Direct determination of gold and silver in rat plasma by graphite furnace atomic absorption spectrometry with Zeeman effect background correction and its application to the pharmacological properties of a mixture of copper,gold and silver salts

Methods for determining gold and silver in rat plasma without prior mineralization are presented. They permit concentrations above 1 μg 1^?1 to be measured. They were applied to 96 rat plasma samples with gold and silver contents up to 3 μg 1^?1. In addition, the anti-inflammatory properties of a solution containing gold, silver and copper at the mg 1^?1 level were tested and demonstrated.     

Synthesis and ligand properties towards gold and silver of the ferrocenylamidobenzimidazole ligand

The treatment of FcCOCl (Fc = (C₅H₅)Fe(C₅H₄)) with aminobenzimidazole in 1:1 or 2:1 ratio gives the ferrocenyl-amido derivatives FcCO(benzimNH₂) or (FcCO)₂(NHbenzim), respectively. The reactivity of FcCO(benzimNH₂) with silver or gold complexes has been studied. The reaction with the basic gold compounds [Au(acac)(PPh₃)] or [O(AuPPh₃)₃]ClO₄ occurs with deprotonation of the NH₂ group and coordination of one or three gold(phosphine) fragments. The treatment of this ligand with silver compounds, such as Ag(OTf) or [Ag(OTf)(PPh₃)], gives the complexes of stoichiometry [Ag(OTf)L] or [Ag(OTf)(PPh₃)L]. The ligand FcCO(benzimNH₂) and the complex [Ag(OTf){FcCO(benzimNH₂)}(PPh₃)] have been characterized by X-ray diffraction studies. DFT calculations were performed on models of this dimeric silver complex and showed that dimerization is energetically favourable, because Ag(I) achieves a four coordination environment, despite some bonds being relatively weak.     

New structural motifs of silver and gold complexes of pyridine-functionalized benzimidazolylidene ligands

Reaction of 1,3-bis(picolyl)benzimidazolium chloride ([HL1]Cl) with Ag₂O yields mononuclear complex [Ag(L1)Cl] (2), further reaction of 2 with Au(Et₂S)Cl afforded [Au(L1)Cl] (3). Treatment of 2 with AgBF₄ gave the trinuclear silver cluster [Ag₃(L1)₃](BF₄)₃ (4), whereas the digold complex [Au₂(L1)₂](BF₄)₂ (5) can be easily obtained from the carbene transfer reaction of 4 with Au(Et₂S)Cl. A one-dimensional coordination polymer {[Ag(L2)](BF₄) · CH₃CN}_n (8) was isolated from the reaction of [Ag(L2)Cl] (7, L2 = 1-benzyl-3-picolylbenzimidazolylidene) with additional Ag⁺ in good yield. The dinuclear [Ag₂(L3)₂](PF₆)₂ (12, L3 = 1,4-di(N-benzylbenzimidazolylidene)but-2-yne) is a 18-membered macrocycle. All these complexes have been structurally characterized. Complex 2 shows a dimeric structure because of intermolecular Ag?Cl interactions. Complex 4 consists of a triangular Ag₃ ring with very short Ag-Ag contacts 2.777(1) Å, the Au-Au distance in 5 is 3.206(2) Å showing very weak Au-Au interaction and the macrocyclic cations in 12 are aligned one above another to form channels filled with hexafluorophosphate anions. The complexes 2-5, 8, and 12 are intensely luminescent upon irradiation of uv light, and their emission properties are briefly described.     

Remarks on the reactions of a tetracarboxylic porphyrin with gold and silver ions: A spectrophotometric,TEM and SEM study

The coproporphyrin-I (CPI) behaves as a reducing agent for silver and gold metal ions and as stabilizing agent for the formed colloidal metallic nanoparticles. The peculiarity of silver and gold nanoparticles obtained in the reactions of monomeric form of CPI with their metal ions has been studied. The optical properties of the colloidal forms of these metals have been investigated by UV–Vis spectrophotometry, and their morphology by TEM and SEM measurements. The structures and the size distributions of Ag and Au particles have been characterized and determined by computerized TEM images.     

