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Science 27 July 2007:
Vol. 317. no. 5837, pp. 490 - 493
DOI: 10.1126/science.1142535
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Reports

Porous Semiconducting Gels and Aerogels from Chalcogenide Clusters

Santanu Bag1,2, Pantelis N. Trikalitis2*, Peter J. Chupas3, Gerasimos S. Armatas1,2 and Mercouri G. Kanatzidis1,2,4{dagger}

1 Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
2 Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
3 Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
4 Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.


Figure 1 Fig. 1. (A) Different building blocks used in chalcogel formation (blue spheres, metal centers; red spheres, chalcogenide atoms). (B and C) Monolithic hydrogel before (B) and after (C) supercritical drying, showing very little volume loss. [View Larger Version of this Image (52K GIF file)]
 

Figure 2 Fig. 2. (A and B) TEM images of Chalcogel-1 (A) and Chalcogel-2 (B). Pores between the particles in the meso- and macrophase regime are clear from these pictures, although they are not ordered. (C) TEM image of Chalcogel-2 shows small pores inside the particle. Large macropores are absent here. (D) Wide-angle powder x-ray diffraction data for Chalcogel-1. The amorphous nature of the aerogel and the lack of other crystalline phases are obvious. [View Larger Version of this Image (151K GIF file)]
 

Figure 3 Fig. 3. Nitrogen adsorption-desorption isotherms of (A) Chalcogel-1 and (B) Chalcogel-2 at 77 K (solid circles, adsorption data; open circles, desorption data). Samples were degassed overnight at 348 K before testing. [View Larger Version of this Image (17K GIF file)]
 

Figure 4 Fig. 4. (A) Reduced atomic pair distribution function G(r) of Chalcogel-1 (black line) and Chalcogel-2 (red dashed line) as a function of interatomic distance r. (B) Interatomic distances (in angstroms) are shown for the [Ge4S10]4– cluster in the proposed Chalcogel-1 structure. (C) Ultraviolet-visible electronic absorption spectra of (a) Chalcogel-1 (red dashed line), (b) Chalcogel-2 (blue dash-dot line), (c) Chalcogel-3 (magenta dashed line), (d) Chalcogel-4 (purple dotted line), (e) Chalcogel-5 (green dashed line), and (f) Chalcogel-6 (violet dash-dot line). [View Larger Version of this Image (27K GIF file)]
 

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