scholarly journals Formation of Star-Like and Core-Shell AuAg Nanoparticles during Two- and Three-Step Preparation in Batch and in Microfluidic Systems

2007 ◽  
Vol 2007 ◽  
pp. 1-7 ◽  
Author(s):  
J. Michael Köhler ◽  
H. Romanus ◽  
U. Hübner ◽  
J. Wagner
Keyword(s):  
Early Stage ◽  
Silver Ions ◽  
Particle Growth ◽  
Core Shell ◽  
Time Interval ◽  
Silver Deposition ◽  
Shell Nanoparticles ◽  
Spherical Core ◽  
Flow Through ◽  
Shell Particles

Regular dendrit-like metal nanoparticles and core-shell nanoparticles were formed by the reduction of mixtures of tetrachloroaurate and silver nitrate solutions with ascorbic acid at room temperature in two- and three-step procedures. The formation of these particles was found in batch experiments as well as in micro flow-through processes using static micromixers. The characteristic diameters of 4-branched star particles were in the range between 60 and 100 nm. The typical particles consist of four metal cores which are embedded in a common shell. Additionally, particles with five and more metallic cores were formed, to some extent, and aggregates of the 4-branched particles also were formed. Larger aggregates and network-like structures of connected star particles were formed after sedimentation. The properties of the formed particles are dependent on the educt concentrations as well as on the order of mixing steps and on the time interval between them. Obviously, the relation of nucleation and particle growth in relation to the concentrations of metal ions determines the composition and the properties of formed nanoparticles. So, star-like particles are observed in case of nucleation of Au in absence of silver ions but with silver deposition after short nucleation time. Spherical core shell particles are formed in case of silver salt addition after complete reduction of tetrachloroaurate in flow-through experiments with sufficient residence time between both mixing steps. Polymer layers are always found in the form of a second outer shell even if the polymer solutions are added in an early stage of particle formation.

scholarly journals Bimetallic Core–Shell Nanoparticles of Gold and Silver via Bioinspired Polydopamine Layer as Surface-Enhanced Raman Spectroscopy (SERS) Platform

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 688 ◽  
Author(s):  
Asli Yilmaz ◽  
Mehmet Yilmaz
Keyword(s):  
Raman Spectroscopy ◽  
Low Cost ◽  
Silver Ions ◽  
Surface Enhanced Raman Spectroscopy ◽  
Core Shell ◽  
Silver Deposition ◽  
Shell Nanoparticles ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Core Shell Nanoparticles

Despite numerous attempts to fabricate the core–shell nanoparticles, novel, simple, and low-cost approaches are still required to produce these efficient nanosystems. In this study, we propose the synthesis of bimetallic core–shell nanoparticles of gold (AuNP) and silver (AgNP) nanostructures via a bioinspired polydopamine (PDOP) layer and their employment as a surface-enhanced Raman spectroscopy (SERS) platform. Herein, the PDOP layer was used as an interface between nanostructures as well as stabilizing and reducing agents for the deposition of silver ions onto the AuNPs. UV-vis absorption spectra and electron microscope images confirmed the deposition of the silver ions and the formation of core–shell nanoparticles. SERS activity tests indicated that both the PDOP thickness and silver deposition time are the dominant parameters that determine the SERS performances of the proposed core–shell system. In comparison to bare AuNPs, more than three times higher SERS signal intensity was obtained with an enhancement factor of 3.5 × 105.

Identification of aggregates of magnetic nanoparticles in ferrofluids at low concentrations

2003 ◽  
Vol 36 (4) ◽  
pp. 1069-1074 ◽  
Author(s):  
D. Eberbeck ◽  
A. Lange ◽  
M. Hentschel
Keyword(s):  
Magnetic Nanoparticles ◽  
Radial Distance ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Core Diameter ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Dilute Suspensions ◽  
Shell Particles ◽  
Core Shell Nanoparticles

Different very dilute suspensions of magnetic nanoparticles (magnetite surrounded by an organic shell) in water (ferrofluids) were investigated using small-angle X-ray scattering. It is shown that the scattering originates not only from noncorrelated core–shell nanoparticles, but also from larger structures. By modelling, these structures can be identified as close-packed clusters consisting of core–shell particles (core diameter ∼10 nm). The analysis of the radial distance distribution function, obtained by Fourier transformation of the scattered intensity, reveals a lower bound of the mean cluster size of about 40 nm. The formation of clusters is persistent, even in very dilute suspensions.

