From Single Molecules to Nanoscopically Structured Functional Materials
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From Single Molecules to Nanoscopically Structured Functional Materials Wolfgang Tremel1, Helen Annal Therese1, Muhammad Nawaz Tahir1, Nicole Zink1, Marc Eberhardt1, Patrick Theato1, Hans Christian Schröder2, and Werner E. G. Müller3 1 Chemistry, Universität Mainz, Duesbergweg 10-14, Mainz, D-55099, Germany 2 Physiological Chemistry, Universität Mainz, Duesbergweg 6, Mainz, Germany 3 Physiological Chemistry, Universität Mainz, Duesbergweg 6, Mainz, D-55099, Germany
ABSTRACT The synthesis of MS2 (M = Mo, W) onion-like nanoparticles by means of a high temperature MOCVD process starting from W(CO)6 and elemental sulfur is reported. The reaction can also be carried out in two steps where the intermediate amorphous WS2 nanoparticles formed through the high temperature reaction of tungsten and sulfur in the initial phase of the reaction are isolated and converted in a separate annealing step to onion-type WS2 nanoparticles. Based on a study of the temperature dependence of the reaction a set of conditions could be derived where onion-like structures were formed in a one-step reaction. Onion-like structures obtained in the single-step process were filled, whereas the particles obtained by the two-step procedure were systematically hollow. A model could be devised to rationalize the different outcome of the reactions. The MOCVD approach therefore allows a selective synthesis of open and filled fullerene-like chalcogenide nanoparticles. Furthermore, we demonstrate the novel surface functionalization of WS2 nanotubes with polymeric ligands by complexation with a combination of Ni2+ via an scorpionate-type nitrilotriacetic acid (NTA) and immobilization of TiO2 nanoparticles onto the surface of nanotubes. Synthesis of such a functional polymeric ligand was achieved via a reactive polymer precursor route. . INTRODUCTION After the discovery of carbon fullerenes and nanotubes about a decade ago [1] it became clear that polyhedral structures are the thermodynamically stable form of carbon under the condition that the number of carbon atoms is limited. When we analyze the physicochemical reasons for the formation of nanostructures we recognize that curved nanostructures are in no way restricted to carbon. The large energy of the “dangling bonds” at the periphery of these nanoparticles is responsible for the pronounced formation tendency of carbon fullerenes and nanotubes. However, the same should apply for inorganic compounds such as MQ2 (M = Ti, V, Mo. W. Re; Q = S, Se)[2] as well. During the past years this hypothesis was substantiated by numerous examples and it can be safely assumed that the phase diagrams of elements which form layered compounds contain fullerene- and nanotube-like structures.
Our approach to the synthesis of these nested fullerene-type particles is based on a gas phase MOCVD reaction. In the first synthetic step chalcogenide nanoparticles are formed in a gas phase reaction between Mo, produced by thermal decomposition of Mo(CO)6, and sulfur or selenium, respectively [3]. One might speculate, t
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