Synthesis and plasmonic properties of silver and gold nanoshells on polystyrene cores of different size and of gold–silver core–shell nanostructures

Simple methods of preparing silver and gold nanoshells on the surfaces of monodispersed polystyrene microspheres of different sizes as well as of silver nanoshells on free-standing gold nanoparticles are presented. The plasmon resonance absorption spectra of these materials are presented and compared to predictions of extended Mie scattering theory. Both silver and gold nanoshells were grown on polystyrene microspheres with diameters ranging from 188 to 543 nm. The commercially available, initially carboxylate-terminated polystyrene spheres were reacted with 2-aminoethanethiol hydrochloride (AET) to yield thiol-terminated microspheres to which gold nanoparticles were then attached. Reduction of silver nitrate or gold hydroxide onto these gold-decorated microspheres resulted in increasing coverage of silver or gold on the polystyrene core. The nanoshells were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV–vis spectroscopy. By varying the core size of the polystyrene particles and the amount of metal (silver or gold) reduced onto them, the surface plasmon resonance of the nanoshell could be tuned across the visible and the near-infrared regions of the electromagnetic spectrum. Necklace-like chain aggregate structures of gold core–silver shell nanoparticles were formed by reducing silver nitrate onto free citrate-gold nanoparticles. The plasmon resonance absorption of these nanoparticles could also be systematically tuned across the visible spectrum.     

One-step synthesis of amino-dextran-protected gold and silver nanoparticles and its application in biosensors

A sensitive method for the detection of the lectin protein concanavalin A (Con A) was developed using amino-dextran (AD)-protected gold (AD-Au) and silver nanoparticles (AD-Ag) as sensitive optical probes. The AD-Au and AD-Ag nanoparticles were synthesized by directly applying amino-dextran as a reductive and protective reagent. The size of the nanoparticles could be altered by changing the molar ratio of AD to the metal salt. The amino-dextran bound to Con A by forming a 4:1 Au-Con A complex at neutral pH, and the nanoparticles were induced to aggregate by Con A. The absorption intensity of the nanoparticles decreased linearly with as the Con A concentration was increased from 3.85×10^–8 to 6.15×10^–7 M. The Au-Con A complex was dissociated by the disaccharide isomaltose, which has a higher affinities for Con A than Au; this competitive strategy could also be used to detect similar types of saccharides.     

Model studies of the chemisorption of hydrogen and oxygen on nickel surfaces

Atomic chemisorption of hydrogen and oxygen on the Ni(100) surface has been studied using an Effective Core Potential (ECP) approach described in a previous paper. Clusters of up to 50 nickel atoms have been used to model the surface. The computed chemisorption energies are 62 kcal/mol (exp. 63 kcal/mol) for hydrogen and 106 kcal/mol (exp. 115–130 kcal/mol) for oxygen. Correlating the adsorbate and the cluster-adsorbate bonds is extremely important for obtaining accceptable results, particularly for oxygen. Reasonable convergence of chemisorption energies is obtained with 40–50 cluster atoms for both hydrogen and oxygen. For hydrogen the addition of a third cluster layer stabilizes the results considerably. Both hydrogen and oxygen are adsorbed at (or close to) the four-fold hollow site. The calculated barriers for surface migration are also in good agreement with the experimental estimates. The calculated equilibrium heights above the surface are on the other hand too high compared with experiments. This disagreement is believed to be due to core-valence correlation effects, which are not incorporated in the present ECP. The cluster convergence for the height above the surface is much slower than for the chemisorption energy.     

An infrared study on the chemisorption of tertiary phosphines on coinage and platinum group metal surfaces