Monodisperse Fe3O4/Fe Core/Shell Nanoparticles with Enhanced Magnetic Property

2011 ◽  
Vol 306-307 ◽  
pp. 410-415
Author(s):  
Li Sun ◽  
Fu Tian Liu ◽  
Qi Hui Jiang ◽  
Xiu Xiu Chen ◽  
Ping Yang
Keyword(s):  
Average Diameter ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
Core Shell ◽  
X Ray Diffraction ◽  
Shell Nanoparticles ◽  
X Ray ◽  
Transmission Electron ◽  
Shell Particles ◽  
Core Shell Nanoparticles

Core/shell type nanoparticles with an average diameter of 20nm were synthesized by chemical precipitation method. Firstly, Monodisperse Fe3O4 nanoparticles were synthesized by solvethermal method. FeSO4ž7H2O and NaBH4 were respectively dissolved in distilled water, then moderated Fe3O4 particles and surfactant(PVP) were ultrasonic dispersed into the FeSO4ž7H2O solution. The resulting solution was stirred 2 h at room temperature. Fe could be deposited on the surface of monodispersed Fe3O4 nanoparticles to form core-shell particles. The particles were characterized by using various experimental techniques, such as transmission electron microscopy (TEM), X-ray diffraction (XRD), AGM and DTA. The results suggest that the saturation magnetization of the nanocomposites is 100 emu/g. The composition of the samples show monodisperse and the sides of the core/shell nanoparticles are 20-30nm. It is noted that the formation of Fe3O4/Fe nanocomposites magnetite nanoparticles possess superparamagnetic property.

Preparation of Silica/Polymer Hybrid Nanoparticles via a Semi-Continuous Soup-Free Emulsion Polymerization

2015 ◽  
Vol 1120-1121 ◽  
pp. 233-242
Author(s):  
Joshua Qing Song Li ◽  
Hai Wang ◽  
Yan Qiu Wang
Keyword(s):  
Emulsion Polymerization ◽  
Early Stage ◽  
Size Exclusion ◽  
Hybrid Nanoparticles ◽  
Core Shell ◽  
Particle Coagulation ◽  
Shell Nanoparticles ◽  
Sem Images ◽  
Spectra Analysis ◽  
Polymer Hybrid

Hybrid nanoparticles were prepared by direct polymerization of methyl methacrylate, vinyl acetate, and styrene monomers onto the unmodified hydrophilic surfaces of 33 nm silica nanoparticles in a semi-continuous soap-free emulsion polymerization at a monomer starved condition. The polymerization was initiated by potassium persulfate with constant monomer feed at 0.01, 0.02, or 0.04 mL/min. The growth of the core-shell nanoparticles were measured by a laser particle size analyzer. FT-IR spectra analysis confirmed the hybrid structures of the synthesized nanoparticles. SEM images and size exclusion chromatography (SEC) results indicated regular core-shell microsphere structures. The hybrid nanoparticles increased in monodispersity and size over 100 nm with the reaction. However, SiO2/polystyrene (PS) nanoparticles grew much faster compared with SiO2/polymethyl methacrylate (PMMA) and SiO2/polyvinyl acetate (PVAC). There was particle coagulation, about 12 SiO2/PS particles aggregating to one, in the early stage of the seeded process. In addition, PS secondary particles were formed before the particle coagulation, and then merged with the SiO2/PS nanoparticles in the particle coagulation. The formation of SiO2/polymer hybrid nanoparticles depended on the hydrophilic characteristics of the polymer, and the size of silica seeds.

Synthesis and Magnetic Properties of FePt Nanoparticles with Hard Nonmagnetic Shells

2007 ◽  
Vol 7 (1) ◽  
pp. 350-355 ◽  
Author(s):  
Shishou Kang ◽  
Shifan Shi ◽  
G. X. Miao ◽  
Zhiyong Jia ◽  
David E. Nikles ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Crystallographic Orientation ◽  
Sol Gel ◽  
Molar Ratio ◽  
Core Shell ◽  
Fept Nanoparticles ◽  
Shell Nanoparticles ◽  
Spherical Core ◽  
Size And Morphology ◽  
Core Shell Nanoparticles

Chemically synthesized FePt nanoparticles were coated with nonmagnetic SiO2 and MnO shells by sol–gel and polyol processes. TEM images show that the FePt/SiO2 nanoparticles exhibit a thick spherical shell. The size and morphology of the MnO shell can be controlled by changing the reaction temperature, the molar ratio of surfactants/Mn(acac)2, and/or the concentration of precursor. The morphology of the MnO shell can be either spherical-like or cubic-like, depending on whether the molar ratio of surfactants/Mn(acac)2 is less than or larger than 2. From XRD measurements, the spherical core/shell nanoparticles exhibit 3D random crystallographic orientation, while the cubic core/shell nanoparticles prefer (200) texture. The magnetic moment of FePt particles can be enhanced by coating with SiO2 and MnO shells. Furthermore, the agglomeration of FePt particles upon the thermal annealing can be significantly inhibited with SiO2 and MnO shells.

