Studying the localized deposition of Ag nanoparticles on self-assembled monolayers by scanning electrochemical microscopy (SECM)

The local deposition of Ag nanoparticles (NPs) on ω-mercaptoalkanoic acid, HS(CH₂)_nCO₂H, (n = 2, 10) self-assembled monolayers (SAMs) by scanning electrochemical microscopy (SECM) is reported. We found that the presence of a SAM had a pronounced effect on Ag deposition. Experiments were conducted by applying different potentials to an Au(1 1 1) substrate either in the presence of a constant concentration of Ag⁺ ions in solution (bulk deposition) or by generating a flux of Ag⁺ from an Ag microelectrode that was positioned close to the Au(1 1 1) substrate (SECM deposition). SECM was used for generating a controlled flux of silver ions by anodic dissolution of an Ag microelectrode close to the SAMs modified Au(1 1 1). We found that the shape of the NPs was affected by the length of the carbon-chain of the SAM. Tetrahedral NPs were obtained on bare Au(1 1 1) surfaces while rod like and cubic Ag NPs were deposited onto 3-mercaptopropanoic acid (MPA) and 11-mercaptoundecanoic acid (MUA) SAMs, respectively. The size and shape of the deposited NPs were influenced by the deposition potential.We conclude that the shape and distribution of locally deposited Ag NPs on Au(1 1 1) can be controlled by modification of the substrate with a SAM and through controlling the Ag⁺ flux generated by SECM.     

Facile preparation of cds quantum dots using hyperbranched poly(amidoamine)s with hydrophobic end‐groups as nanoreactors

Hyperbranched poly(amidoamine)s with methyl ester terminals (HPAMAM) were synthesized by one‐pot approach and subsequently used as nanoreactors to prepare CdS quantum dots (QDs). HPAMAM could bind Cd²⁺ through their internal amines, while the external methyl ester groups prevented the aggregation of polymers. After reaction with S^2?, CdS QDs sequestered within individual hyperbranched polymers were obtained. The resulting CdS/HPAMAM nanocomposites were characterized by dynamic light scattering, transmission electron microscopy, ultraviolet‐visible spectroscopy, photoluminescence spectroscopy, and Fourier transform infrared spectroscopy, confirming the formation of CdS QDs with small particle size and narrow size‐distribution. Furthermore, the effects of Cd²⁺/S^2? ratio and aging time on the photoluminescence of CdS QDs were also investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Antimicrobial properties of silver nanoparticles synthesized by bioaffinity adsorption coupled with TiO2 photocatalysis

BACKGROUND: On the basis of effective bioaffinity adsorption of Ag⁺, silver nanoparticles (Ag NPs) were synthesized on the surface of chitosan‐TiO₂ adsorbent (CTA) by TiO₂ photocatalysis for crystal growth. RESULTS: Among the microstructure characterizations of the resulting silver nanoparticles‐ loaded chitosan‐TiO₂ adsorbent (Ag‐CTA), X‐ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive X‐ray (EDX) revealed the formation of metallic Ag on the CTA, which was further confirmed by the surface plasmon resonance of Ag NPs in the UV‐visible absorption spectrum. The underlying mechanism behind the formation of Ag NPs on the CTA by TiO₂ photoreduction was studied by Fourier transform infrared (FTIR) spectroscopy. The distinctive feature of Ag‐CTA after adsorption was the highly efficient antimicrobial activity in inactivating different test strains. In the case of Escherichia coli, 1.50 mg 1.67 wt% Ag‐CTA could totally inhibit 1.0–1.2 × 10⁷ colony forming units (CFU) in 100 mL nutrient medium, which was superior to that previously reported. CONCLUSIONS: CTA effectively adsorbed the precious metal ion Ag⁺ onto active imprinting sites on the adsorbent and then exerted efficient antimicrobial effects against diverse microbes. This research will be useful for designing a novel CTA‐based wastewater treatment for multi‐functional performance. Copyright © 2010 Society of Chemical Industry     

