Au Pd Bimetallic Nanoparticles Research Articles

Enhanced Acetone Sensing Properties Based on Au-Pd Decorated ZnO Nanorod Gas Sensor.

The mature processes of metal oxide semiconductors (MOS) have attracted considerable interest. However, the low sensitivity of metal oxide semiconductor gas sensors is still challenging, and constrains its practical applications. Bimetallic nanoparticles are of interest owing to their excellent catalytic properties. This excellent feature of bimetallic nanoparticles can solve the problems existing in MOS gas sensors, such as the low response, high operating temperature and slow response time. To enhance acetone sensing performance, we successfully synthesized Au-Pd/ZnO nanorods. In this work, we discovered that Au-Pd nanoparticles modified on ZnO nanorods can remarkably enhance sensor response. The Au-Pd/ZnO gas sensor has long-term stability and an excellent response/recovery process. This excellent sensing performance is attributed to the synergistic catalytic effect of bimetallic AuPd nanoparticles. Moreover, the electronic and chemical sensitization of noble metals also makes a great contribution. This work presents a simple method for preparing Au-Pd/ZnO nanorods and provides a new solution for the detection of acetone based on metal oxide semiconductor.

Effect of Electrode Potential on the Surface Chemical Composition of Au-Pd Nanoparticles

Palladium (Pd) nanoparticles have been investigated for the hydrogen evolution reaction, the hydrogen oxidation reaction, the oxygen reduction reaction, and the methanol and ethanol oxidation reaction. The high methanol/ethanol tolerance of Pd is noteworthy.A powerful approach to further improving the catalytic properties of Pd is through alloying with suitable co-metals. In the case of the ethanol oxidation reaction in alkaline media, Pd alloyed with Au has demonstrated excellent activity exceeding even that of highly active Pt catalysts (1). A complete miscibility, small lattice mismatch, and contrasting properties of Pd and Au make Au-Pd a unique model system. Marked changes in the reactivity of Au-Pd catalysts have been reported when conditioning and operating conditions are altered, which should be related to physico-chemical changes in the nanoparticles. Indeed, dealloying/dissolution and segregation of metals at the surface of nanoparticles (NPs) takes place during conditioning and operation, which have pronounced effect on the activity and stability of NPs. The migration of metals from the bulk to the nanoparticles’ surface may take place during pre-catalytic conditioning and during operation, and can be triggered by the presence of oxidation and reducing agents (2), changes in temperature, and potential cycling (3). Thus, it is critical to investigate the effect of electrode potential on metals dissolution and segregation occurring in alloyed nanoparticles.In the present work, Au-Pd NPs prepared by pulsed laser ablation in liquids were used. Pulsed laser ablation is a simple method to synthesize alloy NPs with high purity out of different material systems and with different compositions. Typically, alloy-metal targets or pressed micro-powder mixture targets are ablated or fragmentated in liquid, respectively. Notably, the technique does not require any surfactant additives to achieve NPs stability in the electrolyte, thus allowing for NPs to remain free of associated contamination from the capping agents. We will show how one can fine-tuned the Au and Pd surface fraction of bimetallic Au-Pd nanoparticles using electrochemistry. The method involves electrochemical cycling in alkaline medium at a suitable upper vertex potential, resulting in a controllable diffusion of Pd atoms from the core to the shell. This preferential outward diffusion of Pd atoms occurs because of the electrochemical adsorption of oxygen atoms at the surface of NPs, which is driven by the application of a potential. This potential has to be positive enough for oxygen atoms to adsorb at the surface of the NPs, and therefore is dependent on the nature of the surface atoms. On AuPd NPs that are enriched with Au atoms, a potential of +1.5 V vs. RHE must be applied to form ca. 1 ML of adsorbed oxygen at the surface of gold and initiate the diffusion of Pd atoms from the core to the NP surface. This approach marks a new avenue in the development of compositionally-controlled electrocatalysts and can be tailored to suit different applications with a simple switch of voltage or a controlled pretreatment.

