AuPt Alloy Nanoparticles Research Articles

Gamma irradiation and microemulsion assisted synthesis of monodisperse flower-like platinum-gold nanoparticles/reduced graphene oxide nanocomposites for ultrasensitive detection of carcinoembryonic antigen

The platinum-gold (PtAu)/reduced graphene oxide (rGO) nanocomposites were obtained via the gamma irradiation assisted by microemulsion while PtAu NPs showed the monodispersed flower-like shape with small-sized (below 15 nm). Gamma irradiation controlled the reduction of graphene oxide and PtAu NPs meanwhile the microemulsion endowed PtAu NPs with porous monodisperse flower-like structure and inhibited the agglomeration of nanoparticles. The size of PtAu NPs was limited by confinement effects of graphene oxide and fragmentation ability of gamma irradiation. An ultra-sensitive, label-free immunosensor was developed on the base of above rGO supported PtAu alloy nanoparticles for the determination of carcinoma embryonic antigen (CEA). The flower-like PtAu/rGO nanocomposites had a higher faradaic current than other nanocomposites, and the obtained PtAu NPs/rGO nanocomposites not only improve the electrocatalytic activity and increase the electrode surface area in nanoscale dimension, but also provide a stable and biocompatible matrix for the convenient conjugation of antibody, thus providing a high-efficiency immunoassay platform. The developed immunosensor showed excellent performance for the detection of CEA with a low detection limit of 7 fg·mL−1 and a wide dynamic range from 10 fg·mL−1 to 1 × 108 fg·mL−1. In addition, the immunosensor system showed high specificity with the interference of ascorbic acid, bovine serum albumin, L-tryptophan and alpha fetal protein. The contribution of this work lies in the research of the synergistic effect of gamma irradiation and microemulsion in the formation of flower-like PtAu NPs/rGO nanoparticles applied in preparation of immunosensor. In view of the versatility of self-assembled nanoparticles, this strategy has great application prospects in fabrication of immunosensors and other biological devices.

Hierarchical Cu7S4-Cu9S8 heterostructure hollow cubes for photothermal aerobic oxidation of amines

Copper-based chalcogenides have been paid intensive attention as alternate photothermal catalysts for solar energy conversion. Despite considerable progress of copper sulfides nanostructure fabrication, combining independent copper sulfides polymorphs with various stoichiometries by forming heterojunction is still challenging. Herein, unique hierarchical nanosheet-assembled Cu7S4-Cu9S8 heterostructure hollow cubes with remarkable photothermal aerobic oxidation activity were prepared by a facile onepot chemical transformation route using Cu2O cubes as sacrificial template for the first time. In this reaction system, the introduction of proper sulfur source thioacetamide and moderate alkaline conditions plays a crucial role in phase transformation, and through tunning the reaction time, a series of Cu7S4, Cu7S4-Cu9S8, and Cu9S8 can be selectively prepared. Furthermore, the Cu7S4-Cu9S8 polymorphic heterostructure hollow cubes exhibit significantly enhanced photothermal aerobic oxidation performance of amines to the corresponding imines compared with the individual Cu7S4 and Cu9S8 in both N, N-dimethylformamide and acetonitrile solvent medium. Our results indicated that the strong near-infrared plasmonic absorption of Cu7S4-Cu9S8 facilitated hot carrier transport between Cu7S4 and Cu9S8, which subsequently promoted the catalytic reactions. Especially after uniform load of Au-Pt alloy nanoparticles, the photothermal aerobic oxidation activity was further enhanced due to their boosted synergistic local coupling enhancement effect between distinct components in the N, N-dimethylformamide solvent medium. Such enhanced photothermal reaction could effectively promote sunlight utilization in a wide range of photocatalytic reactions.

