Au-Pd Alloy Research Articles

Polyhedral-AuPd nanoparticles-based dual-mode cytosensor with turn on enable signal for highly sensitive cell evalution on lab-on-paper device

A novel dual-mode cytosensor based on polyhedral AuPd alloy nanoparticles (PH-AuPd NPs) and three-dimentional reduced graphene oxide (3D-rGO) was constructed for highly sensitive detection of MCF-7 cells. The 3D-rGO was in situ synthesized on the paper working electrode (PWE) by a pollution-free hydrothermal method, increasing the specific surface area and further facilitating the modification of Au nanoparticles (AuNPs). After modified with AuNPs, the Au@ 3D-rGO/PWE was then functionalized by aptamer H1 to trap MCF-7 cells. To construct the cytosensor, PH-AuPd NPs was prepared as a novel catalytic material, and further modified with aptamer H2 for recognizing MCF-7 cells. With the occurrence of efficient recognition of MCF-7 cells, PH-AuPd NPs were bound onto the surface of the cells, and could catalyze H2O2 to generate •OH, leading to an amplified electrochemical signal. Meanwhile, as the electrolyte solution flowed, the •OH are transferred outward to the colorimetric detection zone, and catalyzed a chromogenic substrate TMB forms a colored product. The electrical signal measurement and colorimetric detection were carried out on a compatibly designed lab-on-paper device (LPD), realizing a dual-mode signal readout. This paper-based dual-mode cytosensor provided a relatively low detection limit of 20 cells mL−1 and a sensitive detection from 50 cells mL−1 to 107 cells mL−1 for MCF-7 cells, providing a reliable pathway of sensitively detecting cancer cells in clinical applications.

Ti-Doped Pd-Au Catalysts for One-Pot Hydrogenation and Ring Opening of Furfural

Pd-Au bimetallic catalysts with different Pd/Au atomic ratios, supported on ordered structured silica (Hexagonal mesoporous silica—HMS, or Santa Barbara Amorphous-15—SBA-15) were evaluated for one-pot hydrogenation of furfural to 1,2-pentanediol. The surface and structural properties of the catalysts were deeply investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), N2 adsorption isotherms (BET), Infrared spectroscopy (IR), and acid capacity measurements. XPS studies revealed that Ti doped supports had higher dispersion of the active phase, particularly in the case of Pd-Au materials in which Ti played an important role in stabilizing the metallic species. Among the various process conditions studied, such as temperature (160 °C), catalyst amount (10% w/w), and reaction time (5 h), H2 pressure (500 psi) was found to improve the 1,2-pentanediol selectivity. The SBA silica bimetallic Ti-doped system showed the best performance in terms of stability and reusability, after multiple cycles. Under specific reaction conditions, the synergism between Pd-Au alloy and Ti doping of the support allowed the ring opening pathway towards the formation of 1,2-pentanediol in furfural hydrogenation.

Promoting effect of Au on Pd/TiO2 catalyst for the selective catalytic reduction of NOx by H2

Au promoted Pd/TiO2 catalysts with different Pd loading were investigated for the selective catalytic reduction of NOx by hydrogen (H2-SCR). The results showed that 1%Pd-0.5%Au/TiO2 catalyst exhibited the highest NOx conversion and N2 selectivity, as well as a wide activity temperature window. Moreover, the 1%Pd-0.5%Au/TiO2 catalyst offered remarkable resistance to high gas hourly space velocity (GHSV). XRD, XPS and TEM results illustrated that the excellent H2-SCR performance of 1%Pd-0.5%Au/TiO2 catalyst was closely related to the formed PdAu alloy and the higher dispersion of active sites compared with 1%Pd/TiO2. In-situ DRIFTS results revealed that more and new adsorbed nitrogen oxides species, as well as more adsorbed NH3 and NH4+ active species generated over 1%Pd-0.5%Au/TiO2 catalyst, thus accelerating the ability to active H2 atom and the subsequent reaction with adsorbed nitrogen oxides species.

