Limits...
Structural damage reduction in protected gold clusters by electron diffraction methods

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.


Theoretical structures used for simulation. a Au144(SR)60 [21] and b Au102(MBA)44 [20] oriented along the fivefold direction
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5037159&req=5

Fig1: Theoretical structures used for simulation. a Au144(SR)60 [21] and b Au102(MBA)44 [20] oriented along the fivefold direction

Mentions: The gold clusters (Au102-pMBA44 and Au144(SCH2CH2Ph)60) were produced by the two-phase transfer method [19, 20], their expected structures are shown in Fig. 1, both nanoparticles have been optimized by first-principles density functional theory (DFT) calculations [19, 21]. Quality and size distribution of Au clusters were confirmed by polyacrylamide gel electrophoresis and electrospray ionization mass spectrometry (ESI–MS) using a Bruker micro-TOF instrument. The stock Au clusters were diluted 100-fold with ddH2O, then 3–4 drops (20 µl) were loaded on a holey carbon film-coated grids and air dried at room temperature for at least 2 h.Fig. 1


Structural damage reduction in protected gold clusters by electron diffraction methods
Theoretical structures used for simulation. a Au144(SR)60 [21] and b Au102(MBA)44 [20] oriented along the fivefold direction
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: Theoretical structures used for simulation. a Au144(SR)60 [21] and b Au102(MBA)44 [20] oriented along the fivefold direction
Mentions: The gold clusters (Au102-pMBA44 and Au144(SCH2CH2Ph)60) were produced by the two-phase transfer method [19, 20], their expected structures are shown in Fig. 1, both nanoparticles have been optimized by first-principles density functional theory (DFT) calculations [19, 21]. Quality and size distribution of Au clusters were confirmed by polyacrylamide gel electrophoresis and electrospray ionization mass spectrometry (ESI–MS) using a Bruker micro-TOF instrument. The stock Au clusters were diluted 100-fold with ddH2O, then 3–4 drops (20 µl) were loaded on a holey carbon film-coated grids and air dried at room temperature for at least 2 h.Fig. 1

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.