Icosahedral AuPd/carbonized poly-dopamine sphere@TiO2 yolk-shell nano-photoreactor for plasmon-enhanced catalytic activity and stability

Icosahedral AuPd bimetallic nanoparticles exhibit the localized surface plasmon resonance effect with their excellent thermocatalytic activity. However, the nanoparticle aggregation and recovery difficulty challenge the widespread adoption. In this work, we designed and fabricated a yolk-shell structured icosahedral AuPd/carbonized poly-dopamine sphere@titanium dioxide (I-AuPd/C-PDA@TiO2), which exhibited excellent catalytic performance towards photocatalytic selective oxidation of benzyl alcohol (BA). Specifically, the introduction of C-PDA not only improved the chemical stability of AuPd nanoparticles but also promoted electron transfer. Meanwhile, the controlled growth of monodisperse icosahedral AuPd benefited the selective oxidation of BA due to the LSPR effect. Compared to yolk-shell Pd/C-PDA@TiO2, Au/C-PDA@TiO2 and spherical AuPd/C-PDA@TiO2 (S-AuPd/C-PDA@TiO2) photocatalysts, I-AuPd/C-PDA@TiO2 showed the highest catalytic performance with 96.0% conversion rate and 99% selectivity in 6 h under an O2-saturated reaction environment. Moreover, no obvious performance decay was observed with I-AuPd/C-PDA@TiO2 after five successive cycles, confirming the outstanding stability of I-AuPd/C-PDA@TiO2. The current strategy would be a significant contribution of AuPd bimetallic nanocrystals for plasmon-enhanced catalysis.

Electrosynthesis of Nanocomposites of Catalytic Active Pd–Cu and Pd–Au Bimetallic Nanoparticles with Poly(N-vinylpyrrolidone) and Nanocellulose

Electrosynthesis of Nanocomposites of Catalytic Active Pd–Cu and Pd–Au Bimetallic Nanoparticles with Poly(N-vinylpyrrolidone) and Nanocellulose

ELECTROSYNTHESIS OF CATALYTIC ACTIVE Pd-Cu AND Pd-Au BIMETALLIC NANOPARTICLES NANOCOMPOSITES WITH POLY(N-VINYLPYRROLIDONE) AND NANOCELLULOSE

It was investigated the preparation in an undivided cell of Pd-Cu and Pd-Au bimetallic nanoparticles (NPs) by methylviologen (MV2+) -mediated electrochemical reduction of equimolar amounts of Cu(II), Pd(II) and Au(I) in the presence of poly(N-vinylpyrrolidone) (PVP) and nanocellulose (NC) at controlled potential of generating MV cation radical in aqueous medium at room temperature. Electrosyntheses were performed by sequential or joint reduction of metal ions by passing a theoretical amount of electricity. When Pd(II) ions are added to CuNPs, as well as Au(I) ions are added to PdNPs, a galvanic replacement process is observed, namely oxidation of Cu0 by Pd(II) and Pd0 Au(I) ions. The results of complete reduction are nanocomposites of mainly spherical MNPs, dispersed in the solution bulk, and stabilized by PVP on the surface of the NC. In the sequential synthesis of CuNPs and then PdNPs, the nanocomposite is presented as Cu2O nanoroses coated with fine PdNPs. Nanocomposites of Pd NPs with Cu2O or Au shows the mainly formation of spherical particles with the size of 4 to 50 nm depending on the production method. X-ray powder diffraction (XRD) data of nanocomposites confirm the formation of a mixture of PdNPs (0.8 - 10 nm) with large gold crystallites (until 24 nm), as well as the oxidation of CuNPs to cuprite (Cu2O). The size of metal crystallites and copper oxide varies in the range from 0.8 to 24 nm. In the test reaction of p-nitrophenol reduction with sodium borohydride in aqueous medium, all tested nanocomposites showed time-increasing catalytic activity. When Cu is added to Pd, the catalytic reduction reaction is maintained, while the addition of Au to Pd decreases the catalytic activity of PdNPs by an order of magnitude.

