- pH-insensitive fabrication of gold nanoparticles with high concentration by ultrasound-assisted electrochemical process via aid of chitosan
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In this work, we report a new pathway to prepare pure gold nanoparticles with high concentrations in acid solutions via the aid of chitosan without the addition of other stabilizers and reductants based on electrochemical methods. Interestingly, this fabrication of gold nanoparticles with high concentrations in solutions is pH-insensitive. The characteristics of prepared gold nanoparticles were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (HRXPS) measurements. Experimental results indicate the concentration and the particle size of Au nanoparticles prepared in 0.1N HCl are ca. 50 ppm and 12 nm in diameter, respectively. Similar experiment performed in 0.1N NaCl with the aid of chitosan shows that the corresponding concentration of prepared Au nanoparticles is ca. 100 ppm. Further similar experiments performed in 0.1N HCl and 0.1N NaCl without the aid of chitosan show that the corresponding concentrations of prepared Au nanoparticles are ca. 1 and 60 ppm, respectively.
- Yang, Kuang-Hsuan,Liu, Yu-Chuan,Hsu, Ting-Chu,Tsai, Huei-Ian
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- Decamethylferrocene redox chemistry and gold nanowire electrodeposition at salt crystal|electrode|nonpolar organic solvent contacts
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This report describes exploratory experimental findings for electrochemical processes in nonpolar solvents (hexane, toluene, and dichloroethane). Conventional 3 mm diameter glassy-carbon-disk electrodes are used in contact with a crystalline salt electrolyte (ammonium nitrate) immersed in nonpolar solvents. The insoluble salt is employed as a "surface thin film electrolyte", with humidity causing electrical connection from the working electrode to the SCE counter-reference electrode. The organic solvents are employed without intentionally added electrolyte. Humidity in the nonpolar solvents is shown to be essential for the processes to work. The oxidation of decamethylferrocene is demonstrated as a test organometallic redox system. The electrochemical reduction of Au(III) in toluene (solubilized with tetraoctylammonium bromide, TOABr) is employed to demonstrate and visualize the reaction zone around salt crystal|working electrode contact points. Gold nanowire bundle formation is observed, presumably due to an ordered interfacial surfactant microphase at salt|electrode contact points. The triple phase boundary nature of these processes is discussed, and future applications are suggested.
- Watkins, John D.,Hotchen, Christopher E.,Mitchels, John M.,Marken, Frank
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- Gold(III) extraction by 1,3-Bis(2'-acetoxymethylthiobutyl-3'- thiobutylpropyl)-6-methyluracyl from hydrochloric acid solutions
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Gold(III) extraction by 1,3-bis(2'-acetoxymethylthiobutyl-3'- thiobutylpropyl)-6-methyluracyl from 0.5 M HCl solutions to chloroform is studied. The reagent has a high efficiency, separates gold(III) ions from the sum of nonprecious and ferrous metals, and can be repeatedly used after stripping. The extraction mechanism is solvation, with Au-S coordination bonds formed with all sulfur atoms of the reagent; the solvation number changes from 1 to 0.25 with increasing gold(III) aqueous concentration.
- Khisamutdinov,Murinov,Baikova
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- Extraction of gold(III), palladium(II), and platinum(IV) by 1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole from hydrochloric acid solutions
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The extraction of gold(III), palladium(II), and platinum(IV) with 1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole from hydrochloric acid solutions into toluene has been studied. The extraction follows the anion-exchange mec
- Khisamutdinov,Murinov,Shitikova
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- Photooxidation of dicyanoaurate(I) induced by metal-to-ligand charge transfer excitation
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The irradiation of [Au(CN)2]- in oxygen-saturated acetonitrile leads to photooxidation of Au(I). In the presence of additional chloride [Au(CN)2Cl2]- is formed with φ = 0.5 × 10-4 at λ
- Kunkely, Horst,Vogler, Arnd
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- Mixed valent gold oxides: Syntheses, structures, and properties of Rb5Au3O2, Rb7Au5O2, and Cs7Au5O2
