Noble-Metal Nanoframes and Their Catalytic Applications

Effect of H2O and CO2 on CO oxidation over Pt/SSZ-13 with active sites regulated by Lewis acidity

Strategies for controlling the size of metal species using zeolites and their catalytic behavior in industrially relevant processes have attracted widespread attention, but the effect of H2O and CO2 on the catalytic performance of zeolite-based metal catalysts remains obscure. This study investigated the influence of H2O and CO2 on CO oxidation over zeolite-based metal catalysts, along with the precise control of active sites through the regulation of Lewis acidity. It was found that the presence of H2O enhanced CO oxidation and alleviated the inhibitory effect of CO2. Abundant Lewis acid sites of low SiO2/Al2O3 ratios in the Pt/SSZ-13 catalyst facilitate Pt dispersion (61.07%), a high Ptn+/Pt ratio (4.43), and small Pt particles (2.31 nm) formation. In situ DRIFTS revealed that CO2 inhibits CO adsorption and the decomposition of carbon intermediates. Water alters the CO adsorption configuration of Pt0, thereby weakening the Pt-CO bond to promote the CO oxidation reaction. Meanwhile, water dissociated into hydroxyl groups on the surface adsorbs oxygen species, participating in reactions and promoting CO2 production from carbon intermediates. H218O isotope labeling experiments validated the water involvement in the reaction and emphasized the importance of the presence of oxygen species during the water dissociation process. Regulation of Lewis acid sites promotes the Ptn+ species formation, enhancing the CO oxidation activity, while Pt0 species enhance the water-promotion effect.

One-Step Synthesis Strategy for a Platinum-Based Alloy Catalyst Designed via Crystal-Structure Prediction

The industrial application of polymer electrolyte membrane fuel cells is limited by the high cost of platinum catalysts. In this study, we developed a one-step synthesis strategy for low-platinum alloy catalysts based on crystal-structure predictions. Using this method, we successfully prepared a low-platinum alloy catalyst, i.e., CaPt2, which exhibits the same structure as its theoretically predicted counterpart in a single step via arc melting. There was no hazardous waste emission during the preparation of the alloy catalyst. Electrons were successfully enriched on the surfaces of platinum atoms, and the electronic structures of the platinum atoms were adjusted. The migration of oxygen intermediates during oxygen reduction was determined via an extensive oxygen-intermediate adsorption site test. The reaction path for the oxygen reduction process was determined. Electronic-structure analysis revealed the interaction mechanism between the oxygen intermediate and the platinum atom on the catalyst surface. The incorporation of calcium atoms into the alloy catalyst effectively improved the adsorption/dissociation state of the oxygen intermediates on the catalyst surface. Meanwhile, the molar fraction of platinum atoms in the CaPt2 alloy catalyst reduced by 33%, thus decreasing the feedstock cost of the catalyst. The double reduction in raw materials and manufacturing costs is conducive to the popularization and application of alloy catalysts. This study provides a reference for the design and production of other functional catalysts.

Au@Pt@Pd nanozymes based lateral flow immunoassay for quantitative detection of SARS-CoV-2 nucleocapsid protein in nasal swab samples

Three-metal-core-shell nanoparticles (Au@Pt@PdNPs) providing excellent peroxidase-like activity were applied in lateral flow immunoassay (LFIA), designated as Au@Pt@Pd-LFIA, for detecting the nucleocapsid protein (NP) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). An Au@Pt@Pd-LFIA was developed for quantitatively testing of SARS-CoV-2 NP with a range 0.12-31.25 ng/mL. The limit of detection (LOD) of Au@Pt@Pd-LFIA strip was 0.06 ng/mL, which was 16-fold or eightfold more sensitive than that of the gold lateral flow immunoassay (Au-LFIA) and the gold flower flow immunoassay (AF-LFIA) strips, respectively. For detection of clinical samples from nasal swabs using test strips, Au@Pt@Pd-LFIA had 84.09% sensitivity, 100% specificity, and 92.55% accuracy. In terms of detection time, the testing of Au@Pt@Pd-LFIA strip was 16 min similar to Au-LFIA (15 min) and AF-LFIA (10 min), but much shorter than ELISA (2 h). In conclusion, Au@Pt@Pd-LFIA is a sensitive, rapid, and simple test for quantitative detection of SARS-CoV-2 NP in nasal swab samples.

Nanozyme linked multi-array gas driven sensor for real-time quantitative detection of Group A streptococcus

Group A streptococcus (GAS) is a pathogen typically transmitted through respiratory droplets and skin contact, causing an estimated 700 million mild non-invasive infections worldwide each year. There are approximately 650 000 infections that progress to severe invasive infections, even resulting in death. Therefore, the ability to detect GAS rapidly, accurately and in real time is important. Herein, we developed a nanozyme linked multi-array gas driven sensor (NLMAGS) to point-of-care testing of GAS within 2 h. The NLMAGS demonstrated excellent performance as it combined the advantages of nanozyme techniques, immunoassay techniques, and 3D printing techniques. Platinum- and palladium-rich nanozyme particles (Au@Pt@PdNPs) were synthesized and used to label monocloning antibodies as detection probes. Magnetic beads were labeled with monocloning antibodies as capture probes to establish a double-antibody sandwich immunoassay for the detection of GAS. The sandwich immune complex can catalyze the H2O2 substrate and produce O2. GAS quantification can be achieved by measuring the distance that the O2 pushes the ink drops forward in the sensor. Under optimized conditions, the NLMAGS quantitatively detected 24 spiked samples with a limit of detection (LOD) of 62 CFU mL-1, which was 5 times lower than that of ELISA (334 CFU mL-1). A strong correlation with the conventional ELISA was found (r = 0.99, P < 0.001). In comparison, the traditional lateral flow immunoassay based on Au@Pt@PdNPs-mAb2 (Au@Pt@PdNPs-LFIA) had a LOD of 104 CFU mL-1, which was significantly higher than that of NLMAGS. The NLMAGS demonstrated excellent sensitivity to GAS. The intra- and inter-assay precisions of the sensor were below 15%. Overall, the established NLMAGS has promising potential as a rapid and quantitative method for detecting GAS and can also be used to detect various pathogens.

Crystal-Phase-Selective Etching of Heterophase Au Nanostructures

Selective oxidative etching is one of the most effective ways to prepare hollow nanostructures and nanocrystals with specific exposed facets. The mechanism of selective etching in noble metal nanostructures mainly relies on the different reactivity of metal components and the distinct surface energy of multimetallic nanostructures. Recently, phase engineering of nanomaterials (PEN) offers new opportunities for the preparation of unique heterostructures, including heterophase nanostructures. However, the synthesis of hollow multimetallic nanostructures based on crystal-phase-selective etching has been rarely studied. Here, a crystal-phase-selective etching method is reported to selectively etch the unconventional 4H and 2H phases in the heterophase Au nanostructures. Due to the coating of Pt-based alloy and the crystal-phase-selective etching of 4H-Au in 4H/face-centered cubic (fcc) Au nanowires, the well-defined ladder-like Au@PtAg nanoframes are prepared. In addition, the 2H-Au in the fcc-2H-fcc Au nanorods and 2H/fcc Au nanosheets can also be selectively etched using the same method. As a proof-of-concept application, the ladder-like Au@PtAg nanoframes are used for the electrocatalytic hydrogen evolution reaction (HER) in acidic media, showing excellent performance that is comparable to the commercial Pt/C catalyst.

