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A comparative study of two different approaches for the incorporation of silver nanoparticles into layer-by-layer films.

Rivero PJ, Goicoechea J, Matias IR, Arregui FJ - Nanoscale Res Lett (2014)

Bottom Line: In this work, a comparative study about the incorporation of silver nanoparticles (AgNPs) into thin films is presented using two alternative methods, the in situ synthesis process and the layer-by-layer embedding deposition technique.The influence of several parameters such as color of the films, thickness evolution, thermal post-treatment, or distribution of the AgNPs along the coatings has been studied.Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanostructured Optical Devices Laboratory, Electric and Electronic Engineering Department, Public University of Navarra, Edif. Los Tejos, Campus Arrosadía, Pamplona 31006, Spain.

ABSTRACT
In this work, a comparative study about the incorporation of silver nanoparticles (AgNPs) into thin films is presented using two alternative methods, the in situ synthesis process and the layer-by-layer embedding deposition technique. The influence of several parameters such as color of the films, thickness evolution, thermal post-treatment, or distribution of the AgNPs along the coatings has been studied. Thermal post-treatment was used to induce the formation of hydrogel-like AgNPs-loaded thin films. Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment. This work contributes for a better understanding of these two approaches for the incorporation of AgNPs into thin films using wet chemistry.

No MeSH data available.


Evolution of the UV-vis spectra of thin films obtained by ISS and LbL-E deposition technique. Evolution of the UV-vis spectra of the thin films obtained by ISS process and LbL-E deposition technique as a function of two temperatures values (ambient and 200°C).
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Figure 8: Evolution of the UV-vis spectra of thin films obtained by ISS and LbL-E deposition technique. Evolution of the UV-vis spectra of the thin films obtained by ISS process and LbL-E deposition technique as a function of two temperatures values (ambient and 200°C).

Mentions: Figure 8 shows the UV-vis spectra of the thin films obtained by ISS process and LbL-E deposition technique before and after thermal post-treatment (200°C). First of all, the location of the LSPR absorption band without thermal treatment for the ISS process appears at a shorter wavelength position (424.6 nm) in comparison with the LbL-E deposition technique (432.6 nm). This aspect related to the wavelength location of the LSPR absorption band shows a high dependence with the size of the AgNPs in the films. When AgNPs of higher size are incorporated into thin films, LSPR absorption band is located at higher wavelength position as it occurs in the LbL-E deposition technique. However, when smaller AgNPs are incorporated into the films, the LSPR absorption band is located at a lower wavelength position as it occurs in the ISS process. In addition, a shift of the LSPR absorption bands is observed in both processes after thermal post-treatment, being more notorious for the ISS process. One of the reasons of this displacement in wavelength is the better proximity of the AgNPs because of the partial thickness reduction after thermal post-treatment (confirmed in Tables 2 and 4) and as a result, the maxima absorbance values of the LSPR bands are increased.In Figure 9, normalized UV-vis spectra for the ISS and LbL-E films are shown after thermal post-treatment where it is possible to appreciate their maximal wavelength shifts respect untreated films (ambient) and the full width at half maximum (FWHM). The maximal wavelength shift is only 13 nm for the LbL-E films, whereas the shift for the ISS process is 46 nm. This great difference between both processes is associated to the use of a specific protective agent (PAA-AgNPs) in the LbL-E films, which prevents the agglomeration of the AgNPs during the fabrication process and after thermal post-treatment. However, ISS process shows a higher maximal wavelength shift because AgNPs are randomly synthesized into the polymeric matrix without any control in their distribution and aggregation state. This aspect related to the aggregation of the AgNPs into the films is corroborated by FWHM which it is duplicated for the ISS process (224 nm) in comparison with the LbL-E deposition technique (108 nm). In addition, the widening of the LSPR absorption band for the ISS is associated to the presence of AgNPs with a variable size (polydispersity) or to the presence of silver clusters (aggregates) in the films. However, LbL-E films show the possibility of incorporating AgNPs with a desired size (monodispersity) and perfectly encapsulated PAA-AgNPs and due to this, no aggregation of the AgNPs is observed after thermal post-treatment.In order to corroborate this hypothesis related to the size, aggregation, and distribution of the AgNPs into the thin films, cross-sectional TEM micrographs of the upper part of the thin film close to the surface as well as AFM phase images (1 × 1 μm) in tapping mode for the ISS and LbL-E films were taken, as it can be observed in Figure 10. The cluster formation is perfectly observed in the cross-sectional TEM micrograph (Figure 10a) for the ISS process, mostly in the outer surface of the film. In addition, AFM phase image (Figure 10b) reveals the presence of AgNPs with variable size and random distribution which are mixed with clusters in the specific zones of the topographic distribution. This aggregation in the film has a significant influence in the maximal wavelength position of the LSPR absorption band, corroborated by UV-vis spectra. Finally, the cross-sectional TEM image (Figure 10c) for the LbL-E film shows a gradual incorporation of AgNPs from the inner to the outer surface of the film, and AFM phase image in Figure 10d reveals that no aggregation of AgNPs is observed in the topographic distribution. An important consideration is that the size of the AgNPs using LbL-E is higher than the size observed in the ISS process, whereas a high amount of AgNPs are synthesized using the ISS process.This aspect related to the amount and size of the AgNPs is corroborated by SEM images. In Figure 11a, it is possible to appreciate that a higher amount of smaller AgNPs size is obtained for the ISS process. In opposition to this, the LbL-E deposition technique (Figure 11b) shows the incorporation of AgNPs with a higher size in the topographic distribution of the films.