Electrochemical synthesis of AuPt nanoflowers in deep eutectic solvent at low temperature and their application in organic electro-oxidation

Deep eutectic solvents (DESs), called a new generation of green solvents, have broad applied in synthesis of nanomaterials due to their remarkable physicochemical properties. In this work, we used a unique strategy (adding moderate water (10%) to DES) to effectively prepare nanomaterials. Flower-like AuPt alloy nanoparticles were successfully synthesized using one-step electrochemical reduction method at a low potential of −0.30 V (vs. Pt) and a low temperature of 30 °C. In this process, the DES acted as solvent and shape-directing agent. More importantly, we used the electrode modified with the as-prepared nanomaterials as the anode to the electrochemical oxidation synthesis. The glassy carbon electrode modified with the AuPt nanoflowers was directly employed to the electro-oxidation of xanthene (XT) to xanthone (XO) under a constant low potential of 0.80 V (vs. Ag/AgCl) and room temperature, with a high yield of XO. Moreover, the synthesis process was milder and more environment-friendly than conventional organic syntheses. This new strategy would have a promising application in electroorganic synthesis fields.

Forming a Highly Active, Homogeneously Alloyed AuPt Co-catalyst Decoration on TiO2 Nanotubes Directly During Anodic Growth.

Au and Pt do not form homogeneous bulk alloys as they are thermodynamically not miscible. However, we show that anodic TiO2 nanotubes (NTs) can in situ be uniformly decorated with homogeneous AuPt alloy nanoparticles (NPs) during their anodic growth. For this, a metallic Ti substrate containing low amounts of dissolved Au (0.1 atom %) and Pt (0.1 atom %) is used for anodizing. The matrix metal (Ti) is converted to oxide, whereas at the oxide/metal interface direct noble metal particle formation and alloying of Au and Pt takes place; continuously these particles are then picked up by the growing nanotube wall. In our experiments, the AuPt alloy NPs have an average size of 4.2 nm, and at the end of the anodic process, these are regularly dispersed over the TiO2 nanotubes. These alloyed AuPt particles act as excellent co-catalyst in photocatalytic H2 generation, with a H2 production rate of 12.04 μL h-1 under solar light. This represents a strongly enhanced activity as compared to TiO2 NTs decorated with monometallic particles of Au (7 μL h-1) or Pt (9.96 μL h-1).

Electrochemical Detection of Hydroxylamine via Au-Pt Alloy Nanoparticle-modified Single-walled Carbon Nanotube Electrodes.

In the present study, we developed an electrochemical sensor for highly sensitive detection of hydroxylamine using Au-Pt alloy nanoparticles. Au-Pt alloy nanoparticles were electrochemically deposited on a working electrode made of single-walled carbon nanotubes. The framework composition in the Au-Pt alloy nanoparticle was easily controlled by adjusting the Au3+:Pt4+ composition ratio in the precursor solution. Morphological and chemical characterizations of the resulting Au-Pt alloy nanoparticles were performed using field emission scanning electron microscopy, X-ray diffraction, and energy dispersion X-ray spectroscopy. When the Au3+:Pt4+ ratio in the precursor solution was 1:5, the ratio of Au:Pt atom in alloy nanoparticle was about 6:4. Au60Pt40 alloy nanoparticles were found to have the optimum synthetic ratio for hydroxylamine detection. The electrocatalytic performance of Au-Pt alloy nanoparticles in the presence of hydroxylamine was also characterized using cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. In the chronoamperometric detection of hydroxylamine, the sensor exhibited a detection limit of 0.80 μM (S/N = 3) and a high sensitivity of 184 μA mM-1 cm-2. Moreover, the amperometric response of the sensor in 1 mM hydroxylamine was stable for a long time (450 s). Long-term stability tests showed that the current responses to hydroxylamine were 96, 91 and 85% of the initial signal value after storage for 5, 10, and 20 days, respectively.