Strain-Controlled Galvanic Synthesis of Platinum Icosahedral Nanoframes and Their Enhanced Catalytic Activity toward Oxygen Reduction

The unique strain distribution on the surface of a Pd icosahedral nanocrystal is leveraged to control the sites for oxidation and reduction involved in the galvanic replacement reaction. Specifically, Pd is oxidized and dissolved from the center of each {111} facet due to its tensile strain, while the Pt(II) precursor adsorbs onto the vertices and edges featuring a compressive strain, followed by surface reduction and conformal deposition of the Pt atoms. Once the galvanic reaction is initiated, the {111} facets become more vulnerable to oxidation and dissolution, as the vertices and edges are protected by the deposited Pt atoms. The site-selected galvanic reaction naturally results in the formation of Pt icosahedral nanoframes covered by compressively strained {111} facets, which show enhanced catalytic activity and durability toward oxygen reduction relative to commercial Pt/C.

Unveiling Spatial and Temporal Dynamics of Plasmon-Enhanced Localized Fields in Metallic Nanoframes through Ultrafast Electron Microscopy

Plasmonic nanomaterials, particularly noble metal nanoframes (NFs), are important for applications such as catalysis, biosensing, and energy harvesting due to their ability to enhance localized electric fields and atomic efficiency via localized surface plasmon resonance (LSPR). Yet the fundamental structure-function relationships and plasmonic dynamics of the NFS are difficult to study experimentally and thus far rely predominately on computational methodologies, limiting their utilization. This study leverages the capabilities of ultrafast electron microscopy (UEM), specifically photon-induced near-field electron microscopy (PINEM), to probe the light-matter interactions within plasmonic NF structures. The effects of shape, size, and plasmonic coupling of Pt@Au core-shell NFs on spatial and temporal characteristics of plasmon-enhanced localized electric fields are explored. Importantly, time-resolved PINEM analysis reveals that the plasmonic fields around hexagonal NF prisms exhibit a spatially dependent excitation and decay rate, indicating a nuanced interplay between the spatial geometry of the NF and the temporal evolution of the localized electric field. These results and observations uncover nanophotonic energy transfer dynamics in NFs and highlight their potential for applications in biosensing and photocatalysis.

Metal-Organic Skeleton-Derived W-Doped Ga2O3-NC Catalysts for Aerobic Oxidative Dehydrogenation of N-Heterocycles

N-heterocycles with quinoline structures hold significant importance within the chemical and pharmaceutical industries. However, achieving their efficient transformations remains a vital yet challenging endeavor. Herein, a series of W-doped Ga2O3-NC catalysts were synthesized using a Ga-MOF-derived strategy through a simple solvothermal method, with a remarkably high activity and selectivity towards the oxidative dehydrogenation of N-heterocycles. Furthermore, the MOF-derived W-doped Ga2O3-NC catalysts exhibit remarkable substrate tolerance and recyclability. The outstanding catalytic activity was attributed to the robust synergistic interaction between the W species and the Ga2O3-NC carrier, which facilitates the activation of hydrogen atoms in the C-H and C=N bonds on both the oxygen molecule and the substrate to produce H2O2. Additionally, the solvent effect of methanol can significantly enhance dehydrogenation due to its strong ability to donate and accept protons of hydrogen bonding. The present work provides a new approach to MOF-derived non-precious metal catalysts for achieving the efficient oxidation dehydrogenation of N-heterocycles.

C60 Fullerene-Induced Reduction of Metal Ions: Synthesis of C60-Metal Cluster Heterostructures with High Electrocatalytic Hydrogen-Evolution Performance

Metal clusters, due to their small dimensions, contain a high proportion of surface atoms, thus possessing a significantly improved catalytic activity compared with their bulk counterparts and nanoparticles. Defective and modified carbon supports are effective in stabilizing metal clusters, however, the synthesis of isolated metal clusters still requires multiple steps and harsh conditions. Herein, we develop a C60 fullerene-driven spontaneous metal deposition process, where C60 serves as both a reductant and an anchor, to achieve uniform metal (Rh, Ir, Pt, Pd, Au and Ru) clusters without the need for any defects or functional groups on C60. Density functional theory calculations reveal that C60 possesses multiple strong metal adsorption sites, which favors stable and uniform deposition of metal atoms. In addition, owing to the electron-withdrawing properties of C60, the electronic structures of metal clusters are effectively regulated, not only optimizing the adsorption behavior of reaction intermediates but also accelerating the kinetics of hydrogen evolution reaction. The synthesized Ru/C60-300 exhibits remarkable performance for hydrogen evolution in an alkaline condition. This study demonstrates a facile and efficient method for synthesizing effective fullerene-supported metal cluster catalysts without any pretreatment and additional reducing agent.

Construction of Metal/Zeolite Hybrid Nanoframe Reactors via in-Situ-Kinetics Transformations

Metal/zeolite hybrid nanoframes featuring highly accessible compartmental environments, abundant heterogeneous interfaces, and diverse chemical compositions are expected to possess significant potential for heterogeneous catalysis, yet their general synthetic methodology has not yet been established. In this study, we developed a two-step in-situ-kinetics transformation approach to prepare metal/ZSM-5 hybrid nanoframes with exceptionally open nanostructures, tunable metal compositions, and abundant accessible active sites. Initially, the process involved the formation of single-crystalline ZSM-5 nanoframes through an anisotropic etching and recrystallization kinetic transformation process. Subsequently, through an in situ reaction of the Ni2+ ions and the silica species etched from ZSM-5 nanoframes, layered nickel silicate emerged on both the inner and outer surfaces of the zeolite nanoframes. Upon reduction under a hydrogen atmosphere, well-dispersed Ni nanoparticles were produced and immobilized onto the ZSM-5 nanoframes. Strikingly, this strategy can be extended to immobilize a variety of ultrasmall monometallic and bimetallic alloy nanoparticles on zeolite nanoframes. Benefiting from the structural and compositional advantages, the resultant hybrid nanoframes with a high loading of discrete Ni nanoparticles exhibited enhanced performance in the hydrodeoxygenation of stearic acid into liquid fuels. Overall, the methodology shares fresh insights into the rational construction of intricate frame-like metal/zeolite hybrid nanoreactors for many potential catalytic applications.

