Showing papers on "Nanoparticle published in 2020"

Multidimension-Controllable Synthesis of MOF-Derived Co@N-Doped Carbon Composite with Magnetic-Dielectric Synergy toward Strong Microwave Absorption

Abstract: Metal-organic framework (MOF) is highly desirable as a functional material owing to its low density, tunable pore size, and diversity of coordination formation, but limited by the poor dielectric properties. Herein, by controlling the solvent and mole ratio of cobalt/linker, multidimension-controllable MOF-derived nitrogen-doped carbon materials exhibit tunable morphology from sheet-, flower-, cube-, dodecahedron- to octahedron-like. Tunable electromagnetic parameters of Co@N-doped carbon composites (Co@NC) can be obtained and the initial MOF precursor determines the distribution of carbon framework and magnetic cobalt nanoparticles. Carbonized Co@NC composites possess the following advantages: i) controllable dimension and morphology to balance the electromagnetic properties with evenly charged density distribution; ii) magnetic-carbon composites offer plenty of interfacial polarization and strong magnetic coupling network; iii) a MOF-derived dielectric carbon skeleton provides electronic transportation paths and enhances conductive dissipation. Surface-mediated magnetic coupling reflects the stray magnetic flux field, which is corroborated by the off-axis electron holography and micro-magnetic simulation. Optimized octadecahedral Co@NC sample exhibits the best microwave absorption (MA) of -53.0 dB at the thickness of 1.8 mm and broad effective frequency from 11.4 to 17.6 GHz (Ku-band). These results pave the way to fabricate high-performance MA materials with balanced electromagnetic distribution and controlled morphology.

Metal oxides nanoparticles via sol–gel method: a review on synthesis, characterization and applications

Abstract: Metal oxide nanoparticles (MONPs) have enormous applications such as in optical devices, purification systems, biomedical systems, photocatalysis, photovoltaics etc. In this review, we have explored a stable and efficient synthesis protocol of particularly four MONPs: titanium dioxide (TiO2), tin oxide (SnO2), tungsten oxide (WO3) and zinc oxide (ZnO) for getting desired chemical composition, nanostructure, and surface properties. The selection of an efficient synthesis process is a key factor that significantly influences the efficacy of the MONPs. The chemical synthesis of nanoparticles (NPs) via sol–gel route is an effective method to produce high-quality MONPs in comparison to other physical and chemical methods. Sol–gel synthesis is one of the simple, fastest and economically less expensive method, and has its own advantages like low processing temperature, homogeneity of the produced material and formation of the complex structures or composite materials. We believe that this detailed review will provide an insight into sol–gel synthesis of MONPs along with their characterization and diverse applications.

Detail review on chemical, physical and green synthesis, classification, characterizations and applications of nanoparticles

Abstract: Nanotechnology is an emerging field of science. The base of nanotechnology is nanoparticles. The size of nanoparticles ranges from 1 to 100 nm. The nanoparticles are classified into different class...

Toxicity of metal and metal oxide nanoparticles: a review

Abstract: Nanotechnology has recently found applications in many fields such as consumer products, medicine and environment Nanoparticles display unique properties and vary widely according to their dimensions, morphology, composition, agglomeration and uniformity states Nanomaterials include carbon-based nanoparticles, metal-based nanoparticles, organic-based nanoparticles and composite-based nanoparticles The increasing production and use of nanoparticles result in higher exposure to humans and the environment, thus raising issues of toxicity Here we review the properties, applications and toxicity of metal and non-metal-based nanoparticles Nanoparticles are likely to be accumulated in sensitive organs such as heart, liver, spleen, kidney and brain after inhalation, ingestion and skin contact In vitro and in vivo studies indicate that exposure to nanoparticles could induce the production of reactive oxygen species (ROS), which is a predominant mechanism leading to toxicity Excessive production of ROS causes oxidative stress, inflammation and subsequent damage to proteins, cell membranes and DNA ROS production induced by nanoparticles is controlled by size, shape, surface, composition, solubility, aggregation and particle uptake The toxicity of a metallic nanomaterial may differ depending on the oxidation state, ligands, solubility and morphology, and on environmental and health conditions

Silver nanoparticles: various methods of synthesis, size affecting factors and their potential applications–a review