Design of a difunctional Zn-Ti LDHs supported PdAu catalyst for selective hydrogenation of phenylacetylene

To suppress hydrogenation of alkene at complete alkyne conversion, a difunctional Zn-Ti layered double hydroxides (LDHs) supported bimetallic PdAu alloy catalyst with alkalinity was designed and prepared by a photochemical reduction method. On the basic of TEM and XPS results, the formation of Pd-Au alloy was determined. The alloy nanoparticles had incorporated into the interlayer region of LDHs, giving a strong interaction between them. As expected, the PdAu/ZnTi catalysts exhibited excellent styrene selectivity (over 90%) even when the reaction time was prolonged (6 h) after full conversion of phenylacetylene. Such excellent selectivity is attributed to the synergistic effect between bimetallic alloy nanoparticles and Zn-Ti LDHs. The selective formation of polar hydrogen species derived from the heterolytic dissociation of H2 at the interface between PdAu alloy and basic sites of Zn-Ti LDHs is more favorably reactive to alkyne compared with alkene. Moreover, the Zn-Ti LDHs supported PdAu catalyst exhibited great recyclability. The difunctional catalyst is expected to be potentially promising for industrial applications.

Facile synthesis of AuPd nanoparticles anchored on TiO2 nanosheets for efficient dehydrogenation of formic acid

Safe and efficient hydrogen storage is one of the key technologies for the widespread utilization of hydrogen energy. Formic acid (FA) is regarded as a safe and convenient chemical hydrogen storage material. However, the lack of highly efficient heterogeneous catalysts hinders its practical application. Herein, we presented a facile wet-impregnated deposition method to synthesize ultrafine AuPd alloy nanoparticles anchored on TiO2 nanosheets (AuPd/TiO2 nanosheets) which were used as high efficient catalysts for the dehydrogenation of FA. TiO2 nanosheets were calcined at different temperatures to modify the catalytic activity of catalyst. AuPd/TiO2 nanosheets-400 exhibits the superior activity for catalyzing the FA to release 96% of overall hydrogen content with an initial turnover frequency value of 592 mol H2 mol−1 metal h−1 at 25 °C and low activation energy of 11.8 kJ mol−1. Detailed characterizations show that the superior catalytic performance can be ascribed to the alloy structure of AuPd centers, the phase and crystallinity of TiO2 nanosheets, and the strong electron transfer interaction between AuPd nanoparticles and TiO2 nanosheets substrate.

Hydrogen permeation and surface properties of PdAu and PdAgAu membranes in the presence of CO, CO2 and H2S

Using the electroless deposition technique with different deposition sequences, it was possible to obtain a single phase PdAgAu ternary alloy after treatment at 773 K during 7 days. Despite the order of deposition, the samples exhibited similar hydrogen permeation flux at the same temperature and pressure. In the presence of CO, the PdAgAu ternary alloy membranes showed a lower inhibition on the hydrogen permeance compared with the binary PdAu alloy at 623 and 673 K. On the contrary, under CO2 containing streams, the ternary alloy showed a higher inhibition with a complete hydrogen recovery after removing CO2 from the stream. When H2S was introduced in the 13% CO2/13% Ar/74% H2 stream, a higher permeance decrease was observed on both the PdAu and PdAgAu alloy membranes. After removal of H2S, a hydrogen recovery of 60% and 76% was measured for the PdAu and PdAgAu membranes, respectively. Pd surface segregation was observed on the Pd82Ag15Au3–873 K-5 d and the Pd78Au6Ag16–773 K-7 d samples upon exposure to CO containing streams. Instead, silver surface segregation was observed by XPS after exposing the PdAgAu ternary alloy to CO2 containing streams.

