Galvanic Replacement Synthesis of Metal Nanostructures: Bridging the Gap between Chemical and Electrochemical Approaches

Ultrasensitive Analysis of Escherichia coli O157:H7 Based on Immunomagnetic Separation and Labeled Surface-Enhanced Raman Scattering with Minimized False Positive Identifications

It is a big challenge to monitor pathogens in food with high selectivity. In this study, we reported an ultrasensitive method for Escherichia coli O157:H7 detection based on immunomagnetic separation and labeled surface-enhanced Raman scattering (SERS). The bacterium was identified by heterogeneous recognition elements, monoclonal antibody (mAb), and aptamer. E. coli O157:H7 was separated and enriched by magnetic nanoparticles modified by mAb, and then a plasmonic nanostructure functionalized by aptamers with embedded Raman tags and interior gaps was utilized for further discrimination and detection. The selectivity was enhanced by two binding sites. The higher Raman enhancement was obtained by strong local electromagnetic field oscillation in the gap and the firm embedment of 4-mercaptopyridine (4-Mpy). Optimum experiments created that SERS signals of 4-Mpy at 1010 cm-1 had a good linearity with E. coli O157:H7 at a large range of 10 to 107 CFU/mL with a limit of detection of 2 CFU/mL. This method has great potential for on-site food pathogenic bacterial detection.

The Liquid Metal Age: A Transition From Hg to Ga

This review offers an illuminating journey through the historical evolution and modern-day applications of liquid metals, presenting a comprehensive view of their significance in diverse fields. Tracing the trajectory from mercury applications to contemporary innovations, the paper explores their pivotal role in industry and research. The analysis spans electrical switches, mechanical applications, electrodes, chemical synthesis, energy storage, thermal transport, electronics, and biomedicine. Each section examines the intricacies of liquid metal integration, elucidating their contributions to technological advancements and societal progress. Moreover, the review critically appraises the challenges and prospects inherent in liquid metal applications, addressing issues of recycling, corrosion management, device stability, economic feasibility, translational hurdles, and market dynamics. By delving into these complexities, the paper advances scholarly understanding and offers actionable insights for researchers, engineers, and policymakers. It aims to catalyze innovation, foster interdisciplinary collaboration, and promote liquid metal-enabled solutions for societal needs. Through its comprehensive analysis and forward-looking perspective, this review serves as a guide for navigating the landscape of liquid metal applications, bridging historical legacies with contemporary challenges, and highlighting the transformative potential of liquid metals in shaping future technologies.

Direct Electroplating Ruthenium Precursor on the Surface Oxidized Nickel Foam for Efficient and Stable Bifunctional Alkaline Water Electrolysis

Water electrolysis to produce hydrogen (H2) using renewable energy is one of the most promising candidates for realizing carbon neutrality, but its reaction kinetics is hindered by sluggish anodic oxygen evolution reaction (OER). Ruthenium (Ru) in its high-valence state (oxide) provides one of the most active OER sites and is less costly, but thermodynamically unstable. The strong interaction between Ru nanoparticles (NPs) and nickel hydroxide (Ni(OH)2) is leveraged to directly form Ru-Ni(OH)2 on the surface of a porous nickel foam (NF) electrode via spontaneous galvanic replacement reaction. The formation of Ru─O─Ni bonds at the interface of the Ru NPs and Ni(OH)2 (Ru-Ni(OH)2) on the surface oxidized NF significantly enhance stability of the Ru-Ni(OH)2/NF electrode. In addition to OER, the catalyst is active enough for the hydrogen evolution reaction (HER). As a result, it is able to deliver overpotentials of 228 and 15 mV to reach 10 mA cm-2 for OER and HER, respectively. An industry-scale evaluation using Ru-Ni(OH)2/NF as both OER and HER electrodes demonstrates a high current density of 1500 mA cm-2 (OER: 410 mV; HER: 240 mV), surpassing commercial RuO2 (OER: 600 mV) and Pt/C based performance (HER: 265 mV).

