Revealing the Electrocatalytic Self-Assembly Route from Building Blocks into Giant Mo-Blue Clusters.

The assembly of single-core molybdate into hundreds of cores of giant molybdenum blue (Mo-blue) clusters has remained a long-standing unresolved scientific puzzle. To reveal this fascinating self-assembly behavior, we demonstrate an aqueous flowing in-operando Raman characterization system to capture the building blocks' evolution from the "black box" reaction process. We successfully visualized the sequential transformation of Na2MoO4 into Mo7O246- ({Mo7}), high nuclear Mo36O1128- ({Mo36}) cluster, and finally polymerization product of [H6K2Mo3O12(SO4)]n ({Mo3(SO4)}n) during the H2SO4 acidification. Notably, the facile conversion of {Mo3(SO4)}n back to the {Mo36} cluster by simple dilution is also discovered. Furthermore, we identified {Mo36} and {Mo3(SO4)}n as exclusive precursors responsible for driving the electrochemical self-assembly of {Mo154} and {Mo102}, respectively. The study also unravels a pivotal intermediate, the pentagonal reduced state fragment [H18MoVI4MoVO24]-, originating from {Mo36}, which catalyzes the autocatalytic self-assembly of {Mo154} with electron and proton injection during electrochemical processes. Concurrently, {Mo3(SO4)}n serves as the indispensable precursor for {Mo102} formation, generating sulfation pentagon building blocks of [H2Na2O2(H4MoVMoVI4O16SO4)4]4- that facilitate the consecutive assembly of giant {Mo102} sphere clusters. As a result, a complete elucidation of the assembly pathway of giant Mo-blue clusters derived from single-core molybdate was obtained, and H+/e- redox couple is revealed to play a critical role in catalyzing the deassembly of the precursor, leading to the formation of thermodynamically stable intermediates essential for further self-assembly of reduced state giant clusters.

Insights into the self-assembly of giant polyoxomolybdates from building blocks to supramolecular structures.

Giant polyoxomolybdates are a special class of polyoxometalate clusters which can bridge the gap between small molecule clusters and large polymeric entities. Besides, giant polyoxomolybdates also show interesting applications in catalysis, biochemistry, photovoltaic and electronic devices, and other fields. Revealing the evolution route of the reducing species into the final cluster structure and also their further hierarchical self-assembly behaviour is undoubtedly fascinating, aiming to guide the design and synthesis. Herein, we reviewed the self-assembly mechanism study of giant polyoxomolybdate clusters, and the exploration of a new structure and new synthesis methodology is also summarized. Finally, we emphasize the importance of in-operando characterization in revealing the self-assembly mechanism of giant polyoxomolybdates, and especially for the further reconstruction of intermediates into the designable synthesis of new structures.

[Bacterial community composition of the Yellow Sea Cold Water Mass studied by PCR-denaturing gradient gel electrophoresis].

Bacterial community composition and predominant bacteria were analyzed by PCR-denaturing gradient gel electrophoresis (DGGE) in the Yellow Sea Cold Water Mass (YSCWM). The results analysed by Glyko Bandscan software showed that samples from all stations in April and stations in the YSCWM area in October had almost the same number of different DNA bands (17 and 16 respectively ) with high diversity. However, samples from the stations out of YSCWM area had fewer DNA bands (about 12) with lower diversity. 24 DGGE bands reflecting varying phylotypes were excised, cloned and sequenced. Phylogenetic analysis of 24 cloned bands showed that bacterial phylotypes were made up of two phyla bacteria, Proteobacteria and Bacteroides. Among these sequences, 16 were related to gamma-Proteobacteria and delta-Proteobacteria and 5 were related to Bacteroides. It indicated that bacterial community composition, as well as the predominant bacterial groups, from all sampling stations in April (the temperature of seawater was around 7-12 degrees C) and the inter of YSCWM in October (< or = 10 degrees C) was the same, different from the exterior of YSCWM (> or = 19 degrees C). By comparing, from samples of exterior of YSCWM, the predominant bacteria groups were different with the different sampling stations. So it suggested that bacterial community composition and the characteristic of predominant bacteria of the YSCWM may have something to do with the development of the YSCWM.