Structure Of Metal Nanoparticles Research Articles

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.

Enhanced CO oxidation by reversible structural variation of supported Ag nanoparticle catalyst from single to twin by CO treatment

Twinned structure of metal nanoparticles can strongly affect catalysis because of its unique atomic alignment and bond strain in metal nanoparticles. Here, the twin and single crystal structures of supported Ag nanoparticles are controlled reversibly by gas treatment. The single crystal Ag nanoparticles were formed in Ag/Al2O3 by H2 treatment, and subsequent CO gas treatment changed the Ag particle structure to twin. The change in the Ag particle structure from single to twin caused enhancement of CO oxidation activity. In addition, the catalytic activity was reversibly changed from low to high by applying H2 and CO gas treatment to Ag/Al2O3. The kinetic analysis for CO oxidation revealed that the twin Ag nanoparticles have stronger CO adsorption energy than the single crystal ones, which is responsible for the enhanced CO oxidation activity of twin Ag nanoparticles.

Structure of Polyhedral Nanoparticles with Cubic Lattice: Theoretical Analysis

We examine the structure of compact metal nanoparticles (NPs) forming polyhedral sections of face-centered cubic (fcc) and body-centered cubic (bcc) lattices, which are confined by facets characterized by highly dense [Formula: see text], [Formula: see text] and [Formula: see text] monolayers. Together with the constraint that the NPs exhibit the same point symmetry as the ideal cubic lattice, i.e., [Formula: see text], different types of generic NPs serve for the definition of general compact polyhedral cubic NPs. Their structural properties, such as shape, size and surface facets, can be described by only three integer-valued polyhedral NP parameters [Formula: see text], [Formula: see text] and [Formula: see text]. Corresponding analytical details are discussed with visualization of characteristic examples. While the overall NP shapes are quite similar between the different cubic lattice types, structural fine details differ. In particular, monolayer planes of adjacent NP facets can join at corners and edges which are not occupied by atoms of the ideal lattice. This gives rise to microfacets and narrow facet strips depending on the lattice type. The discussion illustrates the complexity of seemingly simple NPs in a quantitative account. The geometric relationships of the model particles can also be used to classify shapes and estimate sizes of real compact metal NPs observed by experiment.

Synthesis and Characterization of Ag/ZnO Nanoparticles for Bacteria Disinfection in Water.

In this study, two green synthesis routes were used for the synthesis of Ag/ZnO nanoparticles, using cassava starch as a simple and low-cost effective fuel and Aloe vera as a reducing and stabilizing agent. The Ag/ZnO nanoparticles were characterized and used for bacterial disinfection of lake water contaminated with Escherichia coli (E. coli). Characterization indicated the formation of a face-centered cubic structure of metallic silver nanoparticles with no insertion of Ag into the ZnO hexagonal wurtzite structure. Physicochemical and bacteriological analyses described in “Standard Methods for the Examination of Water and Wastewater” were used to evaluate the efficiency of the treatment. In comparison to pure ZnO, the synthesized Ag/ZnO nanoparticles showed high efficiencies against Escherichia coli (E. coli) and general coliforms present in the lake water. These pathogens were absent after treatment using Ag/ZnO nanoparticles. The results indicate that Ag/ZnO nanoparticles synthesized via green chemistry are a promising candidate for the treatment of wastewaters contaminated by bacteria, due to their facile preparation, low-cost synthesis, and disinfection efficiency.

Nonlinear Optical Microscopy and Plasmon Enhancement.

Improving nonlinear optics efficiency is currently one of the hotspots in modern optical research. Moreover, with the maturity of nonlinear optical microscope systems, more and more biology, materials, medicine, and other related disciplines have higher imaging resolution and detection accuracy requirements for nonlinear optical microscope systems. Surface plasmons of metal nanoparticle structures could confine strong localized electromagnetic fields in their vicinity to generate a new electromagnetic mode, which has been widely used in surface-enhanced Raman scattering, surface-enhanced fluorescence, and photocatalysis. In this review, we summarize the mechanism of nonlinear optical effects and surface plasmons and also review some recent work on plasmon-enhanced nonlinear optical effects. In addition, we present some latest applications of nonlinear optical microscopy system research.

Terahertz photoconductive antennas based on arrays of metal nanoparticle structures

In this study, in order to amplify the radiation at Terahertz photoconductive antennas, metal nanoparticles are used in semiconductor layers based on plasmonic principles. The use of nanoparticles between antenna electrodes and semiconductor layers not only enhances the THz radiation intensity but also changes the radiation frequency peak. The changes of electric charge carriers versus the incidence of laser pulses and the production of an electric current on the antenna surface are simulated with the COMSOL Multiphysics software through the FEM method. The changes of the electric current at the semiconductive surface generate electric field radiation. This has been simulated using the CST STUDIO software through the FDTD method.