Abstract: Currently, synthesis of nanoparticles from several noble metals like palladium, tin, copper, silver and gold etc. has received more attention because of their unique properties as well as their application in different fields. Furthermore, silver nanoparticles play an important role in pharmaceutical industries because they function like antibacterial agents which carry less toxic effects. In case of industrial applications, silver particles (inkjet inks) having regular dispersions are helpful in making different electronic circuits. Over the period, various synthetic methods for the synthesis of silver nanoparticles were reported i.e. physical, chemical, and photochemical. However, most of the available techniques are expensive and not eco-friendly i.e. environmentally harmful. There are various factors such as the methods of synthesis, temperature, dispersing agent, surfactant etc. which greatly influence the quality and quantity of the synthesized nanoparticles and ultimately affect their properties. It is also pertinent to mention here that the main target for these silver nanoparticles was not only to synthesize in nano range, but also require easy, eco-friendly and economical synthesis of the nanoparticles. Therefore, this review mainly goes through the several methods of synthesis of nanoparticles which should be based on the green approach, and easy to be synthesized at low cost. In addition, we also discussed some approaches to fabricate silver-based nanoparticles, their enhanced properties and their different type of applications such as electrical conductivity, antibacterial, optical, photocatalytic properties.

Efficient synergism of NiSe2 nanoparticle/NiO nanosheet for energy-relevant water and urea electrocatalysis

Abstract: Herein, we highlighted that a catalyst system of NiSe2 nanoparticle/NiO nanosheet catalyst exhibited efficient synergism for energy and environmental-relevant urea-assisted water electrolysis reactions. The spectral study and microscopic analysis demonstrated the formation of NiSe2 nanoparticle/NiO nanosheet heterostructure and efficient Ni O bond and Ni Se bond synergism. Owing to various factors such as the strong synergetic coupling effects between NiSe2 nanoparticle and NiO nanosheet, unique structure features, increased active sites and amount of intrinsic Ni3+ ions, efficient synergism was found on the NiSe2 Nanoparticle/NiO nanosheet for urea-assisted water electrolysis by comparing with the NiSe2 Nanoparticle and NiO nanosheet alone. It required a cell voltage of 1.39 V, about 210 mV less than that of water electrolysis, confirming the less energy consumption during the electrolysis. Notably, it also shows remarkably superior long-term durability. The current work may extend the nanoparticle-nanosheet catalysts system for simultaneous wastewater treatment and clean energy production.

Evaluation of the Efficiency of Detection and Capture of Manganese in Aqueous Solutions of FeCeOx Nanocomposites Doped with Nb2O5.

Abstract: The main purpose of this work is to study the effectiveness of using FeCeOx nanocomposites doped with Nb2O5 for the purification of aqueous solutions from manganese. X-ray diffraction, energy–dispersive analysis, scanning electron microscopy, vibrational magnetic spectroscopy, and mossbauer spectroscopy were used as research methods. It is shown that an increase in the dopant concentration leads to the transformation of the shape of nanoparticles from spherical to cubic and rhombic, followed by an increase in the size of the nanoparticles. The spherical shape of the nanoparticles is characteristic of a structure consisting of a mixture of two phases of hematite (Fe2O3) and cerium oxide CeO2. The cubic shape of nanoparticles is typical for spinel-type FeNbO4 structures, the phase contribution of which increases with increasing dopant concentration. It is shown that doping leads not only to a decrease in the concentration of manganese in model solutions, but also to an increase in the efficiency of adsorption from 11% to 75%.

Polymer-guided assembly of inorganic nanoparticles.

Abstract: The self-assembly of inorganic nanoparticles is of great importance in realizing their enormous potentials for broad applications due to the advanced collective properties of nanoparticle ensembles. Various molecular ligands (e.g., small molecules, DNAs, proteins, and polymers) have been used to assist the organization of inorganic nanoparticles into functional structures at different hierarchical levels. Among others, polymers are particularly attractive for use in nanoparticle assembly, because of the complex architectures and rich functionalities of assembled structures enabled by polymers. Polymer-guided assembly of nanoparticles has emerged as a powerful route to fabricate functional materials with desired mechanical, optical, electronic or magnetic properties for a broad range of applications such as sensing, nanomedicine, catalysis, energy storage/conversion, data storage, electronics and photonics. In this review article, we summarize recent advances in the polymer-guided self-assembly of inorganic nanoparticles in both bulk thin films and solution, with an emphasis on the role of polymers in the assembly process and functions of resulting nanostructures. Precise control over the location/arrangement, interparticle interaction, and packing of inorganic nanoparticles at various scales are highlighted.

