Bimetallic Nanostructures Research Articles

The preparation of NiCo2O4 nanoboulders and their application in the electrochemical detection of ofloxacin drug

A sensitive electroactive platform relies directly upon the efficient and conductive interface. This work offers a simple and effective method for synthesizing NiCo2O4 using CTAB surfactant, suited for trace-level antibiotic detection. The route realized the controlled growth of tiny NiCo2O4 nanoboulders with an exposed interface. A comparative evaluation of the bimetallic nanostructures with their pristine compositional counterparts, i.e., NiO and Co3O4, supports its superior electrochemical characteristics based on the synergism of strong redox activity and conductivity from the bimetallic components. The NiCo2O4 nanoboulders exhibited strong electrochemical activity when configured as electrode material for detecting ofloxacin (OFL), a common antibiotic. The sensor exhibited excellent working linearity in a low-concentration range of 0.01–5 ​μM with a detection limit of 1 ​× ​10−3 ​μM for OFL. The kinetics of the NiCo2O4 further supported the electrocatalytic oxidation of OFL to be diffusion controlled with an estimated diffusion coefficient of 2.03310−6 ​cm2 ​s−1. Moreover, the constructed sensor is applicable for detecting OFL from environmental samples, reflecting its workability in complex real-environment.

Zn and Zn-Fe Nanostructures with Multifunctional Properties as Components for Food Packaging Materials.

Metallic and bimetallic nanostructures have shown interesting chromatic and antibacterial properties, and they can be used in various applications. In this work, zinc (Zn) and iron (Fe) nanostructures were produced with different morphologies: (i) pure Zn; (ii) Zn-Fe nanoalloys; (iii) Zn-Fe nanolayers (Zn-Fe NLs); and (iv) Zn nanolayers combined with Fe nanoparticles (Zn NLs + Fe NPs). The aim was to produce components for food packaging materials with active and intelligent properties, including oxygen absorption capacity, chromatic properties, and antibacterial properties. Thus, the morphology, structure, and chemical composition of the samples were characterized and correlated with their oxidation, chromatic, and antibacterial properties. The results revealed a relevant reduction in the coating’s opacity after oxidation varying from 100 to 10% depending on the morphology of the system. All coatings exhibited significant antibacterial activity against S. aureus, revealing a direct correlation with Zn content. The incorporation of Fe for all atomic arrangements showed a negative impact on the antibacterial effect against E. coli, decreasing to less than half the zone of inhibition for Zn-Fe NLs and Zn NLs + Fe NPs and suppressing the antibacterial effect for Zn-Fe alloy when compared with the pure Zn system.

Au–Cu Bimetallic Nanostructures for Photothermal Antibacterial and Wound Healing Promotion

Au–Cu Bimetallic Nanostructures for Photothermal Antibacterial and Wound Healing Promotion

Galvanic Restructuring of Exsolved Nanoparticles for Plasmonic and Electrocatalytic Energy Conversion.

There is a growing need to control and tune nanoparticles (NPs) to increase their stability and effectiveness, especially for photo- and electrochemical energy conversion applications. Exsolved particles are well anchored and can be re-shaped without changing their initial location and structural arrangement. However, this usually involves lengthy treatments and use of toxic gases. Here, the galvanic replacement/deposition method is used, which is simpler, safer, and leads to a wealth of new hybrid nanostructures with a higher degree of tailorability. The produced NiAu bimetallic nanostructures supported on SrTiO3 display exceptional activity in plasmon-assisted photoelectrochemical (PEC) water oxidation reactions. In situ scanning transmission electron microscopy is used to visualize the structural evolution of the plasmonic bimetallic structures, while theoretical simulations provide mechanistic insight and correlate the surface plasmon resonance effects with structural features and enhanced PEC performance. The versatility of this concept in shifting catalytic modes to the hydrogen evolution reaction is demonstrated by preparing hybrid NiPt bimetallic NPs of low Pt loadings on highly reduced SrTiO3 supports. This powerful methodology enables the design of supported bimetallic nanomaterials with tunable morphology and catalytic functionalities through minimal engineering.

