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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.


(a) Representative RAIR spectra of surface-grown copper(II) oxalate prepared by the indicated numbers of deposition cycles with acquisition being performed after dipping in oxalic acid solution (b) Band intensities as a function of the deposition cycles. All samples were grown on MUA-coated gold substrates, which were also used for recording background spectra.
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Figure 1: (a) Representative RAIR spectra of surface-grown copper(II) oxalate prepared by the indicated numbers of deposition cycles with acquisition being performed after dipping in oxalic acid solution (b) Band intensities as a function of the deposition cycles. All samples were grown on MUA-coated gold substrates, which were also used for recording background spectra.

Mentions: As described previously, the deposition of copper(II) oxalate using a step-by-step approach of alternating dipping steps in ethanolic solutions of copper(II) acetate monohydrate and oxalic acid dihydrate can be monitored by RAIRS [26]. In close agreement with earlier results [26], spectra recorded after oxalic acid dipping steps (Fig. 1) show four bands in the range between 600 and 1800 cm−1, which can be assigned to characteristic vibrations of the oxalate anions. The broad band at 1620 cm−1 and the band at 830 cm−1 are uniquely assigned to the asymmetric CO2 stretching vibration (ν9, b2u in Herzberg notation [27]) and to the asymmetric CO2 deformation (ν12, b3u [27]). An assignment to the symmetric stretching mode of the carboxylic group has been suggested for the two sharp bands between 1400 and 1300 cm−1 [26]. In analogy to the band splitting described earlier for monomeric oxalate complexes [28–29], the band located at 1315 cm−1 in potassium oxalate [30] can split in two components in copper(II) oxalate due to coupling between oxalate ligands coordinated to a common copper atom. The band intensities show a steady increase with the number of deposition cycles (Fig. 1). This behavior has been observed before during the first 10 deposition cycles [26] but continues here to higher thickness. This result thus supports that the chosen step-by-step approach allows us to prepare surface layers with well-defined amounts of metal ions over a wide range of thicknesses.


Efficient electron-induced removal of oxalate ions and formation of copper nanoparticles from copper(II) oxalate precursor layers
(a) Representative RAIR spectra of surface-grown copper(II) oxalate prepared by the indicated numbers of deposition cycles with acquisition being performed after dipping in oxalic acid solution (b) Band intensities as a function of the deposition cycles. All samples were grown on MUA-coated gold substrates, which were also used for recording background spectra.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4979688&req=5

Figure 1: (a) Representative RAIR spectra of surface-grown copper(II) oxalate prepared by the indicated numbers of deposition cycles with acquisition being performed after dipping in oxalic acid solution (b) Band intensities as a function of the deposition cycles. All samples were grown on MUA-coated gold substrates, which were also used for recording background spectra.
Mentions: As described previously, the deposition of copper(II) oxalate using a step-by-step approach of alternating dipping steps in ethanolic solutions of copper(II) acetate monohydrate and oxalic acid dihydrate can be monitored by RAIRS [26]. In close agreement with earlier results [26], spectra recorded after oxalic acid dipping steps (Fig. 1) show four bands in the range between 600 and 1800 cm−1, which can be assigned to characteristic vibrations of the oxalate anions. The broad band at 1620 cm−1 and the band at 830 cm−1 are uniquely assigned to the asymmetric CO2 stretching vibration (ν9, b2u in Herzberg notation [27]) and to the asymmetric CO2 deformation (ν12, b3u [27]). An assignment to the symmetric stretching mode of the carboxylic group has been suggested for the two sharp bands between 1400 and 1300 cm−1 [26]. In analogy to the band splitting described earlier for monomeric oxalate complexes [28–29], the band located at 1315 cm−1 in potassium oxalate [30] can split in two components in copper(II) oxalate due to coupling between oxalate ligands coordinated to a common copper atom. The band intensities show a steady increase with the number of deposition cycles (Fig. 1). This behavior has been observed before during the first 10 deposition cycles [26] but continues here to higher thickness. This result thus supports that the chosen step-by-step approach allows us to prepare surface layers with well-defined amounts of metal ions over a wide range of thicknesses.

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.