Showing papers on "Nanoparticle published in 2019"

The Role of Ligands in the Chemical Synthesis and Applications of Inorganic Nanoparticles.

Abstract: The design of nanoparticles is critical for their efficient use in many applications ranging from biomedicine to sensing and energy. While shape and size are responsible for the properties of the inorganic nanoparticle core, the choice of ligands is of utmost importance for the colloidal stability and function of the nanoparticles. Moreover, the selection of ligands employed in nanoparticle synthesis can determine their final size and shape. Ligands added after nanoparticle synthesis infer both new properties as well as provide enhanced colloidal stability. In this article, we provide a comprehensive review on the role of the ligands with respect to the nanoparticle morphology, stability, and function. We analyze the interaction of nanoparticle surface and ligands with different chemical groups, the types of bonding, the final dispersibility of ligand-coated nanoparticles in complex media, their reactivity, and their performance in biomedicine, photodetectors, photovoltaic devices, light-emitting devices, sensors, memory devices, thermoelectric applications, and catalysis.

Generation of Nanoparticle, Atomic-Cluster, and Single-Atom Cobalt Catalysts from Zeolitic Imidazole Frameworks by Spatial Isolation and Their Use in Zinc-Air Batteries

Abstract: The size effect of transition-metal nanoparticles on electrocatalytic performance remains ambiguous especially when decreasing the size to the atomic level. Herein, we report the spatial isolation of cobalt species on the atomic scale, which was achieved by tuning the zinc dopant content in predesigned bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo-ZIFs), and led to the synthesis of nanoparticles, atomic clusters, and single atoms of Co catalysts on N-doped porous carbon. This synthetic strategy allowed an investigation of the size effect on electrochemical behavior from nanometer to Angstrom dimensions. Single-atom Co catalysts showed superior bifunctional ORR/OER activity, durability, and reversibility in Zn-air batteries compared with the other derivatives and noble-metal Pt/C+RuO2 , which was attributed to the high reactivity and stability of isolated single Co atoms. Our findings open up a new avenue to regulate the metal particle size and catalytic performance of MOF derivatives.

Metal oxide nanoparticles and their applications in nanotechnology

Abstract: Considering metal oxide nanoparticles as important technological materials, authors provide a comprehensive review of researches on metal oxide nanoparticles, their synthetic strategies, and techniques, nanoscale physicochemical properties, defining specific industrial applications in the various fields of applied nanotechnology. This work expansively reviews the recent developments of semiconducting metal oxide gas sensors for environmental gases including CO2, O2, O3, and NH3; highly toxic gases including CO, H2S, and NO2; combustible gases such as CH4, H2, and liquefied petroleum gas; and volatile organic compounds gases. The gas sensing properties of different metal oxides nanoparticles towards specific target gases have been individually discussed. Promising metal oxide nanoparticles for sensitive and selective detection of each gas have been identified. This review also categorizes metal oxides sensors by analyte gas and also summarizes the major techniques and synthesis strategies used in nanotechnology. Additionally, strategies, sensing mechanisms and related applications of semiconducting metal oxide materials are also discussed in detail. Related applications are innumerable trace to ultratrace-level gas sensors, batteries, magnetic storage media, various types of solar cells, metal oxide nanoparticles applications in catalysis, energy conversion, and antennas (including microstrip and patch-type optically transparent antennas), rectifiers, optoelectronic, and electronics.

Stabilization of Silver and Gold Nanoparticles: Preservation and Improvement of Plasmonic Functionalities.

Abstract: Noble metal nanoparticles have been extensively studied to understand and apply their plasmonic responses, upon coupling with electromagnetic radiation, to research areas such as sensing, photocatalysis, electronics, and biomedicine. The plasmonic properties of metal nanoparticles can change significantly with changes in particle size, shape, composition, and arrangement. Thus, stabilization of the fabricated nanoparticles is crucial for preservation of the desired plasmonic behavior. Because plasmonic nanoparticles find application in diverse fields, a variety of different stabilization strategies have been developed. Often, stabilizers also function to enhance or improve the plasmonic properties of the nanoparticles. This review provides a representative overview of how gold and silver nanoparticles, the most frequently used materials in current plasmonic applications, are stabilized in different application platforms and how the stabilizing agents improve their plasmonic properties at the same time. Specifically, this review focuses on the roles and effects of stabilizing agents such as surfactants, silica, biomolecules, polymers, and metal shells in colloidal nanoparticle suspensions. Stability strategies for other types of plasmonic nanomaterials, lithographic plasmonic nanoparticle arrays, are discussed as well.

