MAGNETIC CORE SHELL STRUCTURES: from 0D to 1D assembling

Magnetic ferrite nanoparticles (MFNs) with high heating efficiency are highly desirable for hyperthermia applications. As conventional MFNs usually show low heating efficiency with a lower specific loss power (SLP), extensive efforts to enhance the SLP of MFNs have been made by varying the particle compositions, sizes, and structures. In this study, we attempted to increase the SLP values by creating core-shell structures of MFNs. Accordingly, first we synthesized three different types of core ferrite nanoparticle of magnetite (mag), cobalt ferrite (cf) and zinc cobalt ferrite (zcf). Secondly, we synthesized eight bi-magnetic core-shell structured MFNs; Fe3O4@CoFe2O4 (mag@cf1, mag@cf2), CoFe2O4@Fe3O4 (cf@mag1, cf@mag2), Fe3O4@ZnCoFe2O4 (mag@zcf1, mag@zcf2), and ZnCoFe2O4@Fe3O4 (zcf@mag1, zcf@mag2), using a modified controlled co-precipitation process. SLP values of the prepared core-shell MFNs were investigated with respect to their compositions and core/shell dimensions while varying the applied magnetic field strength. Hyperthermia properties of the prepared core-shell MFNs were further compared to commercial magnetic nanoparticles under the safe limits of magnetic field parameters (<5 × 109 A/(m·s)). As a result, the highest SLP value (379.2 W/gmetal) was obtained for mag@zcf1, with a magnetic field strength of 50 kA/m and frequency of 97 kHz. On the other hand, the lowest SLP value (1.7 W/gmetal) was obtained for cf@mag1, with a magnetic field strength of 40 kA/m and frequency of 97 kHz. We also found that magnetic properties and thickness of the shell play critical roles in heating efficiency and hyperthermia performance. In conclusion, we successfully enhanced the SLP of MFNs by engineering their compositions and dimensions.

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Magnetic Core-Shell to Yolk-Shell Structures in Palladium-Catalyzed Suzuki-Miyaura Reactions: Heterogeneous versus Homogeneous Nature

ChemPlusChem ◽

10.1002/cplu.201600094 ◽

2016 ◽

Vol 81 (6) ◽

pp. 564-573 ◽

Cited By ~ 10

Author(s):

Yinle Li ◽

Zhuqing Zhang ◽

Tao Fan ◽

Xiaoguang Li ◽

Jin Ji ◽

...

Keyword(s):

Magnetic Core ◽

Shell Structures ◽

Core Shell ◽

Palladium Catalyzed

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Magnetic Pt single and double core-shell structures for the catalytic selective hydrogenation of cinnmaladehyde

Pure and Applied Chemistry ◽

10.1515/pac-2018-1227 ◽

2020 ◽

Vol 92 (3) ◽

pp. 413-427 ◽

Cited By ~ 1

Author(s):

Robinson B. Dinamarca ◽

Rodrigo Espinoza-González ◽

Cristian H. Campos ◽

Gina Pecchi

Keyword(s):

Particle Size ◽

Average Particle Size ◽

Pt Nanoparticles ◽

Magnetic Core ◽

Shell Structures ◽

Pt Catalyst ◽

Core Shell ◽

Average Particle ◽

Cinnamyl Alcohol ◽

Metal Support Interaction

AbstractThis study reports the catalytic preparation, characterization, and evaluation of nanoscale core-shell structures with a γ-Fe2O3 core covered by a SiO2 monoshell or by a SiO2@TiO2 multishell as a support for Pt nanoparticles (NPs) to synthesize active and operationally stable catalysts for selective liquid-phase cinnamaldehyde hydrogenation. The structures were designed with a magnetic core so they could be easily recovered from the catalytic bed by simple magnetization and with a SiO2 monoshell or a SiO2@TiO2 multishell to protect the magnetic core. At the same time, this study details the effect of the shell on the catalytic performance. Moreover, the effect of particle size on the selective production of cinnamyl alcohol was studied by preparing two families of catalysts with metal loadings of 1 wt% and 5 wt% Pt with respect to the core-shell. The particle size effect enabled the Fe2O3@SiO2-5%Pt system, with an average particle size of 5.6 nm, to reach 100 % conversion of cinnamaldehyde at 300 min of reaction, producing cinnamyl alcohol with 90 % selectivity; this result differed greatly from that of the Fe2O3@SiO2-1%Pt (dPt = 3.5 nm) system, which reached a maximum conversion at 600 min with 49 % selectivity for the product of interest. However, the Fe2O3@SiO2@TiO2-x%Pt systems showed lower levels of conversion and selectivity compared to those of the Fe2O3@SiO2-x%Pt catalysts, which is attributed to the fact that average metal particle sizes below 5.0 nm were obtained in both cases. After reduction in H2 at 773 K, the Fe2O3@SiO2@TiO2-1%Pt catalyst showed deactivation, reaching 10 % conversion at 600 min of reaction and 60 % selectivity for the product of interest. However, the reduced Fe2O3@SiO2@TiO2-5%Pt system showed 98 % conversion with 95 % selectivity for cinnamyl alcohol at 24 h of operation; the increase in selectivity is attributed to the combined effects of the increase in average particle size (~7.5 nm) and the presence of strong metal-support interaction – SMSI – effects after reduction. Finally, the most selective systems were tested for operational stability, where the Fe2O3@SiO2@-5%Pt catalyst could be reused in three consecutive operating cycles while maintaining its activity and selectivity for cinnamyl alcohol – unlike the Fe2O3@SiO2@TiO2-5%Pt reduced system, which was deactivated after the third reaction cycle due to active phase leaching.

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Editorial (Thematic Issue: Engineered Magnetic Core@Shell Structures)

Current Pharmaceutical Design ◽

10.2174/1381612821999151001143718 ◽

2015 ◽

Vol 21 (37) ◽

pp. 5299-5300 ◽

Cited By ~ 1

Author(s):

Anton Ficai

Keyword(s):

Magnetic Core ◽

Thematic Issue ◽

Shell Structures ◽

Core Shell

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Magnetic Nanoparticles with Core/Shell Structures

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2008.18307 ◽

2008 ◽

Vol 8 (6) ◽

pp. 2781-2792

Author(s):

W. Liu ◽

W. Zhong ◽

Y. W. Du

Keyword(s):

Magnetic Nanoparticles ◽

Self Assembly ◽

Functional Materials ◽

New Physics ◽

Magnetic Core ◽

Shell Structures ◽

Core Shell ◽

Materials Synthesis ◽

Magnetic Shell ◽

And Control

Magnetic nanoparticles with core/shell structures are an important class of functional materials, possessing unique magnetic properties due to their tailored dimensions and compositions. This paper reviews mainly our recent advances in the preparation and characterizations of core/shell structured magnetic materials, focusing in nonmagnetic, antiferromagnetic, or ferro/ferri-magnetic shell coated magnetic core particles. And some of the unique properties of core–shell materials and their self-assembly are presented. Shell layers are shown to serve various functions. A broad demonstration of the successful blend of these types of materials synthesis, microstructural evolution and control, new physics and novel applications that is central to research in this field is presented.

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