1. Could you explain the significance of your article to the non-specialist? 

We reported on the organometallic synthesis and the oxidation behaviour on very small sized brass particles, i.e. nanoparticles of alloyed copper (Cu) and zinc (Zn), for the first time. Below a critical amount of the zinc component in the alloy particle preferential oxidation of zinc occurred, leading to zinc oxide (ZnO) species as surface decoration of a more or less pure copper core particle. These special composite particles denoted as "ZnO/Cu" are likely to be interesting novel models for studying the important synergetic interfacial effect between Cu and ZnO in methanol synthesis.

 

2. What has motivated you to conduct this work? 

One of the subjects that our group is working on is the development of colloidal models of heterogeneous catalysts used for the industrial large-scale syntheses of important chemicals. The methanol synthesis employing the ternary Cu/ZnO/Al2O3 solid-state catalyst represents such an example. Classical catalyst preparation techniques are however reaching their limitations. Alternative concepts of catalyst development and engineering are thus desired. Most recently, we have reported on novel ZnO decorated Cu nanoparticles being very active as a colloidal catalyst in methanol synthesis (Chem. Commun., 2006, DOI: 10.1039/b602261h). This finding prompted us to systematically study the chemistry of nano-sized Cu/Zn (brass) particles and in particular characterising their oxidation behaviour. Our article is a first step towards a novel concept of catalyst preparation which is based on the controlled oxidation of alloy nanoparticles.

 

3. Where do you see this work developing in the future? 

Research on nanoparticles in general represents a highly active and very promising field. Organometallic colloid chemistry as we describe it can contribute to fundamental insights and also offer alternative concepts for preparation. Many established heterogeneous catalysts are composed of so-called active metals being in close interfacial contact with other inorganic components typically oxides as "supports" and/or "promoters" to achieve the catalyst performance. 

Catalyst development includes optimising both, the accessible surface area of the catalytically active metal component together with the interfacial interactions with support and promoters. Our concept is likely to be extendable for example to other catalytically active metals such as ruthenium (Ru) or nickel (Ni) and magnesiumoxide (MgO) and silicondioxide (SiO2) as other typical catalyst components.

 

4. Are there any particular challenges facing future research in this area? 

We feel particularly challenged by the development of the nano chemistry of classical intermetallic phases such as aluminides and silicides which has not been in the focus of nano particle research, so far. This is partly due to the lack of suitable precursors to release aluminium atoms in solution. Recently we have reported on the soft chemical synthesis of Cu/Al phases, i.e. CuAl2 (Chem. Mater., 2006, 18, 1634) by using a special metastable aluminium precursor. A particular challenge is to take advantage of the selective oxidation of the aluminium component in the metal aluminide particles to achieve size-selected well defined core-shell particles with a dense alumina (Al2O3) shell over a core of the other metal. Such alumina protected metal nano particles may have significant applications in the field of magnetic data recording and storage.