Structure Of Metal Nanoparticles Research Articles

Aggregation Inducing Reversible Conformational Isomerization of Surface Staple in Au18SR14 Nanoclusters.

The conformation of molecules and materials is crucial in determining their properties and applications. Here, this work explores the reversible transformation between two distinct conformational isomers in metal nanoclusters. This work demonstrates the successful manipulation of a controllable and reversible isomerization of Au18SR14 within an aqueous solution through two distinct methods: ethanol addition and pH adjustment. The initial driver is the alteration of the solution environment, leading to the aggregation of Au18SR14 protected by ligands with smaller steric hindrance. At the atomic level, the folding mode of the unique Au4SR5 staple underpins the observed structural transformation. The reversal of staple conformation leads to color shifting between green and orange-red, and tailors a second emission peak at 725nm originating from charge transfer from the thiolate to the Au9 core. This work not only deepens the understanding of the surface structure and dual-emission of metal nanoparticles, but also enhances the comprehension of their isomerization.

Coulomb effect in hybrid double quantum dot-metal nanoparticle systems considering the wetting layer

Many body effects in the wetting layer (WL)-double quantum dot (DQD)-metal nanoparticle (MNP) structure have been studied by modeling the Coulomb scattering rates in this structure. The strong coupling between WL-DQD-MNPs was considered. An orthogonalized plane wave (OPW) is assumed between WL-QD transitions. The transition momenta are calculated accordingly to specify the normalized Rabi frequency on this structure, considering the strong coupling between the WL-DQD-MNP structures. This approach is important for realizing scattering rates, including in-and-out capture and relaxation rates, which are essential for specifying the type of structure used depending on the optimum value of the scattering time required to fit the application. The QD hole capture rate is the highest, and the hole capture times are the shortest. The relaxation times are less than the electron capture times by one order, while they are half of the hole capture times. The capture rates increase with increasing distance R between the DQDs and the MNP. High tunneling increases hole-capture rates and changes the relaxation rates, showing the importance of tunneling in controlling the scattering rates.

Electron-rich ruthenium nanoparticles on nitrogen-doped carbon for the efficient catalytic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid

Modulating the electronic structure of metal nanoparticles (NPs) demonstrates to be useful for the optimization of the catalytic performance. Herein, electron-sufficient ruthenium NPs were successfully constructed on a nitrogen-doped carbon support (Rux-NC), which displayed excellent catalytic activity for the oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). Especially, a high FDCA yield of 97% was implemented over Ru2.0/NC catalyst in water. The FDCA productivity in this case is also as high as 4.8 molFDCA‧molRu−1‧h−1, which value exceeds most of the previous reported Ru-based catalysts for the production of FDCA. It has been disclosed that the Ru2.0/NC was endowed with high N content and abundant electron-rich Ru0 NPs evoked by the electronic interactions between the NC support the Ru NPs. These facts greatly contribute to the activation of O2, and accelerate the oxidation both of the hydroxymethyl and aldehyde groups of HMF to the carboxyl one. This work provides new understanding for the development of effective Ru-based catalysts for the catalytic oxidation reactions by the electronic structure regulation strategy.

Electroless Deposition of Palladium Nanoparticles on Graphdiyne Boosts Electrochemiluminescence.

Modulating the electronic structure of metal nanoparticles via metal-support interaction has attracted intense interest in the field of catalytic science. However, the roles of supporting substrates in regulating the catalytic properties of electrochemiluminescence (ECL) remain elusive. Here, we find that the use of graphdiyne (GDY) as the substrate for electroless deposition of Pd nanoparticles (Pd/GDY) produces the most pronounced anodic signal enhancement in luminol-dissolved oxygen (O2) ECL system as co-reactant accelerator over other carbon-based Pd composite nanomaterials. Pd/GDY exhibits electrocatalytic activity for the reduction of O2 through a four-electron pathway at approximately -0.059 V (vs Ag/AgCl) in neutral solution forming reactive oxygen species (ROS) as intermediates. The study shows that the interaction of Pd and GDY increases the amount and stability of ROS on the Pd/GDY electrode surface and promotes the reaction of ROS and luminol anion radical to generate excited luminol, which significantly boosts the luminol anodic ECL emission. Based on quenching of luminol ECL through the consumption of ROS by antioxidants, we develop a platform for the detection of intracellular antioxidants. This study provides an avenue for the development of efficient luminol ECL systems in neutral media and expands the biological application of ECL systems.