The chemisorption of dimethylphenyl-, methyldiphenyl- and triphenylphosphine on evaporated gold, silver, copper, rhodium, iridium, palladium, platinum and nickel surfaces has been studied by means of infrared reflection–absorption spectroscopy (IRAS). Multilayers of physisorbed phosphine are formed on the surfaces of all metals studied except nickel after deposition from dilute toluene solution. The deposition rate varies for different metal surfaces and it is sometimes quite slow. The standard immersion time was 20 h in this study to secure that an equilibrium between the surface and the solution is reached. Several minutes of ultrasonic treatment are required to get rid of the physisorbed phosphine, leaving a very thin layer of chemisorbed phosphine on the metal surface. Most of the absorption bands in IRAS spectra of these thin layers show significant shifts, which are especially large for dimethylphenylphosphine. It is evident that the electron distribution in the entire phosphine molecules is changed and that the chemisorption to the coinage and platinum group metal surfaces is strong. Infrared spectra of coordination compounds of gold(I), silver(I) and copper(I) with dimethylphenyl-, methyldiphenyl- and triphenylphosphine and of the corresponding phosphine oxides have served as reference material for the chemisorbed phosphines. The spectra of the coordination compounds show similar shifts and intensity changes as the IRAS spectra of tertiary phosphines chemisorbed on the coinage and platinum group metals. This suggests that the studied phosphines are as strongly bound to the coinage and platinum group metal surfaces as to the monovalent coinage metal ions known to form very stable complexes with tertiary phosphines.     

Labelling and binding of poly-( -lysine) to functionalised gold surfaces. Combined FT-IRRAS and XPS characterisation

We compare herein the interfacial reactivity of self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA), 1-undecanethiol (UDT) and 11-mercaptoundecanol (MUD) on gold surfaces towards aqueous solutions of poly-( -lysine) (PL). Liquid-phase labelling of PL with the alkyne dicobalt hexacarbonyl cluster 1 combined with analysis of the substrates by Fourier transform infrared reflection–absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS) revealed that irreversible binding of PL occurred in all cases. However, the mechanism of binding involved differed markedly from one monolayer to the other. The main mode of interaction of PL to MUA SAM was of electrostatic nature between the terminal carboxylate of MUA and the ammonium groups of PL. For a similar number of bound thiolate molecules, the UDT adsorbed layer was found less continuous than the MUA one, allowing a higher fraction of PL to directly bind to the gold surface. As for MUD, very little thiolate molecules were adsorbed, leaving bare gold surface areas for non specific adsorption of PL.     

Synthesis and anticancer properties of gold(I) and silver(I) N-heterocyclic carbene complexes

Bis(1,3-dimethylimidazol-2-ylidene)silver(I) nitrate and bis(4,5-dichloro-1,3-dimethylimidazol-2-ylidene)silver(I) nitrate were prepared by reacting the corresponding imidazolium nitrate salts with silver oxide. Bis(1,3-dimethylimidazol-2-ylidene)gold(I) nitrate and bis(4,5-dichloro-1,3-dimethylimidazol-2-ylidene)gold(I) nitrate salts were prepared via transmetallation of their silver precursors with chloro dimethylsulfide gold. The anticancer properties were determined using NCI-H460 lung cancer cells. Efficacy was established by comparison of the gold and silver compounds with cisplatin.     

Sorption and binding of nanocrystalline gold by Merino wool fibres--an XPS study

Uniform, monodisperse gold nanocrystals have been adsorbed and chemically bound to Merino wool fibres, providing a permanent colouration through the interaction of visible light with the plasmon resonant modes of the nanocrystals. Surface analysis by X-ray photoelectron spectroscopy confirmed that the nanocrystalline gold was bound through the nitrogen of the amino groups on the surface of the gold to the keratin of the fibres. No shift in the absorptions attributed to the plasmon resonance modes of the nanocrystals were observed.     

Novel scorpionate-type triscarbene ligands and their silver and gold complexes

New silver(I) carbene complexes were obtained starting from the N-heterocyclic carbene ligand precursors {[HB(RImH)₃]Br₂} (R = Bn, Mes and t-Bu) and {[HC(MeBImH)₃](BF₄)₃}, by treatment of the imidazolium salt with Ag₂O. Use of the tris-imidazolylborate precursors resulted in stable, well-characterized trimetallic complexes of general formula {Ag₃[HB(RIm)₃]₂}Br, which were successfully employed as carbene transfer reagents in the synthesis of related gold(I) complexes by transmetallation. The silver complexes also proved to be active catalysts of the coupling of aryl iodides with terminal alkynes (the Sonogashira reaction), although related bimetallic silver complexes were found to exhibit enhanced reactivity.     