Preparation of Ag nanoparticles in the presence of low generational poly(ester‐amine) dendrimers

Stable Ag nanoparticles of 10–20 nm were prepared by reduction of AgNO₃ with NaBH₄ in water solution in the presence of low generational hydroxyl‐ terminated poly(ester‐amine) dendrimer G1.0 (OH)₁₆ and amino‐terminated poly(ester‐amine) dendrimer G1.5 (NH₂)₈ by optimizing preparation conditions. UV–vis absorption spectra and transmission electron microscopy were adopted to characterize absorption properties of Ag⁺/dendrimer complex, Ag/dendrimer nanocomposite aqueous solutions, and the morphology of the formed Ag nanoparticles, respectively. The results showed that the size of the Ag particles increased with Ag⁺/dendrimer molar ratio, and the size of Ag nanoparticles in Ag/G1.0 (OH)₁₆ system was larger than that of Ag nanoparticles in Ag/G1.5 (NH₂)₈ system, while the polydispersities of two systems were similar. Moreover, the Ag/G1.5 (NH₂)₈ nanocomposite system was more stable than the Ag/G1.0 (OH)₁₆ one. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 422–426, 2007     

Ag and Si Codoped Phosphate Glasses: Plasmonic Nanocomposites with Enhanced UV Transparency

The use of silicon powder to produce plasmonic Ag nanocomposite phosphate glasses which also exhibit improved transparency in the ultraviolet (UV) is proposed. Ag₂O/Si codoped glasses were prepared in a barium‐phosphate matrix by a simple melt‐quench method in ambient atmosphere. The as‐prepared glasses exhibit enhanced UV transparency, whereby the surface plasmon resonance of Ag nanoparticles (NPs) is manifested for the glasses with higher Ag₂O contents. ³¹P nuclear magnetic resonance spectroscopy is consistent with the formation of P–O–Si bonds, thus suggesting their possible role on the improved UV light transmission. Consequently, a model was presented accounting for the influence of silicon on the polymerization of the phosphate network concomitant with the creation of highly reactive oxygen species. Further exploiting the proposed reactive species, a real‐time spectroscopic study of the plasmonic response of Ag NPs in Ag/Si codoped glass samples was carried out during an in situ thermal processing. The temperature dependence of the Ag particle precipitation was studied in the 400°C–430°C range, from which an Arrhenius‐type plot allowed for estimating the activation energy of the process at 3.42 (±0.38) eV. Ultimately, the vanishing of the luminescence ascribed to Ag⁺ ions was observed in a heat‐treated sample, consistent with the high reactivity acquired by the glass matrix. Silicon thus appears promising for producing UV transparent glasses for high‐performance optics and for the reduction of Ag⁺ ions to produce Ag nanocomposites valuable for photonic (nanoplasmonic) applications.     

Graphene-gold nanostructure composites fabricated by electrodeposition and their electrocatalytic activity toward the oxygen reduction and glucose oxidation

A gold nanoparticles (Au NPs)-graphene nanocomposite (Au-graphene nanocomposite) was prepared by electrochemically depositing Au NPs on the surface of graphene sheets, and characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and electrochemical methods. The morphology and size of the Au NPs could be easily controlled by adjusting the electrodeposition time and the concentration of precursor (AuCl₄⁻). The electrocatalytic activities of the nanocomposites toward oxygen reduction and glucose oxidation were investigated by cyclic voltammetry. The results indicated that the nanocomposites had a higher catalytic activity than the Au NPs or graphene alone, indicating the synergistic effect of graphene and Au NPs. Therefore, this study has provided a general route for fabrication of graphene-based noble metal nanomaterials composite, which could be potential utility to fuel cells and bioelectroanalytical chemistry.     

