Structure of the Au-Rh bimetallic system formed on titanate nanowires and nanotubes

Au, Rh and Au-Rh nanoclusters were studied on one-dimensional titania nanostructures by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR). On titanate nanowire and tube supports the gold 4f_7/2 XP emission appeared after reduction at 83.6 eV and 85.6 eV indicating two different sizes or chemical environments of gold nanoclusters. Small clusters also developed in rhodium containing samples besides the pure metallic state. Upon CO adsorption on the 1% Rh/titanate nanostructures the IR stretching frequencies characteristic of the twin (geminal) form were dominant, whereas bimetallic nanosystems featured a pronounced linear CO stretching vibration. At the same time the highest binding energy state disappeared almost completely indicating the enlargement of nanoclusters which was in agreement with SEM results. Very likely “core-shell” bimetallic clusters form, where gold covers the rhodium.     

Templated synthesis of Ag-Au bimetallic nanoparticles by amphiphilic PVC-g-PSSA graft copolymer film

Amphiphilic comb-like copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly(styrene sulfonic acid) (PSSA) side chains, i.e. PVC-g-PSSA at 68:32 wt.% was synthesized via atom transfer radical polymerization (ATRP). This self-assembled graft copolymer film was used to template the growth of Ag-Au bimetallic nanoparticles in the solid state by introducing NaBH₄ as a reducing agent. The in situ formation of Ag-Au bimetallic nanoparticles in the graft copolymer film was confirmed by UV-visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). High resolution TEM picture showed the formation of spherical Ag-Au core-shell nanoparticles. To the best of our knowledge, this is the first report on the solid-state synthesis of Ag-Au bimetallic core-shell nanoparticles using amphiphilic comb-like copolymer film.     

Template- and surfactant-free synthesis of mesoporous TiO2 spheres with hollow core-shell structure for dye-sensitized solar cells

We have demonstrated a simple and effective hydrothermal route to synthesize titania mesoporous spheres with hollow core-shell structure. The synthesis is free of any surfactants or templates. The formation mechanism is investigated on the basis of the results of time-dependent experiments. The as-obtained mesoporous titania spheres with a specific surface area of 21.5?m²?g^?1 and diameters of 1.2–2.3?μm are composed of anatase titania nanocrystals. The excellent light scattering property of mesoporous titania spheres with hollow core-shell structure is proved. A higher cell efficiency of 8.27% is achieved with mesoporous titania spheres with hollow core-shell structure as a light scattering layer, compared with a cell efficiency of 6.63% for the P25 film electrode with the similar thickness. The higher cell efficiency is attributed to the hollow core-shell structure scattering layer, resulting in excellent pore fitting for electrolyte diffusion, enhanced light scattering ability, and reduced charge recombination.     

Structural,electrical, and rheological properties of palladium/silver bimetallic nanoparticles prepared by conventional and ultrasonic-assisted reduction methods

Polyvinylpyrrolidone stabilized Pd/Ag bimetallic nanoparticles (NPs) with average particle sizes of 9 and 6 nm were synthesized by simultaneous reduction in the presence and absence of ultrasound waves, respectively. The prepared NPs were characterized by six methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution-TEM (HRTEM), UV–vis spectroscopy, scanning tunneling microscopy (STM), and energy dispersive X-ray (EDX) analysis. The rheological properties of Pd/Ag NPs in ethylene glycol as a base fluid with various mass fractions of NPs from 2% to 5% at different temperatures were studied experimentally and theoretically. The experimental results showed that viscosity of Pd/Ag NPs in ethylene glycol increases with increasing particle mass fraction and decreases with increasing temperature. A maximum of 31.58% increase in viscosity of ethylene glycol at 20 °C was observed when 5% Pd/Ag NPs was added. Measurement of the electrical conductivity of nanofluids of Pd/Ag bimetallic NPs in distilled water at different mass fractions and temperatures was performed. A 3841% increase in electrical conductivity of distilled water at 25 °C was observed when 1% Pd/Ag NPs was added. Both the rheological and electrical properties of Pd/Ag bimetallic NPs were measured in ethylene glycol and distilled water, respectively for the first time.     

