Search results for "nanoparticle"
showing 10 items of 2198 documents
Self-Assembly of Amphiphilic Nanocrystals
2009
Amphiphilic hybrid materials are formed from polymer-coated semiconductor nanoparticles that simulate a surfactant-like response (see picture). The strength and density of the surface coating are the key assembling forces driving a transition from single particles to cylindrical or vesicular superstructures.
Low temperature synthesis of monodisperse nanoscaled ZrO2with a large specific surface area
2012
Thermal decomposition of Zr(C(2)O(4))(2)·4H(2)O within an autoclave or in a conventional tube furnace at temperatures below 380 °C resulted in nano- and micron-sized ZrO(2), respectively. Reactions under autogenic pressure yielded monodisperse monoclinic (m) and tetragonal (t) ZrO(2) nanoparticles with an average diameter of ~8 nm and interconnected t-ZrO(2) nanoparticles with diameters of ~4 nm, depending on the synthesis temperature. Samples were characterised by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) associated with energy dispersive X-ray spectroscopy (EDS), Raman microspectroscopy and phot…
Multifunctional clickable and protein-repellent magnetic silica nanoparticles
2016
Silica nanoparticles are versatile materials whose physicochemical surface properties can be precisely adjusted. Because it is possible to combine several functionalities in a single carrier, silica-based materials are excellent candidates for biomedical applications. However, the functionality of the nanoparticles can get lost upon exposure to biological media due to uncontrolled biomolecule adsorption. Therefore, it is important to develop strategies that reduce non-specific protein-particle interactions without losing the introduced surface functionality. Herein, organosilane chemistry is employed to produce magnetic silica nanoparticles bearing differing amounts of amino and alkene func…
Molecular-mediated assembly of silver nanoparticles with controlled interparticle spacing and chain length
2012
In the present work, we report on a one-pot method for the assembly of noble metal nanoparticles with tunable optical properties, assembly length and interparticle spacing. The synthetic colloidal route is based on the covalent binding among OH-terminated silver nanoparticles by means of dicarboxylic acids with a defined molecular length. As a result, the initially symmetric plasmon band of silver nanoparticles splits into two plasmonic modes when nanoparticles are assembled due to the strong near-field plasmon coupling. We noticed a very good correlation between the plasmon wavelength shift and the interparticle spacing that is represented by the universal scaling law of the surface plasmo…
Spherical microparticles production by supercritical antisolvent precipitation: Interpretation of results
2008
Abstract Supercritical antisolvent micronization has been the subject of many works aimed at the production of precipitates with controlled particle size and morphology. Several morphologies have been observed; but, the production of spherical micrometric particles has been the major objective of most of the studies performed. Therefore, in this work, literature data analysis on spherical and related morphologies has been performed. The ranges of process conditions at which spherical microparticles have been obtained have been listed and discussed. A possible formation mechanism is proposed that is based on the competition between jet break-up and liquid surface tension vanishing characteri…
Unraveling the Formation of Core−Shell Structures in Nanoparticles by S-XPS
2010
The combination of the surface sensitivity of X-ray photoelectron spectroscopy (XPS) with the high flux and variable photon energy excitation of Synchrotron radiation (S-XPS) is used to probe the atomic distribution of bimetallic nanoparticles. Based on the energy dependence of the photoemission differential cross section of core level photoelectrons, we propose a methodology to monitor the formation and to evaluate sizes of the core−shell structure. We have successfully applied it to unveil the mechanism involved in the atomic rearrangement of thermally treated Pt0.7Pd0.3 nanoparticles.
Cobalt hexacyanoferrate–poly(methyl methacrylate) composite: Synthesis and characterization
2010
Abstract The preparation of cobalt hexacyanoferrate nanoparticles–poly(methyl methacrylate) (CoHCF–PMMA) composites are described together with their characterization and thermochromic properties. CoHCF nanoparticles – investigated by dynamic light scattering – were prepared by optimizing solvent composition and temperature to obtain nanoparticles with a reduced degree of aggregation. The nanoparticles were embedded in a PMMA matrix to obtain a transparent coloured composite which was studied by transmission electron microscopy. The nanoparticle chromic features, enhanced by their reduced sizes, were investigated by UV–vis and FT-IR spectroscopy.
Tuning the Ultrafast Response of Fano Resonances in Halide Perovskite Nanoparticles
2020
International audience; The full control of the fundamental photophysics of nanosystems at frequencies as high as few THz is key for tunable and ultrafast nanophotonic devices and metamaterials. Here we combine geometrical and ultrafast control of the optical properties of halide perovskite nanoparticles, which constitute a prominent platform for nanophotonics. The pulsed photoinjection of free carriers across the semiconducting gap leads to a subpicosecond modification of the far-field electromagnetic properties that is fully controlled by the geometry of the system. When the nanoparticle size is tuned so as to achieve the overlap between the narrowband excitons and the geometry-controlled…
Selective Synthesis of Monodisperse CoO Nanooctahedra as Catalysts for Electrochemical Water Oxidation
2020
Thermal decomposition is a promising route for the synthesis of metal oxide nanoparticles because size and morphology can be tuned by minute control of the reaction variables. We synthesized CoO nanooctahedra with diameters of ∼48 nm and a narrow size distribution. Full control over nanoparticle size and morphology could be obtained by controlling the reaction time, surfactant ratio, and reactant concentrations. We show that the particle size does not increase monotonically with time or surfactant concentration but passes through minima or maxima. We unravel the critical role of the surfactants in nucleation and growth and rationalize the observed experimental trends in accordance with simu…
Effect of precursor concentration on size evolution of iron oxide nanoparticles
2017
Thermal decomposition is a promising route for the synthesis of magnetic nanoparticles. The simplicity of the synthesis method is counterbalanced by the complex chemistry of the system such as precursor decomposition and surfactant–reducing agent interactions. Control over nanoparticle size is achieved by adjusting the reaction parameters, namely, the precursor concentration. The results, however, are conflicting as both an increase and a decrease in nanoparticle size, as a function of increasing concentration, have been reported. Here, we address the issue of size-controlled synthesis via the precursor concentration. We synthesized iron oxide nanoparticles with sizes from 6 nm to 24 nm wit…