Au-Pt alloy nanoparticles obtained by nanosecond laser irradiation of gold and platinum bulk targets in an ethylene glycol solution

Au-Pt alloy nanoparticles (NPs) of different compositions ( Au0Pt100 , Au30Pt70 , Au50Pt50 , Au70Pt30 , and Au100Pt0 were obtained using the nanosecond laser ablation of gold and platinum bulk targets in ethylene glycol, followed by mixing highly monodisperse Au and Pt nanocolloids, for the first time. UV-vis absorption spectra of NPs showed that by increasing the Au content in the Au-Pt NPs, the surface plasmon resonance (SPR) peak red-shifted, from 260 to 573nm in a nonlinear way. In addition, the mean crystalline size, crystal structure, d-spacing, and lattice parameters of NPs were estimated from the XRD spectra. Microscopy studies revealed the most NPs have a spherical or near-spherical shape, and the average sizes of Au0Pt100 , Au30Pt70 , Au50Pt50 , Au70Pt30 , and Au100Pt0 NPs were calculated to be 12.50, 14.15, 18.53, 19.29, and 26.38nm, respectively. Also, the chemical identity of the molecules adhering to the NPs surface was considered by Raman and FT-IR spectroscopy techniques. Among different synthesis methods, the demonstrated technique allows easy synthesis of alloy NPs in aqueous media at room temperature with no formation of by-products.

Selective deposition of Au-Pt alloy nanoparticles on ellipsoidal zirconium titanium oxides for reduction of 4-nitrophenol

Au-Pt alloy nanoparticles that are selectively anchored on TiO2 surface of the ellipsoidal zirconium titanium composite oxides were successfully prepared by a facile two-step method: prefabricated binary composite oxides on the ellipsoidal Fe2O3@SiO2 by a versatile cooperative template-directed coating method, and then in situ formation of Au-Pt alloy NPs with Sn2+ as the reduction agent. The alloy catalysts were characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The result suggested that highly dispersive and ultrafine Au-Pt alloy nanoparticles were deposited onto TiO2 surface of the binary oxides solely. The particle size of nanoalloys was closely related to the ratio of Zr: Ti in the composite oxides shell. Increasing the content of Zr element led to a growth in the size of alloy nanoparticles. When used as catalysts for the reduction of 4-nitrophenol, the prepared supported alloyed catalysts exhibited high catalytic activity, and the sample could be easily recycled without a significant decrease of the catalytic activity.

AuPt Alloy Nanostructures with Tunable Composition and Enzyme-like Activities for Colorimetric Detection of Bisulfide

Tuning the enzyme-like activity and studying the interaction between biologically relevant species and nano-enzymes may facilitate the applications of nanostructures in mimicking natural enzymes. In this work, AuPt alloy nanoparticles (NPs) with varying compositions were prepared through a facile method by co-reduction of Au3+ and Pt2+ in aqueous solutions. The composition could be tuned easily by adjusting the molar ratios of added Pt2+ to Au3+. It was found that both peroxidase-like and oxidase-like activity of AuPt alloy NPs were highly dependent on the alloy compositions, which thus suggesting an effective way to tailor their catalytic properties. By investigating the inhibitory effects of HS− on the enzyme-like activity of AuPt alloy NPs and natural enzyme, we have developed a method for colorimetric detection of HS− and evaluation of the inhibiting effects of inhibitors on natural and artificial enzymes. In addition, the responsive ability of this method was influenced largely by the composition: AuPt alloy NPs show much lower limit of detection for HS− than Pt NPs while Pt NPs show wider linear range than AuPt alloy NPs. This study suggests the facile way not only for synthesis of alloy nanostructures, but also for tuning their catalytic activities and for use in bioanalysis.

Monitoring of an Anti-Ulcer Drug Rabeprazole Using Au-Pt Bimetallic Alloy Nanoscale Electrochemical Sensor

A new highly selective and sensitive electrochemical sensor has been developed, whereby working electrode is modified with bimetallic Au-Pt alloy nanoparticles (NPs). Au-Pt alloy NPs were prepared by a facile method using non/less toxic chemicals. The optical properties of the synthesized NPs were studied by UV-Visible spectroscopy. The surface structure was characterized by X-ray diffraction and scanning electron microscopy. The NPs were found spherical with an average diameter of 14.6 nm. The electrochemical response of modified electrode with polypyrrole and Au-Pt alloy NPs toward the detection of rabeprazole (antiulcer drug) was systematically investigated though cyclic, square wave and differential pulse voltammetry methods. Under optimized conditions, the developed sensor showed its promise for the trace level (1.29 μM) detection of the analyte. Moreover, the designed sensor demonstrated excellent reproducibility and maintained its integrity in a wide pH range and different supporting electrolytes for the sensing of rabeprazole. The Au-Pt alloy NPs based electrochemical sensor exhibited good selectivity, high sensitivity and stability, fast response time, ease of use and reproducibility.