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The title compounds Rb5Au3O2, Rb7Au5O2, and Cs7Au5O2 are the first examples of mixed valent phases containing gold in the oxidation states +1 and -1. Their
- Mudring, Anja-Verena,Nuss, Juergen,Wedig, Ulrich,Jansen, Martin
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- Synthesis of: N-(3-aminopropyl)imidazole-based poly(ionic liquid) as an adsorbent for the selective recovery of Au(III) ions from aqueous solutions
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The synthesis of a novel poly(ionic liquid) adsorbent (PIL-APIBCl) through the modification of poly(styrene-co-maleic anhydride) (PSMA) composites with N-(3-aminopropyl)imidazole (API) and benzyl chloride (BCl) is presented. The structural analysis was carried out by nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FT-IR). Batch adsorption experiments revealed that the investigated adsorbent exhibited good selectivity and a high adsorption capacity of 236.68 mg g-1 towards tetrachloroaurate (Au(III)) ions at pH 1.0 over a wide temperature range. The adsorption isotherms and kinetics of Au(III) on the PIL-APIBCl were fitted well by the Langmuir isotherm model and pseudo-second-order model, respectively, indicating successful chemical adsorption of Au(III) ions on the adsorbent surfaces. According to FESEM, FT-IR, XPS and NMR analysis, the adsorption mechanisms of Au(III) on PIL-APIBCl could be ascribed to electrostatic and intermolecular interactions. Therefore, due to its good cyclability and low cost, PIL-APIBCl is a promising adsorbent for Au(III) recovery from wastewater on a large scale. This journal is
- Gui, Wenjun,Shi, Yun,Wei, Jia,Zhang, Zhifang,Li, Ping,Xu, Xia,Cui, Yanjun,Yang, Ying
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- Ionic gold demonstrates antimicrobial activity against Pseudomonas aeruginosa strains due to cellular ultrastructure damage
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Due?to the ever-increasing rise of antimicrobial?resistant (AMR)?bacteria, the?development of?alternative antimicrobial agents is a global priority. The antimicrobial activity of ionic gold was explored against four Pseudomonas aeruginosa strains with different AMR profiles in order?to determine the antimicrobial activity of ionic gold and elucidate the mechanisms of action. Disc diffusion assays (zone of inhibition: ZoI) coupled with minimum inhibitory/bactericidal concentrations (MIC/MBC) were conducted to determine the antimicrobial efficacy of ionic gold. Scanning electron microscopy (SEM) was used to visualise morphological changes to the bacterial cell ultrastructure. Strains with increased AMR were slower to grow?which is likely a?fitness cost due to?the enhanced AMR activity. Although greater concentrations of ionic gold were required to promote antimicrobial activity, ionic gold demonstrated similar antimicrobial values?against all strains tested. Lowry assay results indicated that protein leakage was apparent following incubation with ionic gold, whilst SEM revealed?cellular ultrastructure damage. This study suggests that the application of ionic gold as an alternative antimicrobial?is promising, particularly against AMR P. aeruginosa. The antimicrobial activity of ionic gold against P. aeruginosa could potentially be utilised as an alternative therapeutic option in wound management, an approach that could benefit healthcare systems worldwide.
- Torres, Miguel Reyes,Slate, Anthony J.,Ryder, Steven F.,Akram, Maliha,Iruzubieta, Conrado Javier Carrascosa,Whitehead, Kathryn A.
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- DISPLACEMENT BY CHLORIDE OF PYRIDINE-2-CARBOXYLATE FROM DICHLORO(PYRIDINE-2-CARBOXYLATO)GOLD(III) IN ACIDIC SOLUTION; THE POSITION OF RING OPENING
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The kinetics of the reaction + 2Cl- - + +HN-OH (where N-O = pyridine-2-carboxylate) have been studied at 25 deg C in methanol-water (95:5,v/v).In the presence of excess of chloride, the reaction involves a fast and reversible ring opening with Au-N bond breaking (K1 = 3.16 dm3 mol-1) and a reversible protonation of the free nitrogen (K2 = 640 dm3 mol-1, corresponding to a pKa of 2.80) followed by a typical associatively activated displacement of the O-bonded ligand by chloride, with the usual rate law, kobs. = k1 + k2-> where k1 (the solvolytic rate constant) = 1.9 1E-4 s-1 and k2 = 4.54 1E-2 dm3 mol-1 s-1.In the absence of chloride a solvolytic ring opening can be observed but the reaction stops before the monodentate ligand is displaced.
- Annibale, Giuliano,Canovese, Luciano,Cattalini, Lucio,Marangoni, Giampaolo,Michelon, Gianni,Tobe, Martin L.