Atomic-Scale 3D Structure of a Supported Pd Nanoparticle Revealed by Electron Tomography with Convolution Neural Network-Based Image Inpainting.

Electron tomography based on scanning transmission electron microscopy (STEM) is used to analyze 3D structures of metal nanoparticles on the atomic scale. However, in the case of supported metal nanoparticle catalysts, the supporting material may interfere with the 3D reconstruction of metal nanoparticles. In this study, a deep learning-based image inpainting method is applied to high-angle annular dark field (HAADF)-STEM images of a supported metal nanoparticle to predict and remove the background image of the support. The inpainting method can separate an 11nm Pd nanoparticle from the θ-Al2 O3 support in HAADF-STEM images of the θ-Al2 O3 -supported Pd catalyst. 3D reconstruction of the extracted images of the Pd nanoparticle reveals that the Pd nanoparticle adopts a deformed structure of the cuboctahedron model particle, resulting in high index surfaces, which account for the high catalytic activity for methane combustion. Using the xyz coordinate of each Pd atom, the local Pd-Pd bond distance and its variance in a real supported Pd nanoparticle are visualized, showing large strain and disorder at the Pd-Al2 O3 interface. The results demonstrate that 3D atomic-scale analysis enables atomic structure-based understanding and design of supported metal catalysts.

Novel P-doping-tuned Pd nanoflowers/S,N-GQDs photo-electrocatalyst for high-efficient ethylene glycol oxidation

Traditional photo-electcatalyst structures of small noble metal nanoparticles assembling into large-scale photoactive semiconductors still suffer from agglomeration of noble metal nanoparticles, insufficient charge transfer, undesirable photoresponse ability that restricted the photo-electrocatalytic performance. To this end, a novel design strategy is proposed in this work, namely integrating small-scale photoactive materials (doped graphene quantum dots, S,N-GQDs) with large-sized noble metal (PdP) nanoflowers to form novel photo-electrocatalysts for high-efficient alcohol oxidation reaction. As expected, superior electrocatalytic performance of PdP/S,N-GQDs for ethylene glycol oxidation is acquired, thanks to the nanoflower structure with larger specific surface area and abundant active sites. Furthermore, nonmetal P are demonstrated, especially optimizing the adsorption strength, enhancing the interfacial contact, reducing metal agglomeration, ensuring uniform and efficient doping of S,N-GQDs, and ultimately significantly boost the catalytic activity of photo-electrocatalysts.

Modelling of metal nanoparticles’ structures and dynamics under reaction conditions

Metal nanoparticles (NPs) are widely used in heterogeneous catalysis. Their performance in catalytic reactions is closely related to the shape, surface structure, and composition. In the past two decades, a number of in-situ experiments have observed that under real reaction conditions, the structures of metal NPs are not static, but undergo remarkable dynamic evolution due to the presence of gas molecules. Therefore, it is imminent to develop reliable theoretical models to provide accurate predictions and comprehensive understandings of the structure reconstructions and dynamic behaviors of catalysts in response to the different reactive environments. In this review, we summarize a series of progress and achievements made by first-principle-based theoretical models in analyzing the shape evolution of metal NPs and surface segregation of alloys under different gas conditions in recent years. We also discuss the understanding of the catalytic performance of NPs by considering the reaction-condition-dependent structures. In addition, the real-time dynamic simulation methods of catalysts under reaction conditions are introduced. The perspective of simulating the kinetic process of in situ structural change is provided at last.

Silk fibroin and gelatin composite nanofiber combined with silver and gold nanoparticles for wound healing accelerated by reducing the inflammatory response

The design and development of silver and gold nanoparticles incorporated into silk fibroin and gelatin composite nanofibers were prepared using the electrospun method. The functional group, chemical composition, and thermal stability of composite nanofibrous scaffolds were investigated using different characterization techniques. The confirmation of SF/GL/Ag-Au composite nanofibers was achieved through FE-SEM and AFM images, which proved to be highly beneficial for assessing surface morphology, thickness, and roughness area (Ra) with dimensions of 777 nm and 292.71 nm, respectively. Furthermore, HR-TEM images were used to elucidate the morphological structure and size of metal nanoparticles in SF/GL/Ag-Au composite nanofibers, revealing an average diameter length of 220.85 ± 82.65 nm for Ag and Au nanoparticles sizes noted at 6.25 nm and 11.56 nm. In addition, flow cytometry analysis of SF/GL/Ag-Au composite nanofibers was conducted to assess the viability of L929 cells and detect the apoptosis levels. Furthermore, invivo wound healing studies were performed on Sprague-Dawley rat animals. The results demonstrated that SF/GL/Ag-Au composite nanofiber scaffolds significantly accelerated wound closure, achieving a remarkable 99.58 % wound healing rate in the 21 days compared to control groups. In conclusion, our findings highlight that SF/GL/Ag-Au composite nanofiber scaffolds are highly suitable for wound dressing applications.