A comparative study of two different approaches for the incorporation of silver nanoparticles into layer-by-layer films.

Rivero PJ, Goicoechea J, Matias IR, Arregui FJ - Nanoscale Res Lett (2014)

Evolution of the UV-vis spectra of thin films obtained by ISS and LbL-E deposition technique. Evolution of the UV-vis spectra of the thin films obtained by ISS process and LbL-E deposition technique as a function of two temperatures values (ambient and 200°C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 8: Evolution of the UV-vis spectra of thin films obtained by ISS and LbL-E deposition technique. Evolution of the UV-vis spectra of the thin films obtained by ISS process and LbL-E deposition technique as a function of two temperatures values (ambient and 200°C).
Mentions: Figure 8 shows the UV-vis spectra of the thin films obtained by ISS process and LbL-E deposition technique before and after thermal post-treatment (200°C). First of all, the location of the LSPR absorption band without thermal treatment for the ISS process appears at a shorter wavelength position (424.6 nm) in comparison with the LbL-E deposition technique (432.6 nm). This aspect related to the wavelength location of the LSPR absorption band shows a high dependence with the size of the AgNPs in the films. When AgNPs of higher size are incorporated into thin films, LSPR absorption band is located at higher wavelength position as it occurs in the LbL-E deposition technique. However, when smaller AgNPs are incorporated into the films, the LSPR absorption band is located at a lower wavelength position as it occurs in the ISS process. In addition, a shift of the LSPR absorption bands is observed in both processes after thermal post-treatment, being more notorious for the ISS process. One of the reasons of this displacement in wavelength is the better proximity of the AgNPs because of the partial thickness reduction after thermal post-treatment (confirmed in Tables 2 and 4) and as a result, the maxima absorbance values of the LSPR bands are increased.In Figure 9, normalized UV-vis spectra for the ISS and LbL-E films are shown after thermal post-treatment where it is possible to appreciate their maximal wavelength shifts respect untreated films (ambient) and the full width at half maximum (FWHM). The maximal wavelength shift is only 13 nm for the LbL-E films, whereas the shift for the ISS process is 46 nm. This great difference between both processes is associated to the use of a specific protective agent (PAA-AgNPs) in the LbL-E films, which prevents the agglomeration of the AgNPs during the fabrication process and after thermal post-treatment. However, ISS process shows a higher maximal wavelength shift because AgNPs are randomly synthesized into the polymeric matrix without any control in their distribution and aggregation state. This aspect related to the aggregation of the AgNPs into the films is corroborated by FWHM which it is duplicated for the ISS process (224 nm) in comparison with the LbL-E deposition technique (108 nm). In addition, the widening of the LSPR absorption band for the ISS is associated to the presence of AgNPs with a variable size (polydispersity) or to the presence of silver clusters (aggregates) in the films. However, LbL-E films show the possibility of incorporating AgNPs with a desired size (monodispersity) and perfectly encapsulated PAA-AgNPs and due to this, no aggregation of the AgNPs is observed after thermal post-treatment.In order to corroborate this hypothesis related to the size, aggregation, and distribution of the AgNPs into the thin films, cross-sectional TEM micrographs of the upper part of the thin film close to the surface as well as AFM phase images (1 × 1 μm) in tapping mode for the ISS and LbL-E films were taken, as it can be observed in Figure 10. The cluster formation is perfectly observed in the cross-sectional TEM micrograph (Figure 10a) for the ISS process, mostly in the outer surface of the film. In addition, AFM phase image (Figure 10b) reveals the presence of AgNPs with variable size and random distribution which are mixed with clusters in the specific zones of the topographic distribution. This aggregation in the film has a significant influence in the maximal wavelength position of the LSPR absorption band, corroborated by UV-vis spectra. Finally, the cross-sectional TEM image (Figure 10c) for the LbL-E film shows a gradual incorporation of AgNPs from the inner to the outer surface of the film, and AFM phase image in Figure 10d reveals that no aggregation of AgNPs is observed in the topographic distribution. An important consideration is that the size of the AgNPs using LbL-E is higher than the size observed in the ISS process, whereas a high amount of AgNPs are synthesized using the ISS process.This aspect related to the amount and size of the AgNPs is corroborated by SEM images. In Figure 11a, it is possible to appreciate that a higher amount of smaller AgNPs size is obtained for the ISS process. In opposition to this, the LbL-E deposition technique (Figure 11b) shows the incorporation of AgNPs with a higher size in the topographic distribution of the films.

Bottom Line: In this work, a comparative study about the incorporation of silver nanoparticles (AgNPs) into thin films is presented using two alternative methods, the in situ synthesis process and the layer-by-layer embedding deposition technique.The influence of several parameters such as color of the films, thickness evolution, thermal post-treatment, or distribution of the AgNPs along the coatings has been studied.Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanostructured Optical Devices Laboratory, Electric and Electronic Engineering Department, Public University of Navarra, Edif. Los Tejos, Campus Arrosadía, Pamplona 31006, Spain.

ABSTRACT
In this work, a comparative study about the incorporation of silver nanoparticles (AgNPs) into thin films is presented using two alternative methods, the in situ synthesis process and the layer-by-layer embedding deposition technique. The influence of several parameters such as color of the films, thickness evolution, thermal post-treatment, or distribution of the AgNPs along the coatings has been studied. Thermal post-treatment was used to induce the formation of hydrogel-like AgNPs-loaded thin films. Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment. This work contributes for a better understanding of these two approaches for the incorporation of AgNPs into thin films using wet chemistry.

No MeSH data available.