多孔硅上贵金属的浸入沉积

将多孔硅浸入含贵金属盐的HF溶液20 s, 制备了Ag, Au, Pd和Pt的沉积层. AFM形貌显示, 这4种贵金属都能在多孔硅上直接沉积, 但Pt的沉积量比其他3种少. SEM图及能谱(Energy dispersive X-ray spectrometer, EDS)分析显示, 沉积层优先生长在孔边上, 孔边上的沉积量约是孔底的4.6倍. 电化学方法分析显示, Pd和Pt, Ag和Au的沉积层分别具有类似的开路电位和交流阻抗特性, 其中Pd层的溶出电流比其他3种大1个数量级, 而阻抗比其他小1个数量级, 说明Pd层与硅基底的结合程度好, 结合界面导电性好.     

Graphene nanosheets decorated with Pd,Pt,Au,and Ag nanoparticles:Synthesis,characterization,and catalysis applications

We report that noble metal nanopartcles (Pd,Pt,Au,and Ag) decorated-graphene nanosheets can be synthesized with the template of graphene oxide by a one-pot solution-based method.The resulting hybrid materials are characterized by transmission electronic microscopy,energy dispersive X-ray spectroscopy,scanning electronic microscopy,atomic force microscopy,X-ray diffraction,and Raman spectroscopy,which demonstrate that the metal nanoparticles have been uniformly deposited on the surfaces of graphene nanosheet...     

多孔铜基催化剂的制备及对苯甲醇的选择性催化氧化

采用去合金化法制备了多孔铜(PC), 并以此为还原剂和模板与含有贵金属离子的溶液进行置换反应, 简单有效地制备了多孔M/PC(M=Ag, Au, Pt, Pd)双金属催化剂, 并对样品的形貌\, 结构和化学组成进行了表征, 利用苯甲醇气相选择性催化氧化实验评价了其催化性能. 实验结果表明, 所制备的多孔铜基催化剂具有良好的双金属协同催化效应, 对苯甲醇气相选择性氧化具有很好的催化活性和选择性, 其中Ag/PC具有最优的催化性能.     

Retention and elution of precious metals on cyano-modified solid phase microparticle sorbent

We report on a study on the retention and elution of ions of the precious metals Au, Ir, Pd, Pt, Rh and Ru, sometimes in the presence of ions of the nonprecious elements Co, Cu, Fe, Ni, Pb and Te. A commercial cyano-modified microparticle-based solid phase was used as a sorbent and hydrochloric acid in various concentrations for sample solution and elution. Only Au and Pd (in the form of their chloro complexes) were retained, and Au is found to have a much higher affinity for the sorbent compared to Pd. In addition to the affinity of the metal towards the functional groups, the retention behavior of the precious metals seems to be mainly influenced by steric factors of their respective chloro complexes. Elution with 7.5 M HCl does not require the addition of organic eluent as required in other cases. The method can separate Au or both Au and Pd, from hydrochloric acid solutions containing ions of other precious metals or nonprecious elements. The sorbent was applied to recover gold from a mineral digest containing large amounts of metals such as Fe, Pb, Te, Cu, Ni and Zn.

Fabrication of metal nanoparticles–carbon nanotubes composite materials in solution

A new solution-phase method for synthesis of metal nanoparticles–carbon nanotubes (CNTs) assemblies is described. By injection of CNTs solution into the diethyl ether/aqueous solution of metal salt biphasic mixture, metal (Ag, Au, Pd, and Pt) nanoparticles–decorated CNTs composite materials can be prepared. Metal nanoparticles have spontaneously and selectively formed on the sidewalls of CNTs through redox reaction between CNTs and metal ions. This phenomenon has been probed by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy.     