Room-Temperature Laser Synthesis in Liquid of Oxide, Metal-Oxide Core-Shells, and Doped Oxide Nanoparticles

Abstract: Although oxide nanoparticles are ubiquitous in science and technology, a multitude of compositions, phases, structures, and doping levels exist, each one requiring a variety of conditions for their synthesis and modification. Besides, experimental procedures are frequently dominated by high temperatures or pressures and by chemical contaminants or waste. In recent years, laser synthesis of colloids emerged as a versatile approach to access a library of clean oxide nanoparticles relying on only four main strategies running at room temperature and ambient pressure: laser ablation in liquid, laser fragmentation in liquid, laser melting in liquid and laser defect-engineering in liquid. Here, established laser-based methodologies are reviewed through the presentation of a panorama of oxide nanoparticles which include pure oxidic phases, as well as unconventional structures like defective or doped oxides, non-equilibrium compounds, metal-oxide core-shells and other anisotropic morphologies. So far, these materials showed several useful properties that are discussed with special emphasis on catalytic, biomedical and optical application. Yet, given the endless number of mixed compounds accessible by the laser-assisted methodologies, there is still a lot of room to expand the library of nano-crystals and to refine the control over products as well as to improve the understanding of the whole process of nanoparticle formation. To that end, this review aims to identify the perspectives and unique opportunities of laser-based synthesis and processing of colloids for future studies of oxide nanomaterial-oriented sciences.

MOF-Mediated Fabrication of a Porous 3D Superstructure of Carbon Nanosheets Decorated with Ultrafine Cobalt Phosphide Nanoparticles for Efficient Electrocatalysis and Zinc-Air Batteries.

Abstract: Superstructures have attracted great interest owing to their potential applications. Herein, we report the first scalable preparation of a porous nickel-foam-templated superstructure of carbon nanosheets decorated with ultrafine cobalt phosphide nanoparticles. Uniform two-dimensional (2D) Co-metal organic framework (MOF) nanosheets (Co-MNS) grow on nickel foam, followed by a MOF-mediated tandem (carbonization/phosphidation) pyrolysis. The resulting superstructure has a porous 3D interconnected network with well-arranged 2D carbon nanosheets on it, in which ultrafine cobalt phosphide nanoparticles are tightly immobilized. A single piece of this superstructure can be directly used as a self-supported electrode for electrocatalysis without any binders. This "one-piece" porous superstructure with excellent mass transport and electron transport properties, and catalytically active cobalt phosphide nanoparticles with ultrasmall size (3-4 nm), shows excellent trifunctional electrocatalytic activities for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR), achieving great performances in water splitting and Zn-air batteries.

ZnO Photocatalyst Revisited: Effective Photocatalytic Degradation of Emerging Contaminants Using S-Doped ZnO Nanoparticles under Visible Light Radiation

Abstract: Zinc oxide (ZnO) nanoparticles were synthesized by the hydrothermal method and incorporated with diverse amounts of the nonmetal element sulfur (0.5, 0.8, 1.1, 1.3, 2.1, 2.5, 3.2, 6.8, 7.8, 11.9, 1...

New Horizon of Nanoparticle and Cluster Catalysis with Dendrimers

Abstract: Among various approaches synthesizing metal nanoparticles and tiny clusters, a template method using dendrimers has significant advantages over other chemical approaches with respect to their synthetic precision and the scalability. A dendrimer of polydentate ligands assembles metal ions or salts into the interior allowing production of metal nanoparticles in the dendrimer. The dendrimer-encapsulated nanoparticles (DENs) exhibit unique and remarkable catalytic properties depending on the size and elemental formula. Recent advances in dendrimer chemistry even enabled the atom precise synthesis of subnanometer metal clusters that have been impossible to prepare by wet chemical methods. In addition, not only for the synthesis of metal nanoparticles and clusters, the dendrimer itself can also provide the modulation of activity and selectivity in the catalysis. In this review, we summarized the most relevant research in which the dendrimer was employed as the template, modulator, or stabilizer for nanoparticle synthesis for catalytic applications.