Solvothermal Fabrication of Mesoporous Pd Nano-Corals at Mild Temperature for Alkaline Hydrogen Evolution Reaction

Porous metallic nanomaterials exhibit interesting physical and chemical properties, and are widely used in various fields. Traditional fabrication techniques are limited to metallurgy, sintering, electrodeposition, etc., which limit the control of pore size and distribution, and make it difficult to achieve materials with high surface areas. On the other hand, the chemical preparation of metallic nanoparticles is usually carried out with strong reducing agents or at high temperature, resulting in the formation of dispersed particles which cannot evolve into porous metal. In this study, we reported the simple fabrication of coral-like mesoporous Pd nanomaterial (Pd NC) with a ligament size of 4.1 nm. The fabrication was carried out by simple solvothermal reduction at a mild temperature of 135 °C, without using any templates. The control experiments suggested that tetrabutylammonium bromide (TBAB) played a critical role in the Pd(II) reduction into Pd nanoclusters and their subsequent aggregation to form Pd NC, and another key point for the formation of Pd NC is not to use a strong reducing agent. In alkaline water electrolysis, the Pd NC outperforms the monodisperse Pd NPs and the state-of-the-art Pt (under large potentials) for H2 evolution reaction, probably due to its mesoporous structure and large surface area. This work reports a simple and novel method for producing porous metallic nanomaterials with a high utilization efficiency of metal atoms, and it is expected to contribute to the practical preparation of porous metallic nanomaterials by solvothermal reductions.

Interfacial galvanic replacement strategy for Pd-doped NiFe MOF nanosheets with highly efficient dopamine detection

An interfacial galvanic replacement strategy to controllable synthesize palladium nanoparticles (Pd NPs)-modified NiFe MOF nanocomposite on nickel foam, which served as an efficient sensing platform for quantitative determination of dopamine (DA). Pd NPs grown in situ on the nanosheets of NiFe MOF via self-driven galvanic replacement reaction (GRR) and well uniform distribution was achieved. This method effectively reduced the aggregation of metallic nanoparticles and significantly promoted the electron transfer rate during the electrochemical process, leading to improved electrocatalytic activity for DA oxidation. Remarkably, the precisely constructed biosensor achieved a low detection limit (LOD) of 0.068 µM and recovery of 94.1% (RSD 6.7%, N = 3) for simulated real sample detection and also exhibited superior selectivity and stability. The results confirmed that the as-fabricated Pd-NiFe/NF composite electrode could realize the quantitative determination of DA and showed promising prospects in real sample biosensing.

Electrifying Energy and Chemical Transformations with Single-Atom Alloy Nanoparticle Catalysts

Single-atom alloys (SAAs) have attracted considerable attention as promising electrocatalysts in reactions central to energy conversion and chemical transformation. In contrast to monometallic nanocrystals and metal alloys, SAAs possess unique and intriguing physicochemical properties, positioning them as ideal model systems for studying structure-property relationships. However, the field is still in its early stages. In this Perspective, we first review and summarize rational synthesis methods and advanced characterization techniques for SAA nanoparticle catalysts. We then emphasize the extensive applications of SAAs in a range of electrocatalytic reactions, including fuel cell reactions, water splitting, and carbon dioxide and nitrate reductions. Finally, we provide insights into existing challenges and prospects associated with the controlled synthesis, characterization, and design of SAA catalysts.

Applications of hollow nanostructures in water treatment considering organic, inorganic, and bacterial pollutants

One of the major issues of modern society is water contamination with different organic, inorganic, and contaminants bacteria. Finding cost-effective and efficient materials and methods for water treatment and environment remediation is among the scientists' most important considerations. Hollow-structured nanomaterials, including hollow fiber membranes, hollow spheres, hollow nanoboxes, etc., have shown an exciting capability for wastewater refinement approaches, including membrane technology, adsorption, and photocatalytic procedure due to their extremely high specific surface area, high porosity, unique morphology, and low density. Diverse hollow nanostructures could potentially eliminate organic contaminants, including dyes, antibiotics, oil/water emulsions, pesticides, and other phenolic compounds, inorganic pollutants, such as heavy metal ions, salts, phosphate, bromate, and other ions, and bacteria contaminations. Here, a comprehensive overview of hollow nanostructures' fabrication and modification, water contaminant classification, and recent studies in the water treatment field using hollow-structured nanomaterials with a comparative attitude have been provided, indicating the privilege abd detriments of this class of nanomaterials. Eventually, the future outlook of employing hollow nanomaterials in water refinery systems and the upcoming challenges arising in scaling up are also propounded.