具有核壳结构的纳米CaCO3@SiO2的制备与表征

采用简单的溶胶-沉淀法制备了具有核壳结构的纳米CaCO3@SiO2复合产物。用X-射线衍射、电子扫描显微镜、X-射线能谱以及耐酸性测试等方法对粒子的包覆效果、化学组成等做了分析和表征。结果表明,用硬脂酸改性后的碳酸钙比较容易包覆无机的SiO2,SiO2在CaCO3表面包覆后形成了CaCO3为核,SiO2为壳的核壳结构。     

Tunable synthesis of mesoporous titania with different morphologies for dye-sensitized solar cells

Different TiO₂ mesoporous structures, including core-shell spheres (CCSs) and micro-tubes (MTs), are synthesized through adjusting the pH of the solution using TiOSO₄ as titanium source in a hydrothermal route. TiO₂ CSSs with an average diameter of 1.3–3.5 μm exhibit excellent light scattering property and high specific surface area (177.63 m² g^?1). TiO₂ MTs show ultrahigh specific surface area of 276.03 m² g^?1. Dye-sensitized solar cell is fabricated using TiO₂ CSSs as the light scattering layer and TiO₂ nanoparticles (NPs) layer as the bottom layer. The efficiency of Cell-NPs + CSSs is up to 9.24% due to the good light scattering effect and excellent dye loading capacity. Furthermore, TiO₂ MTs are introduced to form the NPs/MTs bottom layer. The Cell-NPs/MTs + CSSs achieves an outstanding efficiency of 9.60% due to the further optimized electron transport path.     

Rapid synthesis of Ag@Ni core-shell nanoparticles using a microwave-polyol method

Mixtures of AgNO₃ and NiSO₄·6H₂O, NiCl₂·6H₂O, or Ni(NO₃)₂·6H₂O were reduced in ethylene glycol (EG) in the presence of NaOH and poly(vinylpyrrolidone) (PVP) under microwave (MW) heating for 10 min. Then, we succeeded in the synthesis of Ag core-Ni shell nanoparticles, denoted as Ag@Ni, in high yield. The formation of Ag@Ni particles was confirmed using energy dispersed X-ray spectroscopic (EDS) measurements and selected area electron diffraction (SAED) patterns. The growth mechanism of Ag@Ni is discussed. The UV-Vis spectra of Ag@Ni were similar to those of Ni particles.     

On the operating mode of bimetallic systems for environmental remediation

This letter challenges the concept that Fe(0)/Me(0) bimetallic systems enhance contaminant reduction on Me(0) surfaces. It is shown on a pure thermodynamic perspective that any enhancement of contaminant reduction by Fe(0) in the presence of a second more electropositive elemental metal (Me(0)) is the result of an indirect process resulting from iron corrosion. This demonstration validates the concept that aqueous contaminant removal in the presence of Fe(0) mostly occurs within an in situ generated oxide film on Fe(0).     

Radiation induced synthesis of Au-Pd nanoparticles of random alloy structure supported on carbon particles using the high energy electron beam

Au-Pd bimetallic nanoparticles supported on carbon particles were synthesized by reduction of precursor ions in an aqueous solution irradiated with a high energy electron beam. The composition of the samples was analyzed by the inductively coupled plasma atomic emission spectrometry (ICP-AES), and the morphology of the samples was observed by the transmission electron microscope (TEM). TEM micrographs indicated that Au-Pd particles of ca. 5-nm were well dispersed on the surface of carbon particles of ca. 30-nm without any serious agglomeration. Addition of citric acid to the initial solution and high pH were found to be effective for formation of random alloy structure in the resultant bimetallic nanoparticles. The change in the bimetallic structure from core-shell to random alloy was identified by techniques of the X-ray diffraction (XRD) and the extended X-ray absorption fine structure (EXAFS).     

Study on the microstructure and mechanical properties of explosive welded 2205/X65 bimetallic sheet

In this study, microstructural inhomogeneity and mechanical properties of explosive welded 2205 stainless steel/X65 pipe steel bimetallic sheets were investigated. The explosion-bonded 2205/X65 bimetallic sheets had good shear strength. The tensile shear fracture primarily occurred in the interior of X65 material and primarily exhibited dimple morphology. Fine crystal grains in the 0.5–2 μm range were found all over the narrow localized melted zone near the 2205/X65 interface, whereas a coarse columnar crystal structure growing along the perpendicular direction to the interface formed in the wider localized melted zone. Quasi-cleavage fracture morphology was observed in the coarse columnar crystal region after the stratified tensile test. The junction of the three regions near the interface with large differences in morphology was the weak point in the bimetallic sheet, where Y-shaped cracking easily occurred under a loading force. Stratified tensile test and micro-hardness tests for the explosively welded bimetallic sheet showed that severe hardening occurred in the 2205 cladding, and the most severe metal hardening occurred near the interface. Tests for 45° face bending and root bending tests were conducted under extreme conditions. The results showed that voids were prone to appeared in the peninsula and island morphologies near the interface.     

