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Kozin, L. F.; Bogdanova, A. K.

doi:10.1023/a:1012532729676

Cited by 10 publications

(15 citation statements)

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“…The authors of [6], by analogy with gold complexes [AuX 2 ] -(where X is Cl -, Br -, and CN -) assumed that a complex [AuRCA 2 ]X should be formed in the Au-TCA system. However, according to [10][11][12][13][14], the elements of the Ib subgroup of the Mendeleev Periodic System, viz., Cu(I), Cu(II), Ag(I), and Au(I) form thiocarbamide complexes of a [MeTCA n ] + composition (where n = 1, 2, 3, 4). According to [14], depending on the experimental conditions of the anodic dissolution of Ib-subgroup metals, the reaction order in TCA can equal 1, 2, and 3.…”

Section: Resultsmentioning

confidence: 99%

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

2005

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Kinetics and mechanism of gold electrooxidation in sulfuric acid solutions of thiocarbamide ( TCA ) are studied by measuring voltammograms ( VA ) of gold and glassy carbon ( GC ) electrodes. In a potential ( E ) range from -0.2 to 1.2 V ( SCE ), VA of a gold electrode demonstrate three peaks. The first and the second peaks correspond to gold electrooxidation to [AuTCA ads ] + and [Au(TCA ads ) 3 ] 3+ ions at E of 0.152 and 0.554 V, while the third one corresponds to TCA electrooxidation. The electrooxidation of TCA on GC electrodes is characterized by two VA peaks at 0.983 and 1.437 V. The first peak corresponds to the formation of formamidine disulfide (FADS) ( k a1 = 6.40 × 10 -4 cm/s), while the second peak corresponds to TCA oxidation to sulfides and hydrosulfides ( k a2 = 7.78 × 10 -5 cm/s). The composition of adsorption layers formed at the Au electrode is analyzed by Auger spectroscopy. The introduction of sodium sulfide into TCA solutions eliminates the formation of adsorption layers and accelerates Au oxidation in such solutions. The rate constants of gold electrooxidation k a = 6.31 × 10 -3 cm/s and Au(I) electroreduction k c = 5.46 × 10 -4 cm/s in TCA solutions are estimated. Kinetic parameters (charge transfer coefficients, reactions orders in carbamide) are determined and the mechanisms of Au and TCA oxidation in sulfuric acid solutions are proposed.

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Section: Resultsmentioning

confidence: 99%

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

2005

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“…Corrosion dissolution of silver in ligand solutions (cyanates, thiocarbamides, chlorides, and bromides) proceeds at a sufficiently high rate only in the presence of such oxidizers as hydrogen peroxide, iron (III) sulfate, potassium dichromate, oxygen, and other [1,2]. Of a particular interest is the mechanism of the corrosion dissolution of silver in solutions of (NH 2 ) 2 C = S thiocarbamide, which is an analog of (NH 2 ) 2 (NH)C = S thiosemicarbazide ( TSC ).…”

Section: Introductionmentioning

confidence: 99%

“…Thus appeared positively charged silver (I) dithiocarbamide complexes are electrostatically repulsed from the surface of a positively charged metallic silver and transferred to the diffusion layer of the solution where they can interact with thiocarbamide molecules to form [{(NH 2 ) 2 C=S} 3 Ag] + silver (I) trithiocarbamide ions. Therefore, during the corrosion dissolution of silver in acidic solutions, thiocarbamide acts simultaneously as an oxidizer (FAD) and a ligand in a two-step formation of the silver (I) trithiocarbamide complex [1,2]. Thiocarbamide is unstable in aqueous solutions and undergoes hydrolysis with time.…”

Section: Introductionmentioning

confidence: 99%

“…Thiocarbamide is unstable in aqueous solutions and undergoes hydrolysis with time. Hydrolysis of thiocarbamide in aqueous solutions results in the appearance of hydrosulfide and sulfide ions, which adsorb on the silver surface and interact with Ag(I) ions (the silver oxidation products) to produce complex adsorption layers composed of silver sulfides and hydrosulfides, as well as adsorbed TSC molecules [2]. The TSC molecules inhibit the corrosion dissolution of silver similarly to gold in thiocarbamide solutions.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Sodium Thiocyanate on the Corrosion Dissolution Rate of Silver in Thiosemicarbazide Solutions

Kozin

Danil’tsev

2005

Prot Met

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The effect of thiocyanate on the corrosion dissolution rate of silver in thiosemicarbazide (TSC) ammonium-chloride-bromide solutions was studied by using gravimetry and rotating disc electrode technique. The corrosion dissolution of silver was shown to be preceded by the formation of dithiosemicarbazide molecules due to the oxidation with iron (III) ions. The "second ligand" phenomenon is discussed, which consists in an increase in the corrosion dissolution rate of silver upon adding sodium thiocyanate (STC) to a TSC solution because of the decrease in the adsorption layer thickness. A synergism was discovered in the case of the corrosion dissolution of silver in a solution containing both thiosemicarbazide and sodium thiocyanate. The composition of the adsorption layer formed on a silver electrode and involving silver, sulfur (AgHS and Ag 2 S), as well as carbon, nitrogen, and oxygen forming the base of adsorption layers, was investigated by means of Auger spectrometry. The kinetic parameters (rate constants and reaction orders) were determined and a mechanism of the corrosion dissolution of silver in TSC, STC, and TSC + STC solutions is proposed.

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“…Chen et al [61] reported on diaminosubstituted dicarbene silver-containing compounds. Kozin and Bogdanova [62] established that silver forms well-soluble tri-coordinated complex ions in thiocarbamide solutions:…”

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Ligands of biologically active compounds in the nanochemistry of silver and gold (A review)

Evstigneeva

Пчелкин

2006

Pharm Chem J

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Examples of the interactions of gold and silver clusters with various organic compounds containing olefinic and carbonyl groups capable of acting as ligands for the formation of coordination compounds with these metals are considered. Common physicochemical properties of the coordination complexes of silver ions with olefins are described. The behavior of olefins as ligands of the coordination complexes with silver ions in liquid chromatographic systems is analyzed. There is a correlation between the lipophilicity of such organic molecules and the possible variations of the coordination numbers of metal atoms, as well as between the degree of unsaturation of olefin chains in these molecules and the electrical conductivity of thin films of related lipids (including those of natural origin). Such complexes can be used in nanotechnology for the creation of biocomputer memory cells.

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Cited by 10 publications

References 1 publication

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

The Effect of Sodium Thiocyanate on the Corrosion Dissolution Rate of Silver in Thiosemicarbazide Solutions

Ligands of biologically active compounds in the nanochemistry of silver and gold (A review)

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