Metal-metal interactions in heterobimetallic d8-d10 complexes. Structures and spectroscopic investigation of [M'M' '(mu-dcpm)2(CN)2]+ (M' = Pt,Pd; M' ' = Cu,Ag, Au) and related complexes by UV-vis absorption and resonance Raman spectroscopy and ab initio calculations

X-ray structural and spectroscopic properties of a series of heterodinuclear d(8)-d(10) metal complexes [M'M' '(mu-dcpm)(2)(CN)(2)](+) containing d(8) Pt(II), Pd(II), or Ni(II) and d(10) Au(I), Ag(I), or Cu(I) ions with a dcpm bridging ligand have been studied (dcpm = bis(dicyclohexylphosphino)methane; M' = Pt, M' ' = Au 4, Ag 5, Cu, 6; M' ' = Au, M' = Pd 7, Ni 8). X-ray crystal analyses showed that the metal...metal distances in these heteronuclear metal complexes are shorter than the sum of van der Waals radii of the M' and M' ' atoms. The UV-vis absorption spectra of 4-6 display red-shifted intense absorption bands from the absorption spectra of the mononuclear trans-[Pt(phosphine)(2)(CN)(2)] and [M' '(phosphine)(2)](+) counterparts, attributable to metal-metal interactions. The resonance Raman spectra confirmed assignments of (1)[nd(sigma)-->(n + 1)p(sigma)] electronic transitions to the absorption bands at 317 and 331 nm in 4 and 6, respectively. The results of theoretical calculations at the MP2 level reveal an attractive interaction energy curve for the skewed [trans-Pt(PH(3))(2)(CN)(2)-Au(PH(3))(2)(+)] dimer. The interaction energy of Pt(II)-Au(I) was calculated to be ca. 0.45 ev.     

Synthesis and characterisation of morin-functionalised silica gel for the enrichment of some precious metal ions

Silica gel was firstly functionalised with aminopropyltrimethoxysilane obtaining the aminopropylsilica gel (APSG). The APSG was reacted subsequently with morin yielding morin-bonded silica gel (morin-APSG). The structure was investigated and confirmed by elemental and thermogravimetric analyses, IR and (13)C NMR spectral studies. Morin-APSG was found to be highly stable in common organic solvents, acidic medium (<2molL(-1) HCl, HNO(3)) or alkaline medium up to pH 8. The separation and preconcentration of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) from aqueous medium using morin-APSG was studied. The optimum pH values for the separation of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) on the sorbent are 5.7, 2.2, 3.7, 3.7 and 6.8, giving rise to separation efficiencies of 43.9, 85.9, 97.7, 60.9 and 91.0%, respectively, where the activity was found to be >90% in the presence of acetate ion. The ion sorption capacity of morin-APSG towards Cu(II) at pH 5.5 was found to be 0.249mmolg(-1) where the sorption capacities of Ag(I) and Pd(II) were 0.087 and 0.121mmolg(-1) and 0.222 and 0.241mmolg(-1) at pH 2.2 and 5.7, respectively. This indicates a 1:1 and 1:2 morin/metal ratios at pH 2.2 and 5.7, respectively. Complete elution of the sorbed metal ions was carried out using 10mL (0.5molL(-1) HCl+0.01molL(-1) thiourea) in case of Au(III), Pd(II), Pt(II) and Rh(III) and 10mL 0.5molL(-1) HNO(3) in case of Ag(I). Morin-APSG was successfully employed in the separation and preconcentration of the investigated precious metal ions from some spiking water samples yielding 100-folds concentration factor. The relative standard deviation (R.S.D.) and the T-test (|t|(1)) were calculated.     

