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Ozone reacts slowly with Ag+ (circumneutral pH, k = (11 +/- 3) x 10(-2) M-1 s(-1)). After some time, ozone decay kinetics may suddenly become faster with the concomitant formation of silver sol. As primary process, an O-transfer f...
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Ozone reacts slowly with Ag+ (circumneutral pH, k = (11 +/- 3) x 10(-2) M-1 s(-1)). After some time, ozone decay kinetics may suddenly become faster with the concomitant formation of silver sol. As primary process, an O-transfer from O-3 to Ag(I) is suggested, whereby Ag(III) is formed [Ag+ + O-3 + 2 H2O Ag(OH)(3) + O-2 + H+]. This conproportionates with Ag(I), which is in large excess, leading to Ag(II) [Ag+ + Ag(OH)(3) ? 2 Ag(OH)(+) + HO-]. Further, Ag(II) reacts with ozone in a high exergonic reaction [Ag(OH)(+) + O-3 Ag + 2 O-2 + H+], where ozone acts as a reducing agent. Thereby, a single silver atom, Ag, is formed that can be oxidized by O-2 and O-3 or can aggregate to a silver sol. Aggregation slows down the rate of oxidation. When Ag+ is complexed by acetate ions, ozone decay and silver sol formation are speeded up by enhancing Ag(II) formation [Ag(I)acetate + O-3 Ag(III)acetate Ag(II) + CO2 + center dot CH3]. In the presence of oxalate, the formed complex reacts faster with ozone than Ag+, and Ag(III)oxalate decarboxylates rapidly [Ag(I)oxalate + O-3 Ag(III)oxalate Ag+ + 2 CO2]. This enhances ozone decay but prevents silver sol formation. Quantum chemical calculations have been carried out for substantiating mechanistic suggestions.
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Ion-selective electrodes (ISEs) are used in a wide variety of applications for determining the concentrations of various ions in aqueous solutions. When compared to many other analytical techniques, ISEs are relatively inexpensive...
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Ion-selective electrodes (ISEs) are used in a wide variety of applications for determining the concentrations of various ions in aqueous solutions. When compared to many other analytical techniques, ISEs are relatively inexpensive, simple to use, and have an extremely wide range of applications and concentrations. In recent reports, cytotoxicity of silver nanoparticles (AgNPs) showed that AgNPs were ionized in the cells and led to causing cell-death. Thus, the measurement of silver ions in aqueous phase is important. In this work, several sodium and potassium salts were considered as ionic-strength adjusters (ISA) and were used in the calibration step to enhance sensitivity of detection the target ion. The result showed that potassium iodine (0.05M KI) acted as a very effective ISA, compared to conventional ISA (5M NaNO3).
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Metal ions, especially the silver ion, were used to treat infection before the initiation of antibiotic therapy. Unfortunately, there is a lack of research on the metallic nanoparticle suspension as a reservoir for metal ion relea...
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Metal ions, especially the silver ion, were used to treat infection before the initiation of antibiotic therapy. Unfortunately, there is a lack of research on the metallic nanoparticle suspension as a reservoir for metal ion release application. For medical purposes, conversion of colloidal silver into an ionic form is necessary, but not using silver salts (e.g., AgNO_3, Ag_2SO_4), due to the fact that the counter-ion of silver salts may cause problems to the body as the silver ion (Ag~+) is consumed. The goal of this research is to develop a silver nanoparticle iontophoresis system (NIS) which can provide a relatively safe bactericidal silver ion solution with a controllable electric field. In this study, ion-selective electrodes were used to identify and observe details of the system's activity. Both qualitative and quantitative data analyses were performed. The experimental results show that the ion releasing peak time (R_(PT)) has an inversely proportional relationship with the applied current and voltage. The ion releasing maximum level (R_(ML)) and dosage (R_D) are proportional to the current density and inversely proportional to the voltage, respectively. These results reveal that the nanoparticle iontophoresis system (NIS) is an alternative method for the controlled release of a metal ion and the ion's concentration profile, by controlling the magnitude of current density (1 μA/cm~2 equal to 1 ppm/hour) and applied voltage.
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Background: The purpose of this study was to compare the effect of silver fluoride, silver nitrate and potassium fluoride on remineralization of demineralized enamel and dentine in vitro. Methods: Forty premolars were cut into cub...
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Background: The purpose of this study was to compare the effect of silver fluoride, silver nitrate and potassium fluoride on remineralization of demineralized enamel and dentine in vitro. Methods: Forty premolars were cut into cuboidal blocks. Acid-resistant varnish was painted onto each block to cover all surfaces, except two windows, one in enamel and one in dentine. The tooth blocks were placed in demineralizing solution for 96 hours. They were then randomly divided into four groups of 10 blocks each and immersed in solutions of AgF, AgNO3, KF or water for 3 minutes. Afterwards, they were immersed in a remineralizing solution for 108 hours. Micro CT scanning was conducted before and after remineralization. Results: The increase in linear attentuation coefficient (LAC) for the enamel lesions after remineralization was 1.08/cm, 0.95/cm, 0.86/cm and 0.60/cm in the AgF, AgNO3, KF and control groups, respectively (ANOVA, p < 0.001; AgF, AgNO3, KF > control; AgF > KF). The increase in LAC for the dentine lesions was 1.01/cm, 0.92/cm, 0.88/cm and 0.53/cm, respectively (ANOVA, p < 0.001; AgF, AgNO3, KF > control). Conclusions: Topical application of silver or fluoride ions can increase the mineral density of demineralized enamel and dentine lesions during remineralization. The synergistic effect of silver and fluoride ions is relatively small.