Biogenic synthesis of shape-tunable Au-Pd alloy nanoparticles with enhanced catalytic activities

Herein, we report the synthesis of bimetallic Au-Pd and monometallic Au and Pd nanoparticles (NPs) by successive reduction of the respective metal ions using phytochemicals in the form of plant extract under ambient conditions. Phytochemicals act both as reducing and shape directing agent for metal and alloy NPs. The synthesized nanostructures were characterized by different microscopic, spectroscopic and diffractometric techniques. Microscopic results confirmed that the shape and size of the alloy nanostructures can be tuned by varying the concentration ratio of metal ions in the reaction medium. Energy dispersive X-ray and X-ray photoelectron spectroscopic analysis confirmed the formation of bimetallic Au-Pd nanostructures. The purity and crystalline properties were studied by X-ray diffraction technique. UV–vis spectra were recorded to study the optical properties of the synthesized nanostructures. Further, we tested the catalytic activity of both the monometallic and bimetallic alloy nanostructures in borohydride reduction of hazardous organic dye molecules in aqueous medium. The bimetallic alloy NPs exhibit better catalytic activities compared to their respective monometallic nanoparticles.

Concerted Catalysis by Adjacent Palladium and Gold in Alloy Nanoparticles for the Versatile and Practical [2+2+2] Cycloaddition of Alkynes.

A Pd-Au alloy efficiently catalyzed the [2+2+2] cycloaddition of substituted alkynes. Whereas monometallic Pd and Au catalysts were totally ineffective, Pd-Au alloy nanoparticle catalysts with a low Pd/Au molar ratio showed high activity to give the corresponding polysubstituted arenes in high yields. A variety of substituted alkynes participated in various modes of cycloaddition under Pd-Au alloy catalysis. The Pd-Au alloy catalysts exhibited high air tolerance and reusability.

Hydrosilylation of Allenes Over Palladium–Gold Alloy Catalysts: Enhancing Activity and Switching Selectivity by the Incorporation of Palladium into Gold Nanoparticles

An efficient synthetic route to alkenylsilanes involving the hydrosilylation of allenes with supported Pd–Au alloy catalysts has been developed. The incorporation of Pd atoms into Au nanoparticles remarkably enhanced the catalytic activity and product selectivity. Pd–Au alloy catalysts with a low Pd/Au ratio were highly effective for the hydrosilylation at an ambient temperature, and the corresponding β‐alkenylsilanes were obtained as a main product in good to high yields.

Toxicity of porcelain-fused-to-metal substrate to zebrafish (Danio rerio) embryos and larvae

AimsPorcelain-fused-to-metal (PFM) crowns are a standard restoration technique in dentistry, but toxicity of PFM in vivo has not been systematically evaluated. The present study evaluated the effects of various metal alloy shells of PFM crowns on the development of zebrafish embryos and larvae in order to determine the safety of these materials. Main methodsGold palladium (Au-Pd), silver palladium (Ag-Pd), Nickel chromium (Ni-Cr), cobalt chromium (Co-Cr), titanium (Ti) alloy porcelain crowns were immersed in artificial saliva for 1, 4, and 7 weeks, and the leach solution was collected and used to treat zebrafish embryos at 4–144 h PFM. Toxicity was assessed based on mortality, spontaneous movement, heart rate, hatchability, malformation, and swimming behavior. Key findingsThe 1-week leachates of the five PFMs were not toxic to zebrafish. The rates of mortality and malformation of zebrafish in the Ni-Cr alloy group were increased whereas spontaneous movement, heart rate, and swimming behavior were decreased for 4- and 7-week leachates. SignificanceAmong metal substrates commonly used in dental work, Ni-Cr alloy was most toxic, followed by Co-Cr and Ag-Pd alloys. Ti and Au-Pd alloys showed good biocompatibility and are therefore the most suitable materials for clinical applications.

Synthesis of AuPd alloy nanoparticles on ZnO nanorod arrays by sputtering for surface enhanced Raman scattering

AuPd alloy nanoparticles (NPs) on ZnO nanorod arrays were synthesized by a facile physical vapor deposition (PVD) method – sputtering. The AuPd/ZnO heterostructures can be controlled by varying the sputtering time. Various spectroscopic and microscopic techniques were employed to characterize the nanocomposites. Surface enhanced Raman scattering (SERS) experiments showed that the nanocomposites possess excellent molecule sensing ability. Owing to the surface plasmon resonance (SPR) of noble metal nanostructures and the synergetic effect between AuPd alloy nanoparticles and ZnO nanorods, the AuPd/ZnO nanocomposites hold promise in molecule detection applications.