Effects of CO and NO atmospheres on the morphology of Ag, Ni, and Ir nanoparticles

Metal nanoparticles are widely used in multiphase catalytic reactions due to their excellent physicochemical properties, which are mainly determined by their size and shape. Therefore, predicting and controlling the shape and structure of metal nanoparticles under reaction conditions has been a popular topic of interest among researchers. In this study, we conducted a systematical investigation to the equilibrium structure of Ag, Ni, and Ir nanoparticles within a mixed gas environment of CO and NO, employing a multiscale structural reconstruction model. This model demonstrates the ability to accurately predict the equilibrium configuration of metal nanoparticles under reactive conditions. Our investigation reveals a notable presence of negative surface energy in the phase diagrams representing Ag, Ir, and Ni nanoparticle configurations. This distinctive feature signifies that the nanoparticles undergo a process of splitting. While undergoing temperature and total pressure variations, the transformation in the structure of Ni nanoparticles is comparatively less evident in contrast to that of Ag and Ir nanoparticles. This discrepancy primarily stems from the pronounced energy barrier posed by the substantial rejection of CO and NO molecules at the surface of Ni nanoparticles. Notably, the structural modifications within Ag nanoparticles manifest solely within the confines of low-temperature ranges. Furthermore, our observations underscore the significant impact exerted by the ratios of CO and NO partial pressures on both the structure and the count of active sites within the metal nanoparticles.

Plasmonic Nanostructure Biosensors: A Review.

Plasmonic nanostructure biosensors based on metal are a powerful tool in the biosensing field. Surface plasmon resonance (SPR) can be classified into localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (PSPP), based on the transmission mode. Initially, the physical principles of LSPR and PSPP are elaborated. In what follows, the recent development of the biosensors related to SPR principle is summarized. For clarity, they are categorized into three groups according to the sensing principle: (i) inherent resonance-based biosensors, which are sensitive to the refractive index changes of the surroundings; (ii) plasmon nanoruler biosensors in which the distances of the nanostructure can be changed by biomolecules at the nanoscale; and (iii) surface-enhanced Raman scattering biosensors in which the nanostructure serves as an amplifier for Raman scattering signals. Moreover, the advanced application of single-molecule detection is discussed in terms of metal nanoparticle and nanopore structures. The review concludes by providing perspectives on the future development of plasmonic nanostructure biosensors.

Alkaline Water-Assisted Polyol Synthesis of Pt/Vulcan PEMFC Cathode Electrocatalysts

Sluggish oxygen reduction reaction (ORR) kinetics motivates great focus on PEMFC cathode electrocatalyst development.1 Electrocatalysts based on Pt are often prepared via the so-called polyol process, a solvothermal process that allows controlling of the structure, morphology, and chemical nature of various metal nanoparticles.2 Several parameters have been well-studied and thoroughly discussed in literature over the years, varying from surfactant removal or water addition to pH or NaOH/Pt molar ratio effect on Pt particle size. 3,4 Here, we present a slight modification of the well-established surfactant-free alkaline one-pot polyol synthesis of Pt-nanoparticles on Vulcan XC 72R carbon support and the subsequent PEMFC characterization tests with respect to initial electrochemical performance and standardized accelerated stress tests (AST). In this approach, the solvent composition is systematically changed by the substitution of ethylene glycol to water and by increasing the Pt precursor concentration per mass of solvent to ultimately minimize the amount of ethylene glycol used.The so-synthesized electrocatalyst powders, with Pt particle sizes ranging from 2 to 6 nm, were physico-chemically analyzed by powder X-ray diffraction, thermogravimetric analysis, and transmission/scanning electron microscopy. The initial electrochemical performance as well as the stability were evaluated by implementing membrane electrode assemblies (MEAs), prepared from a series of synthesized electrocatalysts in a differential flow single cell setup (12 cm2). The electrochemical performance of the prepared MEAs was evaluated and compared to a commercial reference catalyst coated membrane (CCM), as well as to an internal reference CCM, that was prepared using a cathode Pt/C catalyst synthesized via pure ethylene glycol-based polyol route.Beginning-of-life MEA data indicate the possibility of reducing the required ethylene glycol amount per mass of synthesized catalyst by up to 98%. Taking catalyst durability as an additional optimization criterion into account, a Pt/C electrocatalyst synthesized with 45 vol% H2O at a Pt precursor concentration of 32 mM, ultimately leading to an ethylene glycol reduction of 90%, showed a decent initial electrochemical performance (716 mV at 1 A cm-2), as well as an AST stability similar to the internal reference (Pt/C synthesized using pure EG and Pt precursor concentration of 16 mM).In summary, we conclude that water content and Pt precursor concentration have a crucial impact on the characteristics of Pt/C electrocatalysts in the modified polyol route. At optimum parameter values, catalysts with optimized electrochemical performance in PEMFC applications can be synthesized, with substantially lowered synthesis cost due to solvent substitution.

