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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.


Data acquisition on a S-NBD technique. Set of electron diffraction patterns acquired on a scanned area at 500 K× in a JEOL 2010F, taken with a scanning time of 100 ms per pattern the estimated radiation dose, recorded within the screen of the microscope, is ∼1350  Å−2
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Fig4: Data acquisition on a S-NBD technique. Set of electron diffraction patterns acquired on a scanned area at 500 K× in a JEOL 2010F, taken with a scanning time of 100 ms per pattern the estimated radiation dose, recorded within the screen of the microscope, is ∼1350  Å−2

Mentions: The acquisition of the scanning nanobeam diffraction patterns was performed with a probe current of 2 pA cm−2 and a probe size of 2 nm to scan ~1.6 nm Au102(MBA)44 cluster. As shown in Fig. 3h the patterns have been registered with an estimated dose of 13,500  Å−1s−1. This dose rate can then be reduced adjusting the acquisition/interaction time of the probe with the nanoparticle during the scanning procedure. In this setup, each pattern is collected every 100 milliseconds yielding a dose of approximately 1350   Å−2. Due to the probe size and the scanning steps, the electron beam interacts with the cluster more than one time, causing oscillations that can be detected in the adjacent patterns of one cluster. The patterns shown in Fig. 4 represent a fraction of the whole area scanned and registered in the CMOS camera. The patterns highlighted within the yellow square correspond to frames surrounding an individual cluster. The indexing of these patterns have been analyzed using the xyz cluster coordinates from the relaxed structure of the Au102(p-MBA)44 cluster determined by X-ray diffraction and optimized by density functional theory (DFT) [21]. The simulated diffraction patterns were indexed using the module “Nanodiffraction” in the java electron microscopy simulations software package [26]. Image processing has been made in order to enhance the features already present in the images, those filters and parameter were implemented for all images acquired.Fig. 4


Structural damage reduction in protected gold clusters by electron diffraction methods
Data acquisition on a S-NBD technique. Set of electron diffraction patterns acquired on a scanned area at 500 K× in a JEOL 2010F, taken with a scanning time of 100 ms per pattern the estimated radiation dose, recorded within the screen of the microscope, is ∼1350  Å−2
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig4: Data acquisition on a S-NBD technique. Set of electron diffraction patterns acquired on a scanned area at 500 K× in a JEOL 2010F, taken with a scanning time of 100 ms per pattern the estimated radiation dose, recorded within the screen of the microscope, is ∼1350  Å−2
Mentions: The acquisition of the scanning nanobeam diffraction patterns was performed with a probe current of 2 pA cm−2 and a probe size of 2 nm to scan ~1.6 nm Au102(MBA)44 cluster. As shown in Fig. 3h the patterns have been registered with an estimated dose of 13,500  Å−1s−1. This dose rate can then be reduced adjusting the acquisition/interaction time of the probe with the nanoparticle during the scanning procedure. In this setup, each pattern is collected every 100 milliseconds yielding a dose of approximately 1350   Å−2. Due to the probe size and the scanning steps, the electron beam interacts with the cluster more than one time, causing oscillations that can be detected in the adjacent patterns of one cluster. The patterns shown in Fig. 4 represent a fraction of the whole area scanned and registered in the CMOS camera. The patterns highlighted within the yellow square correspond to frames surrounding an individual cluster. The indexing of these patterns have been analyzed using the xyz cluster coordinates from the relaxed structure of the Au102(p-MBA)44 cluster determined by X-ray diffraction and optimized by density functional theory (DFT) [21]. The simulated diffraction patterns were indexed using the module “Nanodiffraction” in the java electron microscopy simulations software package [26]. Image processing has been made in order to enhance the features already present in the images, those filters and parameter were implemented for all images acquired.Fig. 4

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.