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Efficient electron-induced removal of oxalate ions and formation of copper nanoparticles from copper(II) oxalate precursor layers

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ABSTRACT

Copper(II) oxalate grown on carboxy-terminated self-assembled monolayers (SAM) using a step-by-step approach was used as precursor for the electron-induced synthesis of surface-supported copper nanoparticles. The precursor material was deposited by dipping the surfaces alternately in ethanolic solutions of copper(II) acetate and oxalic acid with intermediate thorough rinsing steps. The deposition of copper(II) oxalate and the efficient electron-induced removal of the oxalate ions was monitored by reflection absorption infrared spectroscopy (RAIRS). Helium ion microscopy (HIM) reveals the formation of spherical nanoparticles with well-defined size and X-ray photoelectron spectroscopy (XPS) confirms their metallic nature. Continued irradiation after depletion of oxalate does not lead to further particle growth giving evidence that nanoparticle formation is primarily controlled by the available amount of precursor.

No MeSH data available.


Proposed mechanism for the electron-induced decomposition of the oxalate ion.
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C1: Proposed mechanism for the electron-induced decomposition of the oxalate ion.

Mentions: RAIRS reveals that the decomposition of oxalate ions under electron exposure is accompanied by the formation of CO2 and CO. Both compounds have also been observed before as products of the electron-induced fragmentation of carboxylic acids with CO2 being dominant [43]. The reaction proceeds via both, dissociative electron attachment at electron energies around 1 eV, which are typical for secondary electrons and, with higher yield, above the ionization threshold. C–C bond cleavage has also been observed in mass spectra of oxalic acid as deduced from the appearance of the fragments CO2+, CO2H+ and CO2H2+ [44]. As electron energies above the ionization threshold have also been applied in the present study and it is difficult to conceive ionization from the copper ions, we propose that the decomposition of copper(II) oxalate is initiated by ionization of the oxalate ion and subsequent C–C bond cleavage (α-cleavage) yielding CO2 and a CO2 radical anion (Scheme 1).


Efficient electron-induced removal of oxalate ions and formation of copper nanoparticles from copper(II) oxalate precursor layers
Proposed mechanism for the electron-induced decomposition of the oxalate ion.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979688&req=5

C1: Proposed mechanism for the electron-induced decomposition of the oxalate ion.
Mentions: RAIRS reveals that the decomposition of oxalate ions under electron exposure is accompanied by the formation of CO2 and CO. Both compounds have also been observed before as products of the electron-induced fragmentation of carboxylic acids with CO2 being dominant [43]. The reaction proceeds via both, dissociative electron attachment at electron energies around 1 eV, which are typical for secondary electrons and, with higher yield, above the ionization threshold. C–C bond cleavage has also been observed in mass spectra of oxalic acid as deduced from the appearance of the fragments CO2+, CO2H+ and CO2H2+ [44]. As electron energies above the ionization threshold have also been applied in the present study and it is difficult to conceive ionization from the copper ions, we propose that the decomposition of copper(II) oxalate is initiated by ionization of the oxalate ion and subsequent C–C bond cleavage (α-cleavage) yielding CO2 and a CO2 radical anion (Scheme 1).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Copper(II) oxalate grown on carboxy-terminated self-assembled monolayers (SAM) using a step-by-step approach was used as precursor for the electron-induced synthesis of surface-supported copper nanoparticles. The precursor material was deposited by dipping the surfaces alternately in ethanolic solutions of copper(II) acetate and oxalic acid with intermediate thorough rinsing steps. The deposition of copper(II) oxalate and the efficient electron-induced removal of the oxalate ions was monitored by reflection absorption infrared spectroscopy (RAIRS). Helium ion microscopy (HIM) reveals the formation of spherical nanoparticles with well-defined size and X-ray photoelectron spectroscopy (XPS) confirms their metallic nature. Continued irradiation after depletion of oxalate does not lead to further particle growth giving evidence that nanoparticle formation is primarily controlled by the available amount of precursor.

No MeSH data available.