Bimetallic Au–Pd nanoparticles decorated electrospun spinel CoFe2O4 nanostructures as efficient electrocatalysts for ethanol fuel oxidation in alkaline media

Spinel-based materials are promising candidates as electro-catalysts for the oxidation of alcohol fuels. In the present study, electrospun CoFe2O4 spinel nanostructures were prepared by electrospinning technique and the subsequent thermal treatment processes. Then, the bimetallic Au–Pd–CoFe2O4 composite as electro-catalysts were synthesized by precipitation method. The surface morphology, composition and structure of the resulting composite nanostructures were studied by FE-SEM, EDS, TEM, XPS, XRD and FT-IR. The catalytic performance of resultant composite has been examined in ethanol electro-oxidation reactions under alkaline conditions. The effect of different Au:Pd ratios on the electrocatalytic performance of Au–Pd–CoFe2O4 composite nanostructures for ethanol oxidation was evaluated. The synthesized composite Au–Pd–CoFe2O4 (APCo22) illustrates a superior ethanol oxidation activity in comparison to other electrocalysts, and the peak current of this spinel-type electro-catalysts is 9.89 times that of Pd–CoFe2O4 with a scan rate of 50 mVs−1, which is due to the synergistic effect of Au and Pd on CoFe2O4. Furthermore, the remarkable electrochemical property can be due to the production of OH−, which leads to the species present on the surface of the electro-catalysts during the activation process.

Oxygen Vacancy-Induced Metal-Support Interactions in AuPd/ZrO2 Catalysts for Boosting 5-Hydroxymethylfurfural Oxidation.

The construction of strong metal-support interactions in oxide-supported noble metal nanocatalysts has been considered an emerging and efficient way in improving catalytic performance in biomass-upgrading reactions. Herein, a citric acid (CA)-assisted synthesized ZrO2 layer with improved oxygen vacancy (Ov) concentrations on a natural clay mineral of halloysite nanotubes (HNTs) was designed. Moreover, AuxPdy/ZrO2@HNTs-zCA catalysts were prepared by loading AuPd bimetal and employed for aerobic oxidation of the lignocellulosic biomass-derived 5-hydroxymethylfurfural (HMF) platform to the bioplastic monomer 2,5-furandicarboxylic acid (FDCA) with water as the solvent. The results of catalytic experiments revealed that the Au3Pd1/ZrO2@HNTs-1.0CA catalyst exhibited excellent catalytic activity at 0.5 MPa O2, with a satisfactory FDCA yield of 99.5% and outstanding FDCA formation rate of 1057.9 mmol·g-1·h-1. The improved Ov concentration in the ZrO2 support enhanced the adsorption and activation ability of the catalyst for O2, and a higher Lewis acid concentration provided a stronger adsorption ability of the catalyst for reaction substrates. Besides, the synergistic effect of AuPd bimetallic nanoparticles steered the tandem oxidation of aldehyde and alcohol groups in HMF and accelerated the rate-determining step. More importantly, the relationship between the Ov concentration and catalytic performance also demonstrated that the enhanced catalytic activity for HMF oxidation was mainly attributed to the active interface of AuPd-ZrOx. This work offers fresh insights into rationally designing oxygen vacancy-driven strong interactions between the oxide support and noble nanoparticles for the catalytic upgrade of biomass platform chemicals.

Synthesis and Structural Characterization of Branched Bimetallic AuPd Nanoparticles with a Highly Tunable Optical Response.

Bimetallic nanostructures composed of gold (Au) and palladium (Pd) have garnered increased interest for their applications in heterogeneous catalysis. This study reports a simple strategy for manufacturing Au@Pd bimetallic branched nanoparticles (NPs), which offer a tunable optical response, using polyallylamine-stabilized branched AuNPs as template cores for Pd overgrowth. The palladium content can be altered by manipulating the concentration of PdCl42- and ascorbic acid (AA) that are injected, which permit an overgrowth of the Pd shell up to ca. 2 nm thick. The homogeneous distribution of Pd at the surfaces of Au NPs can be carried out regardless of their size or branching degree, which allows for an adjustment of the plasmon response in the near-infrared (NIR) spectral range. As a proof of concept, the nanoenzymatic activity of pure gold and gold-palladium NPs was compared, exploring their peroxidase-like activity in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The bimetallic AuPd NPs demonstrate an increase in the catalytic properties attributed to the presence of palladium at the surface of gold.