Synthesis of amidinothioureido-silica gel and its application to flame atomic absorption spectrometric determination of silver, gold and palladium with on-line preconcentration and separation

A simple and highly selective flow injection (FI) on-line preconcentration and separation flame atomic absorption spectrometric (FAAS) method was developed for the determinations of trace amounts of silver, gold and palladium. The selective preconcentration of the noble metals was achieved in a wide range of sample acidity (0.1-6 M HNO₃ or HCl) on a microcolumn packed with amidinothioureido-silica gel (ATuSG). The analytes retained on the column were effectively eluted with 5.0% thiourea solution. The analytical procedure was optimized for sample acidity, elution, interferences, flow rate of sampling and eluting, and concentration of sample. Common co-existing cations and anions did not interfere with the preconcentration and determination of the three metals. At a sample loading flow rate of 4.5 ml min⁻¹ with 60 s preconcentration, detection limits (3σ) of 1.1 ng ml⁻¹ Ag, 13 ng ml⁻¹ Au and 17 ng ml⁻¹ Pd were obtained. The precisions (R.S.D., n=11) were 1.2% for Ag, 1.2% for Au and 1.7% for Pd, respectively. The detection limits can be further improved by increasing sample volume. The analytical results obtained by the proposed method for a number of standard reference materials were in good agreement with the certified values.     

Biogenic synthesis of gold and silver nanoparticles used in environmental applications: A review

Due to their physical, chemical, optical, and mechanical properties, metallic nanoparticles (MNPs) are increasingly being used, with an emphasis on silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs). In recent years, green synthesis has gained prominence for exploring the use of naturally available biological sources for the obtention of metallic nanoparticles. Among these, algae and plants stand out due to the presence of polysaccharides, proteins, polyphenols, and vitamins (among others) in their composition, which can act in the reduction and stabilisation of MNPs, and these biogenic materials have been characterised mainly by spectrometric and microscopic techniques. In addition, due to the numerous advantages of nanoparticles (NPs) synthetize from biogenic source, such as their simplicity and cost benefits, they have been used in the development of sensors applied in the determination of contaminants present in environmental samples and in the catalytic reduction of organic and inorganic contaminants. Therefore, this review describes the synthesis, mechanisms, characterization, and environmental analytical applications of NPs obtained by biogenic synthesis as well as the perspectives and challenges of these NPs.     

Numerical approximation of AR‐XPS spectra for rough surfaces considering the effect of electron shadowing

A computational scheme is presented that takes into account the topography, i.e. the shadowing and hence the local emission angle of the electrons when evaluating AR‐XPS data of macroscopic rough surfaces. The topography of the sample surface is supposed to be recorded by atomic force microscopy and/or optical microscopy. The emitted photoelectrons are simulated based on an extension of the Beer–Lambert law that includes the shadowing, the current local emission angle, and the geometrical instrument setup. The obtained angle‐resolved XPS spectra are optimized in accordance with experimental ones via a self‐consistent minimization algorithm that also allows one to determine the layer thicknesses of the corrugated sample. In order to validate the proposed numerical scheme, the simulation program simulation of electron spectra for surface analysis is used. An additional analysis is then performed considering only experimental data. The numerical scheme gives good agreement in simulation–simulation as well as simulation–experiment comparisons and permits a comprehensible interpretation of the measured data. Copyright © 2014 John Wiley & Sons, Ltd.     

SiO_2包覆超细CaCO_3的微晶分析和XPS研究

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Functionalization of silver and gold nanoparticles using amino acid conjugated bile salts with tunable longitudinal plasmon resonance

The vital bioactivities of bile salts are physiologically important molecules. The concept of using bile acids and their conjugates in nanoscience is a novel idea, which opens up fascinating prospects and gives way for various versatile properties. Here in, we report novel strategy for the synthesis of aqueous stable, silver and gold nanoparticles (Ag & AuNPs) using naturally occurring amino acid conjugated sodium salt of taurocholate (NaTC) and glycocholate (NaGC) as reducing and capping agents. The formation of nanoparticles was kinetically monitored using UV–vis spectroscopy at different time intervals. It was noticed, that the rate of reduction of AgNO₃ is much faster than the HAuCl₄ at fixed concentration of bile salts. Furthermore, the size and shape of the NPs are controlled and achieved by changing the nature of bile salts. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques for morphological studies. The interaction between nanoparticles with bile salts was investigated using FT-IR spectroscopy, cyclic voltammetry (CV) and thermogravimetric analysis (TGA).     