Biological synthesis of bimetallic Au/Ag nanoparticles using Persimmon (<Emphasis Type="Italic">Diopyros kaki</Emphasis>) leaf extract

Persimmon (Diopyros kaki) leaf extract was used for the synthesis of bimetallic Au/Ag nanoparticles. Competitive reduction of Au³⁺ and Ag⁺ ions present simultaneously in solution during exposure to Persimmon leaf extract leads to the formation of bimetallic Au/Ag nanoparticles. UV-visible spectroscopy was monitored as a function of reaction time to follow the formation of Au/Ag nanoparticles. The synthesized bimetallic Au/Ag nanoparticles were characterized with energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). SEM images showed that large Au/Ag particles of 50–500 nm were formed with some cubic structure, while pure Ag particles obtained by reduction of only Ag+ ion were smaller with diameter of 15–90 nm and predominantly spherical. The atomic Ag contents of the bimetallic Au/Ag nanoparticles from EDS and XPS analysis were 36 and 71 wt%, respectively, suggesting that bimetallic Au core/Ag shell structure was formed by competitive reduction of Au³⁺ and Ag+ ions with Persimmon leaf extract. This work was presented at 13 ^th YABEC symposium held at Seoul, Korea, October 20–22, 2007.     

Selective preparation of Ag species on photoluminescence of Sm3+ in borosilicate glass via Ag+-Na+ ion exchange

Photoluminescence (PL) of rare earth ion-doped glasses could be enhanced by diverse Ag species such as Ag⁺ ions, Ag⁺-Ag⁺ pairs, Ag nano-clusters (NCs), and Ag nanoparticles (NPs). Selective preparation of silver species in rare earth ion-doped glasses is a crucial step to obtain the luminescence enhancement of rare earth ions caused by the different silver species. In this work, Ag⁺ ions and Ag NCs were selectively prepared in the Sm³⁺-doped borosilicate glass via the Ag⁺-Na⁺ ion exchange. The influence of AgNO₃/NaNO₃ ratio in the molten salt on the Ag existing states was investigated. The results demonstrate that the isolated Ag⁺ ions exist in the Sm³⁺-doped borosilicate glass when the ratio of AgNO₃/NaNO₃ is 1/1000. The Ag NCs are formed in the Sm³⁺-doped borosilicate glass when the AgNO₃/NaNO₃ ratio is 1/10. The influence of Ag⁺ ions or Ag NCs on the PL of Sm³⁺ was systematically investigated. The results show that the PL of Sm³⁺ was enhanced by the energy transfer from Ag⁺ ions or Ag NCs to Sm³⁺.     

Enhanced mechanical properties and bactericidal activity of polypropylene nanocomposite with dual‐function silica–silver core‐shell nanoparticles

Dual‐function silica–silver core‐shell (SiO₂@Ag) nanoparticles (NPs) with the core diameter of 17 ± 2 nm and the shell thickness of about 1.5 nm were produced using a green chemistry. The SiO₂@Ag NPs were tested in vitro against gram‐positive Staphylococcus aureus (S. aureus) and gram‐negative Escherichia coli (E. coli), both of which are human pathogens. Minimal inhibitory concentrations of the SiO₂@Ag NPs based on Ag content are 4 and 10 μg mL^?1 against S. aureus and E. coli, respectively. These values are similar to those of Ag NPs. SiO₂@Ag NPs were for the first time incorporated to a commodity polypropylene (PP) polymer. This yielded an advanced multifunctional polymer using current compounding technologies i.e., melt blending by twin‐screw extruder and solvent (toluene) blending. The composite containing 5 wt % SiO₂@Ag NPs (0.05 wt % Ag) exhibited efficient bactericidal activity with over 99.99% reduction in bacterial cell viability and significantly improved the flexural modulus of the PP. Anodic stripping voltammetry, used to investigate the antibacterial mechanism of the composite, indicated that a bactericidal Ag⁺ agent was released from the composite in an aqueous environment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Green Chemical Synthesis of Silver Nanoparticles and its Catalytic Activity