Self-driven electron enrichment of ultrafine PdAu nanoparticles for electrochemical CO2 reduction: High applicability of work function as an activity descriptor

Highly coupled metal/dopant-incorporated carbon dyads provide a possibility to modulate the electron density of metallic materials by forming a rectifying interface, thus showing an enhanced activity in electrochemical CO2 reduction reaction (ECRR). However, understanding the promotion effects of dopants for ECRR is limited to the prediction by theoretical interpretation and case-by-case studies. Herein, we report the direct experimental evidence that the work function, regulated by single structural factor-dopant contents, is significantly correlated to the ECRR reaction activity and kinetics. We prepared a series of PdAu/NxC electrocatalysts composed of ultrafine (∼5.7 nm) PdAu bimetallic nanoparticles and tailorable N-doped carbon supports. The wide range of the amount of N dopants allowed the modification of the band gap of the carbon easily. Using ultraviolet photoelectron spectroscopy (UPS) measurements, we demonstrate that the reactivity and kinetics trends of the PdAu/NxC in the ECRR can be intrinsically correlated with the work function of the catalysts. PdAu/N7.50C electrocatalyst with the highest N contents displays a 100% CO2-to-CO conversion and high conversion efficiency over a wide potential window, superior over other reported PdAu catalysts. This work provides a novel way to boost ECRR performance by deliberately lowering the work function of the metal/carbon electrocatalysts through the enhancement by dopants.

From AuPd Nanoparticle Alloys towards Core‐Shell Motifs with Enhanced Alcohol Oxidation Activity

AbstractThe best activity of bimetallic AuPd nanoparticles for alcohol oxidation reaction is usually achieved by adjusting the Au/Pd molar ratio. Herein, alloy AuPd nanoparticles of ∼2.5–3.5 nm, ranging from Au‐rich to Pd‐rich compositions, were synthesized through a sol‐immobilization method. A calcination step under air conditions caused an increase in size up to 5.5 nm, but also driven the segregation of Pd to the surface, which generated an Au rich core with Pd on the shell. At high Pd content, the shell structure is formed by PdO. The catalytic activity of Pd‐rich samples (1 : 1, 1 : 2 and 1 : 4 Au : Pd) for benzyl alcohol oxidation increased ∼4‐fold after calcination. Upon reduction with H2, surface PdO motifs are reduced to Pd that did not dissolve back into the AuPd alloy core, maintaining the metallic Pd shell. The catalytic activity decreased. Therefore, restructuring alloyed AuPd nanoparticles into core‐shell like structures with PdO in the shell is beneficial to the catalytic activity, but reduction of PdO layer was detrimental. These results provide new insights on the optimization of AuPd catalysts, considering not only the Au/Pd molar ratio, but also the importance of PdO, which was not anticipated in the previous literature.

The porous hollow cobalt-based oxides encapsulated with bimetallic PdAu Nanoparticles of electrochemical biosensor for highly sensitive pesticides detection

Efficient and portable electrochemical biosensors are received to evaluation of pesticides in the environment, which can make great significance for food safety. In this study, the Co-based oxides with a kind of hierarchical porous hollow and nanocages were constructed, in which the materials (Co3O4-NC) were encapsulated with PdAu nanoparticles (NPs). Due to the unique porous structure, the changeable valence state of cobalt and the synergistic effect of bimetallic PdAuNPs, PdAu@Co3O4-NC possessed excellent electron pathways, and showed more exposed active sites. Accordingly, the porous Co-based oxides have been applied to construct an acetylcholinesterase (AChE) electrochemical biosensor, which showed good performance for organophosphorus pesticides (OPs) detection. The optimum biosensing platform based on nanocomposites was applied to exhibit highly sensitive determination of omethoate and chlorpyrifos, with the relative low detection limit of 6.125 × 10−15 M and 5.10 × 10−13 M, respectively. And a wide detection range of 6.125 × 10−15 ∼ 6.125 × 10−6 M and 5.10 × 10−13 ∼ 5.10 × 10−6 M for these two pesticides were achieved. Therefore, the PdAu@Co3O4-NC may represent a powerful tool for ultrasensitive sensing of OPs, and have great potential application.

