Topochemical reactions of layered materials - including intercalation, ion exchange, exfoliation/restacking, dehydration, and redox reactions - can be used to convert layered solids into new materials with unusual crystal textures, magnetic, and electronic transport properties.  Most layered oxides contain negatively charged sheets interleaved by cations.  Recently, we have found that it is possible to convert layered oxides into anion exchangers by intercalating polycations that overcompensate the negative charge of the sheets.  The resulting compounds intercalate metal nanoparticles, which typically have negative surface charge near neutral pH. Using poly(tetrafluoroethylene) as a reducing and fluorinating agent, fluorine can be substituted for oxygen in layer perovskites and other oxides, resulting in compounds that are electrically conducting, even after exfoliating and re-stacking.  Layered oxides typically have very anisotropic transport properties, and so it is advantageous to control the orientation of sheets and microcrystals in composite materials and devices. Suspended layer perovskite microcrystals orient strongly in magnetic fields with their stacking axis perpendicular to the field direction.  This orientation, which arises from the magnetic anisotropy of the sheets, can be understood in terms of the symmetry of bonding at the faces of the sheets.  Together these synthetic techniques provide access to �designed� oxide materials with a range of interesting physical and chemical properties.

Synthesis of functional materials through topochemical reactions of layered solids

243rd National Meeting (2012)

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