Electrochemical Fragmentation of Cu 2 O Nanoparticles Enhancing Selective C-C Coupling from CO 2 Reduction Reaction

Abstract: In this study, we demonstrate that the initial morphology of nanoparticles can be transformed into small fragmented nanoparticles, which were densely contacted to each other, during electrochemical CO2 reduction reaction (CO2RR). Cu-based nanoparticles were directly grown on a carbon support by using cysteamine immobilization agent, and the synthesized nanoparticle catalyst showed increasing activity during initial CO2RR, doubling Faradaic efficiency of C2H4 production from 27% to 57.3%. The increased C2H4 production activity was related to the morphological transformation over reaction time. Twenty nm cubic Cu2O crystalline particles gradually experienced in situ electrochemical fragmentation into 2-4 nm small particles under the negative potential, and the fragmentation was found to be initiated from the surface of the nanocrystal. Compared to Cu@CuO nanoparticle/C or bulk Cu foil, the fragmented Cu-based NP/C catalyst achieved enhanced C2+ production selectivity, accounting 87% of the total CO2RR products, and suppressed H2 production. In-situ X-ray absorption near edge structure studies showed metallic Cu0 state was observed under CO2RR, but the fragmented nanoparticles were more readily reoxidized at open circuit potential inside of the electrolyte, allowing labile Cu states. The unique morphology, small nanoparticles stacked upon on another, is proposed to promote C-C coupling reaction selectivity from CO2RR by suppressing HER.

Green synthesis of zinc oxide nanoparticles: a comparison

Abstract: Green synthesis of nanoparticles by biological systems especially plant extracts has become an emerging field in nanotechnology. In this study, zinc oxide nanoparticles were synthesized using Lauru...

Electrosynthesis of high-entropy metallic glass nanoparticles for designer, multi-functional electrocatalysis.

Abstract: Creative approaches to the design of catalytic nanomaterials are necessary in achieving environmentally sustainable energy sources. Integrating dissimilar metals into a single nanoparticle (NP) offers a unique avenue for customizing catalytic activity and maximizing surface area. Alloys containing five or more equimolar components with a disordered, amorphous microstructure, referred to as High-Entropy Metallic Glasses (HEMGs), provide tunable catalytic performance based on the individual properties of incorporated metals. Here, we present a generalized strategy to electrosynthesize HEMG-NPs with up to eight equimolar components by confining multiple metal salt precursors to water nanodroplets emulsified in dichloroethane. Upon collision with an electrode, alloy NPs are electrodeposited into a disordered microstructure, where dissimilar metal atoms are proximally arranged. We also demonstrate precise control over metal stoichiometry by tuning the concentration of metal salt dissolved in the nanodroplet. The application of HEMG-NPs to energy conversion is highlighted with electrocatalytic water splitting on CoFeLaNiPt HEMG-NPs.

Electrochemistry of Atomically Precise Metal Nanoclusters.

Abstract: Thiolate-protected metal nanoparticles containing a few to few hundred metal atoms are interesting materials exhibiting unique physicochemical properties. They encompass the bulk-to-molecule transition region, where discrete electronic states emerge and electronic band energetics yield to quantum confinement effects. Recent progresses in the synthesis and characterization of ultrasmall gold nanoparticles have opened up new avenues for the isolation of extremely monodispersed nanoparticles with atomically precision. These nanoparticles are also called nanoclusters to distinguish them from other regular metal nanoparticles with core diameter >2 nm. These nanoclusters are typically identified by their actual molecular formulas; prominent among these are Au25(SR)18, Au38(SR)24, and Au102(SR)44, where SR is organothiolate. A number of single crystal structures of these nanoclusters have been disclosed. Researchers have effectively utilized density functional theory (DFT) calculations to predict their atomic an...

Pea-like Fe/Fe3C Nanoparticles Embedded in Nitrogen-Doped Carbon Nanotubes with Tunable Dielectric/Magnetic Loss and Efficient Electromagnetic Absorption

Abstract: One-dimensional microstructure has been regarded as one of the most desirable configurations for magnetic carbon-based microwave absorbing materials (MAMs). Herein, pea-like Fe/Fe3C nanoparticles embedded in nitrogen-doped carbon nanotubes (Fe/Fe3C@NCNTs) are successfully prepared through a direct pyrolysis of the mixture of FeCl3·6H2O and melamine under inert atmosphere. The chemical composition and microstructural feature of these Fe/Fe3C@NCNTs composites are highly dependent on the pyrolysis temperature. As a result, their electromagnetic properties can be also manipulated, where dielectric loss gradually decreases with the increasing pyrolysis temperature and magnetic loss presents a reverse variation trend. When the pyrolysis temperature reaches 600 °C, the as-obtained composite, Fe/Fe3C@NCNTs-600 can perform a maximum reflection loss of −46.0 dB at 3.6 GHz with a thickness of 4.97 mm and a qualified bandwidth of 14.8 GHz with the integrated thickness from 1.00 to 5.00 mm. It is very interesting that...