Mechanistic Studies into the Selective Production of 2,5-furandicarboxylic Acid from 2,5-bis(hydroxymethyl)furan Using Au-Pd Bimetallic Catalyst Supported on Nitrated Carbon Material

Aerobic oxidation of bio-sourced 2,5-bis(hydroxymethyl)furan (BHMF) to 2, 5-furandicarboxylic acid (FDCA), a renewable and green alternative to petroleum-derived terephthalic acid (TPA), is of great significance in green chemicals production. Herein, hierarchical porous bowl-like nitrogen-rich (nitrated) carbon-supported bimetallic Au-Pd nanocatalysts (AumPdn/ N-BNxC) with different nitrogen content and bimetal nanoparticle sizes were developed and employed for the highly efficient aerobic oxidation of BHMF to FDCA in sodium carbonate aqueous solution. The reaction pathway for catalytic oxidation of BHMF went through the steps of BHMF→HMF→HMFCA→FFCA→FDCA. Kinetics studies showed that the activation energies of BHMF, HMF, HMFCA, and FFCA were 58.1 kJ·moL−1, 39.1 kJ·moL−1, 129.2 kJ·moL−1, and 56.3 kJ·moL−1, respectively, indicating that the oxidation of intermediate HMFCA to FFCA was the rate-determining step. ESR tests proved that the active species was a superoxide radical. Owing to the synergy between the nitrogen-rich carbon support and bimetallic Au-Pd nanoparticles, the Au1Pd1/N-BN2C nanocatalysts exhibited BHMF conversion of 100% and FDCA yield of 95.8% under optimal reaction conditions. Furthermore, the nanocatalysts showed good stability and reusability. This work provides a versatile strategy for the design of heterogeneous catalysts for the highly efficient production of FDCA from BHMF.

Hierarchical Flower-like WO3 Nanospheres Decorated with Bimetallic Au and Pd for Highly Sensitive and Selective Detection of 3-Hydroxy-2-butanone Biomarker.

Listeria monocytogenes, which is abundant in environment, can lead to many kinds of serious illnesses and even death. Nowadays, indirectly detecting the metabolite biomarker of L. monocytogenes, 3-hydroxy-2-butanone, has been verified to be an effective way to evaluate the contamination of L. monocytogenes. However, this detection approach is still limited by sensitivity, selectivity, and ppb-level detection limit. Herein, low-cost and highly sensitive and selective 3-hydroxy-2-butanone sensors have been proposed based on the bimetallic AuPd decorated hierarchical flower-like WO3 nanospheres. Notably, the 1.0 wt % AuPd-WO3 based sensors displayed the highest sensitivity (Ra/Rg = 84 @ 1 ppm) at 250 °C. In addition, the sensors showed outstanding selectivity, rapid response/recovery (8/4 s @ 10 ppm), and low detection limit (100 ppb). Furthermore, the evaluation of L. monocytogenes with high sensitivity and specificity has been achieved using 1.0 wt % AuPd-WO3 based sensors. Such a marvelous sensing performance benefits from the synergistic effect of bimetallic AuPd nanoparticles, which lead to thicker electron depletion layer and increased adsorbed oxygen species. Meanwhile, the unique hierarchical nanostructure of the flower-like WO3 nanospheres benefits the gas-sensing performance. The AuPd-WO3 nanosphere-based sensors exhibit a particular and highly selective method to detect 3-hydroxy-2-butanone, foreseeing a feasible route for the rapid and nondestructive evaluation of foodborne pathogens.