Sol-gel Synthesis and Characterization of Zn[sub 2]SiO[sub 4]:Mn@SiO[sub 2] Spherical Core-Shell Particles

2005 ◽  
Vol 152 (9) ◽  
pp. H146 ◽  
Author(s):  
D. Y. Kong ◽  
M. Yu ◽  
C. K. Lin ◽  
X. M. Liu ◽  
J. Lin ◽  
...  
Keyword(s):  
Sol Gel ◽  
Synthesis And Characterization ◽  
Core Shell ◽  
Spherical Core ◽  
Shell Particles ◽  
Sol Gel Synthesis

Synchrotron Radiation X-ray Photoelectron Spectroscopy as a Tool To Resolve the Dimensions of Spherical Core/Shell Nanoparticles

2014 ◽  
Vol 118 (46) ◽  
pp. 26621-26628 ◽  
Author(s):  
Won Hui Doh ◽  
Vasiliki Papaefthimiou ◽  
Thierry Dintzer ◽  
Véronique Dupuis ◽  
Spyridon Zafeiratos
Keyword(s):  
Synchrotron Radiation ◽  
Photoelectron Spectroscopy ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
X Ray ◽  
Spherical Core ◽  
Core Shell Nanoparticles

scholarly journals Self-Assembly of Pluronic F127—Silica Spherical Core–Shell Nanoparticles in Cubic Close-Packed Structures

2015 ◽  
Vol 27 (15) ◽  
pp. 5161-5169 ◽  
Author(s):  
Stef Kerkhofs ◽  
Tom Willhammar ◽  
Heleen Van Den Noortgate ◽  
Christine E. A. Kirschhock ◽  
Eric Breynaert ◽  
...  
Keyword(s):  
Self Assembly ◽  
Pluronic F127 ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Spherical Core ◽  
Core Shell Nanoparticles

scholarly journals Building effective core/shell polymer nanoparticles for epoxy composite toughening based on Hansen solubility parameters

2021 ◽  
Vol 10 (1) ◽  
pp. 1183-1196
Author(s):  
Na Ning ◽  
Yiping Qiu ◽  
Yi Wei
Keyword(s):  
Interfacial Interaction ◽  
Solubility Parameters ◽  
Core Shell ◽  
Hansen Solubility Parameters ◽  
Shell Nanoparticles ◽  
Shell Particle ◽  
Uniform Dispersion ◽  
Shell Particles ◽  
Core Shell Nanoparticles ◽  
Hansen Solubility

Abstract Particles have been demonstrated to toughen epoxy resins, especially for fiber-reinforced epoxy composites, and core/shell particles are one of them. It is known that not all particles toughen the same but most evaluations are through experimentation, and few studies have been conducted to accurately predict the particles’ toughening effect or guide the design of effective particles. In this study, efforts were made to find the control factors of core/shell particles, primarily interfacial compatibility and degree of dispersion, and how to predict them. Nanocomposites were fabricated by incorporating core/shell nanoparticles having various shell polymer compositions, especially their polarities. Their compatibility was estimated using a novel quantitative approach via adopting the theory of Hansen solubility parameters (HSP), in which the HSP of core/shell nanoparticles and the epoxy matrix were experimentally determined and compared. It was found that the HSP distance was a good predictor for particle dispersion and interfacial interaction. Particles having a small HSP distance (R a) to the epoxy resin, represented by the polybutylacrylate core/polymethyl methacrylate shell particle having the smallest R a of 0.50, indicated a uniform dispersion and strong interfacial bonding with the matrix and yielded outstanding toughening performance. In contrast, polybutylacrylate core/polyacrylonitrile shell particle having the largest HSP distance (6.56) formed aggregates and exhibited low interfacial interaction, leading to poor toughness. It was also demonstrated that HSP can provide an effective strategy to facilitate the design of effective core/shell nanoparticles for epoxy toughening.

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