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A much studied oil-soluble surfactant, bis[2-ethylhexyljsulfosuccinate, sodium salt, was ion exchanged into the silver ion form and dissolved into microemulsionsof immiscible polyurethane step monomers. Coating andcuring of these ...
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A much studied oil-soluble surfactant, bis[2-ethylhexyljsulfosuccinate, sodium salt, was ion exchanged into the silver ion form and dissolved into microemulsionsof immiscible polyurethane step monomers. Coating andcuring of these microemulsions produced polyurethanecoatings that exhibit bactericidal activity against representative Gram negative bacteria. After 24 h exposure, 0.006-0.012% weight Ag relative to coating weight (0.0013-0.0025 mu mol Ag/cm~2) results in the three-log reduction in Escherichia coli. A slightly higher level of 0.031% weightAg relative to coating weight (0.006 mu mol Ag/cm~2) killedall of the E. coli after 12 h exposure. Similar results wereobtained for Pseudomonas aeruginosa. Since the doubletail surfactant anion promotes reverse micelle formation in many different kinds of oils and solvents, it appears anexcellent vector for incorporating low and effectiveamounts of silver ion into many industrial, hospital, andhousehold coating formulations.
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Owing to their antimicrobial properties, silver nanopartides (MPs) are the most commonly used engineered nanomaterial for use in a wide array of consumer and medical applications. Many discussions are currently ongoing as to wheth...
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Owing to their antimicrobial properties, silver nanopartides (MPs) are the most commonly used engineered nanomaterial for use in a wide array of consumer and medical applications. Many discussions are currently ongoing as to whether or not exposure of silver NPs to the ecosystem (i.e. plants and animals) may be conceived as hjirmful or not. Metallic silver, if released into the environment, can undergo chemical and biochemical conversion which strongly influence its availability towards any biological system. During this process, in the presence of moisture, silver can be oxidized resulting in the release of silver ions. To date, it is still debatable as to whether any biological impact of nanosized silver is relative to either its size, or to its ionic constitution. The aim of this review therefore is to provide a comprehensive, interdisciplinary overview-for biologists, chemists, toxicologists as wefl as physicists-regarding the production of silver NPs, its (as well as in their iorvic form) chemical and biochemical behaviours towards/within a multitude of relative and realistic biological environments and also how such interactions may be correlated across a plethora of different biological organisms.
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Silver nanoparticles (AgNPs) are increasingly used in various fields. However, little is known about the environmental effects of widespread use of products containing AgNPs. The objective of this study was to determine the ecotox...
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Silver nanoparticles (AgNPs) are increasingly used in various fields. However, little is known about the environmental effects of widespread use of products containing AgNPs. The objective of this study was to determine the ecotoxicity caused by AgNPs. The 48-h effective concentration 50 (EC50) values for Daphnia magna of suspensions of 60 nm and 300 nm AgNPs were 1.0 (95% confidence interval [CI] = 0.1-1.3) and 1.4 (95% CI = 0.3-2.1) μg Ag/l, respectively. The 96 h LC50 values for Oryzias latipes of 60 nm and 300 nm AgNP suspensions were 28 (95% CI = 23-34) and 67 (95% CI = 45-108) μg Ag/l, respectively. To show that toxicity is caused only by Ag~+ and not by AgNPs, Ag~+ was adsorbed onto the synthesized sorbents packed in a column and D. magna was exposed to the column-passed-300 nm AgNP suspensions. There was no acute toxicity with the AgNP suspensions not containing Ag ~+.
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The a.c. conductivity behaviour in the 20-300 K temperature range has been investigated for (Ag_2S)_x(AgPO_3)_(1-x) and (Ag_2SO_4)_x(AgPO_3)_(1-x) glasses at various salt contents (x). The temperature dependence at selected freque...
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The a.c. conductivity behaviour in the 20-300 K temperature range has been investigated for (Ag_2S)_x(AgPO_3)_(1-x) and (Ag_2SO_4)_x(AgPO_3)_(1-x) glasses at various salt contents (x). The temperature dependence at selected frequencies in the radio-and micro-wave region displays several relaxational contributions which are indistinct in the frequency domain. The low temperature experimental data are discussed and a proposed 'new universality' has been examined.
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The ease of generation of silver nanoparticles by using hexazamacrocyde ligand, L1 is utilized for the visual detection of the presence of silver ions at lower concentrations.
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