Silver valence and local environments in borosilicate and calcium aluminoborate waste glasses as determined from X-ray absorption spectroscopy

McKeown, David A.; Gan, Hao; Pegg, Ian L.

doi:10.1016/j.jnoncrysol.2005.10.011

Cited by 16 publications

(9 citation statements)

References 13 publications

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“…The position of the X-ray absorption edge in each spectrum contains information on the oxidation state of the silver present. The edge position of AgO, which contains a mixture of Ag I and Ag III ions (28), appears at the highest energy since it requires more energy to remove electrons from the higher-valence ions. The absorption edges of Ag I compounds appear at a lower energy.…”

Section: Resultsmentioning

confidence: 99%

Effect of Silver Content on the Structure and Antibacterial Activity of Silver-Doped Phosphate-Based Glasses

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Carroll

et al. 2007

Antimicrob Agents Chemother

104

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Staphylococcus aureus can cause a range of diseases, such as osteomyelitis, as well as colonize implanted medical devices. In most instances the organism forms biofilms that not only are resistant to the body's defense mechanisms but also display decreased susceptibilities to antibiotics. In the present study, we have examined the effect of increasing silver contents in phosphate-based glasses to prevent the formation of S. aureus biofilms. Silver was found to be an effective bactericidal agent against S. aureus biofilms, and the rate of silver ion release (0.42 to 1.22 g ⅐ mm ؊2 ⅐ h ؊1 ) from phosphate-based glass was found to account for the variation in its bactericidal effect. Analysis of biofilms by confocal microscopy indicated that they consisted of an upper layer of viable bacteria together with a layer (ϳ20 m) of nonviable cells on the glass surface. Our results showed that regardless of the silver contents in these glasses (10, 15, or 20 mol%) the silver exists in its ؉1 oxidation state, which is known to be a highly effective bactericidal agent compared to that of silver in other oxidation states (؉2 or ؉3). Analysis of the glasses by 31 P nuclear magnetic resonance imaging and high-energy X-ray diffraction showed that it is the structural rearrangement of the phosphate network that is responsible for the variation in silver ion release and the associated bactericidal effectiveness. Thus, an understanding of the glass structure is important in interpreting the in vitro data and also has important clinical implications for the potential use of the phosphate-based glasses in orthopedic applications to deliver silver ions to combat S. aureus biofilm infections.Staphylococcus aureus, a leading cause of nosocomial infections worldwide, is the etiological agent of a wide range of diseases, from relatively benign skin infections to potentially fatal systemic disorders (41). Many of these diseases, including endocarditis, osteomyelitis, and foreign body-related infections, appear to be caused by biofilm-associated S. aureus (14,18,27,38). Biofilms are sessile communities characterized by cells that are attached to a substratum or interface or to each other, embedded in a matrix of extracellular polymeric substances that they have produced, and exhibit an altered phenotype with respect to growth rate and gene transcription (14). Biofilm formation occurs as a result of a sequence of events: microbial surface attachment, cell proliferation, matrix production, and detachment (34). Biofilm-associated bacteria show decreased susceptibilities to antibiotics (10), disinfectants (31), and clearance by host defenses (14, 37). Work by Mulligan et al. (29,30) showed that the inclusion of copper or silver ions in phosphate-based glasses was useful in treating biofilms of Streptococcus sanguis. Silver cations exhibit broad antimicrobial action at low concentrations, and they are already being used for the treatment of burn wounds (32) and traumatic injuries (5, 15). Feng et al. (15) studied the antibacterial effects of si...

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Section: Resultsmentioning

confidence: 99%

Effect of Silver Content on the Structure and Antibacterial Activity of Silver-Doped Phosphate-Based Glasses

Valappil

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Carroll

et al. 2007

Antimicrob Agents Chemother

104

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“…Several studies [21][22][23][24][25] have reported the variations in the N 4 ratio (ratio of the concentration of BO 4 to the concentrations of different borate structural units of the network) upon addition of the network former SiO 2 to the network of lead borate-based glasses. The studies using moderate concentrations of PbO showed that SiO 4 tetrahedra were tied to the sequences with their apexes and, in such cases, the PbO entered the glass network as a glass modifier by forming [PbO 6 ] pyramids [26].…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic and structural features of some borosilicate glasses modified with heavy metals

Saddeek

2017

Bull Mater Sci

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A quaternary glass system Na 1.4 B 2.8 Si x Pb 0.3−x O 5.2+x , with 0 ≤ x ≤ 0.3, was prepared and studied by Fourier transform infrared spectroscopy, density and ultrasonic techniques to debate the issue of the role of SiO 2 in the structure of lead alkali borate glasses. The results indicate that SiO 2 generates an abundance of bridging oxygen atoms, [BO 4 ] and [SiO 4 ] structural units and changes the bonds B-O-B and Pb-O-B to Si-O-Si and B-O-Si. The latter bonds have higher bond strength and higher average force constant than the former bonds. Therefore, the glass structure becomes contracted and compacted, which decreases its molar volume and increases its rigidity. This concept was asserted from the increase in the ultrasonic velocity, Debye temperature and elastic moduli with the increase of SiO 2 content. The present compositional dependence of the elastic moduli was interpreted in terms of the electron-phonon anharmonic interactions and the polarization of Si 4+ cation. A good correlation was observed between the experimentally determined elastic moduli and those computed according to the Makishima-Mackenzie model.

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“…XAS (X-ray Absorption Spectroscopy) studies of glass materials are numerously reported in the material sciences literature, covering such disparate applications as the investigation of historic artifacts (e.g., [6]) or geological specimen (e.g., [7]), characterization of optical glasses for solid state lasers (e.g., [8]) or the encapsulation of radiotoxic residues from nuclear fuel reprocessing (notably the work of McKeown et al [9][10][11][12][13][14][15][16]). These studies benefit from the ability of X-ray Absorption Fine Structure (XAFS) measurements to provide direct chemical speciation (e.g., determination of oxidation states and coordination geometries) through analysis of the Xray Absorption Near Edge Structure (XANES) -without the need for any sample pretreatment -while the Extended X-ray Absorption Fine Structure (EXAFS) reveals structural details on the local coordination environments (bond lengths, neighboring atom types) of glass matrix constituents -unlike standard X-ray Diffraction (XRD) analysis, which is severely hampered by the amorphous nature of elemental networks in glassy materials lacking any long range order.…”

Section: Introductionmentioning

confidence: 99%

XAS and XRF investigation of an actual HAWC glass fragment obtained from the Karlsruhe vitrification plant (VEK)

Dardenne

González-Robles

Rothe

et al. 2015

Journal of Nuclear Materials

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Silver valence and local environments in borosilicate and calcium aluminoborate waste glasses as determined from X-ray absorption spectroscopy

Cited by 16 publications

References 13 publications

Effect of Silver Content on the Structure and Antibacterial Activity of Silver-Doped Phosphate-Based Glasses

Effect of Silver Content on the Structure and Antibacterial Activity of Silver-Doped Phosphate-Based Glasses

Ultrasonic and structural features of some borosilicate glasses modified with heavy metals

XAS and XRF investigation of an actual HAWC glass fragment obtained from the Karlsruhe vitrification plant (VEK)

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