Methods of Gold and Silver Nanoparticles Preparation

Abstract: The versatile family of nanoparticles is considered to have a huge impact on the different fields of materials research, mostly nanoelectronics, catalytic chemistry and in study of cytocompatibility, targeted drug delivery and tissue engineering. Different approaches for nanoparticle preparation have been developed, not only based on "bottom up" and "top down" techniques, but also several procedures of effective nanoparticle modifications have been successfully used. This paper is focused on different techniques of nanoparticles' preparation, with primary focus on metal nanoparticles. Dispergation methods such as laser ablation and vacuum sputtering are introduced. Condensation methods such as reduction with sodium citrate, the Brust-Schiffrin method and approaches based on ultraviolet light or biosynthesis of silver and gold are also discussed. Basic properties of colloidal solutions are described. Also a historical overview of nanoparticles are briefly introduced together with short introduction to specific properties of nanoparticles and their solutions.

Co–Fe Alloy/N‐Doped Carbon Hollow Spheres Derived from Dual Metal–Organic Frameworks for Enhanced Electrocatalytic Oxygen Reduction

Abstract: Metal-organic framework (MOF) composites have recently been considered as promising precursors to derive advanced metal/carbon-based materials for various energy-related applications. Here, a dual-MOF-assisted pyrolysis approach is developed to synthesize Co-Fe alloy@N-doped carbon hollow spheres. Novel core-shell architectures consisting of polystyrene cores and Co-based MOF composite shells encapsulated with discrete Fe-based MOF nanocrystallites are first synthesized, followed by a thermal treatment to prepare hollow composite materials composed of Co-Fe alloy nanoparticles homogeneously distributed in porous N-doped carbon nanoshells. Benefitting from the unique structure and composition, the as-derived Co-Fe alloy@N-doped carbon hollow spheres exhibit enhanced electrocatalytic performance for oxygen reduction reaction. The present approach expands the toolbox for design and preparation of advanced MOF-derived functional materials for diverse applications.

Band gap engineered zinc oxide nanostructures via a sol–gel synthesis of solvent driven shape-controlled crystal growth

Abstract: A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at low temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10−3 S cm−1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.

Dispersed Nickel Cobalt Oxyphosphide Nanoparticles Confined in Multichannel Hollow Carbon Fibers for Photocatalytic CO2 Reduction.

Abstract: Materials for high-efficiency photocatalytic CO2 reduction are desirable for solar-to-carbon fuel conversion. Herein, highly dispersed nickel cobalt oxyphosphide nanoparticles (NiCoOP NPs) were confined in multichannel hollow carbon fibers (MHCFs) to construct the NiCoOP-NPs@MHCFs catalysts for efficient CO2 photoreduction. The synthesis involves electrospinning, phosphidation, and carbonization steps and permits facile tuning of chemical composition. In the catalyst, the mixed metal oxyphosphide NPs with ultrasmall size and high dispersion offer abundant catalytically active sites for redox reactions. At the same time, the multichannel hollow carbon matrix with high conductivity and open ends will effectively promote mass/charge transfer, improve CO2 adsorption, and prevent the metal oxyphosphide NPs from aggregation. The optimized hetero-metal oxyphosphide catalyst exhibits considerable activity for photosensitized CO2 reduction, affording a high CO evolution rate of 16.6 μmol h-1 (per 0.1 mg of catalyst).

Formation of two-dimensional transition metal oxide nanosheets with nanoparticles as intermediates.

Abstract: Two-dimensional (2D) materials have attracted significant interest because of their large surface-to-volume ratios and electron confinement. Compared to common 2D materials such as graphene or metal hydroxides, with their intrinsic layered atomic structures, the formation mechanisms of 2D metal oxides with a rocksalt structure are not well understood. Here, we report the formation process for 2D cobalt oxide and cobalt nickel oxide nanosheets, after analysis by in situ liquid-phase transmission electron microscopy. Our observations reveal that three-dimensional (3D) nanoparticles are initially formed from the molecular precursor solution and then transform into 2D nanosheets. Ab initio calculations show that a small nanocrystal is dominated by positive edge energy, but when it grows to a certain size, the negative surface energy becomes dominant, driving the transformation of the 3D nanocrystal into a 2D structure. Uncovering these growth pathways, including the 3D-to-2D transition, provides opportunities for future material design and synthesis in solution. Liquid phase transmission electron microscopy reveals the growth pathway of 2D cobalt oxide and cobalt nickel oxide, in which 3D nanoparticles are formed first and then spread and transform into 2D nanosheets.