Construction of a binder-free non-enzymatic glucose sensor based on Cu@Ni core–shell nanoparticles anchored on 3D chiral carbon nanocoils-nickel foam hierarchical scaffold

Bimetallic nanostructures composited with carbonaceous materials are the potential contenders for quantitative glucose measurement owing to their unique nanostructures, high biomimetic activity, synergistic effects, good conductivity and chemical stability. In the present work, chemical vapors deposition technique has been employed to grow 3D carbon nanocoils (CNCs) with a chiral morphology on hierarchical macroporous nickel foam (NF) to get a CNCs/NF scaffold. Following, bimetallic Cu@Ni core–shell nanoparticles (CSNPs) are effectively coupled with this scaffold through a facile solvothermal route in order to fabricate a binder-free novel Cu@Ni CSNPs/CNCs/NF hybrid nanostructure. The constructed free-standing 3D hierarchical composite electrode guarantees highly efficient glucose redox activity due to core–shell synergistic effects, enhanced electrochemical active surface area, excellent electrochemical stability, improved conductivity with better ion diffusivity and accelerated reaction kinetics. Being a non-enzymatic glucose sensor, this electrode achieves highly swift response time of 0.1 s, ultra-high sensitivity of 6905 μA mM−1 cm−2, low limit of detection of 0.03 μM along with potential selectivity and good storage stability. Moreover, the proposed sensor is also tested successfully for the determination of glucose concentration in human serum samples under good recovery ranging from 96.6 to 102.1 %. The 3D Cu@Ni CSNPs/CNCs/NF composite electrode with unprecedented catalytic performance can be utilized as an ideal biomimetic catalyst in the field of non-enzymatic glucose sensing.

In situ observation of photo-induced shortening of single Au nanorod for plasmon-enhanced formic acid dehydrogenation

Photo-induced selective shortening strategy was developed to synthesize Au nanorods (NRs) with different aspect ratios, and in situ observation of photo-induced shortening of single Au nanorod was realized, which is helpful for understanding the relationship between SPR decay and geometric nanostructure. The as-synthesized plasmonic Pd–Au NRs exhibit efficient formic acid dehydrogenation. Very impressively, the interfacial interaction between plasmonic bimetallic nanostructures and adsorbed molecules (HCOOH) was explored in situ at the single-particle level. Significant photoluminescence (PL) quenching of Pd–Au NRs was observed when HCOOH contacted the catalyst, confirming the charge transfer between Pd–Au NRs and HCOOH molecules. Finally, we shed light on the catalytic mechanism of plasmon-induced HCOOH dehydrogenation by coupling single-particle PL measurement with finite difference time domain (FDTD) and density functional theory (DFT) calculations.

Facile and Surfactant‐Free Routed Spherical Au@Pt Core–Shell–Satellite Nanoparticles as High‐Efficient and Stable Electrocatalyst for Methanol Oxidation

The spherical Au@Pt core–shell–satellite nanoparticles (NPs) are fabricated via a facile, efficient, and surfactant‐free method of seed‐mediated growth, and the electrocatalytic performance toward the methanol oxidation reaction (MOR) is systematically researched by cyclic voltammetry. Compared with commercial Pt/C, all the obtained Au@Pt NPs with such a core–shell–satellite structure exhibit greatly enhanced electrocatalytic activity and long‐term stability toward MOR. Among them, Au90@Pt10 NPs with less loading of Pt exhibit the most significantly enhanced electrocatalytic performance with a mass activity of 1.470 A mgPt−1, approximately 13 times that of commercial Pt/C (0.111 A mgPt−1) and specific activity (1.469 mA cm−2) approximately 9 times that of commercial Pt/C (0.157 mA cm−2). Au95@Pt5 NPs have the highest value of the oxidation current density (0.2615 mA cm−2), corresponding to 62.8% of its initial maximum value (0.4165 mA cm−2), showing higher stability at approximately 4000 s. Such a surfactant‐free synthesis technique of Au@Pt bimetallic NPs may be a simple method to prepare self‐supported bimetallic nanostructures, which is important to develop highly effective electrocatalysts for MORs.