Polarization-Dependent Sum-Frequency-Generation Spectroscopy for In Situ Tracking of Nanoparticle Morphology.

The surface structure of oxide-supported metal nanoparticles can be determined via characteristic vibrations of adsorbed probe molecules such as CO. Usually, spectroscopic studies focus on peak position and intensity, which are related to binding geometries and number of adsorption sites, respectively. Employing two differently prepared model catalysts, it is demonstrated that polarization-dependent sum-frequency-generation (SFG) spectroscopy reveals the average surface structure and shape of the nanoparticles. SFG results for different particle sizes and morphologies are compared to direct real-space structure analysis by TEM and STM. The described feature of SFG could be used to monitor particle restructuring in situ and may be a valuable tool for operando catalysis.

Plasmon-Mediated Reconfiguration of Twin Defect Structures in Silver Nanoparticles

Defects in metal nanoparticles can play a critical role in directing interfacial processes, such as catalytic reactions, at the surface of these materials. Interest in understanding the fundamental role of crystalline defects in controlling nanoparticle properties has inspired exploration of synthetic methods for tuning the twin defect structure of metal nanoparticles. However, controlling this structural parameter is a challenge due to the subtle reaction kinetics that dictate defect formation. For plasmonic silver (Ag) nanomaterials, the potential for light-induced growth provides a unique opportunity for driving structural reconfiguration between nanoparticle morphologies with different twin defect structures. We report a plasmon-mediated reconfiguration pathway in which {111}-faceted Ag nanoparticles are sequentially converted: first from planar twinned triangular Ag prisms to multiply twinned icosahedra (along with a smaller subpopulation of other twinned shapes), subsequently to multiply twinned Ag nanospheres, and finally back to planar twinned triangular Ag prisms. These consecutive reconfiguration processes occur as a result of the precise manipulation of reaction kinetics using a combination of illumination wavelength and pH. This method provides a valuable tool for reconfiguring, recycling, and regenerating Ag nanoparticles.

Metallic Nanosystems in the Development of Antimicrobial Strategies with High Antimicrobial Activity and High Biocompatibility.

Antimicrobial resistance is a major and growing global problem and new approaches to combat infections caused by antibiotic resistant bacterial strains are needed. In recent years, increasing attention has been paid to nanomedicine, which has great potential in the development of controlled systems for delivering drugs to specific sites and targeting specific cells, such as pathogenic microbes. There is continued interest in metallic nanoparticles and nanosystems based on metallic nanoparticles containing antimicrobial agents attached to their surface (core shell nanosystems), which offer unique properties, such as the ability to overcome microbial resistance, enhancing antimicrobial activity against both planktonic and biofilm embedded microorganisms, reducing cell toxicity and the possibility of reducing the dosage of antimicrobials. The current review presents the synergistic interactions within metallic nanoparticles by functionalizing their surface with appropriate agents, defining the core structure of metallic nanoparticles and their use in combination therapy to fight infections. Various approaches to modulate the biocompatibility of metallic nanoparticles to control their toxicity in future medical applications are also discussed, as well as their ability to induce resistance and their effects on the host microbiome.