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- Ring opening and displacement by chloride of the bidentate chelate ligand from dichloro[pyridine-2-(α-methoxymethanolato)]gold(III) - A kinetic and mechanistic study
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The kinetics of ring opening and displacement of the bidentate chelate ligand from dichloro[pyridine-2-(α-methoxymethanolato)]gold(III) [Au(N-O)Cl2] (1) have been studied spectrophotometrically in methanol/water (95:5, v/v) at 25°C and constant ionic strength (I = 1 mol dm-3, LiClO4). In the presence of LiCl and perchloric acid the reaction consists of a pre-equilibrium protonation of the coordinated oxygen followed first by ring opening at oxygen accompanied by the entry of chloride or solvent and fast acetalisation of the hemiacetalic form of the ligand to give [AuCl3(N-OMe)], and then by displacement of the N-bonded ligand to give [AuCl4]-. The ligand is not displaced in the absence of chloride and no reaction is observed in the presence of chloride alone. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Marangoni, Giampaolo,Pitteri, Bruno,Annibale, Giuliano,Bortoluzzi, Marco
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- The Preparation of Trichloro(phenyl 2-pyridylmethyl sulphoxide)gold(III) and the Kinetics and Equilibria of its Formation and Subsequent Reactions
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In the complex , formed between (1-) and phenyl 2-pyridylmethyl sulphoxide (N-SO), the ligand is bound only through the nitrogen and all attempts to induce chelation were unsuccessful.The kinetics of the forward and reverse reactions i
- Cattalini, Lucio,Chessa, Gavino,Marangoni, Giampaolo,Pitteri, Bruno,Tobe, Martin L.
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- Redispersion of transition metal nanoparticle catalysts in tetraalkylphosphonium ionic liquids
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Despite the fact that particle sintering is one of the most common events leading to the deactivation of metal nanoparticle (NP) catalysts, there is a paucity of studies investigating potential routes for the regeneration of smaller, catalytically active nanoparticles from larger particles formed after repeated catalytic cycles. Here, we reveal a simple yet elegant technique for the 'redispersion' of sintered NPs in tetraalkylphosphonium halide ionic liquids (ILs). The procedure described can use environmentally benign oxidants, be carried out at mild temperatures, and is shown to be applicable to a large number of catalytically important transition metals. TEM and UV-Vis spectroscopy reveal that this methodology can indeed regenerate smaller NPs from sintered systems. A sample catalytic reaction reveals that the redispersed NPs are as catalytically active as they were prior to sintering.
- Banerjee, Abhinandan,Theron, Robin,Scott, Robert W. J.
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supporting information
p. 3227 - 3229
(2013/05/08)
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- Displacement of neutral nitrogen donors by chloride in AuCl3(am) (am = pyridines and amines): Kinetics and DFT calculations show the effects of basicity and π-acceptor ability
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The kinetics of the process AuCl3(am) + Cl- → AuCl4- + am (am = sp2 N-donor isosteric pyridines with different π systems and sp3 amines; they cover a wide range of basicity) have been studied in methanol at 25°C. The reactions obey the usual two-term rate law observed in substitutions on square-planar complexes. The second-order rate constants, k2, are very sensitive to the nature of the leaving group, and plots of log k2 against the pKa of the conjugate acids are linear, with the same slope, -0.68, for both normal pyridines and pyridines with a more extended π system, such as 4-cyanopyridine, isonicotinic acid, methyl isonicotinate and 4-acetylpyridine. The reactivity of the considered N-donors is different and follows the order sp3 N-donors > normal pyridines > π-extended pyridines. This result, with the support of ground-state DFT calculations on the AuCl3(am) derivatives, is explained on the basis of an Au-N bond enforcement due to an increased π-back-donation contribution. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Pitteri, Bruno,Bortoluzzi, Marco
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p. 4456 - 4461
(2008/03/12)
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- Displacement of neutral nitrogen donors by chloride in AuCl 3(3R-py) (3R-py = meta-substituted pyridine): Comparison between meta- and para-substituted pyridines by kinetics and DFT calculations
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The kinetics of the process AuCl3(3R-py) + Cl- → AuCl4- + 3R-py (3R-py = one of a number of meta-substituted pyridines covering a wide range of basicity) have been studied in methanol at 25°C. The reactions obey the usual two-term rate law observed in the substitution reactions of square-planar complexes. The second-order rate constants, k2, are very sensitive to the nature of the leaving group and plots of log k2 against the pKa of the conjugate acids are linear with the same slope of ca. -0.6 already found for para-substituted pyridines (4R-py). Until now the two groups of bases have been considered to behave in the same manner in their displacement from Au III and PtII by various nucleophiles but, on the contrary, the reactivity of the two classes of N donors is slightly different and follows the order: 4R-py > 3R-py. This kinetic result is explained on the basis of an energetic difference between the frontier orbitals of the AuCl 3(3R-py) and AuCl3(4R-py) derivatives. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Pitteri, Bruno,Bortoluzzi, Marco
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p. 5138 - 5143
(2008/04/13)
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- Synthesis and crystal structure of CS3AuO2
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Bright orange single crystals of Cs3AuO2, sensitive to moisture and atmosphere, are obtained by reacting CsAu with a 1:1 molar mixture of Cs2O and CsO2 (CsAu: Cs2O:CsO2 = 3:2:2) in sealed silver crucibles under argon atmosphere at 380°C for a period of 6 days. The crystal structure (Pearsoncode mP72, P21/n, a = 1019.6(3), b = 1984.3(7), c = 1028.5(4) pm, β = 93.96(1)°, Z =12, 2562 reflections mit Io > 2ω(I), R1 = 0.0662, wR2 = 0.1660) is characterized by the presence of dumb-bell-shaped [O-Au-O]-moieties (d(Au-O) = 200,8(2) pm), a common feature of oxoaurates(I). WILEY-VCH Verlag GmbH, 2001.