Study on the possibility of continuous-casting of bimetallic components in condition of direct connection of metals in a liquid state

The possibility of producing bimetals by continuous casting method when composition of components occurs in liquid state without mixing is considered. Contact layers of composite metals were investigated by methods of metallographic, X-ray diffraction, microscopic and ultrasonic analyses. Binary mixtures of eutectic type Al–Zn, Al–Sn, Al–Pb were selected. The numerical estimations for bimetallic casting of some metal-alloy pairs were also conducted to achieve the optimization of casting process condition.It was observed that the size of diffusion zone of interface layer was 0.1–0.5 mm in producing bimetallic compositions by direct connection of liquid phase components. The microstructures observed in bimetallic binary samples were well accorded to those expected from the phase diagrams. It could be concluded from the mathematical simulation for casting process that qualified bimetallic casting billet and plate can be continuously cast by carefully controlling the casting process condition such as withdrawing speed.     

Synthesis and characterization of Ag/polyaniline core-shell nanocomposites based on silver nanoparticles colloid

Ag/polyaniline core-shell nanocomposites were successfully synthesized via in situ chemical oxidation polymerization of aniline based on mercaptocarboxylic acid capped Ag nanoparticles colloid. The morphology and structure of the products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and UV-Vis spectra. A possible formation mechanism of the Ag/polyaniline core-shell nanocomposites was also proposed.     

Hazard reduction for the application of titania nanoparticles in environmental technology

Photocatalytically active titania (TiO2) nanoparticles are applied, and considered for application, in the degradation of hazardous substances. However, these nanoparticles are also hazardous by themselves. High efficiency immobilization of TiO2 nanoparticles on large inorganic supports that are not vulnerable to photocatalytic degradation is conducive to hazard reduction. Immobilization should also aim at minimizing the release of TiO2 nanoparticles from such supports due to attrition. In doing so there may be a trade off between hazard and photocatalytic activity.     

Fabrication of PtNi bimetallic nanoparticles supported on multi-walled carbon nanotubes

Platinum/nickel bimetallic nanoparticles supported on multi-walled carbon nanotubes (xPtNi/CNTs) were synthesised. The fabrication process includes the chemical modification on the graphene surface of CNTs by acid treatment and the subsequent deposition of Pt or PtNi bimetallic nanoparticles with different compositions of Pt (x = 100, 90, 80 and 70 wt%). The deposition was carried out using ethylene glycol as a reducing agent in the polyol method or using poly(amidoamine) dendrimer as a platform and sodium borohydride as a reducing agent to load the metal nanoparticles on the CNT surface. The structures of the produced PtNi/CNT nanoparticles were investigated by ultraviolet absorption spectra, X-ray diffraction (XRD) and the composite ratio consisting of 70 wt% of metal content and 30 wt% of CNTs was confirmed by the thermogravimetric analysis. The morphology and the phase identification of the produced PtNi/CNT nanoparticles were investigated by high-resolution scanning electron microscope, transmission electron microscope and XRD measurements. It was observed that the deposited Pt and PtNi bimetallic nanoparticles on the surface of CNTs had average particle sizes of 2–16 nm, when they were prepared from the polyol method. On the other hand, the PtNi/CNT nanoparticles prepared by using a dendrimer as an intermediate had a smaller particle size and more uniform size distribution of the quantum dot size ranged from 2 to 4 nm.     

