Enhanced Magnetic Transition of Core-Shell Cobalt-Platinum Nanoalloys

2002 ◽  
Vol 721 ◽  
Author(s):  
Jong-Il Park ◽  
aNam-Jung Kang ◽  
Sang-Min Lee ◽  
Sehun Kim ◽  
S. J. Oh ◽  
...  
Keyword(s):  
Solid Solution ◽  
Room Temperature ◽  
Magnetic Transition ◽  
Information Storage ◽  
Core Shell ◽  
Magnetic Alloys ◽  
Shell Nanoparticles ◽  
General Process ◽  
Face Centered ◽  
Core Shell Nanoparticles

AbstractSynthesis of ‘solid solution’ and ‘core-shell’ types of well defined Co-Pt based nanoalloys smaller than 10nm have been achieved by redox transmetalation reactions. This redox transmetalation are selectively observed only if the redox potential between two metals is favorable. The composition of the magnetic alloys can also be tuned by adjusting the ratio of reactants. Annealed core-shell nanoparticles transformed into mixed nanoalloys with face centered tetragonal (fct) structures, which show large coercivity and ferromagnetism at room temperature. These nanoparticles can potentially be used as an independent single magnetic bit of tera-bit information storage. Also, this kind of redox transmetalation reaction can be utilized as a general process to synthesize various types of nanoalloys with controlled composition in a selective fashion.

scholarly journals Superparamagnetic Fe/Au Nanoparticles and Their Feasibility for Magnetic Hyperthermia

2021 ◽  
Vol 11 (14) ◽  
pp. 6637
Author(s):  
Mohamed F. Sanad ◽  
Bianca P. Meneses-Brassea ◽  
Dawn S. Blazer ◽  
Shirin Pourmiri ◽  
George C. Hadjipanayis ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hysteresis Loops ◽  
Magnetic Hyperthermia ◽  
Core Shell ◽  
Face Centered Cubic ◽  
Shell Nanoparticles ◽  
Face Centered ◽  
Shell Particles ◽  
Core Shell Nanoparticles ◽  
Alternating Magnetic Fields

Today, magnetic hyperthermia constitutes a complementary way to cancer treatment. This article reports a promising aspect of magnetic hyperthermia addressing superparamagnetic and highly Fe/Au core-shell nanoparticles. Those nanoparticles were prepared using a wet chemical approach at room temperature. We found that the as-synthesized core shells assembled with spherical morphology, including face-centered-cubic Fe cores coated and Au shells. The high-resolution transmission microscope images (HRTEM) revealed the formation of Fe/Au core/shell nanoparticles. The magnetic properties of the samples showed hysteresis loops with coercivity (HC) close to zero, revealing superparamagnetic-like behavior at room temperature. The saturation magnetization (MS) has the value of 165 emu/g for the as-synthesized sample with a Fe:Au ratio of 2:1. We also studied the feasibility of those core-shell particles for magnetic hyperthermia using different frequencies and different applied alternating magnetic fields. The Fe/Au core-shell nanoparticles achieved a specific absorption rate of 50 W/g under applied alternating magnetic field with amplitude 400 Oe and 304 kHz frequency. Based on our findings, the samples can be used as a promising candidate for magnetic hyperthermia for cancer therapy.

Highly active and stable Au@CuxO core–shell nanoparticles supported on alumina for carbon monoxide oxidation at low temperature

RSC Advances ◽  
2016 ◽  
Vol 6 (79) ◽  
pp. 75126-75132 ◽  
Author(s):  
Weining Zhang ◽  
Qingguo Zhao ◽  
Xiaohong Wang ◽  
Xiaoxia Yan ◽  
Sheng Han ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Low Temperature ◽  
Co Oxidation ◽  
Room Temperature ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Highly Active ◽  
Co Conversion ◽  
Core Shell Nanoparticles

Au@CuxO core–shell nanoparticles and Au@CuxO/Al2O3 used for CO oxidation at low temperature are prepared. CO conversion on Au@CuxO/Al2O3 can reach to 38% at room temperature and the catalytic activity remains unchanged after 108 hours reaction.

A BIO-INSPIRED POLYDOPAMINE APPROACH TO PREPARATION OF GOLD-COATED Fe3O4 CORE–SHELL NANOPARTICLES: SYNTHESIS, CHARACTERIZATION AND MECHANISM

NANO ◽  
2013 ◽  
Vol 08 (06) ◽  
pp. 1350061 ◽  
Author(s):  
PENG AN ◽  
FANG ZUO ◽  
XINHUA LI ◽  
YUANPENG WU ◽  
JUNHUA ZHANG ◽  
...  
Keyword(s):  
Shell Structure ◽  
Room Temperature ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Stabilizing Agent ◽  
X Ray ◽  
Transmission Electron ◽  
Core Shell Structure ◽  
Core Shell Nanoparticles