Structure and Electron Transport at Metal Atomic Junctions Doped with Dichloroethylene

We have investigated the structure and electron transport at dichloroethylene-doped metal atomic junctions at low temperatures (20 K) in ultra-high vacuum, using Fe, Ni, Pd, Cu, Ag, and Au. The metal atomic junctions were fabricated using the mechanically controllable break junction technique. After introducing the dichloroethylene (DCE), the conductance behavior of Fe, Ni, and Pd junctions was considerably changed, whereas little change was observed for Cu, Ag, and Au. For the Pd and Cu junctions, a clear peak was observed in their conductance histograms, showing that the single-molecule junction was selectively formed. To investigate the structure of the metal atomic junctions further, their plateau lengths were analyzed. The length analysis revealed that the Au atomic wire was elongated, and the metal atomic wires were formed for the other transition metals: those that do not normally form metal atomic wires without DCE doping, as DCE adsorption stabilized the metal atomic states. There is a strong interaction between DCE and the metals, where DCE supports the formation of the metal atomic wire for Fe, Ni, and Pd.     

The relationship between adsorption energies of methyl on metals and the metallic electronic properties: a first-principles DFT study

A theoretical study of CH3 adsorbed on the (111) surface of some transition and noble metal surfaces M (M = Cu, Ni, Rh, Pt, Pd, Ag, Au) and on the Fe(100) is presented. We find that the hollow site is preferred more than the top one for Fe, Ni, Rh, and Cu, but it is the other way for Pt, Pd, Au, and Ag. In addition, a good linear relationship was observed between the chemisorption energy and d-band center for Group VIII metals or the square of the coupling matrix element for Group IB metals at the hollow site. Interestingly, with a detailed comparison of the adsorption energies at the top and hollow sites, we find that the adsorption energies among each group are very similar on the top site, which supports the theoretical model of Hammer and Norskov that the coupling between the HOMO of adsorbate and sp states of the metal is dominant and almost equal, and that the second coupling to the d-band contributes less but reflects the change of the adsorption energy. It confirms that the coupling to the d band comprises two opposite factors, that is, the d-band center was attractive and the square of the coupling matrix element was repulsive, such that the contributions from the two factors can counteract each other at the top site.     

Biosorption of precious metal ions by chicken feather

Chicken feather (C-feather) is an intricate network of stable and water-insoluble protein fibers with high surface area and is an abundant bioresource. C-feather protein was found to accumulate various precious metal ions (gold and platinum metals) selectively from their dilute aqueous solutions in high yield and in short contact time, depending on pH and characteristics of the individual precious metal ions. Under certain condition, the sequestering level of precious ions, Au(III), Pt(II), and Pd(II) approaches about 17, 13, and 7% of dry wt of C-feather, respectively. Gold(III) potassium cyanade was also accumulated up to 5.5% at pH 2.0. The presence of 100-fold (mol) of coexisting cations, such as Na⁺, Fe(III), Cu(II), and Ni(II), did not show a discernible effect on the precious metal uptake rate and capacity of C-feather. Experiment suggested C-feather is promising for use in the removal/recovery of precious metals as well as water pollution control. A qualitative discussion is given about the excellent adsorption behavior of C-feather.

     

Gas-chromatographische Trennung der Edelmetalle Au, Pt, Pd, Rh und Ir als Bis(trifluoroethyl)-dithiocarbamato-Chelate

Zusammenfassung Die Bedingungen für die gas-chromatographische Trennung und Bestimmung der Edelmetalle Au, Pt, Pd, Rh und Ir als Bis(trifluoroethyl)-dithiocarbamato-Chelate wurden untersucht. Die besten Trennergebnisse lieferte eine (1000 mm×2 mm i.d.)-Glassäule mit 3% OV-3 auf Chromosorb G-AW-DMCS. Mit dem ECD konnten Edelmetallkonzentrationen im unteren ppb-Bereich erfaßt werden.

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Gas-chromatographic separation of the precious metals Au, Pt, Pd, Rh and Ir as bis(trifluoroethyl)-dithiocarbamate chelates

Summary The gas-chromatographic conditions for the separation and determination of the precious metals Au, Pt, Pd, Rh and Ir as bis(trifluoroethyl)-dithiocarbamate chelates were ascertained. Best results were obtained with a (1000 mm×2 mm i.d.)-glas column packed with 3% OV-3 on Chromosorb G-AW-DMCS. Using the ECD, precious metal concentrations of the lower ppb-range can be determined.