Ag–Ga Bimetallic Nanostructures Ultrasonically Prepared from Silver–Liquid Gallium Core–Shell Systems Engineered for Catalytic Applications

Ag–Ga Bimetallic Nanostructures Ultrasonically Prepared from Silver–Liquid Gallium Core–Shell Systems Engineered for Catalytic Applications

Bimetallic p-ZnO/n-CuO nanocomposite synthesized using Aegle marmelos leaf extract exhibits excellent visible-light-driven photocatalytic removal of 4-nitroaniline and methyl orange.

In the current study, the photocatalytic activity of bimetallic ZnO-CuO hetero-nanocomposite was evaluated and compared with the monometallic ZnO and CuO nanoparticles using 4-nitroaniline (4-NA) and methyl orange (MO). Bimetallic ZnO-CuO hetero-nanocomposite, ZnO, and CuO nanostructure were synthesized utilizing leaf extract of Aegle marmelos and characterized by transmission electron microscopy, X-ray diffraction, and XPS. Benefiting from the p-n heterostructures formation, bimetallic ZnO-CuO hetero-nanocomposite exhibits an excellent photocatalytic activity against 4-NA as well as MO compared to pure ZnO and CuO. In particular, bimetallic ZnO-CuO hetero-nanocomposite expressed the highest photocatalytic activity by reducing 90% of 4-NA in 20min and by degrading 96% of MO in 10min, whereas 65% reduction of 4-NA in 30min and 93% degradation of MO in 45min was exhibited by CuO and 48% reduction of 4-NA in 30min and 98% degradation of MO in 50min was exhibited by ZnO. Moreover, bimetallic ZnO-CuO hetero-nanocomposite maintains excellent photocatalytic activity even after five cycles indicating its stability as photocatalyst and reusability. Based on the experimental findings, bimetallic ZnO-CuO hetero-nanocomposite could be used as a photocatalyst for wastewater treatment with excellent regeneration efficiency.

Surface-Functionalized Au-Pd Nanorods with Enhanced Photothermal Conversion and Catalytic Performance.

Bimetallic nanostructures comprising plasmonic and catalytic components have recently emerged as a promising approach to generate a new type of photo-enhanced nanoreactors. Most designs however concentrate on plasmon-induced charge separation, leaving photo-generated heat as a side product. This work presents a photoreactor based on Au-Pd nanorods with an optimized photothermal conversion, which aims to effectively utilize the photo-generated heat to increase the rate of Pd-catalyzed reactions. Dumbbell-shaped Au nanorods were fabricated via a seed-mediated growth method using binary surfactants. Pd clusters were selectively grown at the tips of the Au nanorods, using the zeta potential as a new synthetic parameter to indicate the surfactant remaining on the nanorod surface. The photothermal conversion of the Au-Pd nanorods was improved with a thin layer of polydopamine (PDA) or TiO2. As a result, a 60% higher temperature increment of the dispersion compared to that for bare Au rods at the same light intensity and particle density could be achieved. The catalytic performance of the coated particles was then tested using the reduction of 4-nitrophenol as the model reaction. Under light, the PDA-coated Au-Pd nanorods exhibited an improved catalytic activity, increasing the reaction rate by a factor 3. An analysis of the activation energy confirmed the photoheating effect to be the dominant mechanism accelerating the reaction. Thus, the increased photothermal heating is responsible for the reaction acceleration. Interestingly, the same analysis shows a roughly 10% higher reaction rate for particles under illumination compared to under dark heating, possibly implying a crucial role of localized heat gradients at the particle surface. Finally, the coating thickness was identified as an essential parameter determining the photothermal conversion efficiency and the reaction acceleration.