A biomimetic and facile approach for integrating Fe 3 O 4 and Au with polydopamine (PDA) was proposed to construct gold-coated Fe 3 O 4 nanoparticles ( Fe 3 O 4@ Au – PDA ) with a core–shell structure by coupling in situ reduction with a seed-mediated method in aqueous solution at room temperature. The morphology, structure and composition of the core–shell structured Fe 3 O 4@ Au – PDA nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectrometry (XPS). The formation process of Au shell was assessed using a UV-Vis spectrophotometer. More importantly, according to investigating changes in PDA molecules by Fourier transform infrared spectroscopy (FTIR) and in preparation process of the zeta-potential data of nanoparticles, the mechanism of core–shell structure formation was proposed. Firstly, PDA-coated Fe 3 O 4 are obtained using dopamine (DA) self-polymerization to form thin and surface-adherent PDA films onto the surface of a Fe 3 O 4 "core". Then, Au seeds are attached on the surface of PDA-coated Fe 3 O 4 via electrostatic interaction in order to serve as nucleation centers catalyzing the reduction of Au 3+ to Au 0 by the catechol groups in PDA. Accompanied by the deposition of Au , PDA films transfer from the surface of Fe 3 O 4 to that of Au as stabilizing agent. In order to confirm the reasonableness of this mechanism, two verification experiments were conducted. The presence of PDA on the surface of Fe 3 O 4@ Au – PDA nanoparticles was confirmed by the finding that glycine or ethylenediamine could be grafted onto Fe 3 O 4@ Au – PDA nanoparticles through Schiff base reaction. In addition, Fe 3 O 4@ Au – DA nanoparticles, in which DA was substituted for PDA, were prepared using the same method as that for Fe 3 O 4@ Au – PDA nanoparticles and characterized by UV-Vis, TEM and FTIR. The results validated that DA possesses multiple functions of attaching Au seeds as well as acting as both reductant and stabilizing agent, the same functions as those of PDA.

Synthesis and Magnetic Properties of FePt /Silica Core-Shell Nanoparticles

2010 ◽  
Vol 178 ◽  
pp. 291-295 ◽  
Author(s):  
Cui Xia Li ◽  
Zhi Hong Li ◽  
Xue Yan Du ◽  
Hai Xia Guo
Keyword(s):  
Magnetic Properties ◽  
Reverse Micelles ◽  
Core Shell ◽  
Fept Nanoparticles ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Shell Nanoparticles ◽  
Transmission Electron ◽  
Face Centered ◽  
Core Shell Nanoparticles

FePt nanoparticles (NPS), ~2nm in diameter, were synthesized and then coated with silica (SiO2) shells ~1.5nm-thick using reverse micelles as nanoreactors. The silica-coated FePt core–shell (FePt @silica) NPS were characterized by direct techniques of transmission electron microscopy (TEM). The results showed that the silica shells prevented the aggregation in liquid comparing to their bare counterparts. The as-synthesized FePt@SiO2 NPS exhibited essential characteristics of superparamagnetic behavior, as investigated by a vibrating sample magnetometer (VSM). X-ray diffraction (XRD) studies proved that the annealing at 700 °C for 30min under argon atmosphere caused the crystal structure of FePt core to transform from disordered face centered cubic (fcc) to the chemically ordered L10 FePt with face-centered tetragonal (fct) structure. This phase transition caused the change of magnetic properties of the FePt@SiO2 particles from superparamagnetism to ferromagnetism.

scholarly journals Seed-mediated growth of MOF-encapsulated Pd@Ag core–shell nanoparticles: toward advanced room temperature nanocatalysts

2016 ◽  
Vol 7 (1) ◽  
pp. 228-233 ◽  
Author(s):  
Liyu Chen ◽  
Binbin Huang ◽  
Xuan Qiu ◽  
Xi Wang ◽  
Rafael Luque ◽  
...  
Keyword(s):  
Ag Nanoparticles ◽  
Room Temperature ◽  
Catalytic Performance ◽  
Reducing Agent ◽  
Growth Strategy ◽  
Core Shell ◽  
Hydrogen Atoms ◽  
Shell Nanoparticles ◽  
Seed Mediated ◽  
Core Shell Nanoparticles

Core–shell Pd@Ag nanoparticles are formed within the pores of MOFs via a seed mediated growth strategy with activated hydrogen atoms as the reducing agent, leading to a family of bimetallic core–shell MOF nanomaterials with excelling catalytic performance in room temperature reactions.

Self-Assembled Core-Shell Fe3O4@SiO2 Nanoparticles with High Magnetic Sensitivity from Electrospun Fibers

2014 ◽  
Vol 1033-1034 ◽  
pp. 1068-1071
Author(s):  
Li Qiang Tian ◽  
Pei Pei Zhang
Keyword(s):  
Self Assembly ◽  
Cetyltrimethylammonium Bromide ◽  
Room Temperature ◽  
Electrospinning Process ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Practical Applications ◽  
Magnetic Sensitivity ◽  
Core Shell Nanoparticles ◽  
Superparamagnetic Properties

Nanofibers composed of the hydrophilic polymer polyvinylpyrrolidone K90 (PVP), cetyltrimethylammonium bromide (CTAB), tetraethyl orthosilicate (TEOS) and Fe3O4were fabricated using an electrospinning process. As a result of the templating and confinement properties of the nanfibers, silica coated magnetite (Fe3O4@SiO2) core-shell nanoparticles (NPs) with high magnetic sensitivity were spontaneously formed through molecular self-assembly when the fibers were added to 80% aqueous ethanol (PH=9.0). The typical saturation magnetization of the Fe3O4@SiO2composite particles is up to 43.8 emu/g, with superparamagnetic properties being observed at room temperature. Since the nanoparticles have high magnetic sensitivity and are preparedviaa facile and convenient strategy, they have much promise in a range of practical applications.

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