Enzyme-like nanoparticle-engineered mesenchymal stem cell secreting HGF promotes visualized therapy for idiopathic pulmonary fibrosis in vivo

Stem cell therapy is being explored as a potential treatment for idiopathic pulmonary fibrosis (IPF), but its effectiveness is hindered by factors like reactive oxygen species (ROS) and inflammation in fibrotic lungs. Moreover, the distribution, migration, and survival of transplanted stem cells are still unclear, impeding the clinical advancement of stem cell therapy. To tackle these challenges, we fabricate AuPtCoPS trimetallic-based nanocarriers (TBNCs), with enzyme-like activity and plasmid loading capabilities, aiming to efficiently eradicate ROS, facilitate delivery of therapeutic genes, and ultimately improve the therapeutic efficacy. TBNCs also function as a computed tomography contrast agent for tracking mesenchymal stem cells (MSCs) during therapy. Accordingly, we enhanced the antioxidant stress and anti-inflammatory capabilities of engineered MSCs and successfully visualized their biological behavior in IPF mice in vivo. Overall, this study provides an efficient and forward-looking treatment approach for IPF and establishes a framework for a stem cell-based therapeutic system aimed at addressing lung disease.

Site-Selective Deposition of Silica Nanoframes and Nanocages onto Faceted Gold Nanostructures Using a Primer-free Tetraethyl Orthosilicate Synthesis

The Stöber method for forming spherical silica colloids is well-established as one of the pillars of colloidal synthesis. In a modified form, it has been extensively used to deposit both porous and protective shells over metal nanomaterials. Current best-practice techniques require that the vitreophobic surface of metal nanoparticles be primed with a surface ligand to promote silica deposition. Although such techniques have proved highly successful in forming core-shell configurations, the site-selective deposition of silica onto preselected areas of faceted metal nanostructures has proved far more challenging. Herein, a primer-free TEOS-based synthesis is demonstrated that is capable of forming architecturally complex nanoframes and nanocages on the pristine surfaces of faceted gold nanostructures. The devised synthesis overcomes vitreophobicity using elevated TEOS concentrations that trigger silica nucleation along the low-coordination sites where gold facets meet. Continued deposition sees the emergence of a well-connected frame followed by the lateral infilling of the openings formed over gold facets. With growth readily terminated at any point in this sequence, the synthesis distinguishes itself in being able to achieve patterned and tunable silica depositions expressing interfaces that are uncorrupted by primers. The so-formed structures are demonstrated as template materials capable of asserting high-level control over synthesis and assembly processes by using the deposited silica as a mask that deactivates selected areas against these processes while allowing them to proceed elsewhere. The work, hence, extends the capabilities and versatility of TEOS-based syntheses and provides pathways for forming multicomponent nanostructures and nanoassemblies with structurally engineered properties.

Crucial Role of Metal Coordination Number in Optimizing Electrocatalyst Activity of Holey Large-Area 2D Ru Nanosheets

Low-dimensional metal nanostructures have attracted considerable research attention, owing to their potential as catalysts. A controlled reductive phase transition of monolayer RuO2 nanosheets could provide an effective way to produce holey large-area 2D Ru nanosheets with tailored defect structures and metal coordination number. The locally optimized holey Ru metal nanosheet, with a metal coordination number of ∼10.2, exhibited excellent electrocatalytic activity for the hydrogen evolution reaction (HER) with a reduced overpotential of 38 mV in a 1 M KOH electrolyte. The creation of a highly anisotropic holey nanosheet morphology with optimization of local structure was quite effective in developing efficient catalyst materials. The universal importance of controlling the coordination number was confirmed through a comparative study of Ru nanoparticles, which showed optimized HER activity with an identical metal coordination number. The coordination number plays a pivotal role in governing electrocatalytic activity, which could be ascribed to the formation of the most active structure for HER at most 2 defects near active sites (2,2'), resulting in the stabilization of a dihydrogen Ru-(H2) intermediate and the increased contribution of Volmer-Tafel mechanism.

Chiral Au-Pd Alloy Nanorods with Tunable Optical Chirality and Catalytically Active Surfaces

Integrating the plasmonic chirality with excellent catalytic activities in plasmonic hybrid nanostructures provides a promising strategy to realize the chiral nanocatalysis toward many chemical reactions. However, the controllable synthesis of catalytically active chiral plasmonic nanoparticles with tailored geometries and compositions remains a significant challenge. Here it is demonstrated that chiral Au-Pd alloy nanorods with tunable optical chirality and catalytically active surfaces can be achieved by a seed-mediated coreduction growth method. Through manipulating the chiral inducers, Au nanorods selectively transform into two different intrinsically chiral Au-Pd alloy nanorods with distinct geometric chirality and tunable optical chirality. By further adjusting several key synthetic parameters, the optical chirality, composition, and geometry of the chiral Au-Pd nanorods are fine-tailored. More importantly, the chiral Au-Pd alloy nanorods exhibit appealing chiral catalytic activities as well as polarization-dependent plasmon-enhanced nanozyme catalytic activity, which has great potential for chiral nanocatalysis and plasmon-induced chiral photochemistry.

Construction of Gold/Rhodium Freestanding Superstructures as Antenna-Reactor Photocatalysts for Plasmon-Driven Nitrogen Fixation

Precisely controlling the architecture and spatial arrangement of plasmonic heterostructures offers unique opportunities to tailor the catalytic property, whereas the lack of a wet-chemistry synthetic approach to fabricating nanostructures with high-index facets limits their practical applications. Herein, we describe a universal synthetic strategy to construct Au/Rh freestanding superstructures (SSs) through the selective growth of ordered Rh nanoarrays on high-index-faceted Au nanobipyramids (NBPs). This synthetic strategy works on various metal nanocrystal substrates and can yield diverse Au/Rh and Pd/Rh SSs. Especially, the obtained Au NBP/Rh SSs exhibit high photocatalytic activity toward N2 fixation as a result of the spatially separated architecture, local electric field enhancement, and the antenna-reactor mechanism. Both theoretical and experimental results reveal that the Au NBPs can function as nanoantennas for light-harvesting to generate hot charge carriers for driving N2 fixation, while the Rh nanoarrays can serve as the active sites for N2 adsorption and activation to synergistically promote the overall catalytic activity in the Au NBP/Rh SSs. This work offers new avenues to rationally designing and constructing spatially separated plasmonic photocatalysts for high-efficiency catalytic applications.

