Single-crystal X-ray diffraction with synchrotron radiation enabled the structure of microcrystalline SSZ-23 (see drawing on the right), the first zeolite with channels bounded by seven- and nine-membered rings, to be solved.

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Atomic-resolution imaging of discrete [γ-SiW10O36]8- lacunary Keggin ions dispersed onto monolayer graphene oxide (GO) films by low voltage aberration corrected transmission electron microscopy is described. Under low electron beam dose, individual anions remain stationary for long enough that a variety of projections can be observed and structural information extracted with ca. ± 0.03 nm precision. Unambiguous assignment of the orientation of individual ions with respect to the point symmetry elements can be determined. The C2v symmetry [γ-SiW10O36]8- ion was imaged along its 2-fold C2 axis or orthogonally with respect to one of two nonequivalent mirror planes (i.e., σv). Continued electron beam exposure of a second ion imaged orthogonal to σv causes it to translate and/or rotate in an inhibited fashion so that the ion can be viewed in different relative orientations. The inhibited surface motion of the anion, which is in response to H-bonding-type interactions, reveals an important new property for GO in that it demonstrably behaves as a chemically modified (i.e., rather than chemically neutral) surface in electron microscopy. This behavior indicates that GO has more in common with substrates used in imaging techniques such as atomic force microscopy and scanning tunneling microscopy, and this clearly sets it apart from other support films used in transmission electron microscopy.

The synthesis of mesoporous silicas in the presence of the dicationic gemini surfactant [CH 3 (CH 2 ) 15 N(CH 3 ) 2 (CH 2 ) 3 N(CH 3 ) 3 ]Br 2 (C16-3-1) has been investigated at low temperatures (24 uC) under basic and acidic conditions. Under basic conditions, the SBA-2 phase (based on a close-packed arrangement of micelles and exhibiting frequent stacking faults) is observed, with hollow sphere morphology. Under strongly acidic conditions, the phase SBA-1 (Pm3 ¯n) and the SBA-2 family of phases (based on the close packing of micelles) are observed, depending on the surfactant and silicate content of the original gel. Conditions under which the pure hexagonally close-packed end member of the family (P6 3 /mmc) is formed have been identified. SBA-1 and the pure hexagonally close-packed end member are prepared with well-defined morphologies. The adsorption of nitrogen and the hydrocarbons cyclopentane and mesitylene reveal that SBA-2 prepared in basic media has a cage structure where the cages are linked through small (v4 A ˚) micropores, whereas the silicas prepared in acidic media have larger pores after calcination. SBA-1 and a poorly ordered SBA-2, prepared using C16-3-1 under acidic conditions, are able to adsorb mesitylene (diameter ca. 8 A ˚), whereas the hexagonal end member of the SBA-2 series prepared under acidic conditions is able to adsorb cyclopentane (diameter ca. 5 A ˚) but not mesitylene.