Demystifying the Chemical Ordering of Multimetallic Nanoparticles

ConspectusMultimetallic nanoparticles (NPs) have highly tunable properties due to the synergy between the different metals and the wide variety of NP structural parameters such as size, shape, composition, and chemical ordering. The major problem with studying multimetallic NPs is that as the number of different metals increases, the number of possible chemical orderings (placements of different metals) for a NP of fixed size explodes. Thus, it becomes infeasible to explore NP energetic differences with highly accurate computational methods, such as density functional theory (DFT), which has a high computational cost and is typically applied to up to a couple of hundred metal atoms. Here, we demonstrate a methodology advancing NP simulations by effectively exploring the vast materials space of multimetallic NPs and accurately identifying the ones with the most thermodynamically preferred chemical orderings. With accuracies reaching that of DFT, our methodology is applicable to practically any NP size, shape, and metal composition. We achieve this by significantly advancing the bond-centric (BC) model, a physics-based model that has been previously shown to rapidly predict bimetallic NP cohesive energies (CEs). Specifically, the BC model is trained in a way to understand how the bimetallic bond strength changes under different coordination environments present on a NP and how the metal composition of every site affects the detailed coordination environment using fractional coordination numbers. This newly modified BC model leads to an improvement from 0.331 (original model) to 0.089 eV/atom in CE predictions when compared to DFT values on a robust data set of 90 different NPs consisting of PtPd, AuPt, and AuPd NPs with varying compositions and chemical orderings. By incorporating the modified BC model into an in-house-developed genetic algorithm (GA) we can effectively and accurately predict the most stable chemical orderings of large, realistic bimetallic NPs consisting of thousands of metal atoms. This is demonstrated on AuPd bimetallic NPs, a challenging system due to the similarity in the cohesion of the two metals. By training our BC model using a unique DFT calculation on a bimetallic NP (one calculation for two metals combining together), we expand to explore the chemical ordering of multimetallic NPs. We first demonstrate the application of our methodology on a AuPdPt NP and validate our stability predictions with literature data. Then, we effectively explore the vast materials space of multimetallic NPs consisting of combinations of Au, Pt, and Pd as a function of metal composition. Our thermodynamic stability trends are presented in a ternary diagram revealing detailed, and yet, unexpected chemical ordering trends. Our computational framework can aid both experimental and computational researchers toward effectively screening multimetallic NP stability. Moreover, we provide an outlook of how this framework can be applied to catalyst discovery, high-entropy alloys, and single-atom alloys.

AuPd bimetallic functionalized monodisperse In2O3 porous spheres for ultrasensitive trimethylamine detection

The use of bimetallic nanoparticles (NPs) to enhance the performance of oxide semiconductor gas sensor is a promising approach. In this work, monodisperse In2O3 porous spheres were synthesized by a simple hydrothermal method, and bimetallic AuPd NPs were decorated on In2O3 nanospheres by in-situ redox reaction, then Au, Pd and AuPd-modified In2O3 were obtained. Characterization results of SEM and TEM showed that the as-synthesized materials had monodisperse porous sphere morphology with uniform diameter of within 300 nm. The gas sensing test results showed that AuPd-In2O3 sensor has excellent gas sensing performance, specifically, lower detection limit (300 ppb, 1.35), and an ultra-short response time (2 s), as well as a high response to 100 ppm trimethylamine (TMA) (Ra/Rg=367.0) which was 12, 127 and 334 times higher than that of Pd-In2O3 (Ra/Rg=30.3), Au-In2O3 (Ra/Rg=2.9) and pristine In2O3 (Ra/Rg=1.1). The gas sensor also has a good long-term stability, repeatability, and cross-selectivity. The mechanism of enhanced gas sensing performance was proposed combining with chemical sensitization of Au, electronic sensitization of Pd, and synergetic catalytic effect of AuPd bimetallic NPs. This work provides a promising material for the design and preparation of gas sensors for TMA detection.

Polystyrene stabilized Pd-Au nanoalloy for efficient synthesis of bis(indolyl)methanes from aryl iodides using oxalic acid as CO and H2 source

Herein, first example of heterogeneously catalyzed carbonylative synthesis of bis(indolyl)methanes from aryl iodides in one-pot and single-step manner has been reported. The reaction was best catalyzed by polystyrene supported bimetallic Pd-Au (Pd-Au@PS) nanoparticles (NPs) in comparison to various supported monometallic Pd-catalysts. The key feature of this protocol involves the application of oxalic acid as economic, solid, and safe multi-functional reagent which acts as a CO, H2 source as well as acid co-catalyst with PEG-200 as green solvent reaction medium for delivering moderate to excellent yields of the desired products, bis(indolyl)methanes (BIMs). The developed protocol is additive, phosphine ligand-free under air/moisture stable recyclable catalyst bearing easy accessibility/affordability to starting materials.