Inclusions in an isoferroplatinum nugget from the Freetown Layered Complex, Sierra Leone

ABSTRACTInclusions of platinum-group minerals (PGM) within alluvial isoferroplatinum nuggets from the Freetown Peninsula, Sierra Leone, are aligned with their shape determined by the structure of their host. The edges of the majority of the inclusions lie at 0°, 45° or 90° to external crystal edges of the nugget which shows that the inclusions are not randomly oriented earlier minerals incorporated within their host. The inclusions are later infills, probably formed at the surface of the nugget during growth and subsequently enclosed by the growing nugget. PGM on the present surface of the nugget represent the last stage of this partnership. A single nugget containing abundant inclusions is described here but similar features are observed in other nuggets from the same area. The inclusions contain laurite (RuS2), irarsite–hollingworthite (IrAsS–RhAsS), Pd–Te–Bi–Sb phases, Ir-alloy, Os-alloy, Pd-bearing Au, an Rh–Te phase, Pd–Au alloy and Pd–Pt–Cu alloy. PGM found on the nugget surface include laurite, irarsite and cuprorhodsite (CuRh2S4). The Pd–Te–Bi–Sb phases may include Sb-rich keithconnite (Pd20S7) and compositions close to the kotulskite–sobolevskite solid-solution series (PdTe–BiTe). Textural evidence suggests that formation of the nuggets began with the isoferroplatinum host and the voids were filled starting intergrowths of laurite and irarsite–hollingworthite with both laurite and irarsite–hollingworthite often showing compositional zonation and each of them replacing the other. Filling of the voids probably continued with Pd-Cu-bearing gold, Sb-rich keithconnite (Pd,Pt)20.06(Te,Sb,Bi)6.94, keithconnite, telluropalladinite Pd9(Te,Bi)4, RhTe and finally Ir-alloy and then Os-alloy. The nuggets are thought to be neoform growths in the organic- and bacterial-rich soils of the tropical rain forest cover of the Freetown intrusion. The mineralogical assemblage in the layered gabbros of the intrusion has been previously shown to differ from the alluvial assemblage in the rivers and these inclusions, not seen in Pt3Fe in the unaltered rocks, add a further item to the catalogue of differences.

Porous Nanocrystalline Silicon Supported Bimetallic Pd-Au Catalysts: Preparation, Characterization, and Direct Hydrogen Peroxide Synthesis.

Bimetallic Pd-Au catalysts were prepared on the porous nanocrystalline silicon (PSi) for the first time. The catalysts were tested in the reaction of direct hydrogen peroxide synthesis and characterized by standard structural and chemical techniques. It was shown that the Pd-Au/PSi catalyst prepared from conventional H2[PdCl4] and H[AuCl4] precursors contains monometallic Pd and a range of different Pd-Au alloy nanoparticles over the oxidized PSi surface. The PdAu2/PSi catalyst prepared from the [Pd(NH3)4][AuCl4]2 double complex salt (DCS) single-source precursor predominantly contains bimetallic Pd-Au alloy nanoparticles. For both catalysts the surface of bimetallic nanoparticles is Pd-enriched and contains palladium in Pd0 and Pd2+ states. Among the catalysts studied, the PdAu2/PSi catalyst was the most active and selective in the direct H2O2 synthesis with H2O2 productivity of 0.5 at selectivity of 50% and H2O2 concentration of 0.023 M in 0.03 M H2SO4-methanol solution after 5 h on stream at −10°C and atmospheric pressure. This performance is due to high activity in the H2O2 synthesis reaction and low activities in the undesirable H2O2 decomposition and hydrogenation reactions. Good performance of the PdAu2/PSi catalyst was associated with the major part of Pd in the catalyst being in the form of the bimetallic Pd-Au nanoparticles. Porous silicon was concluded to be a promising catalytic support for direct hydrogen peroxide synthesis due to its inertness with respect to undesirable side reactions, high thermal stability, and conductivity, possibility of safe operation at high temperatures and pressures and a well-established manufacturing process.