Silver nanoparticles (Ag(0) NPs) were synthesized by the chemical reduction method, in which ceftriaxone (antibiotic) used as reducing (to convert Ag⁺ to Ag(0)) and capping agent. UV–Visible spectroscopy revealed the first indication of formation of Ag(0) NPs. FT-IR spectroscopy showed the interaction of formation of bonding between antibiotic standard and silver. X-ray powder diffraction powder pattern confirmed the crystalline nature of prepared Ag(0) NPs. These Ag(0) NPs were used as catalyst for three organic hazardous chemicals i.e., 4-nitro-1,3-Phenylene diamine, 6-methyl-2-nitroanilline, 4-methyle-2-nitroanilline. The prepared Ag(0) NPs showed good catalytic activity against these compounds.     

Preparation and characterization of SiO2/polydopamine/Ag nanocomposites with long-term antibacterial activity

Silver nanoparticles (Ag NPs) with diameter of approximately 10 nm were prepared by the reduction of silver nitrate using green synthesis, an eco-friendly approach. The synthesized Ag NPs were homogeneously deposited on silicon dioxide (SiO₂) particles modified with dopamine, leading to the formation of SiO₂/polydopamine (PD)/Ag nanocomposites (NCs) with a core–shell–satellite structure investigated by transmission electron microscopy. The Ag content of SiO₂/PD/Ag NCs determined by inductively coupled plasma optical emission spectrometry was approximately 5.92 wt%. The antibacterial properties of both Ag NPs and SiO₂/PD/Ag NCs against Vibrio natriegens (V. natriegens) and Erythrobacter pelagi sp. nov. (E. pelagi) were investigated by bacterial growth curves and inhibition zone. Compared to Ag NPs, the SiO₂/PD/Ag NCs exhibited superior long-term antibacterial activity, attributed to its controlled release of Ag⁺ ions.     

Strategy for the syntheses of isolated fine silver nanoparticles and polypyrrole/silver nanocomposites on gold substrates

In this work, isolated fine silver nanoparticles and polypyrrole/silver nanocomposites with diameters of about 10 nm on gold substrates were first prepared by electrochemical methods. First, an Ag substrate was cycled in a deoxygenated aqueous solution containing 0.1 M HCl from −0.30 to +0.30 V versus Ag/AgCl at 5 mV/s with 30 scans. Subsequently the Ag working electrode was immediately replaced by an Au electrode and a cathodic overpotential of 0.2 V was applied under controlled sonication to synthesize Ag nanoparticles on the Au electrode. Then pyrrole monomers were encouragingly found to be polymerized on the deposited Ag nanoparticles. This polymerization is distinguishable from the known chemical or electrochemical one, due to the electrochemical activity of unreduced species of Ag_n⁺ clusters inside the nanoparticles. Also, this polymerization may be ascribed to the oxidizing agent of AuCl₄⁻, which is present on the Au electrode.     

Luminescence Enhancement of CdS Quantum Dots in Glass by Ag+ Ion Exchange

Luminescence of CdS quantum dots (QDs) enhanced by the induction of Ag nanoparticles (NPs) in glasses was investigated. Ag⁺ ions diffused into glasses containing CdS QDs by ion exchange, then formed Ag NPs after subsequent heat treatment. Luminescence intensity of CdS QDs increased approximately three times when the ion‐exchange duration was 1 min, but was severely quenched when the duration was extended to 30 min. Increasing the amount of Ag⁺ ions increased the number of Ag NPs and decreased the average distance between Ag NPs and CdS QDs. This decrease in the average distance induced the changes of luminescence intensity.     

