Biomedical subjects

Pingyun Feng

Publications and source records attributed to Pingyun Feng.

20 records · Page 2Linked to original sources

PubMed2002

Nanocluster with one missing core atom: a three-dimensional hybrid superlattice built from dual-sized supertetrahedral clusters.

In addition to having size-dependent properties, nanoclusters also behave like large pseudo-atoms and serve as building blocks for the construction of superlattices with properties that differ from either individual clusters or the bulk. While colloidal nanoparticles usually self-assemble into close-packed lattices, supertetrahedral clusters that are regular fragments of the zinc blende-type lattice can form covalent lattices with large pore size and high pore volume. Unfortunately, the size of the known supertetrahedral cluster is still small, and only a few types are currently known. In addition, their superlattices invariably consist of clusters of identical size. Here we report an open framework sulfide (denoted as UCR-15) that extends the cluster size from 20 metal ions in a T4 supertetrahedron to 34 metal ions in a novel T5 supertetrahedron with a missing core atom, [In34S54]6-. T5 clusters are joined by smaller T3 clusters (i.e., [In10S18]6-) to form an extended superlattice. UCR-15 is the first example of a covalent open framework built from supertetrahedral clusters of different sizes, thus revealing new possibilities in the construction of crystalline nanoporous semiconducting superlattices. It is proposed here that the formation of the dual-sized T3 and T5 hybrid framework is related to the host-guest charge density matching.

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PubMed2002

Self-assembly of novel dye molecules and [Cd8(SPh)12]4+ cubic clusters into three-dimensional photoluminescent superlattice.

The use of organic multidentate ligands to organize inorganic species is an effective method to prepare porous solids with tunable pore sizes. However, thus far, inorganic building units are generally limited to individual metal ions (e.g., Zn2+) or their oxide clusters (e.g., Zn4O6+). To expand applications of porous materials to electronic, electrooptic, or optical areas, the organization of semiconducting chalcogenide nanoclusters is desirable. Here we report the organization of cubic [Cd8(SPh)12]4+ clusters by in-situ-generated tetradentate 1,2,4,5-tetra(4-pyridyl)benzene molecules. The structure consists of three-dimensional inorganic-organic open framework with large unidimensional channels. The combination of dye molecules and inorganic cluster units in the same material creates a synergetic effect that enhances the emission of the inorganic cluster at 580 nm. Such an emission can be excited by a broad spectral range down to the UV, which is believed to result from the absorption of dye molecules and the subsequent energy transfer. The inorganic double four-ring cluster, [Cd8(SPh)12]4+, is formed from conversion of supertetrahedral clusters, while the novel tetradentate dye molecule is formed by oxidative coupling of two diamines.

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