Mild and Rapid Light-Driven Suzuki-Miyaura Reactions Catalyzed by AuPd Nanoparticles in Water at Room Temperature.

Organic reactions carried out in water under mild conditions are state-of-the-art in terms of environmentally benign chemical processes. In this direction, plasmonic catalysis can aid in accomplishing such tasks. In the present work, cyclodextrin-mediated AuPd bimetallic nanoparticles (NPs) were applied in room-temperature aqueous Suzuki-Miyaura reactions aiming at preparing biaryl products based on fluorene, isatin, benzimidazole and resorcinol, with yields of 77 % up to 95 %. AuPd NPs were revealed to be a physical mixture of Au and Pd particles circa 20 and 2 nm, respectively, through X-ray diffraction, dynamic light scattering, UV-Vis spectroscopy and transmission electron microscopy analyses.

Self-reduction of bimetallic nanoparticles on flexible MXene-graphene electrodes for simultaneous detection of ascorbic acid, dopamine, and uric acid

Three-dimensional (3D) porous laser-scribed graphene (LSG) is a potential electrode material for flexible electrochemical sensors due to its high efficiency and low cost. However, the growth of nanoparticles usually depends on reducers or harsh conditions, which limit the application of flexible biosensors. To resolve this issue, 2D MXene nanosheets were applied to functionalize 3D LSG sheets with a C-O-Ti covalent crosslink and obtain an LSG-MXene hybrid scaffold. The shape-controlled Au-Pd bimetallic nanoparticles were synthesized on the surface of LSG-MXene by a self-reduction process at room temperature for 6 min to enhance its catalytic performance. As a proof of concept, the obtained hybrid nanocomposite was used to assess ascorbic acid (AA, 10–1600 μM), dopamine (DA, 12–240 μM), and uric acid (UA, 8–100, 200–800 μM). The fabricated sensor exhibited a low detection limit (S/N = 3) of 3 μM AA, 0.13 μM DA, and 1.47 μM UA. Furthermore, the Au-Pd/MXene/LSG was successfully applied to determine AA, DA, and UA in urine samples. Predictably, these outstanding performance sensors have great potential in flexible and wearable electronics.

Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon.

Sol immobilization is used to produce bimetallic catalysts with higher activity to monometallic counterparts for a wide range of environmental and commercial catalytic transformations. Analysis of complementary surface characterization (XPS, Boehm’s titration, and zeta potential measurements) was used to elucidate alterations in the surface functionality of two activated carbon supports during acid exposure. When considered in parallel to the experimentally determined electrostatic and conformational changes of the polymer surrounding the nanoparticles, an electrostatic model is proposed describing polymer protected nanoparticle deposition with several polymer–carbon support examples described. Consideration of the electrostatic interactions ensures full deposition of the polymer protected nanoparticles and at the same time influences the structure of the bimetallic nanoparticle immobilized on the support. The normalized activity of AuPd catalysts prepared with 133 ppm H2SO4 has a much higher activity for the direct synthesis of hydrogen peroxide compared to catalysts prepared in the absence of acid. Detailed characterization by XPS indicates that the surface becomes enriched in Au in the Au–Pd samples prepared with acid, suggesting an improved dispersion of smaller bimetallic nanoparticles, rich in Au, that are known to be highly active for the direct synthesis reaction. Subsequent microscopy measurements confirmed this hypothesis, with the acid addition catalysts having a mean particle size ∼2 nm smaller than the zero acid counterparts. The addition of acid did not result in a morphology change, and random alloyed bimetallic AuPd nanoparticles were observed in catalysts prepared by sol immobilization in the presence and absence of acid. This work shows that the deposition of polymer protected AuPd nanoparticles onto activated carbon is heavily influenced by the acid addition step in the sol immobilization process. The physicochemical properties of both the polymer and the activated carbon support should be considered when designing a bimetallic nanoparticle catalyst by sol immobilization to ensure the optimum performance of the final catalyst.

One-pot biosynthesis of rGO-supported PdAu bimetallic nanoparticles as an efficient catalyst for Suzuki-Miyaura coupling reactions

One-pot biosynthesis of rGO-supported PdAu bimetallic nanoparticles as an efficient catalyst for Suzuki-Miyaura coupling reactions