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Die Untersuchungen wurden durch Mittel der Deutschen Forschungsgemeinschaft (Kr 590/11-1) unterstützt.     

Luminescence Determination of Copper(I), Silver(I), Gold(I), and Platinum(II) Using 2-Mercapto-5-Benzimidazolesulfonic Acid,also Immobilized on a Silica Surface

2-Mercapto-5-benzimidazolesulfonic acid (MBI), also noncovalently bound to a silica surface, is proposed as a reagent for the low-temperature luminescence determination of Cu(I), Ag(I), Au(I), and Pt(II). Luminescence excitation and luminescence spectra of metal complexes with MBI in solutions and on the adsorbent surface represent broad unstructured bands in the regions 250–400 and 450–700 nm, respectively. The developed procedures for the luminescence and sorption–luminescence determination of Cu, Ag, Au, and Pt with limits of detection at a level of 0.001–0.01 μg on 0.1 g of adsorbent are tested in the determination of metals in natural and industrial samples.     

Extractive concentration of platinum-group elements and their determination by atomic-absorption spectrophotometry

The extraction of Pt, Pd, Ir, Rh, Ru, Ag, Au, Co, Cu, Ni and Fe with n-octylaniline has been investigated. Noble metals are extracted 10(3)-10(4) times better than Cu, Ni, Co and Fe. A method of determination of Pt, Pd, Ir, Rh and Ru is proposed. They are first separated from Cu, Ni, Co and Fe by means of extraction (and then determined, in either the aqueous or organic phase, by atomic-absorption spectrophotometry. The atomic absorption of platinum metals (with the exception of Pd) is affected by other elements of the platinum group and by non-noble metals. La(NO(3))(3) and Nd(NO(3))(3) lower the limit of detection for Pt, Rh, Ir and Ru and inhibit the effect of Co, Cu, Ni, Fe, Bi, Zn, Na, etc. on their determination. Lanthanum and neodymium chlorides and sulphates produce a similar effect but only on the determination of Pt and Rh. The coefficient of variation of the determination, in both phases, is within 2-6.8%.     

Determination of precious metals in geological samples by continuous powder introduction microwave induced plasma atomic emission spectrometry after preconcentration on activated carbon

A novel method was developed for analysing geological materials for Au, Ag, Pd and Pt by continuous powder introduction microwave induced plasma atomic emission spectrometry (CPI-MIP-AES). The preconcentration of the trace metals on activated carbon (AC) was performed before conducting MIP-AES measurements in order to obtain accurate and precise analytical results. The method proposed is based on the selective sorption of precious metals that are subsequently introduced to the plasma as a dry particulate aerosol consisted of analytes collected on the sorbent. The technical design and operating conditions of the novel sample introduction system based on the fluidized-bed concept has been optimized. The microwave excitation source with integrated rectangular cavity TE₁₀₁ and vertically positioned plasma torch has been used. The signal stability proved to be adequate for sequential mode of measurements due to the vertical plasma configuration as well as the MIP-AES system compatibility with the CPI technique. Calibration was done using home-made standards obtained by sorption of metals of interest from standard solutions on activated carbon. Precision is typically 1-4% relative standard deviation at the 1 μg g⁻¹ level. Under measurement conditions the detection limits for Ag, Au, Pd and Pt were 24, 43, 57 and 550 ng per 1 g of AC, respectively. The proposed procedure was used for Au, Ag, Pd and Pt determination in the platinum ore SARM-7 as well as Au and Ag in the Chinese soil GBW-07405 certified reference materials. The standard addition technique was used and recoveries revealed that the proposed method shows good accuracy and precision.     