Step-by-Step Nanoscale Top-Down Blocking and Etching Lead to Nanohexapods with Cartesian Geometry

In this research, we designed a stepwise synthetic method for Au@Pt hexapods where six elongated Au pods are arranged in a pairwise perpendicular fashion, sharing a common point (the central origin in a Cartesian-coordinate-like hexapod shape), featured with tip-selectively decorated Pt square nanoplates. Au@Pt hexapods were successfully synthesized by applying three distinctive chemical reactions in a stepwise manner. The Pt adatoms formed discontinuous thin nanoplates that selectively covered six concave facets of a Au truncated octahedron and served as etching masks in the succeeding etching process, which prevented underlying Au atoms from being oxidized. The subsequent isotropic etching proceeded radially, starting from the bare Au surface, carving the central nanocrystal in a concave manner. By controlling the etching conditions, Au@Pt hexapods were successfully fabricated, wherein the core Au domain is connected to six protruding arms, which hold Pt nanoplates at the ends. Due to their morphology, Au@Pt hexapods feature distinctive optical properties in the near-infrared region, as a proof of concept, allowing for surface-enhanced Raman spectroscopy (SERS)-based monitoring of in situ CO electrooxidation. We further extended our synthetic library by tailoring the size of the Pt nanoplates and neck widths of Au branches, demonstrating the validity of selective blocking and etching-based colloidal synthesis.

Effect of copper doping on the photocatalytic performance of Ni2O3@PC membrane composites in norfloxacin degradation

In this study, copper (Cu) and nickel oxide (Ni2O3) microtubes (MTs) were synthesized using an electroless template deposition technique within porous polycarbonate (PC) track-etched membranes (TeMs) to obtain Cu@PC and Ni2O3@PC composite membranes, respectively. The pristine PC TeMs featured nanochannels with a pore density of 4 × 107 pores per cm2 and an average pore diameter of 400 ± 13 nm. The synthesis of a mixed composite, combining Cu and Ni2O3 within the PC matrix, was achieved through a two-step deposition process using a Ni2O3@PC template. An analysis of the resultant composite structure (Cu/Ni2O3@PC) confirmed the existence of CuNi (97.3%) and CuO (2.7%) crystalline phases. The synthesized catalysts were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). In photodegradation assessments, the Cu/Ni2O3@PC mixed composite demonstrated higher photocatalytic activity, achieving a substantial 59% degradation of norfloxacin (NOR) under UV light irradiation. This performance surpassed that of both Ni2O3@PC and Cu@PC composites. The optimal pH for maximum NOR removal from the aqueous solution was determined to be pH 5, with a reaction time of 180 min. The degradation of NOR in the presence of these composites adhered to the Langmuir-Hinshelwood mechanism and a pseudo-first order kinetic model. The reusability of the catalysts was also investigated for 10 consecutive runs, without any activation or regeneration treatments. The Cu@PC membrane catalyst demonstrated a marked decline in degradation efficiency after the 2nd test cycle, ultimately catalyzing only 10% of NOR after the 10th cycle. In contrast, the Ni2O3@PC based catalyst demonstrated a more stable NOR degradation efficiency throughout all 10 runs, with 27% NOR removal observed during the final test. Remarkably, the catalytic performance of the Cu/Ni2O3@PC mixed composite remained highly active even after being recycled 4 times. The degradation efficiency exhibited a gradual reduction, with a 17% decrease after the 6th run and a cumulative 35% removal of NOR achieved by the 10th cycle. Overall, the findings indicate that Cu/Ni2O3@PC mixed composite membranes may represent an advancement in the quest to mitigate the adverse effects of antibiotic pollution in aquatic environments and hold significant promise for sustainable water treatment practices.