Room temperature CO2 reduction to solid carbon species on liquid metals featuring atomically thin ceria interfaces

Abstract: Negative carbon emission technologies are critical for ensuring a future stable climate. However, the gaseous state of CO2 does render the indefinite storage of this greenhouse gas challenging. Herein, we created a liquid metal electrocatalyst that contains metallic elemental cerium nanoparticles, which facilitates the electrochemical reduction of CO2 to layered solid carbonaceous species, at a low onset potential of −310 mV vs CO2/C. We exploited the formation of a cerium oxide catalyst at the liquid metal/electrolyte interface, which together with cerium nanoparticles, promoted the room temperature reduction of CO2. Due to the inhibition of van der Waals adhesion at the liquid interface, the electrode was remarkably resistant to deactivation via coking caused by solid carbonaceous species. The as-produced solid carbonaceous materials could be utilised for the fabrication of high-performance capacitor electrodes. Overall, this liquid metal enabled electrocatalytic process at room temperature may result in a viable negative emission technology.

MOF-Derived Indium Oxide Hollow Microtubes/MoS2 Nanoparticles for NO2 gas sensing

Abstract: In this paper, we fabricated a metal-organic frameworks-derived indium oxide hollow microtubes/molybdenum disulfide nanoparticles (In2O3/MoS2) nanocomposite film sensor using a layer-by-layer self-assembly method. Various characterization methods such as TG, XRD, SEM, TEM, BET and XPS were applied to inspect and verify its preparation and nanostructures. The NO2-sensing characteristics of the sensors based on In2O3/MoS2 composite were systematically examined. The results showed that the response of the In2O3/MoS2 film sensor has significantly improved compared with the In2O3 sensor. More importantly, the In2O3/MoS2 sensor exhibited excellent NO2 sensing performance with a good linearity, excellent reversibility and outstanding selectivity. Finally, based on the above experimental results, we discovered that the possible sensing mechanism was ascribed to the unique structure and the synergistic effects of In2O3 hollow microtubes and MoS2 nanoparticles.

Metal-induced ordered microporous polymers for fabricating large-area gas separation membranes.

Abstract: Metal-induced ordered microporous polymers (MMPs), a class of porous polymer, are synthesized from amine-bearing polymers, small organic linkers and divalent metal ions using a polymer-directed chemical synthesis process. Specifically, small organic linkers first coordinate to metal ions, with the resulting unit cells then self-assembling along the extension of polymer chains to construct three-dimensional frameworks. The MMPs demonstrate good controllability of crystal and framework size, as well as hydrolytic stability. MMP dispersions were coated on a modified polysulfone substrate to fabricate MMP/mPSf membranes with an ultrathin selective layer (below 50 nm) and surface areas of >100 cm2. The MMPs are readily fabricated into defect-free thin selective-layered membranes with high CO2 permeance (3,000 GPU) and stable CO2/N2 selectivity (78) under both humid and dry gas feed conditions, demonstrating promising CO2 membrane separation performance. This synthetic methodology could be extended to other polymers, potentially enabling facile synthesis of membrane materials. Controlling crystallite size can lead to improved applications. Here, this is achieved by a combination of metal ions, organic linkers, and polymers; the resultant membrane displays promising CO2/N2 separation properties and hydrolytic stability.

Aluminum with dispersed nanoparticles by laser additive manufacturing.

Abstract: While laser-printed metals do not tend to match the mechanical properties and thermal stability of conventionally-processed metals, incorporating and dispersing nanoparticles in them should enhance their performance. However, this remains difficult to do during laser additive manufacturing. Here, we show that aluminum reinforced by nanoparticles can be deposited layer-by-layer via laser melting of nanocomposite powders, which enhance the laser absorption by almost one order of magnitude compared to pure aluminum powders. The laser printed nanocomposite delivers a yield strength of up to 1000 MPa, plasticity over 10%, and Young's modulus of approximately 200 GPa, offering one of the highest specific Young's modulus and specific yield strengths among structural metals, as well as an improved specific strength and thermal stability up to 400 °C compared to other aluminum-based materials. The improved performance is attributed to a high density of well-dispersed nanoparticles, strong interfacial bonding between nanoparticles and Al matrix, and ultrafine grain sizes.

Ordered gold nanoparticle arrays on the tip of silver wrinkled structures for single molecule detection

Abstract: We demonstrate a method for fabricating nanoparticles in a line at the top of silver wrinkled structures by tilting the substrate. The center of gravity of the colloidal droplets was moved backward, resulting in a small volume of droplets at the front of the colloidal droplet. The droplet rapidly evaporated, and the nanoparticles that remained formed lines of highly ordered nanoparticles. The distance between the nanoparticles changed after stretching the PDMS substrate due to the Poisson effect. An optimal plasma effect was achieved by controlling the distance between the nanoparticles. Finally, the Surface-Enhanced Raman Scattering (SERS) effects of CV and R6G molecules in water were determined, and the detection limit was 10−20 M. This method provides an extremely high sensitivity SERS substrate for the detection of biomolecules.