidal nanoparticles on powder supports or on monolithic structures will yield catalysts with high particle loadings, which would be of interest for various applications in heterogeneous catalysis.

Although monolithic catalysts offer distinct advantages such as low pressure drops and easy catalyst separation compared to tube bundle reactors filled with pellets and are for instance widely used for automobile exhaust treatment, the coating of the monolithic structures with the catalytically active phase is often complex and recipes need to be established empirically. In contrast to traditional methods, such as dip-coating or impregnation of the monolith, where the active nanoparticles are formed during the preparation on an oxidic washcoat usually used and deposited simultaneously or in a previous step, we demonstrate in this study that alternatively preformed colloidally synthesized nanoparticles can be employed to obtain homogeneous coatings with or without a washcoat. In this way, one can take advantage of the far-reaching possibilities of colloidal methods to control the structure and size of the nanoparticles and also to tune and optimize their binding to the monolithic surface. For cases where beneficial metal-support interactions between the nanoparticles and a washcoat improve the catalytic properties we demonstrate that colloidally prepared nanoparticles can be directly mixed with a washcoat slurry and successfully deposited on monolithic supports. Turnover frequencies comparable to the corresponding powder catalysts could be reached. In a second approach, we present here a facile method to directly coat three different monolithic supports (cordierite honeycomb, Al 2 O 3 foam and Nickel fleece) with preformed Pt nanoparticles in the presence and absence of organic ligands. In order to realize high metal loadings, the beneficial influence of a ligand ''double-layer'' (coating of nanoparticles and the support by organic ligands) enhancing the adhesion between the Pt nanoparticles and the underlying monolithic support will be discussed. In the case of the metallic Ni substrate, this approach furthermore allows to circumvent alloy formation and nanoparticle diffusion into the metallic substrate. This can greatly increase long-term stability of systems coated directly onto metallic substrates without an additional oxidic washcoat.