CO在某些过渡金属表面吸附活化的DFT研究

采用DFT方法对CO在M(100)(M= Cu、Ag、Au、Pd、Pt)表面上的吸附行为进行了系统的比较性研究.结果表明,CO分子在这些过渡金属单晶表面上发生的是非解离性吸附,吸附后C－O键长都变长了,均不同程度地削弱了C－O键,继而活化了CO分子；从表面结合能、重叠集居数、轨道电子数变化等方面分析了成键强弱顺序,发现CO的吸附强度随Pd(100)、Pt (100)、Cu (100)、Ag(100)、Au(100)顺序依次减弱,并且将CO与过渡金属间的结合能(BE)、过渡金属的d电子转移数分别与水煤气变换反应活性数据进行了关联,在定性上比较好地解释了金属铜的催化活性优于其它金属的原因.     

Ion-exchange resins containing s-bonded dithizone and dehydrodithizone as functional groups : Part 3. Determination of Gold,Platinum and Palladium in Geological Samples by means of a Dehydrodithizone Resin and Plasma Emission Spectrometry

A procedure is described for the determination of gold, platinum and palladium in sulphide ores, concentrates and mattes. The method is based on chromatographic separation and selective elution of precious metals on small resin beds (0.7 × 2.5 cm) of the sorbent P-TD. After roasting, the samples were digested with aqua regia, and the residues fused with sodium peroxide. The acid leaching solutions obtained from both procedures were separately passed through an ion-exchange column. The metals were quantitatively retained after one loading step and eluted by a sequence of 2 M perchloric acid and 5% (w/v) thiourea solution. Preconcentrated Au, Pt and Pd were finally quantified with a d.c. plasma emission spectrometer. The effect of roasting temperature on the recovery of precious metals as well as the efficiency of the aqua regia leaching from the different materials were investigated in detail. Repeated analyses of standard reference samples proved the proposed method to be reliable.     

CO adsorption on pure and binary-alloy gold clusters: a quantum chemical study

We performed density-functional theory analysis of nondissociative CO adsorption on 22 binary Au-alloy (Au(n)M(m)) clusters: n=0-3, m=0-3, and m+n=2 (dimers) or 3 (trimers), M=Cu/Ag/Pd/Pt. We report basis-set superposition error corrections to adsorption energies and include both internal energy of adsorption (DeltaU(ads)) and Gibbs free energy of adsorption (DeltaG(ads)) at standard conditions (298.15 K and 1 atm). We found onefold (atop) CO binding on all the clusters except Pd2 (twofold/bridged), Pt2 (twofold/bridged), and Pd3 (threefold). In agreement with the experimental results, we found that CO adsorption is thermodynamically favorable on pure Au/Cu clusters but not on pure Ag clusters and also observed the following adsorption affinity trend: Pd>Pt>Au>Cu>Ag. For alloy dimers we found the following patterns: Au2>M Au>M2 (M=Ag/Cu) and M2>M Au>Au2 (M=Pd/Pt). Alloying Ag/Cu dimers with (more reactive) Au enhanced adsorption and the opposite effect was observed for PdPt dimers. The Ag-Au, Cu-Au, and Pd-Au trimers followed the trends observed on dimers: Au3>M Au2>M2Au>M3 (M=Ag/Cu) and Pd3>Pd2Au>PdAu2>Au3. Interestingly, Pt-Au trimers reacted differently and alloying with Au systematically increased the adsorption affinity: PtAu2>Pt2Au>Pt3>Au3. A strikingly different behavior of Pt is also manifested by the triplet spin state and onefold (atop) binding in Pt3-CO which is in contradiction with the singlet spin state and threefold binding in Pd3-CO. We found a linear correlation between CO binding energy (BE) and elongation of the CO bond. For Ag-Au and Cu-Au clusters, the increase in CO BE (and elongation of the C-O bond which is probably due to the back donation) is accompanied by the decrease in the cluster-CO distance suggesting that the donation (from 5sigma highest occupied molecular orbital in CO to cluster lowest unoccupied molecular orbital) mechanism also contributes to the BE. For Pd-Au clusters, the cluster-CO distance (and CO bond length) increases with increase in the BE, suggesting that the donation mechanism may not be important for those clusters. No clear trend was observed for Pt-Au clusters.     