Direct Observation of Hollow Bimetallic Nanoparticle Formation through Galvanic Replacement and Etching Reactions

Hollow bimetallic nanoparticles (NPs) formed from metal oxide NP templates are widely used catalysts for hydrogen evolution and CO2 reduction reactions. Despite their importance in catalysis, the details of how these NPs form on the NP templates remain unclear. Here, using in situ liquid-phase transmission electron microscopy (TEM) imaging, we describe the conversion of Cu2O template NPs to hollow PdCu NPs. Our observations show that a polycrystalline PdCu shell forms on the surface of the template via a galvanic replacement reaction while the template undergoes anisotropic etching. This study provides important insights into the synthesis of hollow metallic nanostructures from metal oxide templates.

Nanocomposites of Cu2O with plasmonic metals (Au, Ag): design, synthesis, and photocatalytic applications

Metal-semiconductor nanocomposites have been utilized in a multitude of applications in a wide array of fields, prompting substantial interest from different scientific sectors. Of particular interest are semiconductors paired with plasmonic metals due to the unique optical properties that arise from the individual interactions of these materials with light and the intercomponent movement of charge carriers in their heterostructure. This review focuses on the pairing of Cu2O semiconductor with strongly plasmonic metals, particularly Au and Ag. The design and synthesis of Au-Cu2O and Ag-Cu2O nanostructures, along with ternary nanostructures composed of the three components, are described, with in-depth discussion on the synthesis techniques and tunable parameters. The effects of compositing on the optical and electronic properties of the nanocomposites in the context of photocatalysis are discussed as well. Concluding remarks and potential areas for exploration are presented in the last section.

Galvanic Replacement Reaction: Enabling the Creation of Active Catalytic Structures

The galvanic replacement reaction (GRR) is recognized as a redox process where one metal undergoes oxidation by the ions of another metal possessing a higher reduction potential. This reaction takes place at the interface between a substrate and a solution containing metal ions. Utilizing metal or metal oxide as sacrificial templates enables the synthesis of metallic nanoparticles, oxide-metal composites, and mixed oxides through GRR. Growing evidence showed that GRR has a direct impact on surface structures and properties. This has generated significant interest in catalysis and opened up new horizons for the application of GRR in energy and chemical transformations. This review provides a comprehensive overview of the synthetic strategies utilizing GRR for the creation of catalytically active structures. It discusses the formation of alloys, intermetallic compounds, single atom alloys, metal-oxide composites, and mixed metal oxides with diverse nanostructures. Additionally, GRR serves as a postsynthesis method to modulate metal-oxide interfaces through the replacement of oxide domains. The review also outlines potential future directions in this field.

Preventing the Galvanic Replacement Reaction toward Unconventional Bimetallic Core-Shell Nanostructures

A bimetallic core-shell nanostructure is a versatile platform for achieving intriguing optical and catalytic properties. For a long time, this core-shell nanostructure has been limited to ones with noble metal cores. Otherwise, a galvanic replacement reaction easily occurs, leading to hollow nanostructures or completely disintegrated ones. In the past few years, great efforts have been devoted to preventing the galvanic replacement reaction, thus creating an unconventional class of core-shell nanostructures, each containing a less-stable-metal core and a noble metal shell. These new nanostructures have been demonstrated to show unique optical and catalytic properties. In this work, we first briefly summarize the strategies for synthesizing this type of unconventional core-shell nanostructures, such as the delicately designed thermodynamic control and kinetic control methods. Then, we discuss the effects of the core-shell nanostructure on the stabilization of the core nanocrystals and the emerging optical and catalytic properties. The use of the nanostructure for creating hollow/porous nanostructures is also discussed. At the end of this review, we discuss the remaining challenges associated with this unique core-shell nanostructure and provide our perspectives on the future development of the field.