Enhanced room temperature coefficient of resistivity (RT-TCR) and broad metal-insulator transition temperature (TMI) of La0.67Ca0.33-xAgxMnO3 polycrystalline ceramics

Polycrystalline La_0.67Ca_0.33-xAg_xMnO₃ (LCAMO, x = 0, 0.06, 0.15, 0.18, and 0.24) ceramics were fabricated by conventional sol-gel route at relatively low sintering temperature of 1100 °C for 12 h. Effects of silver content (x) on crystal structure, grain size, resistivity and magnetic properties of as-prepared LCAMO specimens were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), elemental mapping and energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and standard four-probe method (ρ-T). The data from XPS, XRD and EDS revealed that silver existed as Ag⁺ ions in the lattice matrix position of LCAMO ceramics. Broad metal-insulator transition temperature (T_MI) values ranging from 267.0 K (x = 0) to 302.6 K (x = 0.24) were obtained with LCAMO specimens prepared with variable Ag⁺ added contents. Peak temperature coefficient of resistivity (TCR) enhanced from 4.1% K⁻¹ at 263.2 K (for x = 0) to 10.9% K⁻¹ at 278.5 K (for x = 0.18), and reached 7.5% K⁻¹ at room-temperature (295.9 K) for x = 0.24. Meanwhile, magnetoresistance (MR) of materials reached 17.7% at room-temperature (299.2 K) for x = 0.24. Overall, these findings demonstrated that Ag doping was beneficial for improving electrical and magnetic properties of LCAMO materials. In summary, LCAMO ceramics achieved RT-TCR and MR at optimal Ag stoichiometric ratio, promising for applications in infrared bolometers or magnetic sensors.     

Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag⁺ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO₃)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO₃/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO₃ and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO₃. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM).     

Polyelectrolytes with sulfonate groups obtained by chemical modification of chitosan useful in green synthesis of Au and Ag nanoparticles

Usually the metal nanoparticles are obtained by different chemical reactions that are not environmentally friendly. This paper describes the synthesis of two polyelectrolytes with sulfonate groups in ortho‐position and in ortho‐ and para‐positions, which were obtained by chemical modification of chitosan. They were used in the green synthesis of Au and Ag nanoparticles by colloidal method in aqueous solution. Polyelectrolytes were used as reducing agents of Au³⁺ and Ag⁺ ions and as stabilizing agents of Ag and Au nanoparticles. The hydroxyl and imine groups in the polyelectrolytes are reducing agents of Au³⁺ and Ag⁺ ions while the sulfonate groups and the polymer backbone stabilized Au and Ag nanoparticles. Polyelectrolyte 1, which has sulfonate group in ortho‐position, favors the obtaining of anisotropic Au nanoparticles with an average size of 19 nm. While the polyelectrolyte 2, with two sulfonate groups in the ortho‐ and para‐positions, yielded quasi‐spherical Au nanoparticles with an average size of 14 nm. In general, Ag nanoparticles stabilized with both polyelectrolytes, show quasi‐spherical forms with good control in size. Finally, both polyelectrolytes have the ability to protect the Au and Ag nanoparticles allowing obtaining colloidal solutions that are stable for several months. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45240.     

Infusion of Ag‐Ion from Aqueous Solution into Solid Calcium Phosphate of Hydroxyapatite (HA) Crystal Structure