- Mudring, Anja-Verena,Jansen, Martin
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- Photooxidation of AuCl2- and AuBr2- induced by ds excitation
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In the presence of electron acceptors such as CH2Cl2 or O2, the irradiation of AuCl2- or AuBr2- in acetonitrile led to the photooxidation of Au(I) to Au(III). AuCl4- and AuBr4- were formed as final products when additional halide was present. The reactive excited states were of the metal-centered ds type. The photooxidations were reversed in solutions of ethanol. AuCl4- and AuBr4- underwent a photoreduction to AuCl2- and AuBr2-, respectively.
- Kunkely, Horst,Vogler, Arnd
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p. 4539 - 4541
(2008/10/08)
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- Reactivity of Heterocyclic Nitrogen Donors in Systems containing the Tetrachloroaurate(III) Anion
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A series of gold(III) complexes of the type has been prepared and characterized (L = oxazole, benzoxazole, thiazole, their benzo and methyl-substituted derivatives, or 2-methylbenzoselenazole).The five-membered N.O-, N,S- and N,Se-heterocyclic bases are all bound to Au(III) through nitrogen.The kinetics of the displacement of L by chloride to give (1-) has been studied in methanol-water (95:5. v/v) at 25.0 deg C and I = 0.20 mol dm-3 (LiClO4).The equilibrium constants for the reversible processes have also been determined.The reactions of the corresponding pyridine, 4-chloro-, 4-cyano- and 2,6-bis(chloromethyl)-pyridine complexes have also been reexamined under the same conditions.The equlibrium constants, K2, depend upon the basicity of the nitrogen in the ligands and points for all ligands, irrespective of ring size and composition, lie roughly on the same log K2 versus pKa curve.There is no significant systematic steric effect on the equilibrium constants of the sort found for the more basic methyl pyridines.The complexes of the five-membered heterocyclic ligands are approximately ten times less reactive than those of the six-membered N-heterocycles of comparable basicity and exhibit steric retardation from ortho-methyl substituents.The nucleophilicities of these ligands have been calculated and five-membered N,O- and N,S-heterocycles are considerably less reactive than six-membered N-heterocycles of similar basicity.
- Canovese, Luciano,Cattalini, Lucio,Tomaselli, Michele,Tobe, Martin L.
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p. 307 - 314
(2007/10/02)
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- Displacement of Pyridine-2-methanol from Dichloro(pyridine-2-methanolato)gold(III) in Acidic Solution. Ring Opening at Oxygen
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The kinetics of displacement of pyridine-2-methanol (N-OH) from dichloro(pyridine-2-methanolato)gold(III), , have been studied in 5percent aqueous methanol at 25 deg C.In the presence of LiCl and perchloric acid the reaction consists of a pre-equilibrium protonation of the oxygen followed, first, by ring opening at oxygen accompanied by the entry of chloride or solvent, and then by displacement of the N-bonded pyridine-2-methanol to give -.This final stage is very similar to the displacement of 2-(methoxymethyl)pyridine (N-OMe) from .The ligand is not displaced in absence of chloride.The reaction between - and excess pyridine-2-methanol in 5percent methanol was also studied at 25 deg C.The initial attachement of the ligand by nitrogen is followed by rapid ring closing and a second molecule of ligand enters more slowly.The final product is + (isomeric form unknown), stabilised by the basic conditions generated by the excess ligand.Monodentate pyridine-2-methanol behaves as if it has a pKa of 5.6 with a steric hindrance comparable to that of 2-methylpyridine.
- Canovese, Luciano,Cattalini, Lucio,Marangoni, Giampaolo,Tobe, Martin L.
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p. 731 - 736
(2007/10/02)
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