In Vivo Neural Recording and Electrochemical Performance of Microelectrode Arrays Modified by Rough-Surfaced AuPt Alloy Nanoparticles with Nanoporosity.

In order to reduce the impedance and improve in vivo neural recording performance of our developed Michigan type silicon electrodes, rough-surfaced AuPt alloy nanoparticles with nanoporosity were deposited on gold microelectrode sites through electro-co-deposition of Au-Pt-Cu alloy nanoparticles, followed by chemical dealloying Cu. The AuPt alloy nanoparticles modified gold microelectrode sites were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and in vivo neural recording experiment. The SEM images showed that the prepared AuPt alloy nanoparticles exhibited cauliflower-like shapes and possessed very rough surfaces with many different sizes of pores. Average impedance of rough-surfaced AuPt alloy nanoparticles modified sites was 0.23 MΩ at 1 kHz, which was only 4.7% of that of bare gold microelectrode sites (4.9 MΩ), and corresponding in vitro background noise in the range of 1 Hz to 7500 Hz decreased to 7.5 from 34.1 at bare gold microelectrode sites. Spontaneous spike signal recording was used to evaluate in vivo neural recording performance of modified microelectrode sites, and results showed that rough-surfaced AuPt alloy nanoparticles modified microelectrode sites exhibited higher average spike signal-to-noise ratio (SNR) of 4.8 in lateral globus pallidus (GPe) due to lower background noise compared to control microelectrodes. Electro-co-deposition of Au-Pt-Cu alloy nanoparticles combined with chemical dealloying Cu was a convenient way for increasing the effective surface area of microelectrode sites, which could reduce electrode impedance and improve the quality of in vivo spike signal recording.

Investigation of oxygen reduction and methanol oxidation reaction activity of PtAu nano-alloy on surface modified porous hybrid nanocarbon supports

We investigate the electrocatalytic activity of PtAu alloy nanoparticles supported on various chemically modified carbon morphologies towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The surface-modification of graphene nanosheets (f-G), multi-walled carbon nanotubes (f-MWNTs) and (graphene nanosheets-carbon nanotubes) hybrid support (f-G-MWNTs) were carried out by soft functionalization method using a cationic polyelectrolyte poly-(diallyldimethyl ammonium chloride). The Pt and PtAu alloy nanoparticles were dispersed over chemically modified carbon supports by sodium-borohydride assisted modified polyol reduction method. The electrochemical performance of all electrocatalysts were studied by half- and full-cell proton exchange membrane fuel cell (PEMFC) measurements and PtAu/f-G-MWNTs catalyst comparatively yielded the best catalytic performance. PEMFC full cell measurements of PtAu/f-G-MWNTs cathode electrocatalyst yield a maximum power density of 319 mW cm−2 at 60 °C without any back pressure,which is 2.1 times higher than that of cathode electrocatalyst Pt on graphene support. The high ORR and MOR activity of PtAu/f-G-MWNTs electrocatalyst is due to the alloying effect and inherent beneficial properties of porous hybrid nanocarbon support.

The Key Gold: Enhanced Platinum Catalysis for the Selective Hydrogenation of α,β-Unsaturated Ketone

AuPt alloy nanoparticles (NPs) were facilely synthesized with oleylamine as the stabilizing ligand and characterized by high-resolution transmission electron microscopy, powder X-ray diffraction, inductively coupled plasma-atomic emission spectrometer analysis, and so on. In addition, the AuPt alloys supported by the nano CeO2 exhibit high selectivity and efficiency in hydrogenation of benzylidene acetone under ambient temperature and pressure. By analyzing the catalytic performance over the NPs with different Au:Pt compositions, we found that the TONPt values (based on the number of Pt atoms) vary in the same trend with the change of conversion. Despite that gold itself shows no catalytic activity, the improved conversion and TONPt with the alloy catalysts clearly show the promotion effect of gold on the catalytic activity of the platinum. The inactive metal significantly improves the catalytic activity of active metal, which shows that the AuPt alloy exhibits an interesting synergistic effect.

