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Long-term aging of Ag/a-C:H:O nanocomposite coatings in air and in aqueous environment

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ABSTRACT

Nanocomposite coatings of silver particles embedded in a plasma polymer matrix possess interesting properties depending on their microstructure. The film microstructure is affected among others also by the RF power supplied during the deposition, as shown by transmission electron microscopy. The optical properties are characterized by UV–vis–NIR spectroscopy. An anomalous optical absorption peak from the Ag nanoparticles is observed and related to the microstructure of the nanocomposite films. Furthermore, a long-term aging of the coatings is studied in-depth in ambient air and in aqueous environments. It is shown that the studied films are not entirely stable. The deposition conditions and the microstructure of the films affect the processes taking place during their aging in both environments.

No MeSH data available.


Electron diffraction patterns of Ag/a-C:H:O nanocomposite films deposited at the RF power of 30 W (top left) and 50 W (top right) as measured right after the deposition and Ag/a-C:H:O nanocomposite film deposited at RF power of 30 W, as measured after 23 months of aging in ambient air (bottom left) and after 1 day of aging in distilled water (bottom right). Each pattern is displayed with corresponding Miller indices.
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Figure 6: Electron diffraction patterns of Ag/a-C:H:O nanocomposite films deposited at the RF power of 30 W (top left) and 50 W (top right) as measured right after the deposition and Ag/a-C:H:O nanocomposite film deposited at RF power of 30 W, as measured after 23 months of aging in ambient air (bottom left) and after 1 day of aging in distilled water (bottom right). Each pattern is displayed with corresponding Miller indices.

Mentions: The deposited Ag/a-C:H:O nanocomposite films were studied by the SAD method to reveal the nature of the crystal structure of the metallic inclusions by analysis of the electron diffraction patterns. Typical diffractograms of selected films with corresponding Miller indices are displayed in figure 6. The diffraction patterns are composed of both rings and spots. While the diffraction rings are attributed to small nanoparticles, the bright spots represent larger crystals. The SAD analysis corresponds to the conclusion from the analysis of the bright field: the size of the silver crystalline inclusions in the nanocomposites increases with the deposition power. From the analysis of the diffractograms, it can be further concluded that all the inclusions in all of the studied films are of pure Ag with the face centered cubic structure with the lattice parameter a = 4.086 Å, which corresponds well to the data obtained from ICDD [45]. However, the SAD analysis does not principally exclude the possibility of presence of thin oxidized layers on surfaces of the Ag nanoparticles. The growth of the nanocomposite film takes place under non-equilibrium conditions, where the deposited energy enables surface mobility and bond opening/formation. Thus, metallic Ag nanoparticles are formed within a plasma polymer matrix. In equilibrium, however, Ag metal nanoparticles get rapidly oxidized at the surface [53]. Furthermore, Ag was found to form oxygen bonds on polymers without any plasma activation and clearly more of them after an O2 plasma treatment [54]. From this, we can expect that the metallic Ag nanoparticles have oxidized surfaces which partly form bonds to the hydrocarbon-based plasma polymer matrix (Ag–O–C bonds).


Long-term aging of Ag/a-C:H:O nanocomposite coatings in air and in aqueous environment
Electron diffraction patterns of Ag/a-C:H:O nanocomposite films deposited at the RF power of 30 W (top left) and 50 W (top right) as measured right after the deposition and Ag/a-C:H:O nanocomposite film deposited at RF power of 30 W, as measured after 23 months of aging in ambient air (bottom left) and after 1 day of aging in distilled water (bottom right). Each pattern is displayed with corresponding Miller indices.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036476&req=5

Figure 6: Electron diffraction patterns of Ag/a-C:H:O nanocomposite films deposited at the RF power of 30 W (top left) and 50 W (top right) as measured right after the deposition and Ag/a-C:H:O nanocomposite film deposited at RF power of 30 W, as measured after 23 months of aging in ambient air (bottom left) and after 1 day of aging in distilled water (bottom right). Each pattern is displayed with corresponding Miller indices.
Mentions: The deposited Ag/a-C:H:O nanocomposite films were studied by the SAD method to reveal the nature of the crystal structure of the metallic inclusions by analysis of the electron diffraction patterns. Typical diffractograms of selected films with corresponding Miller indices are displayed in figure 6. The diffraction patterns are composed of both rings and spots. While the diffraction rings are attributed to small nanoparticles, the bright spots represent larger crystals. The SAD analysis corresponds to the conclusion from the analysis of the bright field: the size of the silver crystalline inclusions in the nanocomposites increases with the deposition power. From the analysis of the diffractograms, it can be further concluded that all the inclusions in all of the studied films are of pure Ag with the face centered cubic structure with the lattice parameter a = 4.086 Å, which corresponds well to the data obtained from ICDD [45]. However, the SAD analysis does not principally exclude the possibility of presence of thin oxidized layers on surfaces of the Ag nanoparticles. The growth of the nanocomposite film takes place under non-equilibrium conditions, where the deposited energy enables surface mobility and bond opening/formation. Thus, metallic Ag nanoparticles are formed within a plasma polymer matrix. In equilibrium, however, Ag metal nanoparticles get rapidly oxidized at the surface [53]. Furthermore, Ag was found to form oxygen bonds on polymers without any plasma activation and clearly more of them after an O2 plasma treatment [54]. From this, we can expect that the metallic Ag nanoparticles have oxidized surfaces which partly form bonds to the hydrocarbon-based plasma polymer matrix (Ag–O–C bonds).

View Article: PubMed Central - PubMed

ABSTRACT

Nanocomposite coatings of silver particles embedded in a plasma polymer matrix possess interesting properties depending on their microstructure. The film microstructure is affected among others also by the RF power supplied during the deposition, as shown by transmission electron microscopy. The optical properties are characterized by UV–vis–NIR spectroscopy. An anomalous optical absorption peak from the Ag nanoparticles is observed and related to the microstructure of the nanocomposite films. Furthermore, a long-term aging of the coatings is studied in-depth in ambient air and in aqueous environments. It is shown that the studied films are not entirely stable. The deposition conditions and the microstructure of the films affect the processes taking place during their aging in both environments.

No MeSH data available.