Nanocrystalline silver supported on activated carbon matrix from hydrosol: Antibacterial mechanism under prolonged incubation conditions

Sukdeb Pal, Yu Kyung Tak, J. Joardar, Wook Kim, Jong Eun Lee, Myun Soo Han, Joon Myong Song

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Nanocrystalline silver-supported activated carbon (AC) was fabricated by directly loading silver nanoparticles into the porous AC matrix from a preformed nanosilver hydrosol. Silver-AC composites were also synthesized using a conventional thermal impregnation method. While XRD calculation indicated the presence of Ag crystallites in nanometer range, silver nanoparticle hydrosol-treated AC having the finest crystallite size CS (<14.4 nm), SEM images clearly revealed that Ag crystals coalesced significantly with increasing temperature resulting in much larger particle size in thermally impregnated silver-AC composities. To clarify the antibacterial mechanism of silver nanoparticles impregnated into AC under prolonged incubation conditions the antibacterial activity was investigated against Gram-negative Escherichia coli. The kinetics of bacterial inactivation, in presence of hydroxyl radical (OH) scavengers, and superoxide anion radical (O -2) inducer suggest the contribution of the reactive oxygen species (ROS) to antibacterial effect. However, these ROS scavengers did not show any inhibition of bactericidal activity after ~1 h, suggesting that generated ROS are responsible for E. coli inactivation only during the initial 1 h of the incubation time. This study clearly indicates the plausible implication of eluted Ag + as major lethal species responsible for the E. coli inactivation over extended process time. The antibacterial process was found to be highly promoted at higher temperature which was ascribed to the enhanced ROS formation and Ag+ elution at higher temperature. SEM images revealed considerable differences in the morphology of E. coli cells contacting" with the virgin AC and that contacting with silver-supported AC. The strong antibacterial ability of formaldehyde-modified silver-supported AC further provided the indirect evidences for catalytic oxidation by ROS, and for the synergis tic antibacterial effects of nanocrystalline silver and adsorbed formaldehyde. Comparison of the antibacterial activities of the silver-supported materials prepared by silver colloid deposition and by conventional thermal impregnation technique indicates that former is more efficient in controlling microorganism.

Original languageEnglish
Pages (from-to)2092-2103
Number of pages12
JournalJournal of Nanoscience and Nanotechnology
Volume9
Issue number3
DOIs
Publication statusPublished - 2009 Mar 1

Fingerprint

activated carbon
Silver
Activated carbon
silver
matrices
Reactive Oxygen Species
Escherichia coli
Oxygen
deactivation
oxygen
Nanoparticles
Impregnation
Formaldehyde
formaldehyde
nanoparticles
Scanning electron microscopy
Catalytic oxidation
scanning electron microscopy
elution
inorganic peroxides

