Osmium Atoms and Os2 Molecules Move Faster on Selenium-Doped Compared to Sulfur-Doped Boronic Graphenic Surfaces.

Nicolas P E Barry,Peter J Sadler,Ana M Sanchez,Rachel K O’Reilly,Andrew P Dove,Adam M Johansen,Anaïs Pitto-Barry,Simon E F Spencer,Robert J Deeth,Johanna Tran,Richard Beanland

doi:10.1021/acs.chemmater.5b01853

Nicolas P E Barry, Peter J Sadler + Show 9 more

Open Access

https://doi.org/10.1021/acs.chemmater.5b01853

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Abstract

We deposited Os atoms on S- and Se-doped boronic graphenic surfaces by electron bombardment of micelles containing 16e complexes [Os(p-cymene)(1,2-dicarba-closo-dodecarborane-1,2-diselenate/dithiolate)] encapsulated in a triblock copolymer. The surfaces were characterized by energy-dispersive X-ray (EDX) analysis and electron energy loss spectroscopy of energy filtered TEM (EFTEM). Os atoms moved ca. 26× faster on the B/Se surface compared to the B/S surface (233 ± 34 pm·s–1versus 8.9 ± 1.9 pm·s–1). Os atoms formed dimers with an average Os–Os distance of 0.284 ± 0.077 nm on the B/Se surface and 0.243 ± 0.059 nm on B/S, close to that in metallic Os. The Os2 molecules moved 0.83× and 0.65× more slowly than single Os atoms on B/S and B/Se surfaces, respectively, and again markedly faster (ca. 20×) on the B/Se surface (151 ± 45 pm·s–1 versus 7.4 ± 2.8 pm·s–1). Os atom motion did not follow Brownian motion and appears to involve anchoring sites, probably S and Se atoms. The ability to control the atomic motion of metal atoms and molecules on surfaces has potential for exploitation in nanodevices of the future.

Highlights

There is a long history of using electron microscopes to image the motion of adatoms on a thin film,[1,2] but only recent advances have made it feasible to study the chemistry of metals at the level of atomic resolution.[3−7] In particular the thickness and regularity of the honeycomb network of graphene provides an exceptional support for the deposition of individual atoms and observation of their motion.[8]
Article first was doped with heteroatoms boron and sulfur (B/S) following the procedure we described recently,[28] while the second was doped with heteroatoms boron and selenium (B/Se)
The new generations of electron microscopes with their atomic resolution capability and ultrafast cameras offer the possibility of imaging dynamic processes in real time

Summary

Introduction

There is a long history of using electron microscopes to image the motion of adatoms on a thin film,[1,2] but only recent advances have made it feasible to study the chemistry of metals at the level of atomic resolution.[3−7] In particular the thickness and regularity of the honeycomb network of graphene provides an exceptional support for the deposition of individual atoms and observation of their motion.[8]. We showed that electron beam irradiation of selfspreading polymer-encapsulated precious metal complexes can generate in situ-doped graphenic surfaces on which the dynamics of single metal atoms can be studied in real time using an aberration-corrected high resolution electron microscope.[28] Here we synthesize novel boron−sulfur-doped and boron− selenium-doped graphenic surfaces and study the atomic trajectories and rate of migration of single osmium atoms and individual Os2 molecules. These experiments reveal the dramatic effect of two chalcogenide (group 16) dopants S and Se on osmium atom migration

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