Synthesis of (Sn,Zn)(O,S) bimetallic oxysulfide catalyst for the detoxification of Cr+6 in aqueous solution

Herein, we report the bimetallic (Sn,Zn)(O,S) oxysulfide nanocatalyst with a facile method. The Sn-based catalyst with the addition of Zn was synthesized with the proportions of 0, 20, 30 and 50% of Zn to Sn precursors for preparation. The catalysts were characterized by XRD, TEM, SEM XPS, and UV–vis instruments. The nanocatalysts were also tested for the detoxification of Cr⁺⁶. The Sn-20 catalyst with 20 M percent of Zn(Ac)₂·2H₂O showed an excellent performance for the induced photocatalytic reduction of Cr⁺⁶ under visible light irradiation at room temperature. The complete reduction of Cr⁺⁶ was achieved within 80 min by Sn-20 catalyst. However, 85.6, 97, and 94% of Cr⁺⁶ reductions were achieved within 80 min under visible light illumination by Sn-0, Sn-30, and Sn-50 catalysts, respectively. Hence, the bimetallic (Sn,Zn)(O,S) oxysulfide nanocatalyst will be a candidate and highly potential material for the detoxification of Cr(VI)-containing polluted water.     

Green synthesis of silver nanoparticles using Beta vulgaris: Role of process conditions on size distribution and surface structure

The present work reports the green synthesis of silver nanoparticles, using Beta vulgaris peel extract with a subsequent investigation on the size distribution and surface structure of nanoparticles formed under various process conditions. The green-chemical reduction mechanism of silver ions to nanoparticles by the active organic functional groups present in the extract was characterized, using the respective spectroscopic techniques. The effects of various process parameters, including induced intraparticle ripening, were attributed to the controlled formation of anisotropic silver nanoparticles within the supporting matrix of the extract. The plasmon absorption and resonance scattering properties were expected to be favourable for small and larger size nanoparticles (below 25 nm and above 75 nm) respectively, which was considered to be an indicative aspect for synthesizing nanoparticles of narrow size distribution. The zeta potential and dynamic light scattering (DLS) results suggest the good stability and mono-dispersed size distribution of the silver nanoparticles. The transmission electron microscope, selective area electron diffraction (SAED) and X-ray diffraction studies infer that the nanoparticles formed were spherical/quasi-spherical in shape, which primarily exhibited a face centred cubic crystal (FCC) structure. The green-chemical reduction of organic phases in the extract (especially amine (NH₂) groups) as reflected through shifts observed in the Fourier-transform infra red (FTIR) peaks, reveal the possible interaction of the organic molecules with the silver ions in the effective formation, surface modification and stabilization of the silver nanoparticles.     

Metallurgical slag properties as a support material for bimetallic nanoparticles and their use in the removal of malachite green dye

Fe-Cu oxides nanoparticles (Nps) were embedded in two steel slag wastes (SSB and SSW) to develop SSB/Fe-Cu and SSW/Fe-Cu nanocomposites. Nps with mean sizes between 10–20 and 6–10 nm on SSW and SSB, respectively are agglomeration with a different shape. Their characteristics were investigated by XRD, TEM, BET, SEM techniques. The Nps modified the morphology of both support materials. XRD pointed out the presence of Cu and Fe. The proportion of Cu concentration was higher than the one of Fe. Nanocomposites were tested in malachite green removal from aqueous solution. The adsorption kinetic indicated physisorption and chemisorption as the main mechanisms of adsorption. The adsorption capacities were 88.26 and 63.55 mg/g for SSW/Fe-Cu and SSB/Fe-Cu, respectively. This novel, easy to prepare and low-cost nanocomposites is an efficient adsorbent material. The presence of calcium compounds may improve Nps deposition an MG removal. Materials with ferric phases are not as efficient as the first one; Fe is not well supported on the material. The removal of MG took place by dye structure modification and by interactions with Cu nanoparticles improving the oxidation-reduction process, through synergic effects.     

Single particle model of SnO2 deposition on silver nanoparticles

Silver nanoparticles coated with almost uniform, thin shell of tin oxide are synthesized via a simple colloid chemistry technique, where the reduction of Ag⁴⁺ to Ag⁰ followed by the encapsulation of oxide takes place. The as prepared dispersions of tin oxide coated silver nanocomposite particles display a surface plasmon band, which is significantly red shifted with respect to that of bare Ag. Morphology of the composite nanoparticles was investigated by TEM. Presence of SnO₂ shell on the silver nanoparticles was also supported by XPS results. A theoretical single particle model has been proposed for the formation of tin oxide shell on the silver nanoparticles.