Schiff base coordination compounds including thiosemicarbazide derivative and 4-benzoyl-1,3-diphenyl-5-pyrazolone: Synthesis, structural spectral characterization and biological activity

A new thiosemicarbazone ligand containing an allyl group and a 5-pyrazolone derivative has been prepared. The reaction of this ligand (H2L) with chloride and nitrate salts of Co(II), Cu(II), Pd(II), and Ni(II), Cu(II) ions resulted in the formation of different chelates having variable chemical formulas. Structural characterization of H2L ligand and its chelates has been established employing microanalytical, molar conductivity, magnetic moment measurements as well as spectral techniques including IR, UV–vis, NMR, mass, XRD, and ESR spectra. The spectral and microanalytical data achieved the monobasic tridentate binding mode with the metal(II) ion through SNO and NNO donor sites in complexes (2,5) and (3,4), respectively. In addition, the thiosemicarbazone ligand acts as a neutral bidentate species (NS) and neutral or mononegative bidentate species (NO) in complexes (6) and (1), respectively. Based on electronic spectra analyses (UV–vis) and magnetic moment measurements, all chelates, with the exception of those of Co(II) and Pd(II) ions, which have square planar geometrical structures, revealed a square pyramidal structure. Furthermore, the ESR spectra of Cu(II) chelates (3–5) have been investigated, yielding 2B1g as an axial ground state. The chemical formulae for the metal chelates were determined using thermogravimetric investigations (TG and DTG), demonstrating both their thermal stability and the presence of various crystalline solvents. Metal oxide (MO) or metal with traces of carbon was the residue of the thermal degradation processes. Based on XRD analysis, the structures of allopalladium (O-dopped Pd), monoclinic CuO, and tetragonal metallic cobalt nanoparticles obtained thermally from chelates (1,3,4,6) were elucidated. Copper(II) chelates (3) and (4) display the highest anticancer activity against hepatocellular carcinoma cells (Hep G-2) testes, according to the biological studies for the ligand and some of its chelates.

Emerging Metal Single-Atom Materials: From Fundamentals to Energy Applications

ConspectusWith the development of nanotechnology and characterization techniques, it has been realized that the reactivity of metal nanoparticles mainly depends on some unsaturated coordination atoms on the surface. However, only a small fraction of the surface exposed atoms can access the reactants and act as reactive sites, resulting in low utilization of metal atoms. Moreover, due to the complex structure of metal nanoparticles, the metal atoms exposed on the surface are likely to be in different chemical environments and may act as multiple active centers to catalyze the reactants, which brings great difficulties in the establishment of the structure–activity relationship of metal nanoparticles. Reducing the size of metal nanoparticles to increase the fraction of atoms on the surface is usually regarded as a straightforward and effective approach to enhancing their activity. When the metal nanoparticles are transformed into metal subnanoclusters or even metal single atoms (MSAs), discrete energy-level distribution and distinctive lowest unoccupied molecular orbital-highest occupied molecular orbital (LUMO–HOMO) gap are generated due to the unique quantum size effect. Because of the uniform active sites, maximum metal utilization, unsaturated coordination environment, and strong metal–support interaction, MSA materials often show distinct reactivity, selectivity, and stability from traditional metal nanomaterials. In the past decade, MSA materials have rapidly become the research frontier in catalysis, battery, sensing, and other fields. MSA materials not only provide a new solution for understanding the mechanism of reaction from atomic and molecular scales and studying the structure–activity relationship but also are expected to become a new family of functional materials with large-scale application potential.This Account highlights the recent advancements in the preparation and applications of MSAs in our group. The Account begins with a brief introduction to the structural properties of MSAs. After understanding the basic structural characteristics of MSAs, we summarize three common stabilization strategies for MSAs, including spatial confinement, coordination, and defect/vacancy design strategies. The controllable fabrication of stable and efficient MSAs is important for the investigation of the structure-performance relationship and a prerequisite for various applications. Some typical bottom-up and top-down strategies for the synthesis of MSAs are also briefly introduced. Furthermore, we review our recent advancements in the design and synthesis of MSAs and their applications, including the oxygen reduction reaction (ORR), the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), photocatalytic H2 production, lithium–sulfur (Li–S) batteries, and the electrocatalytic carbon dioxide reduction reaction (CO2RR). Finally, the current challenges and our perspectives on the preparation and applications of advanced MSAs have been provided.

Label-Free Sensing with Metal Nanostructure-Based Surface-Enhanced Raman Spectroscopy for Cancer Diagnosis.

