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 C_2v 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., σ_v). Continued electron beam exposure of a second ion imaged orthogonal to σ_v 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.

Neil Ebejer, Mathias Schnippering, Alexander W. Colburn, Martin A. Edwards, and Patrick R. Unwin*

Department of Chemistry, University of Warwick

Analytical Chemistry, 15 October 2010

Thursday 9 September saw the official opening of the newly built Ion Cyclotron Resonance Laboratory at Millburn House, which houses state-of-the-art Fourier transform ion cyclotron resonance (FTICR) mass spectrometers.

Opening in pictures here!