Modulating the Electronic States of Pt Nanoparticles on Reducible Metal-Organic Frameworks for Boosting the Oxidation of Volatile Organic Compounds

The adsorption and activation of pollutant molecules and oxygen play a critical role in the oxidation reaction of volatile organic compounds (VOCs). In this study, superior adsorption and activation ability was achieved by modulating the interaction between Pt nanoparticles (NPs) and UiO-66 (U6) through the spatial position effect. Pt@U6 exhibits excellent activity in toluene, acetone, propane, and aldehyde oxidation reactions. Spectroscopic studies, 16O2/18O2 kinetic isotopic experiments, and density functional theory (DFT) results jointly reveal that the encapsulated Pt NPs of Pt@U6 possess higher electron density and d-band center, which is conducive for the adsorption and dissociation of oxygen. The toluene oxidation reaction and DFT results indicate that Pt@U6 is more favorable to activate the C-H of toluene and the C═C of maleic anhydride, while Pt/U6 with lower electron density and d-band center exhibits a higher oxygen dissociation temperature and higher reactant activation energy barriers. This study provides a deep insight into the architecture-performance relation of Pt-based catalysts for the catalytic oxidation of VOCs.

Three-Dimensional Au Octahedral Nanoheptamers: Single-Particle and Bulk Near-Field Focusing for Surface-Enhanced Raman Scattering

Herein, we present a synthetic approach to fabricate Au nanoheptamers composed of six individual Au nanospheres interconnected through thin metal bridges arranged in an octahedral configuration. The resulting structures envelop central Au nanospheres, producing Au nanosphere heptamers with an open architectural arrangement. Importantly, the initial Pt coating of the Au nanospheres is a crucial step for protecting the inner Au nanospheres during multiple reactions. As-synthesized Au nanoheptamers exhibit multiple hot spots formed by nanogaps between nanospheres, resulting in strong electromagnetic near-fields. Additionally, we conducted surface-enhanced Raman-scattering-based detection of a chemical warfare agent simulant in the gas phase and achieved a limit of detection of 100 ppb, which is 3 orders lower than that achieved using Au nanospheres and Au nanohexamers. This pseudocore-shell nanostructure represents a significant advancement in the realm of complex nanoparticle synthesis, moving the field one step closer to sophisticated nanoparticle engineering.

Bridging Together Theoretical and Experimental Perspectives in Single-Atom Alloys for Electrochemical Ammonia Production

Ammonia is an essential commodity in the food and chemical industry. Despite the energy-intensive nature, the Haber-Bosch process is the only player in ammonia production at large scales. Developing other strategies is highly desirable, as sustainable and decentralized ammonia production is crucial. Electrochemical ammonia production by directly reducing nitrogen and nitrogen-based moieties powered by renewable energy sources holds great potential. However, low ammonia production and selectivity rates hamper its utilization as a large-scale ammonia production process. Creating effective and selective catalysts for the electrochemical generation of ammonia is critical for long-term nitrogen fixation. Single-atom alloys (SAAs) have become a new class of materials with distinctive features that may be able to solve some of the problems with conventional heterogeneous catalysts. The design and optimization of SAAs for electrochemical ammonia generation have recently been significantly advanced. This comprehensive review discusses these advancements from theoretical and experimental research perspectives, offering a fundamental understanding of the development of SAAs for ammonia production.

Quantitative Study on the Influence of Bromide Ions toward the Reduction Kinetics for Size-Tunable Palladium Nanocubes

During the preparation of nanocrystals, regulating the dosage of key additives in the reaction system and the reaction temperature commonly affects the sizes and morphologies of the products. Despite the fact that bromide ions play a pivotal role in the synthesis of palladium nanocubes (Pd NCs), there is still a lack of quantitative and in-depth research on how the ions affect the reduction kinetics of Pd precursors and further on products. In this work, Pd NCs with different sizes have been prepared under various reaction conditions coupled to a systematic mechanism study. Quantitative measurements demonstrate that the reduction processes could be considered quasi-first-order reactions, and the corresponding kinetic parameters have been obtained. Furthermore, a linear relationship is discovered between k and the average size (d) of Pd NCs. The investigation on the growth patterns of four chosen systems reveals that given reaction conditions lead to certain results with unique growth patterns.

Multicomponent chiral plasmonic hybrid nanomaterials: recent advances in synthesis and applications

Chiral hybrid nanomaterials with multiple components provide a highly promising approach for the integration of desired chirality with other functionalities into one single nanoscale entity. However, precise control over multicomponent chiral plasmonic hybrid nanomaterials to enable their application in diverse and complex scenarios remains a significant challenge. In this review, our focus lies on the recent advances in the preparation and application of multicomponent chiral plasmonic hybrid nanomaterials, with an emphasis on synthetic strategies and emerging applications. We first systematically elucidate preparation methods for multicomponent chiral plasmonic hybrid nanomaterials encompassing the following approaches: physical deposition approach, galvanic replacement reaction, chiral molecule-mediated, chiral heterostructure, circularly polarized light-mediated, magnetically induced, and chiral assembly. Furthermore, we highlight emerging applications of multicomponent chiral plasmonic hybrid nanomaterials in chirality sensing, enantioselective catalysis, and biomedicine. Finally, we provide an outlook on the challenges and opportunities in the field of multicomponent chiral plasmonic hybrid nanomaterials. In-depth investigations of these multicomponent chiral hybrid nanomaterials will pave the way for the rational design of chiral hybrid nanostructures with desirable functionalities for emerging technological applications.

Au Octahedral Nanosponges: 3D Plasmonic Nanolenses for Near-Field Focusing

Here, we report the synthesis of three-dimensional plasmonic nanolenses for strong near-field focusing. The nanolens exhibits a distinctive structural arrangement composed of nanoporous sponge-like networks within their interior. We denote these novel nanoparticles as "Au octahedral nanosponges" (Au Oh NSs). Employing a carefully planned multistep synthetic approach with Au octahedra serving as sacrificial templates, we successfully synthesized Au Oh NSs in solution. The porous domains resembling sponges contributed to enhanced scattering and absorption of incident light within metal ligaments. This optical energy was subsequently transferred to the nanospheres at the vertex, where near-field focusing was maximized. We named this observed enhancement a "lightning-sphere effect". Using single particle-by-particle surface-enhanced Raman scattering (SERS), we optimized the morphological dimensions of the spheres and porous domains to achieve the most effective near-field focusing. In the context of bulk SERS measurements targeting weakly adsorbing analytes (2-chloroethyl phenyl sulfide) in the gas phase, we achieved a low detection limit of 10 ppb. For nonadsorbing species (dimethyl methyl phosphonate), utilization of hybrid SERS substrates consisting of Au Oh NSs and metal-organic frameworks as gas-adsorbing intermediate layers was highly effective for successful SERS detection.