PdAu@MIL-100(Fe) cooperatively catalyze tandem reactions between amines and alcohols for efficient N-alkyl amines syntheses under visible light

PdAu@MIL-100(Fe), with PdAu alloy nanoparticles of ca. 1.7 nm encapsulated inside MIL-100(Fe) cavities, were prepared via a double-solvent impregnation followed by photoreduction. As compared with bare Pd@MIL-100(Fe), bimetallic PdAu@MIL-100(Fe) showed superior activities for the tandem reactions between amines and alcohols to produce N-alkyl amines under visible-light irradiation, ascribed to the promoting effect of metallic Au in the photocatalytic alcohol-to-aldehyde dehydrogenation. A Pd/Au ratio dependent N-alkylation activity was observed over PdAu@MIL-100(Fe), implying the possibility of synchronizing the reaction rates of two consecutive steps in the N-alkylation reaction, i.e., photocatalytic alcohol-to-aldehyde dehydrogenation and imines hydrogenation, to optimize the whole reaction. This study provides a highly efficient and stable catalytic system for the realization of alkylation of amines via a successful coupling of MOF-based photocatalysis and metal nanoparticle-based hydrogenation. This work also demonstrates that the reaction rates of different catalytic steps in a cascade/tandem reaction can be synchronized for an efficient overall reaction via a rational design of the multifunctional catalysts.

Bimetallic AuPd alloy nanoparticles deposited on MoO3 nanowires for enhanced visible-light driven trichloroethylene degradation

Photocatalytic oxidation reactions are regarded as promising green methods for the photodegradation of volatile organic compounds such as trichloroethylene. However, the low efficiency and selectivity of the existing photocatalysts limit practical applications of this technique. In this work, MoO3 nanowires were easily decorated with well-dispersed bimetallic Au–Pd alloyed nanoparticles (AuPd NPs) by a two-step wet-chemical strategy (hydrothermal and chemical reduction). The morphology, size, crystal structures, and mechanism of operation of the photocatalysts were investigated by a series of techniques (X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy, etc.). Deposition of the AuPd NPs on the surface of the MoO3 nanowires led to a dramatic enhancement (11.5 times higher than that of the pure MoO3 nanowires) of the photocatalytic activity of the synthesized photocatalysts. This remarkable improvement of the activity can be attributed to the synergistic effect between Au and Pd NPs, which results in effective separation of the electron and holes and promotes the charge-separation efficiency. The enlarged specific surface area and enhanced stability of the catalysts also resulted in excellent photocatalytic performance. The developed photocatalysts are promising for the removal of volatile organic compounds.

Thermodynamic properties of Ag–Au–Pd alloys measured by a solid-state EMF method

Although the Ag–Au–Pd system is crucial for several industrial applications and for the research on fundamental physics, no thermodynamic data on this ternary system at low temperatures have been reported in the literature. In the present study, activities of silver are directly measured by employing a solid-state EMF method, by using AgI as the solid electrolyte. The EMF was determined using a galvanic cell $$ \left( - \right){\text{Pt}}\left| {\text{C}} \right.\left| {\text{Ag}} \right|{\text{AgI}}\left| {{\text{Ag-Au-Pd alloy}}} \right|{\text{C}}\left| {{\text{Pt}}\left( + \right)} \right. $$ , which produced novel experimental data on the thermodynamic properties of Ag–Au–Pd alloys. Darken method was used to calculate integral excess thermodynamic properties from the data. New thermodynamic characteristics, such as integral excess mixing Gibbs energy, entropy and enthalpy of the Ag–Au–Pd alloys, have been generated in a temperature range of 475 and 675 K. Isoactivity lines of silver in the system have been drawn throughout the Gibbs triangle. Thermodynamic properties of the binary Au–Pd alloys have been compared with the previous investigations.