TAT peptide immobilization on gold surfaces: a comparison study with a thiolated peptide and alkylthiols using AFM, XPS, and FT-IRRAS

A TAT peptide was used to functionalize a gold surface by three different methods: adsorption from solution, microcontact printing, and dip-pen nanolithography (DPN). The composition and structure of the modified gold was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Fourier transform -infrared reflection absorption spectroscopy (FT-IRRAS). We used two well-studied alkylthiols, mercaptohexadecanoic acid and 1-octadecanethiol, as a comparison in order to understand the structure of the TAT peptide monolayers prepared by the three methods. AFM studies allowed us to assess the homogeneity after each modification protocol. XPS was used to characterize the chemical composition of the gold surface after each functionalization procedure. The XPS results showed that surfaces modified with the TAT peptide by the three methods exhibit similar surface chemistry. Finally, FT-IRRAS experiments allowed us to conclude that the structure of the alkyl chains of the TAT peptides is fairly disordered and different after each procedure. Regardless of the type of surface functionalization method used, the monolayer of TAT peptide formed on the surface was of "liquidlike" nature.     

Characteristics of subtractive anodic stripping voltammetry of Pb and Cd at silver and gold electrodes

Silver and gold electrodes are useful for the quantitative determination of lead and cadmium with subtractive anodic stripping voltammetry (SASV). The use of SASV is essential for achieving good separation between the two peaks, to eliminate the interference of nitrates when cadmium is present and to allow analysis at very low concentrations without the removal of oxygen. The deposition and dissolution of Pb²⁺ and Cd²⁺ proceed at underpotential (UPD) on both electrodes. The UPD properties of the deposits are the main factor determining the analytical characteristics of the ASV method and are strongly affected by the type and concentration of the electrolyte. The effects of anions (Cl⁻, Br⁻, SO₄²⁻, NO₃⁻) and acids (HNO₃, HClO₄, H₂SO₄, HCl) are shown. The two electrodes complement each other and, in addition, enable the qualitative identification of Pb²⁺ and Cd²⁺, since the peaks appear in opposite order on the two electrodes. Analysis of mixtures of the two analytes is restricted on gold but not on silver. At gold the two peaks overlap: (i) at concentrations of cadmium higher than 250 nM at deposition times greater than 30 s, (ii) in the presence of copper at concentrations higher than 1 μM, and (iii) in the presence of Triton X-100 at concentrations above 10 mg/l. The repeatability at 10 nM analyte is better than 2.5%. The detection limits for Pb²⁺ and Cd²⁺ at 120 s deposition time and 3500 rpm rotation rate are: dl_Pb/Ag=0.04 nM; dl_Cd/Ag=0.7 nM; dl_Pb/Au=0.1 nM; dl_Cd/Au=0.3 nM. The analysis of lead and cadmium in natural waters has been performed.     

Quantum mechanical approach to the chemisorption of molecular hydrogen on defect magnesium oxide surfaces

Quantum mechanical theoretical calculations have been performed on the linear atomic chain in order to simulate the interaction of molecular hydrogen with the defects present at the surface of activated MgO. The total energy of the system, the relative energy of the various molecular orbitals, and the electronic charge distribution have been computed for various lattice parameters (d _O-O = 4.0–4.8 Å) as a function of the H-H (or O-H) separation. A symmetrical motion of the hydrogen nuclei with respect to the central Mg²⁺ vacancy was assumed. It is shown that chemisorption of hydrogen on surface O^–ions sites results in the formation of pseudo-hydroxyl groups. For a small lattice parameter (4.0 Å), no stable state of molecular hydrogen has been found while an increase in the lattice parameter results in a uniform increase of the calculated activation energy for the molecular hydrogen activation process. A mechanism is proposed which is not so different from that put forward for the hydrogen activation by transition metal complexes. Molecular hydrogen is found to act as an electron donor.