Investigations on self-organization and nucleation of meta-stable bismuth oxide polymorphs

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The experiments carried out so far within SPP 1415 are based on a combined experimental and theoretical approach and gave a first insight into the nucleation, stability and mechanism of formation for bismuth oxido clusters. The bismuth oxido clusters serve as starting materials for the synthesis of crystalline motifs of metastable bismuth oxides. The studies in terms of formation of bismuth oxide polymorphs and the underlying mechanisms will be extended in the forthcoming period. The use of additives, which are capable of cluster stabilization, and the variation of reaction conditions will give access to parameters that control the growth of bismuth oxido clusters and thus the formation of bismuth oxide polymorphs. Ion mobility mass spectrometry and ESI mass spectrometry will provide in situ information about the process of nucleation in solution and about the influence of additives. In addition DOSY-NMR, light scattering experiments and especially in situ synchrotron scattering and PXRD experiments will be carried out. The first steps of crystallization from solution will be identified and the growth mechanisms will be studied. The experiments regarding cluster growth and the process of nucleation will be complementary studied by molecular dynamics simulations in order to get deeper insight into the fundamental processes on a molecular scale. The formation of bismuth oxido clusters of various size as well as condensation processes leading finally to bismuth oxide will be modeled. Flash lamp annealing and plasma processing of bismuth oxido clusters under non-equilibrium conditions might offer access to novel metastable bismuth oxides. Additionally, the high reactivity of stabilized β-Bi2O3 nanoparticles will be used to prepare metastable homo- and heterometallic bismuth oxides, e.g. by mechanochemical synthesis.