In contrast to extensive literature concerning Ag incorporation in hydroxyapatite, HA, while the phosphate approximated to stoichiometry of Ca₁₀(PO₄)₆(OH)₂, with added Ag has been precipitating from an aqueous solution, the paper presents Ag incorporation through Ag ion infusion from AgNO₃ solution into solid HA pressed in pellet and ignited at 800°C. After Ag ions infused into the HA‐solid (crossed the interfacial solution‐solid boundary), they diffused across the crystal structure to a depth of time‐dependent several mm. The path of Ag diffusion in the solid HA was recorded using SEM‐EDS point analyses of Ag, Ca, P, EDS‐linear analyses of those elements, and elemental mapping. Time‐dependent concentrations of Ag⁺, Ca²⁺, and PO₄^3? in AgNO₃ solutions were also analyzed. The appearance of Ag in the crystalline HA with simultaneous local depletion in Ca and phosphate recorded as P, observed by EDS with simultaneous appearance of Ca²⁺ and PO₄^3? ions and a decrease in Ag⁺ concentration in AgNO₃ solution led the authors to a conclusion that Ag⁺ for Ca²⁺ substitution supported by PO₄^3? charge balancing in the crystalline HA was in process. The HA particles in the section of the pellet without Ag had a uniform shape and size approximated to 300–400 nm. SEM image of the HA solid section, where Ag ions appeared was characterized by irregular aggregates of smaller crystals with sporadically present large, shaped in prism blocks identified by the XRD as Ag₃PO₄.     

Photocatalytic Performance of Nitrogen‐Doped and Cu2+ and Ag+ Co‐Doped Sodium Trititanate

Nano‐sized (i) N‐doped sodium trititanate and (ii) N and Cu²⁺ (Ag⁺) co‐doped sodium trititanates CuTi₃NO_6?x (Ag₂Ti₃NO_6?x) were prepared by a solid‐state and ion‐exchange methods, respectively. The materials were characterized by EDS, PXRD, XPS, FESEM, TEM, UV–visible DRS, and Raman spectroscopy. All the materials were crystallized in monoclinic lattice with P21/m space group. The bandgap energy of all the samples was deduced from their UV–visible DRS profiles. Visible‐light‐induced photocatalytic oxidation of the methylene blue (MB) and methyl orange (MO), cyclohexene and phenol, was examined. The Ag⁺ co‐doped trititanate exhibited the highest photocatalytic activity among the materials investigated.     

A novel shape-controlled synthesis of dispersed silver nanoparticles by combined bioaffinity adsorption and TiO2 photocatalysis

Shape-controlled silver nanoparticles (Ag NPs) were prepared in a well-dispersed mode on the active imprinting sites of chitosan-TiO₂ adsorbent (CTA) by means of bioaffinity adsorption and TiO₂ photocatalysis. Nontoxic hydrogen peroxide (H₂O₂) was used as a suitable etching reagent in our production of shape-controlled Ag NPs, since it could regulate the TiO₂ photocatalysis and accelerate the generation of O₂. With the same amount of H₂O₂ addition, silver nanocubes, nanospheres and truncated triangular nanoplates were individually obtained on the surface of CTA under UV irradiation by facilely adjusting the initial Ag⁺ concentration. The FE-SEM, XRD and UV-visible characterizations confirmed single crystal Ag NPs with different shapes loaded on CTA. The mechanism for the formation of shape-controlled Ag NPs was discussed based on a photocatalytic reaction system. As an example of applications of the Ag NPs, we tested the biocidal properties, and silver nanocubes exhibited the highest antibacterial activity. Our research provided a simple synthesis for shape-regulated Ag NPs steadily loaded on CTA. It might moreover be a guide in preparing metal nanocrystals monodispersely immobilized on chemical substrates.     

Reaction of Ozone with Ag(I)—Mechanistic Considerations

Ozone reacts slowly with Ag⁺ (circumneutral pH, k = (11 ± 3) × 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 O₃ to Ag(I) is suggested, whereby Ag(III) is formed [Ag⁺ + O₃ + 2 H₂O → Ag(OH)₃ + O₂ + 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)⁺ + O₃ → Ag + 2 O₂ + H⁺], where ozone acts as a reducing agent. Thereby, a single silver atom, Ag, is formed that can be oxidized by O₂ and O₃ 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 + O₃ → Ag(III)acetate → Ag(II) + CO₂ + ?CH₃]. In the presence of oxalate, the formed complex reacts faster with ozone than Ag⁺, and Ag(III)oxalate decarboxylates rapidly [Ag(I)oxalate + O₃ → 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.