Controlled One‐pot Synthesis of PdAg Nanoparticles and Their Application in the Semi‐hydrogenation of Acetylene in Ethylene‐rich Mixtures

AbstractIn the present paper, we report the synthesis of highly functionalized nanomaterials carefully nanoengineered to catalyze the semi‐hydrogenation of acetylene in ethylene‐rich mixtures. Surface functionalization and structure modification of a series of bimetallic PdAg nanoparticles was performed using HHDMA as stabilizer and alloying the active palladium phase with silver. Bimetallic PdAg NPs with adjustable Pd/Ag ratio were prepared in water through a novel one‐pot methodology using hydrogen gas as a benign reducing agent and cyanide as additive. UV‐Vis studies indicated the formation of the bimetallic nanostructures through a sequential displacement‐galvanic reduction process mediated by cyanide. The series of colloidal NPs were deposited onto alumina and successfully applied as catalysts in the selective hydrogenation of acetylene in ethylene rich mixtures. Geometric and electronic promotion of Ag over Pd based catalysts was evidenced by the increase of the ethylene selectivity with the Ag content. The reactivity of these materials demonstrated the applicability of HHDMA stabilized NPs in a gas phase reaction of industrial interest and the success of combining several strategies for the enhancement of the alkene selectivity.

Dewetted bimetallic AuPd nanostructures on silicon carbide surface: Effect of film thickness and annealing temperature

Bimetallic nanostructures are, nowadays, largely investigated in several technological applications due to the synergistic combination of the properties of the two constituting metallic elements. In this regard, AuPd nanostructures are particularly promising combining the peculiar plasmonic properties of Au and the catalytic characteristics of Pd in nanoscale form. Hence, we report here on a thermal-induced dewetting process of deposited bimetallic AuPd films in order to obtain two-dimensional arrays of AuPd nanostructures on SiC surface. SiC is chosen, here, as wide band-gap model substrate enabling potential applications in optical, sensing, energy fields. In particular, we focus our study on the effect of the thickness of the AuPd film and of the annealing temperature on the characteristics of the AuPd dewetting process and on the morphology of the resulting dewetted nanostructures. We sputter-deposited, on the surface of 4H–SiC substrate, bimetallic AuPd thin films, thickness in the 4.3–48.6 nm range, and we carried out annealing processes increasing the annealing temperature from 573 K to 1173 K. As a result, we observed, by atomic force microscopy, the evolution of the AuPd films dewetting process towards the formation of two-dimensional arrays of AuPd nanostructures. In particular, we observed the sequential steps involved in the dewetting process by increasing the annealing temperature: heterogeneous voids nucleation in the films resulting in holes formation (leaving SiC surface exposed), holes growth by continuous addition of vacancies, holes coalescence and metal film retraction leaving interconnected metallic filaments, and filaments decay into isolated nanostructures. The quantification of the fraction of the AuPd-uncovered surface area (i.e. dewetted area leaving exposed SiC surface) versus the annealing temperature for each AuPd film thickness allowed us to evaluate the dewetting temperature (the temperature at which the dewetting process of the film starts) and its evolution with the film thickness. Then, the quantification of the particles average planar and vertical sizes (and the corresponding aspect ratio) was carried out versus the annealing temperature and film thickness. Finally, the temperature-dependent and thickness-dependent growth mode for the dewetted AuPd nanostructures is proposed.