MoO3-templated synthesis of TiO2@C-Ni microtubes for efficient catalysis and protein adsorption

The hybrid structure of metallic Ni nanoparticles (NPs)-decorated micro/nanotubes has the merits of both unique property of Ni NPs and tubular structure of micro/nanotubes, which is highly desired for many applications. In this study, Ni NPs decorated porous TiO2 microtubes with N-doped carbon layer from polydopamine (PDA) are directly synthesized by an extend stöber method, mussel chemistry and subsequent annealing treatment for the first time. In the synthetic process, a shell layer of nickel ion-embedded in polydopamine (PDA-Ni2+) was covered on the MoO3@TiO2 microcables by nickel ion mediated dopamine polymerization in ammonia solution, resulting in the formation of amorphous TiO2@PDA-Ni2+ microtubes. Notably, the coating of PDA-Ni2+ layer and the dissolution of the MoO3 cores were easily achieved within one-step reaction, greatly facilitating the synthetic progress. After being annealed in nitrogen atmosphere at different temperature, the TiO2@C-Ni microtubes with anatase, rutile phase of TiO2 can be obtained. Benefiting from the high coverage of Ni NPs, large specific surface area as well as one dimensional tubular structure, the as-prepared TiO2@C-Ni microtubes exhibited excellent performance on adsorption for histidine-rich proteins as well as the reduction of 4-nitrophenol. These results may pave a new avenue on constructing 1D TiO2-based microtubes for potential applications in energy storage, photocatalysis etc.

Metal nanoparticles in ionic liquids: Synthesis and catalytic applications

• Nanoparticles of many metals can be obtained in ionic liquids by physical, chemical, and electrochemical methods. • The ionic liquids medium stabilizes metal nanoparticles without additional stabilizers, surfactants, or capping ligand. • Ionic liquids allow to control the size and shape of metal nanoparticles thus improving their catalytic activity. • Electrochemical approaches allow a smart control of the size, shape, and crystal structure of metal nanoparticles. • Applications of metal nanoparticles in catalysis provide a driving force for developing new nanoscale materials. The development of metal nanoparticle chemistry in ionic liquids (ILs) media has had a paramount impact on various fields, including catalysis, energy research, nanotechnology and materials science, among many other directions. This review highlights various methods for producing metal nanoparticles in ILs, with particular focus on palladium, platinum, ruthenium, copper, nickel, cobalt, gold, silver, iron and alloys. The scope of methods includes chemical syntheses as well as electrochemical and physical approaches. Due to strong practical demand, a particular emphasis is placed on the catalytic activity of the obtained nanoparticles in a variety of reactions.

Optical Analysis of Hole Patterned Ag Nanoparticle Structure.

A structure with periodic sub-wavelength nanohole patterns interacts with incident light and causes extraordinary optical transmission (EOT), with metal nanoparticles leading to localized surface plasmon resonance (LSPR) phenomena. To explore the effects of metal nanoparticles (NPs), optical analysis is performed for metal NP layers with periodic hole patterns. Investigation of Ag NP arrangements and comparisons with metal film structures are presented. Ag NP structures with different hole configuration are explored. Also, the effects of increasing light incident angle are investigated for metal NP structures where EOT peak at 460 nm wavelength is observed. Moreover, electric field distributions at each transmittance peak wavelengths and optical noise are analyzed. As a result, optical characteristics of metal NP structures are obtained and differences in resonance at each wavelength are highlighted.

Recognition of the three-dimensional structure of small metal nanoparticles by a supervised artificial neural network

Recognition of the three-dimensional structure of small metal nanoparticles by a supervised artificial neural network

Exceptional Electrochemical HER Performance with Enhanced Electron Transfer between Ru Nanoparticles and Single Atoms Dispersed on a Carbon Substrate

AbstractPrecisely regulating the electronic structures of metal active species is highly desirable for electrocatalysis. However, carbon with inert surface provide weak metal–support interaction, which is insufficient to modulate the electronic structures of metal nanoparticles. Herein, we propose a new method to control the electrocatalytic behavior of supported metal nanoparticles by dispersing single metal atoms on an O‐doped graphene. Ideal atomic metal species are firstly computationally screened. We then verify this concept by deposition of Ru nanoparticles onto an O‐doped graphene decorated with single metal atoms (e.g., Fe, Co, and Ni) for hydrogen evolution reaction (HER). Consistent with theoretical predictions, such hybrid catalysts show outstanding HER performance, much superior to other reported electrocatalysts such as the state‐of‐the‐art Pt/C. This work offers a new strategy for modulating the activity and stability of metal nanoparticles for electrocatalysis processes.

