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European Microscopy Congress 2020 Abstract Database

ZnFe bimetallic nanoparticles: a detailed characterization by TEM and EELS

ZnFe bimetallic nanoparticles: a detailed characterization by TEM and EELS

Session

PSA.5 - Nanoparticles & Catalysts

Authors

H. Lamsaf (1, 2), V. Lenzi (1), L. Marques (1), L. Rebouta (1), S. Carvalho (1, 3), S Calderon V (1, 2)

Affiliations

1. University of Minho, Department of Physics
2. INL - International Iberian Nanotechnology Laboratory, Av. Mestre José Veiga s/n, 4715-330 Braga, Portugal
3. SEG-CEMMPRE, Mechanical Engineering Department, University of Coimbra

Keywords

Sputtering, Clusters, ZnFe

Abstract text

Bimetallic nanoparticles (NPs) have gained a lot of attention during the last decade due to their unusual characteristics when compared to monometallic counterparts. Such heterostructures demonstrated enhanced characteristics for catalysis, antibacterial, optical and magnetic properties among others. In this work, we produced ZnFe bimetallic nanoparticles (NPs) onto carbon substrates to create a material with tunable oxygen scavenger capacity, by controlling the morphology and composition of the particles. However, to properly control the morphology and composition of the particles, the production process and growth mechanisms of these heterostructures must be well understood. Hence, this report focuses on studying the growth mechanisms taking place during the simultaneous production of ZnFe bimetallic NPs by magnetron sputtering and its effect on the nanoparticles composition. 

The NPs were produced using a hybrid system composed by a cluster gun and a conventional magnetron sputtering chamber. The samples were deposited on ultrathin carbon grids (Ted Pella), and the evolution of their morphology, structure and composition was carried out as a function of thickness by transmission electron microscopy techniques. STEM and HR-TEM images were acquired to determine the structure of the bimetallic nanoparticles, while the chemical composition was evaluated by simultaneous acquisition of EDS and EELS. The structure, morphology and composition of the NPs were determined using a double-corrected FEI Titan-Themis coupled with a dual-EELS Efinium spectrometer. 

Besides, to understand the growth mechanism, the structural, morphological and compositional information was used to carry out molecular dynamic calculation and model the particles collisions during the simultaneous production by the cluster gun and classical magnetron sputtering.

The results demonstrate a frequent morphology, in which the Fe is surrounded by Zn nanoparticles follow a pattern in the initial stage of the growth of the nanoparticles. The composition of the particles shows a significant effect due to the distribution of the two metals in the heterostructures. When Fe or Zn nanoparticles are produced separately, both metals oxidize spontaneously when contacting the environment, forming a passivation layer that prevents further oxidation of the particles. However, for the bimetallic NPs, Fe does not show significant oxidation, being Zn the major element oxidized. This control of oxidation suggests that by adjusting the amount of Zn and Fe in the heterostructures we can tune or regulate the oxygen scavenger capabilities of the nanoparticles. 

 

Acknowledgement

The authors thank the financial support by the Portuguese Foundation for Science and Technology (FCT) in the framework of the project NANOXYPACK co-financed via FEDER (PT2020) POCI-01-0145-FEDER-030789.