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Chemistry(all)
  • Biomedical Engineering
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Pal, Sukdeb ; Kyung Tak, Yu ; Joardar, J. ; Kim, Wook ; Eun Lee, Jong ; Soo Han, Myun ; Myong Song, Joon. / Nanocrystalline silver supported on activated carbon matrix from hydrosol : Antibacterial mechanism under prolonged incubation conditions. In: Journal of Nanoscience and Nanotechnology. 2009 ; Vol. 9, No. 3. pp. 2092-2103.
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abstract = "Nanocrystalline silver-supported activated carbon (AC) was fabricated by directly loading silver nanoparticles into the porous AC matrix from a preformed nanosilver hydrosol. Silver-AC composites were also synthesized using a conventional thermal impregnation method. While XRD calculation indicated the presence of Ag crystallites in nanometer range, silver nanoparticle hydrosol-treated AC having the finest crystallite size CS (<14.4 nm), SEM images clearly revealed that Ag crystals coalesced significantly with increasing temperature resulting in much larger particle size in thermally impregnated silver-AC composities. To clarify the antibacterial mechanism of silver nanoparticles impregnated into AC under prolonged incubation conditions the antibacterial activity was investigated against Gram-negative Escherichia coli. The kinetics of bacterial inactivation, in presence of hydroxyl radical (OH) scavengers, and superoxide anion radical (O -2) inducer suggest the contribution of the reactive oxygen species (ROS) to antibacterial effect. However, these ROS scavengers did not show any inhibition of bactericidal activity after ~1 h, suggesting that generated ROS are responsible for E. coli inactivation only during the initial 1 h of the incubation time. This study clearly indicates the plausible implication of eluted Ag + as major lethal species responsible for the E. coli inactivation over extended process time. The antibacterial process was found to be highly promoted at higher temperature which was ascribed to the enhanced ROS formation and Ag+ elution at higher temperature. SEM images revealed considerable differences in the morphology of E. coli cells contacting{"} with the virgin AC and that contacting with silver-supported AC. The strong antibacterial ability of formaldehyde-modified silver-supported AC further provided the indirect evidences for catalytic oxidation by ROS, and for the synergis tic antibacterial effects of nanocrystalline silver and adsorbed formaldehyde. Comparison of the antibacterial activities of the silver-supported materials prepared by silver colloid deposition and by conventional thermal impregnation technique indicates that former is more efficient in controlling microorganism.",
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Nanocrystalline silver supported on activated carbon matrix from hydrosol : Antibacterial mechanism under prolonged incubation conditions. / Pal, Sukdeb; Kyung Tak, Yu; Joardar, J.; Kim, Wook; Eun Lee, Jong; Soo Han, Myun; Myong Song, Joon.

In: Journal of Nanoscience and Nanotechnology, Vol. 9, No. 3, 01.03.2009, p. 2092-2103.

Research output: Contribution to journalArticle

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T1 - Nanocrystalline silver supported on activated carbon matrix from hydrosol

T2 - Antibacterial mechanism under prolonged incubation conditions

AU - Pal, Sukdeb

AU - Kyung Tak, Yu

AU - Joardar, J.

AU - Kim, Wook

AU - Eun Lee, Jong

AU - Soo Han, Myun

AU - Myong Song, Joon

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AB - Nanocrystalline silver-supported activated carbon (AC) was fabricated by directly loading silver nanoparticles into the porous AC matrix from a preformed nanosilver hydrosol. Silver-AC composites were also synthesized using a conventional thermal impregnation method. While XRD calculation indicated the presence of Ag crystallites in nanometer range, silver nanoparticle hydrosol-treated AC having the finest crystallite size CS (<14.4 nm), SEM images clearly revealed that Ag crystals coalesced significantly with increasing temperature resulting in much larger particle size in thermally impregnated silver-AC composities. To clarify the antibacterial mechanism of silver nanoparticles impregnated into AC under prolonged incubation conditions the antibacterial activity was investigated against Gram-negative Escherichia coli. The kinetics of bacterial inactivation, in presence of hydroxyl radical (OH) scavengers, and superoxide anion radical (O -2) inducer suggest the contribution of the reactive oxygen species (ROS) to antibacterial effect. However, these ROS scavengers did not show any inhibition of bactericidal activity after ~1 h, suggesting that generated ROS are responsible for E. coli inactivation only during the initial 1 h of the incubation time. This study clearly indicates the plausible implication of eluted Ag + as major lethal species responsible for the E. coli inactivation over extended process time. The antibacterial process was found to be highly promoted at higher temperature which was ascribed to the enhanced ROS formation and Ag+ elution at higher temperature. SEM images revealed considerable differences in the morphology of E. coli cells contacting" with the virgin AC and that contacting with silver-supported AC. The strong antibacterial ability of formaldehyde-modified silver-supported AC further provided the indirect evidences for catalytic oxidation by ROS, and for the synergis tic antibacterial effects of nanocrystalline silver and adsorbed formaldehyde. Comparison of the antibacterial activities of the silver-supported materials prepared by silver colloid deposition and by conventional thermal impregnation technique indicates that former is more efficient in controlling microorganism.

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