Controlled Assembly of Plasmonic Nanoparticles: From Static to Dynamic Nanostructures.

The spatial arrangement of plasmonic nanoparticles can dramatically affect their interaction with electromagnetic waves, which offers an effective approach to systematically control their optical properties and manifest new phenomena. To this end, significant efforts were made to develop methodologies by which the assembly structure of metal nanoparticles can be controlled with high precision. Herein, recent advances in bottom-up chemical strategies toward the well-controlled assembly of plasmonic nanoparticles, including multicomponent and multifunctional systems are reviewed. Further, it is discussed how the progress in this area has paved the way toward the construction of smart dynamic nanostructures capable of on-demand, reversible structural changes that alter their properties in a predictable and reproducible manner. Finally, this review provides insight into the challenges, future directions, and perspectives in the field of controlled plasmonic assemblies.

Green synthesis of silver nanoparticles using leaf extract of Euphorbia sanguine: an in vitro study of its photocatalytic and melanogenesis inhibition activity

We report on biosynthesis of silver nanoparticles using aqueous leaf extract of Euphorbia sanguinea and its photocatalytic degradation of Congo red dye and melanogenesis inhibition activity of mushroom tyrosine enzyme. Surface Plasmon resonance bands obtained from UV-Vis spectra were within the range 430–436 nm. FT-IR studies reveal the presence of functional groups of the plant metabolites used as stabilizing agents of nanoparticles. The shape of silver nanoparticles is spherical with size ranges about 20–28.8 nm as confirmed by SEM. XRD patterns displayed well-defined crystalline peaks corresponding to the face-centred cubic structures of metallic silver nanoparticles. The results of photocatalysis showed high photocatalytic efficiency of 86% and 90% within 5 min and 60 min, respectively at a rate of solar radiation of in the degradation of Congo red dye. The AgNPs gave dose dependent melanogenesis inhibition activity with IC50 of 71.96 µg/ml, showing non competitive mode of inhibition. Highlights Rapid formation of silver nanoparticles using 0.5 mL extract of Euphorbia sanguinea. AgNPs are spherical, monodispersed and with sizes in the range of 20–29 nm. High photocatalytic efficiency of 86% was obtained within 5 min of solar radiation of AgNPs in the degradation experiment of Congo red dye. First order kinetics with a correlation coefficient of 0.9472 and a rate of 0.0063 min−1 was established for the photocatalytic process. AgNPs showed dose dependent melanogenesis inhibition activity of IC50 71.96 µg/ml .

Binding Site Effect in Metal‐Organic Frameworks for Property Regulation of Metal Nanoparticles

Metal nanoparticles (MNPs) supported on metal–organic frameworks (MOFs) have exhibited excellent performance in various catalytic reactions. As a class of crystal catalysts, the roles played by MOFs different positions in regulating the MNPs properties are distinct. It is therefore meaningful to clarify the influence of different positions of MOFs on MNPs to help reveal the structure–activity relationship. However, the random dispersion of MNPs in the MOFs matrixes is usually an obstacle existing in the traditional preparation methods. Herein, a facile strategy is developed to precisely control the MNPs growth behavior on the target binding sites of MOFs. The MNPs on edges of MOFs show significantly improved hydrogen evolution reaction performance in comparison to those on the planes of MOFs, mainly because the electronic structure of MNPs is regulated by special interface originating from MNPs growth on the edges of MOFs, which provides high density of unsaturated copper ions. The effect of different binding sites of MOFs on MNPs properties is clarified, which is highly desired for fine‐tuning the structures and properties of the MOF composites.

Superior catalytic performance of Pd-loaded oxygen-vacancy-rich TiO2 for formaldehyde oxidation at room temperature

Modulating the metal–support interaction is a promising way to tailor the electronic structure of metal nanoparticles and hence alter their catalytic performance. Here, we developed a reduced TiO2 with rich oxygen vacancies on which to load Pd for catalytic oxidation of formaldehyde (HCHO) at room temperature. The reduced TiO2 remarkably induced an electronic metal–support interaction by transferring electrons from the support to Pd to form negatively charged Pd nanoparticles, facilitating the oxygen association. Simultaneously, the reduced TiO2 significantly increased the dispersion and the reduction degree of Pd compared with the pristine TiO2 by offering more anchor sites and electron-rich sites. Furthermore, the abundant oxygen vacancies in the reduced TiO2 show a synergistic effect by enabling the effective adsorption and dissociation of water to generate surface hydroxyl groups, accelerating the kinetics of active oxygen species generation and promoting the complete conversion of 100 ppm HCHO at a WHSV of 120,000 mL/(gcat·h). We tentatively propose two reaction mechanisms for HCHO oxidation over Pd-loaded oxygen-vacancy-rich TiO2 involving active oxygen species.