Selective Imaging of Discrete Polyoxometalate Ions on Graphene Oxide under Variable Voltage Conditions

Abstract

Monosubstituted lacunary Keggin [CoSiW11O39](6-) ions on graphene oxide (GO) were used in a comparative imaging study using aberration corrected transmission electron microscopy at two different acceleration voltages, 80 and 200 kV. By performing a set of static and dynamical studies, together with image simulations, we show how the use of lower voltages results in better stability and resolution of the underlying GO support while the use of higher voltages permits better resolution of the individual tungsten atoms and leads to less kinetic motion of the cluster, thus leading to a more accurate identification of cluster orientation and better stability under dynamical imaging conditions. Applying different voltages also influences the visibility of both GO and the lighter Co at lower or higher voltages, respectively.

Electron microscopy of polyoxometalate ions on graphene by electrospray ion beam deposition

“…The discovery of 2D materials such as graphene led to ultrathin electron-transparent substrates, on which the observation of individual atomic defects has been demonstrated. [14][15][16][17][18] In addition, only a chemically pure, contamination-and destruction-free sample deposition of analyte molecules can enable us to correlate the observed structural features to the molecule under investigation. To this end, solution-based deposition techniques can be challenging as unwanted contaminations such as salts or organic residues are left behind and complicate the data analysis.…”

“…In previous TEM studies, POMs have been atomically resolved on 2D electron-transparent substrates such as GO and covalently-functionalized few-layer graphene (FLG). [15][16][17]31 In contrast, TEM analysis of POMs on single-layer graphene (SLG) substrates has not been investigated yet. Beside their unique structural aspects, POMs are of interest for various applications, including surface catalysis and nanoscale magnetism.…”

Atomic-number ( Z )-correlated atomic sizes for deciphering electron microscopic molecular images

“…In an image of a [CoSiW 11 O 39 ] 6– polyoxometalate cluster in Fig. 5 G ( 43 ), we find only Co and W metal atoms. Accordingly, the ZC HN model shows only the heavy metals, while the CPK model shows only the oxygen atoms on the molecular surface.…”

In Situ Electron Beam Amorphization of Sb2Te3 within Single Walled Carbon Nanotubes

“…Local glass transformation of Sb 2 Te 3 in SWNT bundles was achieved in the JEM-ARM200F at 80 kV by gradually increasing the 80 kV electron beam dose from 0.8 pA cm −2 to 1.5 pA cm −2 . Increasing the electron beam dose much beyond 1.5 pA cm −2 tended to be deleterious to the SWNT bundle microstructure due to expected radiolysis [20]. X-ray microanalyses were performed on multiple Sb 2 Te 3 filled SWNT bundles to verify the elemental composition of the former (Fig.…”