Facile and efficient ligand-directed asymmetric growth of Au–Ag bimetallic dimer nanostructures

Facile and efficient ligand-directed asymmetric growth of Au–Ag bimetallic dimer nanostructures

Electrochemical conversion of CO2 to value-added chemicals over bimetallic Pd-based nanostructures: Recent progress and emerging trends

Electrochemical conversion of CO2 to fuels and chemicals as a sustainable solution for waste transformation has garnered tremendous interest to combat the fervent issue of the prevailing high atmospheric CO2 concentration while contributing to the generation of sustainable energy. Monometallic palladium (Pd) has been shown promising in electrochemical CO2 reduction, producing formate or CO depending on applied potentials. Recently, bimetallic Pd-based materials strived to fine-tune the binding affinity of key intermediates is a prominent strategy for the desired product formation from CO2 reduction. Herein, the recent emerging trends on bimetallic Pd-based electrocatalysts are reviewed, including fundamentals of CO2 electroreduction and material engineering of bimetallic Pd-electrocatalysts categorized by primary products. Modern analytical techniques on these novel electrocatalysts are also thoroughly studied to get insights into reaction mechanisms. Lastly, we deliberate over the challenges and prospects for Pd-based catalysts for electrochemical CO2 conversion.

Direct Electrodeposition of Bimetallic Nanostructures on Co-Based MOFs for Electrochemical Sensing of Hydrogen Peroxide

Hydrogen peroxide (H2O2) is the most significant reactive oxygen species in biological systems. Here, we reported an electrochemical sensor for the detection of H2O2 on the basis of bimetallic gold-platinum nanoparticles (Au3Pt7 NPs) supported by Co-based metal organic frameworks (Co-MOFs). First, Au3Pt7 NPs, with optimal electrocatalytic activity and accessible active surface, can be deposited on the surface of the Co-MOF–modified glassy carbon electrodes (Au3Pt7/Co-MOFs/GCE) by one-step electrodeposition method. Then, the electrochemical results demonstrated that the two-dimensional (2D) Co-MOF nanosheets as the supporting material displayed better electrocatalytic properties than the 3D Co-MOF crystals for reduction of H2O2. The fabricated Au3Pt7/2D Co-MOF exhibited high electrocatalytic activity, and the catalytic current was linear with H2O2 concentration from 0.1 μM to 5 mM, and 5–60 mM with a low detection limit of 0.02 μM (S/N = 3). The remarkable electroanalytical performance of Au3Pt7/2D Co-MOF can be attributed to the synergistic effect of the high dispersion of the Au3Pt7 NPs with the marvelous electrochemical properties and the 2D Co-MOF with high-specific surface areas. Furthermore, this sensor has been utilized to detect H2O2 concentrations released from the human Hela cells. This work provides a new method for improving the performance of electrochemical sensors by choosing the proper support materials from diverse crystal morphology materials.

Back Cover Image: Volume 3 Issue 1

Back cover image: Selective synthesis of the liquid commodity from electrochemical reduction of carbon dioxide (CO2) is promising to neutralize carbon footprint. Developing the appropriate catalyst to efficiently and selectively promote ethanol formation is challenging because of the involvement of coupling two types of carbon intermediates with different valence values. This work reports the rational design and synthesis of Ag/Cu bimetallic nanostructures with a high density of Ag/Cu interfaced boundaries. The shallowly reduced intermediates (CO) on the Ag surface and the deeply reduced intermediates (CHx) on the Cu surface simultaneously migrate to the Ag/Cu boundaries and couple into ethanol molecules. The Faradaic efficiency for ethanol formation catalyzed by the synthesized Ag/Cu interfaced nanostructures reaches ~50%. (DOI: https://doi.org/10.1002/smm2.1096)

Analyzing the Influence of Spatial Dispersion on the Optical Characteristics of Cylindrical Bimetallic Nanostructures with the Discrete Sources Method

Analyzing the Influence of Spatial Dispersion on the Optical Characteristics of Cylindrical Bimetallic Nanostructures with the Discrete Sources Method

Interfaced Ag/Cu nanostructures derived from metal thiolate nanoplates: A highly selective catalyst for electrochemical reduction of CO2 to ethanol