Highly-Sensitive and Selective Electrochemiluminescence Biosensor for the Specific Detection of D-alanine

A new biosensor specified for D-amino acids (DAAs) based on the electrochemiluminescence (ECL) of luminol was proposed by coupling D-amino acid oxidase (DAAO) to in situ generate coreactant with functionalized Multi-walled carbon nanotubes (F-MWCNTs) and Au-Pt alloy nanoparticles as catalysts for the ECL reaction. The stepwise fabrication process of the biosensor was characterized via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Furthermore, the Au–Pt nanostructures with different molar ratios between Au and Pt precursors were investigated by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and ECL technique, and the optimum Au/Pt ratio for ECL measurements was 1:1 with an optimized electrodeposition time at 400 s. The proposed biosensor showed excellent performance in the stereoselective recognition of D-alanine with a low detection limit of 1.67 × 10−9 M. Hence, this paper would provide a new platform on the specific detection of D-alanine with high sensitivity, good selectivity and acceptable stability.

Printing graphene-carbon nanotube-ionic liquid gel on graphene paper: Towards flexible electrodes with efficient loading of PtAu alloy nanoparticles for electrochemical sensing of blood glucose

The increasing demands for portable, wearable, and implantable sensing devices have stimulated growing interest in innovative electrode materials. In this work, we have demonstrated that printing a conductive ink formulated by blending three-dimensional (3D) porous graphene–carbon nanotube (CNT) assembly with ionic liquid (IL) on two-dimensional (2D) graphene paper (GP), leads to a freestanding GP supported graphene–CNT–IL nanocomposite (graphene–CNT–IL/GP). The incorporation of highly conductive CNTs into graphene assembly effectively increases its surface area and improves its electrical and mechanical properties. The graphene–CNT–IL/GP, as freestanding and flexible substrates, allows for efficient loading of PtAu alloy nanoparticles by means of ultrasonic-electrochemical deposition. Owing to the synergistic effect of PtAu alloy nanoparticles, 3D porous graphene–CNT scaffold, IL binder and 2D flexible GP substrate, the resultant lightweight nanohybrid paper electrode exhibits excellent sensing performances in nonenzymatic electrochemical detection of glucose in terms of sensitivity, selectivity, reproducibility and mechanical properties.

Dopamine and ascorbic acid electro-oxidation on Au, AuPt and Pt nanoparticles prepared by pulse laser ablation in water

ABSTRACT In this study, we have investigated the use of PtAu alloy nanoparticles (NPs) with four different compositions (from x = 0 to 100) as electrodes for the detection of dopamine (DA) in the presence of ascorbic acid (AA). The Au 100-x Pt x NPs were prepared by pulsed laser ablation in an alkaline solution without using any surfactants or capping agents. The diameter of the particle ranges from 2.5 nm for pure Pt to 5.2 nm for pure Au NPs. Cyclic voltammetry showed that the number of DA molecules being oxidized on the NPs surface decreases with the Au content (from 9.0 × 10 −11 mol on Au to 4.8 × 10 −11 mol on Pt NPs), which emphasizes the preponderant role of Au surface sites on the electrochemical oxidation of DA. On the other hand, the oxidation current of AA is greatly enhanced by alloying Au with Pt, and the peak current of the alloyed NPs is about two (Au 50 Pt 50 ) and four times (Au 70 Pt 30 ) higher than that of Au NPs. It is suggested that the oxidation of the lateral chain of AA on the Pt sites occurs simultaneously to the oxidation of the ascorbate anion to dehydro ascorbic acid on the Au sites. Finally, it was shown by differential pulse voltammetry that Au and Au 100-x Pt x NPs can detect DA in solutions containing AA with a concentration 1000× higher. For example, for Au 70 Pt 30 the sensitivity and detection limit for the detection of DA in presence of 2 mM AA were 3.34 μA μM −1 and 0.06 μM (at S/N = 3) respectively, essentially the same values (3.50 μA μM −1 cm −2 and 0.05 μM) as in the absence of AA.