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful analytical technique for the detection of small analytes with great potential for medical diagnostic applications. Its high sensitivity and excellent molecular specificity, which stems from the unique fingerprint of molecular species, have been applied toward the detection of different types of cancer. The noninvasive and rapid detection offered by SERS highlights its applicability for point-of-care (PoC) deployment for cancer diagnosis, screening, and staging, as well as for predicting tumor recurrence and treatment monitoring. This review provides an overview of the progress in label-free (direct) SERS-based chemical detection for cancer diagnosis with the main focus on the advances in the design and preparation of SERS substrates on the basis of metal nanoparticle structures formed via bottom-up strategies. It begins by introducing a synopsis of the working principles of SERS, including key chemometric approaches for spectroscopic data analysis. Then it introduces the advances of label-free sensing with SERS in cancer diagnosis using biofluids (blood, urine, saliva, sweat) and breath as the detection media. In the end, an outlook of the advances and challenges in cancer diagnosis via SERS is provided.

Simultaneous Optical Detection of Multiple Bacterial Species Using Nanometer-Scaled Metal-Organic Hybrids.

This paper describes a simple strategy to identify bacteria using the optical properties of the nanohybrid structures (NHs) of polymer-coated metal nanoparticles (NPs). NHs, in which many small NPs are encapsulated in polyaniline particles, are useful optical labels because they produce strong scattered light. The light-scattering characteristics of NHs are strongly dependent on the constituent metal elements of NPs. Gold NHs (AuNHs), silver NHs (AgNHs), and copper NHs (CuNHs) produce white, reddish, and bluish scattered light, respectively. Moreover, unlike NPs, the color of the scattered light does not change even when NHs are aggregated. Introducing an antibody into NHs induces antigen-specific binding to cells, enabling the identification of bacteria based on light scattering. Multiple bacterial species adsorbed on the slide can be identified within a single field of view under a dark field microscope based on the color of the scattered light. Therefore, it is a useful development for safety risk assessments at manufacturing sites, such as those for foods, beverages, and drugs, and environmental surveys that require rapid detection of multiple bacteria.

Stick-slip-motion-assisted interfacial self-assembly of noble metal nanoparticles on tapered optical fiber surface and its application in SERS detection

Tapered optical-fiber SERS probes provide a large SERS interaction area and evanescent-wave-based light-matter interaction, but their SERS detection sensitivity is limited due to the difficulty in preparing noble metal nanoparticle structures with large SERS enhancement factor on tapered optical fiber surfaces. In this work, we successfully prepare novel ring-patterned tapered optical-fiber SERS probes with a self-developed stick–slip-motion-assisted interfacial self-assembly method. Unlike the isolated or random distributions of nanoparticles in traditional tapered-optical-fiber SERS probes, the nanoparticles in our probes are aggregated into several rings on optical fiber cones with the help of laser-induced self-assembly of nanoparticles in a meniscus and subsequent meniscus stick–slip motion during the lifting process. These nanoparticle rings provide numerous SERS hotspots due to the formation of clusters. High SERS detection sensitivities of 2 × 10-10 M for crystal violet and 10-9 M for malachite green and thiram in solution are achieved with our ring-patterned tapered optical-fiber SERS probes, and the detection reproducibility is indicated by RSDs of less than 6% for spectral intensity. This work may provide new insights for the design and preparation of tapered optical-fiber SERS probes with high performances.

Coalescence dynamics of platinum group metal nanoparticles revealed by liquid-phase transmission electron microscopy

SummaryCoalescence, one of the major pathways observed in the growth of nanoparticles, affects the structural diversity of the synthesized nanoparticles in terms of sizes, shapes, and grain boundaries. As coalescence events occur transiently during the growth of nanoparticles and are associated with the interaction between nanoparticles, mechanistic understanding is challenging. The ideal platform to study coalescence events may require real-time tracking of nanoparticle growth trajectories with quantitative analysis for coalescence events. Herein, we track nanoparticle growth trajectories using liquid-cell transmission electron microscopy (LTEM) to investigate the role of coalescence in nanoparticle formation and their morphologies. By evaluating multiple coalescence events for different platinum group metals, we reveal that the surface energy and ligand binding energy determines the rate of the reshaping process and the resulting final morphology of coalesced nanoparticles. The coalescence mechanism, based on direct LTEM observation explains the structures of noble metal nanoparticles that emerge in colloidal synthesis.