Growth of ZnO nanowires catalyzed by size-dependent melting of Au nanoparticles

Nanocomposite films consisting of gold nanoparticles embedded in an yttria stabilized zirconia (YSZ) matrix were synthesized at room temperature by radio-frequency co-sputtering from YSZ and Au targets at a 5 mTorr working pressure. The films were subsequently annealed for 2 h in 1 atm argon, with the annealing temperature varied from 600 to 1000 °C in steps of 100 °C. The composition, microstructure, and optical properties of the films were characterized as a function of annealing temperature by Rutherford backscattering spectrometry, scanning electron microscopy, Auger electron spectroscopy, x-ray diffraction, and absorption spectroscopy. An optical absorption band due to the surface plasmon resonance (SPR) of the Au nanoparticles was observed around a wavelength of 600 nm. Furthermore, the SPR band full width at half-maximum exhibited an inverse linear dependence on the radius of the Au nanoparticle, with a slope parameter A = 0.18, indicating a weak interaction between the YSZ matrix and the Au nanoparticles. The experimentally observed SPR dependence on nanoparticle size is discussed within the context of the Mie theory and its size-dependent optical constants.

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Size-dependent dynamic structures of supported gold nanoparticles in CO oxidation reaction condition

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1800262115 ◽

2018 ◽

Vol 115 (30) ◽

pp. 7700-7705 ◽

Cited By ~ 63

Author(s):

Yang He ◽

Jin-Cheng Liu ◽

Langli Luo ◽

Yang-Gang Wang ◽

Junfa Zhu ◽

...

Keyword(s):

Co Oxidation ◽

Oxidation Reaction ◽

Au Nanoparticles ◽

Working Condition ◽

Ab Initio Molecular Dynamics ◽

Present Observation ◽

Size Dependent ◽

Reaction Condition ◽

Au Clusters ◽

Co Oxidation Reaction

Gold (Au) catalysts exhibit a significant size effect, but its origin has been puzzling for a long time. It is generally believed that supported Au clusters are more or less rigid in working condition, which inevitably leads to the general speculation that the active sites are immobile. Here, by using atomic resolution in situ environmental transmission electron microscopy, we report size-dependent structure dynamics of single Au nanoparticles on ceria (CeO2) in CO oxidation reaction condition at room temperature. While large Au nanoparticles remain rigid in the catalytic working condition, ultrasmall Au clusters lose their intrinsic structures and become disordered, featuring vigorous structural rearrangements and formation of dynamic low-coordinated atoms on surface. Ab initio molecular-dynamics simulations reveal that the interaction between ultrasmall Au cluster and CO molecules leads to the dynamic structural responses, demonstrating that the shape of the catalytic particle under the working condition may totally differ from the shape under the static condition. The present observation provides insight on the origin of superior catalytic properties of ultrasmall gold clusters.

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