A new class of electrocatalysts for hydrogen production from water electrolysis: metal monolayers supported on low-cost transition metal carbides

This work explores the opportunity to substantially reduce the cost of hydrogen evolution reaction (HER) catalysts by supporting monolayer (ML) amounts of precious metals on transition metal carbide substrates. The metal component includes platinum (Pt), palladium (Pd), and gold (Au); the low-cost carbide substrate includes tungsten carbides (WC and W(2)C) and molybdenum carbide (Mo(2)C). As a platform for these studies, single-phase carbide thin films with well-characterized surfaces have been synthesized, allowing for a direct comparison of the intrinsic HER activity of bare and Pt-modified carbide surfaces. It is found that WC and W(2)C are both excellent cathode support materials for ML Pt, exhibiting HER activities that are comparable to bulk Pt while displaying stable HER activity during chronopotentiometric HER measurements. The findings of excellent stability and HER activity of the ML Pt-WC and Pt-W(2)C surfaces may be explained by the similar bulk electronic properties of tungsten carbides to Pt, as is supported by density functional theory calculations. These results are further extended to other metal overlayers (Pd and Au) and supports (Mo(2)C), which demonstrate that the metal ML-supported transition metal carbide surfaces exhibit HER activity that is consistent with the well-known volcano relationship between activity and hydrogen binding energy. This work highlights the potential of using carbide materials to reduce the costs of hydrogen production from water electrolysis by serving as stable, low-cost supports for ML amounts of precious metals.     

A new biomaterial,hen egg shell membrane,to eliminate heavy metal ion from their dilute waste solution

The egg shell membrane (ESM) is an intricate lattice network of stable and water-insoluble fibers with high surface area. ESM accumulates and eliminates various heavy metal ions from dilute aqueous solution with high affinity and in short contact time, depending on pH and characteristics of the individual ion. Under certain conditions, the level of precious ions, Au, Pt, and Pd accumulation approaches 55, 25, and 22% of dry wt of ESM, respectively. Also uranium uptake 30% of that of ESM. Experiments suggested that ESM is promising to use for the purpose of removal/recovery of metals and water pollution control.     

Bestimmung der Edelmetalle Au, Pd, Pt, Rh und Ir in Gesteinen und Erzen mit der elektrothermalen Atomabsorptions-Spektrometrie

Zusammenfassung Nach einem Druckaufschluß bei 170°C von 5 g Gesteinsprobe mit HF und aqua regia werden die Edelmetalle Au, Pd, Pt, Rh und Ir durch selektive Adsorption auf den Ionenaustauscher SARAFION NMRR von der restlichen Matrix abgetrennt. Im Thioharnstoffeluat können die Edelmetalle mit der elektrothermalen AtomabsorptionsSpektrometrie quantitativ bestimmt werden. Die Methode wurde durch Analyse von internationalen Gesteinsstandards und Meteoriten geprüft.

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Determination of the precious metals Au, Pd, Pt, Rh and Ir in rocks and ores by electrothermal atomic absorption-spectrometry

Summary After pressure digestion at 170°C of 5 g rock samples with HF and aqua regia the precious metals Au, Pd, Pt, Rh and Ir are separated from the rest matrix with selective adsorption on SARAFION NMRR ion exchange resin. The precious metals can be determinated in the thiourea eluate by electrothermal atomic absorption spectrometry. The reliability of the procedure was confirmed by analysing rock standards and meteoritic material.

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Die Untersuchungen wurden durch Mittel der Deutschen Forschungsgemeinschaft

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Die Untersuchungen wurden durch Mittel der Deutschen Forschungsgemeinschaft