AbstractSelective reduction of CO2 into liquid products such as ethanol through electrochemical catalysis is promising in storing renewable energy in more deliverable chemicals and balancing the carbon footprint in the environment. However, the lack of efficient catalysts for electrochemical CO2 reduction reaction (eCO2RR) makes the promise challenging because the formation of C2+ alcohols requires coupling reactions between the shallow reduction intermediates and deep reduction intermediates that are usually difficult to form on uniform catalyst surfaces simultaneously with appropriate transient kinetics. Herein, we report a new strategy for synthesizing bimetallic nanostructures with high densities of interfaced Ag/Cu boundaries, which facilitate the coupling reaction of the high‐oxidation‐number intermediates (CO) formed on the Ag surface and the low‐oxidation‐number intermediates (CHx) formed on the Cu surface. The synthesis relies on the electrochemical reduction of bilayered nanoplates made of silver thiolate and copper thiolate, resulting in Ag/Cu nanostructures exposing Ag surface, Cu surface, and the Ag/Cu interfaced boundaries. Balancing the accessible surface areas of the Ag surface, Cu surface, and Ag/Cu boundaries is beneficial for maximizing the activity and selectivity of eCO2RR towards ethanol production. Faradaic efficiency of forming ethanol has been observed as high as about 50% using the Ag/Cu nanostructure catalyst with molar ratio nAg:nCu of 1:1. Moreover, the promoted coupling reaction at the Ag/Cu boundaries and surface modification with thiolate anions significantly suppress the undesirable hydrogen evolution reaction, particularly at high cathodic potentials, maintaining high energy efficiency for eCO2RR.

Catalytic Membrane Nanoreactor with Cu-Agx Bimetallic Nanoparticles Immobilized in Membrane Pores for Enhanced Catalytic Performance.

A catalytic membrane nanoreactor (CMNR) with Cu-Agx (where x is the millimolar concentration of AgNO3) bimetallic catalysts immobilized in membrane pores has been fabricated via coupling flowing synthesis and replacement reaction. Surface characterization by transmission electron microscopy (TEM) gives obvious evidence of the formation of Cu-Ag bimetallic core-shell nanostructures with Ag islands deposited on the Cu core metal. An apparent high shift phenomenon for the Cu element and a low shift phenomenon for the Ag element was determined by X-ray photoelectron spectroscopy (XPS), indicating a close interaction with the transfer of electron density from the Cu atom to the Ag atom. The hydrogenation catalysis of p-nitrophenol (p-NP) was tested to evaluate the catalytic performance. During the catalytic process, the Cu core acts as an electron-deficient site to adsorb and activate the -NO2 group for p-NP, and the Ag shell is beneficial for enhancing active H spilling to the Cu surface and then performing hydrogenation. A volcano-shaped apparent reaction rate constant can be achieved, which rises initially with the increasing Ag content and subsequently drops with a further increase in the Ag content. The highest value of 1071 min-1 can be achieved for CMNR immobilized with Cu-Ag2 owing to the suitable adsorption activation behavior and the best hydrogen spillover behavior.

Mechanochemical Strategies for the Preparation of SiO2-Supported AgAu Nanoalloy Catalysts.

Silver-gold nanoalloys were prepared from their metal salts precursors through bottom-up mechanochemical synthesis, using one-pot or galvanic replacement reaction strategies. The nanostructures were prepared over amorphous SiO2 as an inert supporting material, facilitating their stabilization without the use of any stabilizing agent. The nanomaterials were extensively characterized, confirming the formation of the bimetallic nanostructures. The nanoalloys were tested as catalysts in the hydrogenation of 2-nitroaniline and exhibited up to 4-fold the rate constant and up to 37% increased conversion compared to the respective single metal nanoparticles. Our approach is advantageous to produce nanoparticles with clean surfaces with available catalytic sites, directly in the solid-state and in an environmentally friendly manner.