AuPd−Fe3O4 Nanoparticle Catalysts for Highly Selective, One‐Pot Cascade Nitro‐Reduction and Reductive Amination

AbstractExceedingly chemoselective preparation of secondary amines from the cascade reaction of nitro reduction followed by reductive amination of the resulting amine with an aldehyde through the use of bimetallic AuPd alloy nanoparticle catalyst is described. We prepared a AuPd alloy nanocatalyst supported on Fe3O4 in gram scale without calcination. One pot synthesis of a number of secondary amines was achieved from a variety of nitroarenes and aryl or alkyl aldehydes under 1 atm of H2 at room temperature. No N‐debenzylation was observed in the case of the reactions involving aryl aldehydes, which is often observed in the reductive amination catalysed by a transition metal catalyst such as palladium. We also accomplished efficient one‐pot synthesis of a number of N‐aryl substituted isoindolinone derivatives from 1‐formylbenzoic acid and several nitroarenes using the same reaction conditions. Furthermore, thanks to the magnetic property of the Fe3O4 support, the AuPd−Fe3O4 NPs could be easily separated and reused up to 20 times without the loss of its catalytic activity.magnified image

Dual nanoenzyme modified microelectrode based on carbon fiber coated with AuPd alloy nanoparticles decorated graphene quantum dots assembly for electrochemical detection in clinic cancer samples

The development of high-efficient technologies for cancer biomarkers detection has attracted tremendous research effort for its great clinic significance. In this work, we designed a new type of flexible and robust nanohybrid microelectrode by modifying carbon fiber with dual nanoenzyme, i.e., AuPd alloy nanoparticles (AuPd-ANPs) decorated graphene quantum dots (GQDs) assembly, and explored its practical application in electrochemical sensing system for sensitive detection of cancer biomarker hydrogen peroxide (H2O2) in human breast cancer cells and tissue. For the preparation of dual nanoenzyme modified microelectrode, ionic liquid was used as the electrolyte for the effective electrodeposition of GQDs on carbon fiber substrate to form a close-packed assembly under a very negative potential, then the highly dense AuPd-ANPs were uniformly decorated on GQDs assembly by electrodeposition. In virtue of the structural merits and synergistic contribution of dual nanoenzyme in enhancing the electrocatalytic activity to H2O2, the resultant nanohybrid microelectrode exhibited good sensing performances for electrochemical detection of H2O2, including a high sensitivity of 371 μA cm−2 mM−1, a wide linear range from 1.0 μM to 18.44 mM, a low detection limit of 500 nM (a signal-to-noise ratio of 3:1), as well as good selectivity and biocompatibility, which could be used for real-time tracking H2O2 released from different types of human breast cells and in situ sensitive detection of H2O2 in clinical breast cancer tissue.

Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane

This work investigates the influence of activation by microwave irradiation on the catalytic properties of Pd-Au/CSibunit catalysts in the hydrodechlorination of CCl4. Pd and Pd-Au samples were thoroughly characterized by CO chemisorption, X-ray diffraction, TPHD and STEM, and used in gas phase hydrodechlorination of tetrachloromethane. The studies showed that homogenous Pd-Au alloys are formed more efficiently if short-time microwave activation is applied instead of conventional activation by H2 reduction at 380 °C. These catalysts show higher activity, stability and higher selectivity towards the desired products (C1–C5 hydrocarbons) than the catalysts activated by conventional reduction in 10%H2/Ar flow.

Performance of Supported Au-Pd Alloy Nano Particles Catalyst for Base-free Synthesis of Imines by Self-coupling of Amine

Abstract A series of supported nano particles catalysts, Au/γ-Al2O3, Pd/γ-Al2O3 and Au-Pd/γ-Al2O3, were prepared by the impregnation reduction method. The catalytic performance of these catalysts for direct base-free synthesis of imines by self-coupling of benzylamine was investigated. The results show that the yield of imine could reaches 93% over bimetallic alloy Au-Pd/γ-Al2O3 catalyst, much higher than monometallic Au or Pd nano particle catalyst. The used catalyst is recovered and 44% yield of imine could be obtained after 5 recycling use of Au-Pd/γ-Al2O3.