PtAu alloy nanoparticles supported on thermally expanded graphene oxide as a catalyst for the selective oxidation of glycerol

Thermally expanded graphene oxide supported PtAu alloy nanoparticles showed high catalytic activity in the oxidation of glycerol in base-free aqueous solution.

Hollow AuPt alloy nanoparticles as an enhanced immunosensing platform for detection of multiple analytes

Hollow AuPt alloy nanoparticles with a rough surface were prepared by one-step galvanic displacement reaction and were used to fabricate enhanced immunoprobes for detection of multiple analytes.

Facile synthesis of AuPt alloy nanoparticles in polyelectrolyte multilayers with enhanced catalytic activity for reduction of 4-nitrophenol.

In this work, bimetallic AuPt alloy nanoparticles were synthesized in situ in polyelectrolyte multilayers (PEMs) via an ion-exchange and coreduction process, in which the PEM support also served to suppress the Au-Pt phase separation, and thus enabled formation of AuPt alloy nanoparticles over a wide composition range. The PEM supported AuPt alloy nanoparticles exhibited higher catalytic activity than Au and Pt monometallic ones for the reduction of 4-nitrophenol by NaBH4, showing synergistic effects between Au and Pt. This work provides a facile approach to in situ synthesis of polymer supported bimetallic nanoparticles of tailored composition for optimum performance in catalysis and other applications.

Synthesis of AuPt alloy nanoparticles supported on 3D ordered macroporous oxide with enhanced catalytic performance for soot combustion

The supported AuPt alloy nanoparticles (NPs) were designed and successfully synthesized on the surface of 3D ordered macroporous (3DOM) Ce-based oxides by gas bubbling-assisted membrane reduction (GBMR) method. The AuPt alloy NPs were highly dispersed on the pore wall of 3DOM oxides, and their particle sizes are uniformed. 3DOM supports facilitate the contact between reactants and catalysts, and the synergetic effect of the Au–Pt bimetallic alloy particles can obviously increase the content of surface active oxygen species. 3DOM Ce0.8Zr0.2O2-supported AuPt alloy NP catalysts show super catalytic performance for diesel soot oxidation under “loose” contact condition between soot and catalyst. Among the prepared catalysts, 3DOM Au2Pt2/Ce0.8Zr0.2O2 catalyst has the higher catalytic activity for soot oxidation, e.g., its T10, T50 and T90 are 236, 345 and 397°C, respectively. In addition, the second component of Pt in AuPt alloy NPs can remarkably improve the stability of the Au-based catalysts for soot oxidation, which is important for practical application in diesel exhaust after-treatment. The design concept and facile synthesis method of 3DOM oxide-supported AuPt alloy NPs nanocatalysts can be extended to other metal compositions, and could illustrate a promising and efficient way to design active sites for nanocatalysts.

Preparation of PtAu Alloy Colloids by Laser Ablation in Solution and Their Characterization

Stable PtAu alloy colloids with a wide range of compositions were prepared using pulsed laser ablation on single metal-mixture targets in water. The concentration of Pt in the alloys can be tuned by varying the Pt/Au ratio in the targets, which are made by compression molding a mixture of Pt and Au powders at different ratios. Such fabricated PtAu alloy nanoparticles (NPs) show a face-centered cubic structure, and their composition basically follows that of their corresponding targets. The effect of aqueous solution pH and ablating laser fluence on the formation and structure of alloy NPs was further investigated. It is found that PtAu alloy colloids of identical composition can be achieved over a pH range extending from 4.0 to 11.0 and at fluences varying from 4 to 150 J cm–2 as long as the targets of the same composition are used. This finding suggests that alloy formation is essentially insensitive to both factors in certain ranges, and the method developed herein for the alloy NP formation is quite ro...