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Self-reducing copper nanocrystals : how surface chemistry affects sintering

Arnau Oliva Puigdomènech (UGent) , Jonathan De Roo (UGent) , José Martins (UGent) and Zeger Hens (UGent)
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Abstract
Copper nanocrystals (Cu NC) are actively investigated as substitutes for costly silver nanocrystals in conductive inks. However, to be of any use for printed conductors, oxidation of Cu NCs to non-conductive copper oxides must be avoided. Here, we analyze the interplay between the Cu NC surface termination, oxidation suppression and bulk copper formation through thermal annealing using 3 nm Cu NCs synthesized via thermal decomposition of copper formate in oleylamine (OLA). By adapting the method introduced by Sun et al,1 we obtain stable Cu NC dispersions that do not oxidize when stored under inert atmosphere, while showing a rapid conversion into copper oxide when exposed to air or deposited to form a thin NC film. Using solution 1H NMR spectroscopy, we demonstrate that as-synthesized Cu NCs are capped by OLA. OLA is tightly bound at NMR time scales, yet slowly desorbes during storage of the Cu dispersions, a process that is accelerated by oxygen exposure. Addition of carboxylic acids leads to the displacement of OLA from the Cu NCs and the formation of a denser ligand shell, probably consisting of dissociated carboxylic acids. We demonstrate that carboxylic acid ligands make Cu NCs more oxidation proof and facilitate the conversion of films of oxidized Cu NCs into a dense copper film. This offers the prospects of using colloidal Cu NCs as main constituent in conductive, nano-copper inks for applications in printed electronics.
Keywords
Copper, Nanotechnology, Surface Chemistry, NMR, XRD, Sintering, Oxidation

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MLA
Oliva Puigdomènech, Arnau, Jonathan De Roo, José Martins, et al. “Self-reducing Copper Nanocrystals : How Surface Chemistry Affects Sintering.” E-MRS Spring Meeting, Abstracts. 2017. Print.
APA
Oliva Puigdomènech, A., De Roo, J., Martins, J., & Hens, Z. (2017). Self-reducing copper nanocrystals : how surface chemistry affects sintering. E-MRS Spring meeting, Abstracts. Presented at the E-MRS 2017 Spring meeting.
Chicago author-date
Oliva Puigdomènech, Arnau, Jonathan De Roo, José Martins, and Zeger Hens. 2017. “Self-reducing Copper Nanocrystals : How Surface Chemistry Affects Sintering.” In E-MRS Spring Meeting, Abstracts.
Chicago author-date (all authors)
Oliva Puigdomènech, Arnau, Jonathan De Roo, José Martins, and Zeger Hens. 2017. “Self-reducing Copper Nanocrystals : How Surface Chemistry Affects Sintering.” In E-MRS Spring Meeting, Abstracts.
Vancouver
1.
Oliva Puigdomènech A, De Roo J, Martins J, Hens Z. Self-reducing copper nanocrystals : how surface chemistry affects sintering. E-MRS Spring meeting, Abstracts. 2017.
IEEE
[1]
A. Oliva Puigdomènech, J. De Roo, J. Martins, and Z. Hens, “Self-reducing copper nanocrystals : how surface chemistry affects sintering,” in E-MRS Spring meeting, Abstracts, Strasbourg, France, 2017.
@inproceedings{8545792,
  abstract     = {Copper nanocrystals (Cu NC) are actively investigated as substitutes for costly silver nanocrystals in conductive inks. However, to be of any use for printed conductors, oxidation of Cu NCs to non-conductive copper oxides must be avoided. Here, we analyze the interplay between the Cu NC surface termination, oxidation suppression and bulk copper formation through thermal annealing using 3 nm Cu NCs synthesized via thermal decomposition of copper formate in oleylamine (OLA). By adapting the method introduced by Sun et al,1 we obtain stable Cu NC dispersions that do not oxidize when stored under inert atmosphere, while showing a rapid conversion into copper oxide when exposed to air or deposited to form a thin NC film. Using solution 1H NMR spectroscopy, we demonstrate that as-synthesized Cu NCs are capped by OLA. OLA is tightly bound at NMR time scales, yet slowly desorbes during storage of the Cu dispersions, a process that is accelerated by oxygen exposure. Addition of carboxylic acids leads to the displacement of OLA from the Cu NCs and the formation of a denser ligand shell, probably consisting of dissociated carboxylic acids. We demonstrate that carboxylic acid ligands make Cu NCs more oxidation proof and facilitate the conversion of films of oxidized Cu NCs into a dense copper film. This offers the prospects of using colloidal Cu NCs as main constituent in conductive, nano-copper inks for applications in printed electronics.},
  author       = {Oliva Puigdomènech, Arnau and De Roo, Jonathan and Martins, José and Hens, Zeger},
  booktitle    = {E-MRS Spring meeting, Abstracts},
  keywords     = {Copper,Nanotechnology,Surface Chemistry,NMR,XRD,Sintering,Oxidation},
  language     = {eng},
  location     = {Strasbourg, France},
  title        = {Self-reducing copper nanocrystals : how surface chemistry affects sintering},
  year         = {2017},
}