Rhombic dodecahedron nanoframes of PtIrCu with high-index faceted hyperbranched nanodendrites for efficient electrochemical ammonia oxidation via preferred NHx dimerization pathways

Ammonia has been emerging as a sustainable and environmentally friendly fuel. However, direct electrochemical ammonia oxidation reaction (AOR) in low-temperature fuel cells seriously suffers from high overpotential and deficient durability. Herein, rhombic dodecahedron nanoframe of platinum iridium copper (PtIrCu) with high-index faceted hyperbranched nanodendrites (RDNF-HNDs) was developed using a one-step self-etching solvothermal method. The framework structure with the high-index facets enables the PtIrCu nanocrystals to expose more effective active sites. They exhibit an ultra-low onset potential of 0.33 V vs. RHE and high mass activity of 26.1 A gPtIr-1 at 0.50 V, which is 140 mV lower and 7.5 times higher than that of commercial Pt/C in the AOR. In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy verifies that AOR on PtIrCu RDNF-HNDs prefers to the NHx dimerization pathways, effectively alleviating the poison of Nads and NOx. The theoretical calculation also shows that both introducing Cu atoms into PtIr alloy and increasing the content of Ir in PtIrCu alloy can reduce the reaction energy barrier of electrochemical dehydrogenation from *NH2 to *NH. The specific structure of PtIrCu RDNF-NDs provides a new inspiration to solve the critical issue of electrocatalysts for AOR with low activity and durability.

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis

Electrocatalysis underpins the renewable electrochemical conversions for sustainability, which further replies on metallic nanocrystals as vital electrocatalysts. Intermetallic nanocrystals have been known to show distinct properties compared to their disordered counterparts, and been long explored for functional improvements. Tremendous progresses have been made in the past few years, with notable trend of more precise engineering down to an atomic level and the investigation transferring into more practical membrane electrode assembly (MEA), which motivates this timely review. After addressing the basic thermodynamic and kinetic fundamentals, we discuss classic and latest synthetic strategies that enable not only the formation of intermetallic phase but also the rational control of other catalysis-determinant structural parameters, such as size and morphology. We also demonstrate the emerging intermetallic nanomaterials for potentially further advancement in energy electrocatalysis. Then, we discuss the state-of-the-art characterizations and representative intermetallic electrocatalysts with emphasis on oxygen reduction reaction evaluated in a MEA setup. We summarize this review by laying out existing challenges and offering perspective on future research directions toward practicing intermetallic electrocatalysts for energy conversions.

Recent Progress on Phase Engineering of Nanomaterials

As a key structural parameter, phase depicts the arrangement of atoms in materials. Normally, a nanomaterial exists in its thermodynamically stable crystal phase. With the development of nanotechnology, nanomaterials with unconventional crystal phases, which rarely exist in their bulk counterparts, or amorphous phase have been prepared using carefully controlled reaction conditions. Together these methods are beginning to enable phase engineering of nanomaterials (PEN), i.e., the synthesis of nanomaterials with unconventional phases and the transformation between different phases, to obtain desired properties and functions. This Review summarizes the research progress in the field of PEN. First, we present representative strategies for the direct synthesis of unconventional phases and modulation of phase transformation in diverse kinds of nanomaterials. We cover the synthesis of nanomaterials ranging from metal nanostructures such as Au, Ag, Cu, Pd, and Ru, and their alloys; metal oxides, borides, and carbides; to transition metal dichalcogenides (TMDs) and 2D layered materials. We review synthesis and growth methods ranging from wet-chemical reduction and seed-mediated epitaxial growth to chemical vapor deposition (CVD), high pressure phase transformation, and electron and ion-beam irradiation. After that, we summarize the significant influence of phase on the various properties of unconventional-phase nanomaterials. We also discuss the potential applications of the developed unconventional-phase nanomaterials in different areas including catalysis, electrochemical energy storage (batteries and supercapacitors), solar cells, optoelectronics, and sensing. Finally, we discuss existing challenges and future research directions in PEN.

Seeded Synthesis of Hollow PdSn Intermetallic Nanomaterials for Highly Efficient Electrocatalytic Glycerol Oxidation

Intermetallic nanomaterials have shown promising potential as high-performance catalysts in various catalytic reactions due to their unconventional crystal phases with ordered atomic arrangements. However, controlled synthesis of intermetallic nanomaterials with tunable crystal phases and unique hollow morphologies remains a challenge. Here, a seeded method is developed to synthesize hollow PdSn intermetallic nanoparticles (NPs) with two different intermetallic phases, that is, orthorhombic Pd2 Sn and monoclinic Pd3 Sn2 . Benefiting from the rational regulation of the crystal phase and morphology, the obtained hollow orthorhombic Pd2 Sn NPs deliver excellent electrocatalytic performance toward glycerol oxidation reaction (GOR), outperforming solid orthorhombic Pd2 Sn NPs, hollow monoclinic Pd3 Sn2 NPs, and commercial Pd/C, which places it among the best reported Pd-based GOR electrocatalysts. The reaction mechanism of GOR using the hollow orthorhombic Pd2 Sn as the catalyst is investigated by operando infrared reflection absorption spectroscopy, which reveals that the hollow orthorhombic Pd2 Sn catalyst cleaves the CC bond more easily compared to the commercial Pd/C. This work can pave an appealing route to the controlled synthesis of diverse novel intermetallic nanomaterials with hollow morphology for various promising applications.

Post-Assay Chemical Enhancement for Highly Sensitive Lateral Flow Immunoassays: A Critical Review

Lateral flow immunoassay (LFIA) has found a broad application for testing in point-of-care (POC) settings. LFIA is performed using test strips-fully integrated multimembrane assemblies containing all reagents for assay performance. Migration of liquid sample along the test strip initiates the formation of labeled immunocomplexes, which are detected visually or instrumentally. The tradeoff of LFIA's rapidity and user-friendliness is its relatively low sensitivity (high limit of detection), which restricts its applicability for detecting low-abundant targets. An increase in LFIA's sensitivity has attracted many efforts and is often considered one of the primary directions in developing immunochemical POC assays. Post-assay enhancements based on chemical reactions facilitate high sensitivity. In this critical review, we explain the performance of post-assay chemical enhancements, discuss their advantages, limitations, compared limit of detection (LOD) improvements, and required time for the enhancement procedures. We raise concerns about the performance of enhanced LFIA and discuss the bottlenecks in the existing experiments. Finally, we suggest the experimental workflow for step-by-step development and validation of enhanced LFIA. This review summarizes the state-of-art of LFIA with chemical enhancement, offers ways to overcome existing limitations, and discusses future outlooks for highly sensitive testing in POC conditions.

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.

Wet-chemistry synthesis of two-dimensional Pt- and Pd-based intermetallic electrocatalysts for fuel cells

Two-dimensional (2D) noble-metal-based nanomaterials have attracted tremendous attention and have widespread promising applications as a result of their unique physical, chemical, and electronic properties. Especially, 2D Pt- and Pd-based intermetallic nanoplates (IMNPs) and nanosheets (IMNSs) are widely studied for fuel cell (FC)-related reactions, including the cathodic oxygen reduction reaction (ORR) and anodic formic acid, methanol and ethanol oxidation reactions (FAOR, MOR and EOR). Wet-chemistry synthesis is a powerful strategy to prepare metallic nanocrystals with well-controlled dispersity, size, and composition. In this review, a fundamental understanding of the FC-related reactions is firstly elaborated. Subsequently, the current wet-chemistry synthesis pathways for 2D Pt- and Pd-based IMNPs and IMNSs are briefly summarized, as well as their electrocatalytic applications including in the ORR, FAOR, MOR, and EOR. Finally, we provide an overview of the opportunities and current challenges and give our perspectives on the development of high-performance 2D Pt- and Pd-based intermetallic electrocatalysts towards FCs. We hope this review offers timely information on the synthesis of 2D Pt- and Pd-based IMNPs and IMNSs and provides guidance for the efficient synthesis and application of them.