Carbon-coated FeCo nanoparticles as sensitive magnetic-particle-imaging tracers with photothermal and magnetothermal properties.

Abstract: The low magnetic saturation of iron oxide nanoparticles, which are developed primarily as contrast agents for magnetic resonance imaging, limits the sensitivity of their detection using magnetic particle imaging (MPI). Here, we show that FeCo nanoparticles that have a core diameter of 10 nm and bear a graphitic carbon shell decorated with poly(ethylene glycol) provide an MPI signal intensity that is sixfold and fifteenfold higher than the signals from the superparamagnetic iron oxide tracers VivoTrax and Feraheme, respectively, at the same molar concentration of iron. We also show that the nanoparticles have photothermal and magnetothermal properties and can therefore be used for tumour ablation in mice, and that they have high optical absorbance in a broad near-infrared region spectral range (wavelength, 700–1,200 nm), making them suitable as tracers for photoacoustic imaging. As sensitive multifunctional and multimodal imaging tracers, carbon-coated FeCo nanoparticles may confer advantages in cancer imaging and hyperthermia therapy. FeCo nanoparticles with a graphitic carbon shell decorated with poly(ethylene glycol) have photothermal and magnetothermal properties and are sensitive tracers for magnetic particle imaging, magnetic resonance imaging and photoacoustic imaging.

Exploiting the role of nanoparticle shape in enhancing hydrogel adhesive and mechanical properties

Abstract: The ability to control nanostructure shape and dimensions presents opportunities to design materials in which their macroscopic properties are dependent upon the nature of the nanoparticle. Although particle morphology has been recognized as a crucial parameter, the exploitation of the potential shape-dependent properties has, to date, been limited. Herein, we demonstrate that nanoparticle shape is a critical consideration in the determination of nanocomposite hydrogel properties. Using translationally relevant calcium-alginate hydrogels, we show that the use of poly(L-lactide)-based nanoparticles with platelet morphology as an adhesive results in a significant enhancement of adhesion over nanoparticle glues comprised of spherical or cylindrical micelles. Furthermore, gel nanocomposites containing platelets showed an enhanced resistance to breaking under strain compared to their spherical and cylindrical counterparts. This study opens the doors to a change in direction in the field of gel nanocomposites, where nanoparticle shape plays an important role in tuning mechanical properties.

Identification of catalytic sites for oxygen reduction in metal/nitrogen‐doped carbons with encapsulated metal nanoparticles

Abstract: The development of metal-N-C materials as efficient non-precious metal (NPM) catalysts for catalysing the oxygen reduction reaction (ORR) as alternatives to platinum is important for the practical use of proton exchange membrane fuel cells (PEMFCs). However, metal-N-C materials have high structural heterogeneity. As a result of their high-temperature synthesis they often consist of metal-Nx sites and graphene-encapsulated metal nanoparticles. Thus it is hard to identify the active structure of metal-N-C catalysts. Herein, we report a low-temperature NH4 Cl-treatment to etch out graphene-encapsulated nanoparticles from metal-N-C catalysts without destruction of co-existing atomically dispersed metal-Nx sites. Catalytic activity is much enhanced by this selective removal of metallic nanoparticles. Accordingly, we can confirm the spectator role of graphene-encapsulated nanoparticles and the pivotal role of metal-Nx sites in the metal-N-C materials for ORR in the acidic medium.

Molybdenum-based nanoparticles (Mo2C, MoP and MoS2) coupled heteroatoms-doped carbon nanosheets for efficient hydrogen evolution reaction

Abstract: Hierarchical nanostructure of intimately coupled transition metal nanoparticles/carbon-based materials can efficiently boost the electrochemical technologies because of the appealingly coupled interaction between different components and the strongly structural advantages. Herein, a facile and conventional strategy is developed to fabricate ultrafine Mo-based nanoparticles (MoP, Mo2C and MoS2) dispersed on hierarchically porous carbon nanosheets. The involved polymer-confinement pyrolysis process can not only efficiently alleviate the aggregation of Mo-based nanoparticles, but also in-situ achieve different Mo-based components on various heteroatoms-doped carbon nanosheets without further post-modification. The hierarchical nanostructure and synergistic effect between carbon substrates and Mo-based nanoparticles enhance the electrochemical performance of the fabricated materials. For instance, the developed MoP@NPCS exhibits outstanding hydrogen evolution performance with high Faradaic efficiency in both acidic and alkaline electrolytes, being one of the impressive catalysts reported to date for hydrogen evolution reaction. This work would inspire the development of interacted carbon-metal functional materials for improving energy-related devices.

