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Structural damage reduction in protected gold clusters by electron diffraction methods

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ABSTRACT

The present work explores electron diffraction methods for studying the structure of metallic clusters stabilized with thiol groups, which are susceptible to structural damage caused by electron beam irradiation. There is a compromise between the electron dose used and the size of the clusters since they have small interaction volume with electrons and as a consequence weak reflections in the diffraction patterns. The common approach of recording individual clusters using nanobeam diffraction has the problem of an increased current density. Dosage can be reduced with the use of a smaller condenser aperture and a higher condenser lens excitation, but even with those set ups collection times tend to be high. For that reason, the methods reported herein collects in a faster way diffraction patterns through the scanning across the clusters under nanobeam diffraction mode. In this way, we are able to collect a map of diffraction patterns, in areas with dispersed clusters, with short exposure times (milliseconds) using a high sensitive CMOS camera. When these maps are compared with their theoretical counterparts, oscillations of the clusters can be observed. The stability of the patterns acquired demonstrates that our methods provide a systematic and precise way to unveil the structure of atomic clusters without extensive detrimental damage of their crystallinity.

Electronic supplementary material: The online version of this article (doi:10.1186/s40679-016-0026-x) contains supplementary material, which is available to authorized users.

No MeSH data available.


Set of experimental STEM/NBD and simulated patterns extracted from the Au102(p-MBA)44 cluster. Given an arbitrary orientation of the nanoparticle (c), a conical oscillation of the cluster is observed from the surrounding diffraction patterns (a, b, d, e), these one degree variations correspond to a “left, straight, right and back” tilting
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Fig5: Set of experimental STEM/NBD and simulated patterns extracted from the Au102(p-MBA)44 cluster. Given an arbitrary orientation of the nanoparticle (c), a conical oscillation of the cluster is observed from the surrounding diffraction patterns (a, b, d, e), these one degree variations correspond to a “left, straight, right and back” tilting

Mentions: Using this fast scanning electron diffraction method we are able to record and assess the structure of the Au102(p-MBA)44 cluster with an outstanding precision. Due both, the beam probe size and the scan spacing, a single particle can interact with the electron beam several times, this diffraction patterns possess certain similarities but are not equal as depicted on Fig. 5. From this information, we conclude that the particle is oriented almost in the same direction during scanning, i.e., the beam-particle interaction is such that it does not significantly disturb the state (position) of the particle. The simulation procedure for obtain this small angle variations is based on creating a library of diffraction patterns from a given arbitrary position of the Au102(p-MBA)44 structure, that is both azimuth and zenith angle rotated at intervals of one degree. Therefore, each randomly deposited cluster, will produce an experimental pattern that match our library. The map of patterns in the area within the cluster and its surrounding shows a good agreement when is indexed with the simulated patterns of the cluster disoriented one degree. Under the conditions described even after multiple recording events the clusters preserve their structure. The opposite effect, has been observed in a previous work where a long exposure time of the nanobeam diffraction patterns completely transformed the structure of metallic clusters when the electron beam remains static for a few seconds over the clusters [27].Fig. 5


Structural damage reduction in protected gold clusters by electron diffraction methods
Set of experimental STEM/NBD and simulated patterns extracted from the Au102(p-MBA)44 cluster. Given an arbitrary orientation of the nanoparticle (c), a conical oscillation of the cluster is observed from the surrounding diffraction patterns (a, b, d, e), these one degree variations correspond to a “left, straight, right and back” tilting
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037159&req=5

Fig5: Set of experimental STEM/NBD and simulated patterns extracted from the Au102(p-MBA)44 cluster. Given an arbitrary orientation of the nanoparticle (c), a conical oscillation of the cluster is observed from the surrounding diffraction patterns (a, b, d, e), these one degree variations correspond to a “left, straight, right and back” tilting
Mentions: Using this fast scanning electron diffraction method we are able to record and assess the structure of the Au102(p-MBA)44 cluster with an outstanding precision. Due both, the beam probe size and the scan spacing, a single particle can interact with the electron beam several times, this diffraction patterns possess certain similarities but are not equal as depicted on Fig. 5. From this information, we conclude that the particle is oriented almost in the same direction during scanning, i.e., the beam-particle interaction is such that it does not significantly disturb the state (position) of the particle. The simulation procedure for obtain this small angle variations is based on creating a library of diffraction patterns from a given arbitrary position of the Au102(p-MBA)44 structure, that is both azimuth and zenith angle rotated at intervals of one degree. Therefore, each randomly deposited cluster, will produce an experimental pattern that match our library. The map of patterns in the area within the cluster and its surrounding shows a good agreement when is indexed with the simulated patterns of the cluster disoriented one degree. Under the conditions described even after multiple recording events the clusters preserve their structure. The opposite effect, has been observed in a previous work where a long exposure time of the nanobeam diffraction patterns completely transformed the structure of metallic clusters when the electron beam remains static for a few seconds over the clusters [27].Fig. 5

View Article: PubMed Central - PubMed

ABSTRACT

The present work explores electron diffraction methods for studying the structure of metallic clusters stabilized with thiol groups, which are susceptible to structural damage caused by electron beam irradiation. There is a compromise between the electron dose used and the size of the clusters since they have small interaction volume with electrons and as a consequence weak reflections in the diffraction patterns. The common approach of recording individual clusters using nanobeam diffraction has the problem of an increased current density. Dosage can be reduced with the use of a smaller condenser aperture and a higher condenser lens excitation, but even with those set ups collection times tend to be high. For that reason, the methods reported herein collects in a faster way diffraction patterns through the scanning across the clusters under nanobeam diffraction mode. In this way, we are able to collect a map of diffraction patterns, in areas with dispersed clusters, with short exposure times (milliseconds) using a high sensitive CMOS camera. When these maps are compared with their theoretical counterparts, oscillations of the clusters can be observed. The stability of the patterns acquired demonstrates that our methods provide a systematic and precise way to unveil the structure of atomic clusters without extensive detrimental damage of their crystallinity.

Electronic supplementary material: The online version of this article (doi:10.1186/s40679-016-0026-x) contains supplementary material, which is available to authorized users.

No MeSH data available.