Bridging Colloidal and Electrochemical Nanoparticle Growth with In Situ Electrochemical Measurements

ConspectusProspective applications involving the electrification of industrial chemical processes and electrical energy to chemical fuels interconversion as part of the energy transition to renewable energy sources have led to an increasing need for highly tailored nanostructures immobilized on electrode surfaces. Control of surface facet structure across material compositions is of particular importance for ensuring performance in such applications. Colloidal methods for producing shaped nanoparticles in solution are abundant, particularly for noble metals. However, significant technical challenges remain with respect to rationally designing syntheses for the novel compositions and morphologies required to sustainably enable the above technological advances as well as in developing methods for uniformly and reproducibly dispersing colloidally synthesized nanostructures on electrode surfaces. The direct synthesis of nanoparticles on electrodes using chemical reduction approaches remains challenging, though recent advances have been made for certain materials and structures. Electrochemical nanoparticle synthesis─where an applied current or potential instead of a chemical reducing agent drives the redox chemistry of nanoparticle growth─is poised to play an important role in advancing the fabrication of nanostructured electrodes. Specifically, this Account focuses on the colloidal-inspired design of electrochemical syntheses and the interplay between colloidal and electrochemical approaches in terms of understanding the fundamental chemical reaction mechanisms of nanoparticle growth. An initial discussion of the development of electrochemical particle syntheses that incorporate colloidal synthetic tools highlights the promising emergent capabilities that result from blending these two approaches. Furthermore, it demonstrates how existing colloidal syntheses can be directly translated to electrochemical growth on a conductive surface using real-time electrochemical measurements of the chemistry of the growth solution. Measuring the open circuit potential of a colloidal synthesis over time and then replicating that measured potential during electrochemical deposition leads to the formation of the same nanoparticle shape. These in situ open circuit and chronopotentiometric measurements also give fundamental insight about the changing chemical environment during particle growth. We highlight how these time-resolved electrochemical measurements, as well as correlated spectroelectrochemical monitoring of particle formation kinetics, enable the extraction of information regarding mechanisms of particle formation that is difficult to obtain using other approaches. This information can be translated back into colloidal synthesis design via a directed, intentional approach to synthetic development. We additionally explore the added flexibility of synthetic design for methods involving electrochemically driven reduction as compared to the use of chemical reducing agents. The Account concludes with a brief perspective on potential future directions in both fundamental studies and synthetic development enabled by this emerging integrated electrochemical approach.

Oriented Assembled Prussian Blue Analogue Framework for Confined Catalytic Decomposition of Ammonium Perchlorate

The design of highly dispersed active sites of hollow materials and unique contact behavior with the components to be catalyzed provide infinite possibilities for exploring the limits of catalyst capacity. In this study, the synthesis strategy of highly open 3-dimensional frame structure Prussian blue analogues (CoFe-PBA) was explored through structure self-transformation, which was jointly guided by template mediated epitaxial growth, restricted assembly and directional assembly. Additionally, good application prospect of CoFe-PBA as combustion catalyst was discussed. The results show that unexpected thermal decomposition behavior can be achieved by limiting AP(ammonium perchlorate) to the framework of CoFe-PBA. The high temperature decomposition stage of AP can be advanced to 283.6 °C and the weight loss rate can reach 390.03% min^-1 . In-situ monitoring shows that CoFe-PBA can accelerate the formation of NO and NO₂ . The calculation of reaction kinetics proved that catalytic process was realized by increasing the nucleation factor. On this basis, the catalytic mechanism of CoFe-PBA on the thermal decomposition of AP was discussed, and the possible interaction process between AP and CoFe-PBA during heating was proposed. At the same time, another interesting functional behavior to prevent AP from caking was discussed.

Research Progress on Biomimetic Nanomaterials for Electrochemical Glucose Sensors

Diabetes has become a chronic disease that necessitates timely and accurate detection. Among various detection methods, electrochemical glucose sensors have attracted much attention because of low cost, real-time detection, and simple and easy operation. Nonenzymatic biomimetic nanomaterials are the vital part in electrochemical glucose sensors. This review article summarizes the methods to enhance the glucose sensing performance of noble metal, transition metal oxides, and carbon-based materials and introduces biomimetic nanomaterials used in noninvasive glucose detection in sweat, tear, urine, and saliva. Based on these, this review provides the foundation for noninvasive determination of trace glucose for diabetic patients in the future.

Noble metal nanodendrites: growth mechanisms, synthesis strategies and applications

Inorganic nanodendrites (NDs) have become a kind of advanced nanomaterials with broad application prospects because of their unique branched architecture. The structural characteristics of nanodendrites include highly branched morphology, abundant tips/edges and high-index crystal planes, and a high atomic utilization rate, which give them great potential for usage in the fields of electrocatalysis, sensing, and therapeutics. Therefore, the rational design and controlled synthesis of inorganic (especially noble metals) nanodendrites have attracted widespread attention nowadays. The development of synthesis strategies and characterization methodology provides unprecedented opportunities for the preparation of abundant nanodendrites with interesting crystallographic structures, morphologies, and application performances. In this review, we systematically summarize the formation mechanisms of noble metal nanodendrites reported in recent years, with a special focus on surfactant-mediated mechanisms. Some typical examples obtained by innovative synthetic methods are then highlighted and recent advances in the application of noble metal nanodendrites are carefully discussed. Finally, we conclude and present the prospects for the future development of nanodendrites. This review helps to deeply understand the synthesis and application of noble metal nanodendrites and may provide some inspiration to develop novel functional nanomaterials (especially electrocatalysts) with enhanced performance.