Self-limiting directional nanoparticle bonding governed by reaction stoichiometry

Abstract: Nanoparticle clusters with molecular-like configurations are an emerging class of colloidal materials. Particles decorated with attractive surface patches acting as analogs of functional groups are used to assemble colloidal molecules (CMs); however, high-yield generation of patchy nanoparticles remains a challenge. We show that for nanoparticles capped with complementary reactive polymers, a stoichiometric reaction leads to reorganization of the uniform ligand shell and self-limiting nanoparticle bonding, whereas electrostatic repulsion between colloidal bonds governs CM symmetry. This mechanism enables high-yield CM generation and their programmable organization in hierarchical nanostructures. Our work bridges the gap between covalent bonding taking place at an atomic level and colloidal bonding occurring at the length scale two orders of magnitude larger and broadens the methods for nanomaterial fabrication.

Synthesis, characterization and photocatalytic dye degradation capability of Calliandra haematocephala-mediated zinc oxide nanoflowers.

Abstract: An environmentally sound approach towards the green synthesis of zinc oxide nanostructures has been achieved with an aqueous extract of Calliandra haematocephala leaves. The nanoparticles were characterized using various analytical techniques to substantiate the structural details. An absorption band at 358 nm corresponds to the formation of zinc oxide nanoparticles. Scanning electron microscopy revealed the nanoflower morphology of the nanoparticles. Energy dispersive spectral analysis portrayed the strong presence of zinc and oxygen, while X-ray diffraction showed the nanoparticles to conform to hexagonally-formed wurtzite structure. The crystallite size of the nanoflowers was estimated to be 19.45 nm. Vibrational frequencies, typical of zinc‑oxygen and other functional groups, were revealed using Fourier transform infrared spectroscopy. BET analysis revealed that the pores were of mesoporous nature with an estimated specific surface area of 9.18 m2/g. The photocatalytic nature of the nanoparticles was established by the degradation of methylene blue (MB) dye, under solar radiation. Up to 88% degradation was achieved in a duration of 270 min. Kinetic data from the studies proved that the reaction was compliant with first-order model, with rate constant as 0.01 min−1. The study illustrated the synthesis of zinc oxide nanoparticles using a novel source, viz., the leaves of C. haematocephala.

Assessing magnetic and inductive thermal properties of various surfactants functionalised Fe 3 O 4 nanoparticles for hyperthermia

Abstract: This work reports the fabrication of magnetite (Fe3O4) nanoparticles (NPs) coated with various biocompatible surfactants such as glutamic acid (GA), citric acid (CA), polyethylene glycol (PEG), polyvinylpyrrolidine (PVP), ethylene diamine (EDA) and cetyl-trimethyl ammonium bromide (CTAB) via co-precipitation method and their comparative inductive heating ability for hyperthermia (HT) applications. X-ray and electron diffraction analyses validated the formation of well crystallined inverse spinel structured Fe3O4 NPs (crystallite size of ~ 8-10 nm). Magnetic studies confirmed the superparamagnetic (SPM) behaviour for all the NPs with substantial magnetisation (63-68 emu/g) and enhanced magnetic susceptibility is attributed to the greater number of occupations of Fe2+ ions in the lattice as revealed by X-ray photoelectron spectroscopy (XPS). Moreover, distinctive heating response (specific absorption rate, SAR from 130 to 44 W/g) of NPs with similar size and magnetisation is observed. The present study was successful in establishing a direct correlation between relaxation time (~ 9.42-15.92 ns) and heating efficiency of each surface functionalised NPs. Moreover, heat dissipated in different surface grafted NPs is found to be dependent on magnetic susceptibility, magnetic anisotropy and magnetic relaxation time. These results open very promising avenues to design surface functionalised magnetite NPs for effective HT applications.