Exploiting Cation Intercalating Chemistry to Catalyze Conversion-Type Reactions in Batteries

Effective harvest of electrochemical energy from insulating compounds serves as the key to unlocking the potential capacity from many materials that otherwise could not be exploited for energy storage. Herein, an effective strategy is proposed by employing LiCoO₂, a widely commercialized positive electrode material in Li-ion batteries, as an efficient redox mediator to catalyze the decomposition of Na₂CO₃ via an intercalating mechanism. Differing from traditional redox mediation processes where reactions occur on the limited surface sites of catalysts, the electrochemically delithiated Li_1-xCoO₂ forms Na_yLi_1-xCoO₂ crystals, which act as a cation intercalating catalyzer that directs Na⁺ insertion-extraction and activates the reaction of Na₂CO₃ with carbon. Through altering the route of the mass transport process, such redox centers are delocalized throughout the bulk of LiCoO₂, which ensures maximum active reaction sites. The decomposition of Na₂CO₃ thus accelerated significantly reduces the charging overpotential in Na-CO₂ batteries; meanwhile, Na compensation can also be achieved for various Na-deficient cathode materials. Such a surface-induced catalyzing mechanism for conversion-type reactions, realized via cation intercalation chemistry, expands the boundary for material discovery and makes those conventionally unfeasible a rich source to explore for efficient utilization of chemical energy.

Nanoscale Hydrophobicity and Electrochemical Mapping Provides Insights into Facet Dependent Silver Nanoparticle Dissolution

Metal or metallic nanoparticle dissolution influences particle stability, reactivity, potential fate, and transport. This work investigated the dissolution behavior of silver nanoparticles (Ag NPs) in three different shapes (nanocube, nanorod, and octahedron). The hydrophobicity and electrochemical activity at the local surfaces of Ag NPs were both examined using atomic force microscopy (AFM) coupled with scanning electrochemical microscopy (AFM-SECM). The surface electrochemical activity of Ag NPs more significantly affected the dissolution than the local surface hydrophobicity did. Octahedron Ag NPs with dominant surface exposed facets of {111} dissolved faster than the other two kinds of Ag NPs. Density functional theory (DFT) calculation revealed that the {100} facet elicited greater affinities toward H₂O than the {111} facet. Thus, poly(vinylpyrrolidone) or PVP coating on the {100} facet is critical for stabilizing and prevent the {100} facet from dissolution. Finally, COMSOL simulations demonstrated consistent shape dependent dissolution as we observed experimentally.

Multiple Stepwise Synthetic Pathways toward Complex Plasmonic 2D and 3D Nanoframes for Generation of Electromagnetic Hot Zones in a Single Entity

ConspectusRational design of nanocrystals with high controllability via wet chemistry is of critical importance in all areas of nanoscience and nanotechnology research. Specifically, morphologically complex plasmonic nanoparticles have received considerable attention because light-matter interactions are strongly associated with the size and shape of nanoparticles. Among many types of nanostructures, plasmonic nanoframes (NFs) with controllable structural intricacy could be excellent candidates as strong light-entrappers with inner voids as well as high surface area, leading to highly effective interaction with light and analytes compared to their solid counterparts. However, so far studies on single-rim-based NFs have suffered from insufficient near-field focusing capability due to their structural simplicity (e.g., a single rim or NF molded from simple platonic solids), which necessitates a conceptually new NF architecture. If one considers a stereoscopic nanostructure with dual, triple, and multiple resonant intra-nanogaps on each crystallographic facet of nanocrystals, unprecedented physicochemical properties could be expected. Realizing such complex multiple NFs with intraparticle surface plasmon coupling via localized surface plasmon resonance is very challenging due to the lack of synthetic strategic principles with systematic structural control, all of which require a deep understanding of surface chemistry. Moreover, realizing those complex architectures with high homogeneity in size and shape via a bottom-up method where diverse particle interactions are involved is more challenging. Although there have been several reports on NFs used for catalysis, techniques for production of structurally complex NFs with high uniformity and an understanding of the correlation between such complexity in a single plasmonic entity and electromagnetic near-field focusing have remained highly elusive.In this Account, we will summarize and highlight the rational synthetic pathways for the design of complex two-dimensional (2D) and three-dimensional (3D) NFs with unique inner rim structures and characterize their optical properties. This systematic strategy is based on publications from our group during the last 10 years. First, we will introduce a chemical step of shape transformation of triangular Au nanoplates to circular and hexagonal plates, which are used as sacrificial layers for the formation of NFs. Then, we will describe the methods on how to synthesize monorim-based plasmonic NFs using Pt scaffolds with different shapes and correlate with their electromagnetic near-field. Then, we will describe a multiple stepwise synthetic method for the formation of 2D complex NFs wherein different starting Au nanocrystals evolved from systematic shape transformation are used to produce circular, triangular, hexagonal, crescent, and Y-shaped inner hot zones. Then, we will discuss how one can synthesize NFs with multiple rims wherein rims with different diameters are concentrically connected, by exploiting chemical toolkits such as eccentric and concentric growth of Au, borrowing the concept of total synthesis that is frequently adopted in organic chemistry. We then introduce dual-rim-faceted NFs and frame-in-frame 3D matryoshka NF geometries via well-faceted growth of Au with high control of intra-nanogaps. Finally, and importantly, we will provide examples of more advanced hierarchical NF architectures produced by controlling geometrical shapes of nanoparticles, number of rims, and different components, leading to the expansion of the NF library.

A Metal-Organic Frameworks Derived 1T-MoS2 with Expanded Layer Spacing for Enhanced Electrocatalytic Hydrogen Evolution

Metal phase molybdenum disulfide (1T-MoS₂ ) is considered a promising electrocatalyst for hydrogen evolution reaction (HER) due to its activated basal and superior electrical conductivity. Here, a one-step solvothermal route is developed to prepare 1T-MoS₂ with expanded layer spacing through the derivatization of a Mo-based organic framework (Mo-MOFs). Benefiting from N,N-dimethylformamide oxide as external stress, the interplanar spacing of (002) of the MoS₂ catalyst is extended to 10.87 Å, which represents the largest one for the 1T-MoS₂ catalyst prepared by the bottom-up approach. Theoretical calculations reveal that the expanded crystal planes alter the electronic structure of 1T-MoS₂ , lower the adsorption-desorption potentials of protons, and thus, trigger efficient catalytic activity for HER. The optimal 1T-MoS₂ catalyst exhibits an overpotential of 98 mV at 10 mA cm^-2 for HER, corresponding to a Tafel slope of 52 mV dec^-1 . This Mo-MOFs-derived strategy provides a potential way to design high-performance catalysts by adjusting the layer spacing of 2D materials.

Trimetallic Au@Pd@Pt nanozyme-enhanced lateral flow immunoassay for the detection of SARS-CoV-2 nucleocapsid protein

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seriously threatened global public health. Establishing a rapid and sensitive diagnostic test for early detection of the SARS-CoV-2 nucleocapsid protein is urgently required to defend against the pandemic. Herein, an enhanced lateral flow immunoassay (LFIA) was fabricated by trimetallic Au@Pd@Pt core-shell nanozymes for detection of the SARS-CoV-2 nucleocapsid protein. The Au@Pd@Pt nanozymes (Au@Pd@Pt NZs) synthesized via a one-pot method, with a dendrite morphology and uniform particle size, showed excellent peroxidase-like activity. Due to the perfect enzyme-like catalytic activity toward 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂), the catalytic signal could be generated even by a tiny amount of Au@Pd@Pt NZs accumulated on the test strip. Therefore, rapid detection with higher sensitivity was achieved. The Au@Pd@Pt NZs-based LFIA provided a quantitative range of 0.05-100 ng mL^-1 with a limit of detection of 0.037 ng mL^-1, which was 17-fold lower than the LFIA without enhancement. The average recoveries from spiked samples were in the range of 92.5-107.9% with relative standard deviations all less than 4%, indicating the reliability and repeatability of the proposed LFIA. Additionally, the proposed LFIA could report results within 30 min using a microplate reader. In conclusion, the Au@Pd@Pt NZs-LFIA is a rapid, simple, and sensitive method for detecting the SARS-CoV-2 nucleocapsid protein.

PdAu Nanosheets for Visible-Light-Driven Suzuki Cross-Coupling Reactions

Combining a two-dimensional (2D) morphology and plasmonic photocatalysis represents an efficient design for light-driven organic transformations. We report a one-pot synthesis of surfactant templated PdAu nanosheets (NSs). Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses show the formation of 2D PdAu structures was initiated through nanoparticle seeds dispersed in the alkyl ammonium salt surfactant which acted as a template for the growth into NSs. The PdAu NSs were used for visible-light-enhanced Suzuki cross coupling. The PdAu bimetallic NSs outperformed monometallic Pd NSs and commercial Pd/C in room-temperature Suzuki cross-coupling reactions. The high catalytic activity is attributed to a combination of the 2D morphology giving rise to plasmon-enhanced catalysis and a high density of surface atoms, the electron-rich Pd surface due to alloying, and the presence of weakly bound amines. A comparative study of surfactant-assisted NSs and CO-assisted NSs was also carried out to assess the influence of surface ligands on the catalytic and photocatalytic enhancement of NSs with similar morphology. The surfactant-assisted NSs showed substantially superior performance compared to the CO-assisted for room-temperature Suzuki coupling reactions.

A bimodal type of AgPd Plasmonic Blackbody Nanozyme with boosted catalytic efficacy and synergized photothermal therapy for efficacious tumor treatment in the second biological window

Nanozymes are promising for precise cancer treatment, but are typically limited in terms of the low catalytic efficiency and the complexity in tumor microenvironment (TME). Herein, we describe a bimodal type of AgPd plasmonic blackbody (AgPd PB) nanozyme of compact sizes (< 30 nm), which presents not only boosted enzyme efficacy but also efficient photothermal therapy (PTT) for synergized therapy through tissue-penetrating light in the second biological window (1000–1700 nm). The synthesized hyperbranched AgPd PB nanozymes possess intense and broadband localized surface plasmonic resonance absorption of 400–1300 nm, entailing prominent photothermal efficiency (η = 45.1% at 1064 nm) for PTT. Importantly, PTT was found to significantly boost the nanozyme efficacy of both catalase (CAT) and peroxidase (POD) processes, which correspondingly decompose H₂O₂ to into O₂ to relieve tumor hypoxia, and activate H₂O₂ to generate oxidative •OH radical. While the generated •OH was found to be able to minimize heat shock proteins (HSPs), which plays a vital role to counterbalance PTT effect both in vitro and in vivo. As compared to control ground without treatment, the synergized nanozyme and PTT activities resulted in about 7-fold reduction of tumor volume, thus elevating the survival rate from 0 to 80% at 30 days posttreatment. Besides the synergistic therapy, the AgPd PB nanozyme were shown to own fluorescence, computed tomography (CT), and photoacoustic (PA) imaging abilities, thus having implications for uses in imaging-guided precise cancer therapy. This study provides a paradigm of TME responsive theranostics under NIR-II light irradiation.

Engineering ultrathin PdAu nanoring via a facile process for electrocatalytic ethanol oxidation

Ultrathin nanoframes with more available electrocatalytic active sites on both internal and external surfaces have attracted great attention especially in the field of electrocatalysis. Herein, we report a facile process to prepare PdAu nanorings (NRs) in aqueous solution without adding any organic ligands. The growth mechanism of PdAu NRs was explored in detail. The Au precursors were reduced into Au clusters around the edges of Pd nanosheets (NSs) via galvanic replacement, then the center of Pd NSs was oxidatively etched by Cl^-/O₂, and finally the Pd and Au atoms on the edge sites were rearranged to form uniform PdAu alloy. PdAu NRs with different ratios and ternary PdAuPt NRs could be easily prepared using this strategy. Owing to the synergistically structural and compositional advantages, Pd₇₉Au₂₁ NRs exhibited higher electrocatalytic activity and stability, as well as low activation energy (E_a) for the ethanol electrooxidation reaction.

Heterogeneous Component Au (Outer)-Pt (Middle)-Au (Inner) Nanorings: Synthesis and Vibrational Characterization on Middle Pt Nanorings with Surface-Enhanced Raman Scattering

We report a synthetic approach for heterometallic (Au-Pt-Au) nanorings with intertwined triple rings (NITs), wherein three differently sized metal circular nanorings concentrically overlap in a single entity. The synthetic method allows one to control the component of core nanorings (Au or Pt) with a tunable gap distance. The narrow circular nanogaps between inner and outer Au rings strongly enhance the electromagnetic near-field via intraparticle coupling of localized surface plasmon resonance, which realizes surface-enhanced Raman scattering (SERS) at the single-particle level. Importantly, when the component of the middle ring is Pt, in situ SERS measurement for electrochemical reactions on Pt domains could be monitored with electrochemical potential variations due to the near-field focusing that is assisted by plasmonically active inner and outer Au nanorings, which is not feasible with pure Pt nanoparticle systems. The resulting NIT systems are robust and may benefit the synthesis of complicated nanostructures, giving myriad applications.

All-Hot-Spot Bulk Surface-Enhanced Raman Scattering (SERS) Substrates: Attomolar Detection of Adsorbates with Designer Plasmonic Nanoparticles

Here we report a synthetic pathway toward Au truncated octahedral dual-rim nanoframes wherein two functional facets are formed including (1) eight hot nanogaps formed by hexagonal nanoframes embracing core circular nanorings for near-field focusing and (2) six flat squares that facilitate the formation of well-ordered arrays of nanoframes through self-assembly. The existence of intra-nanogaps in a single entity enables strong electromagnetic near-field focusing, allowing single-particle surface-enhanced Raman spectroscopy. Then, we built "all-hot-spot bulk SERS substrates" with those entities, wherein the presence of truncated terraces with high homogeneity in size and shape facilitate spontaneous self-assembly into a highly ordered and uniform superlattice, exhibiting a limit of detection of attomolar concentrations toward 2-naphthalenethiol, which is 6 orders lower than that of monorim counterparts. The observed low limit of detection originates from the combined synergic effect from both inter- and intraparticle coupling in a superlattice, which we dubbed "all-hot-spot bulk SERS substrates".