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Trapping Iron Oxide into Hollow Gold Nanoparticles

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ABSTRACT

Synthesis of the core/shell-structured Fe3O4/Au nanoparticles by trapping Fe3O4 inside hollow Au nanoparticles is described. The produced composite nanoparticles are strongly magnetic with their surface plasmon resonance peaks in the near infrared region (wavelength from 700 to 800 nm), combining desirable magnetic and plasmonic properties into one nanoparticle. They are particularly suitable for in vivo diagnostic and therapeutic applications. The intact Au surface provides convenient anchorage sites for attachment of targeting molecules, and the particles can be activated by both near infrared lights and magnetic fields. As more and more hollow nanoparticles become available, this synthetic method would find general applications in the fabrication of core–shell multifunctional nanostructures.

No MeSH data available.


The plasmonic and magnetic properties of the Fe3O4-loaded PHAuNPs. a Appearance of a bottle of particle water suspension. The particles can be dragged toward a permanent magnet. b Absorption spectrum of the particle water suspension, showing a broad peak centering at 750 nm. c Hysteresis loop of dried particle powder, showing that the suspension consists of a mixture of superparamagnetic and ferromagnetic nanoparticles.
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Figure 4: The plasmonic and magnetic properties of the Fe3O4-loaded PHAuNPs. a Appearance of a bottle of particle water suspension. The particles can be dragged toward a permanent magnet. b Absorption spectrum of the particle water suspension, showing a broad peak centering at 750 nm. c Hysteresis loop of dried particle powder, showing that the suspension consists of a mixture of superparamagnetic and ferromagnetic nanoparticles.

Mentions: Shown in Figure 4a is the appearance of a bottle of particle water suspension. The cyan color indicates that the suspension absorbs red light. The absorption spectrum is shown in Figure 4b, which has a broad peak centering at 750 nm. This absorption peak corresponds to the SPR wavelength. Compared to PHAuNPs before loading iron oxide, the absorption spectrum shows little change. For core/shell nanoparticles, it is well known that the SPR wavelength is dependent on the refractive indices of medium, shell and core. Changing core material usually causes a shift of the SPR wavelength. However, PHAuNPs have a relatively thick shell (>20 nm). Through a three-dimensional finite difference time domain (FDTD) simulation (using a commercial software from Lumerical Inc), we have proved that at this thickness, the red-shifts of SPR peaks are mainly caused by their surface roughness, and the hollow nature of these particles plays only a minor role [17]. The simulation results show that SPR peaks for hollow particles are only slightly red-shifted compared to solid particles with the same outer diameter (100 nm). For particles with a roughness of 5 nm, SPR peak shifts to longer wavelength (~630 nm). As the roughness increases to 8 nm which is the average grain size in the shell, a much greater red-shift (to 720 nm) is observed. This roughness effect is due to the strong interaction of electric fields from adjacent bumps on the surface, similar to the plasmonic properties of the aggregates of several nanoparticles. The simulated results are in good agreement with experimental results. This unique SPR tuning mechanism makes it possible to maintain the optical properties of PHAuNPs even after the loading of iron oxide.


Trapping Iron Oxide into Hollow Gold Nanoparticles
The plasmonic and magnetic properties of the Fe3O4-loaded PHAuNPs. a Appearance of a bottle of particle water suspension. The particles can be dragged toward a permanent magnet. b Absorption spectrum of the particle water suspension, showing a broad peak centering at 750 nm. c Hysteresis loop of dried particle powder, showing that the suspension consists of a mixture of superparamagnetic and ferromagnetic nanoparticles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211847&req=5

Figure 4: The plasmonic and magnetic properties of the Fe3O4-loaded PHAuNPs. a Appearance of a bottle of particle water suspension. The particles can be dragged toward a permanent magnet. b Absorption spectrum of the particle water suspension, showing a broad peak centering at 750 nm. c Hysteresis loop of dried particle powder, showing that the suspension consists of a mixture of superparamagnetic and ferromagnetic nanoparticles.
Mentions: Shown in Figure 4a is the appearance of a bottle of particle water suspension. The cyan color indicates that the suspension absorbs red light. The absorption spectrum is shown in Figure 4b, which has a broad peak centering at 750 nm. This absorption peak corresponds to the SPR wavelength. Compared to PHAuNPs before loading iron oxide, the absorption spectrum shows little change. For core/shell nanoparticles, it is well known that the SPR wavelength is dependent on the refractive indices of medium, shell and core. Changing core material usually causes a shift of the SPR wavelength. However, PHAuNPs have a relatively thick shell (>20 nm). Through a three-dimensional finite difference time domain (FDTD) simulation (using a commercial software from Lumerical Inc), we have proved that at this thickness, the red-shifts of SPR peaks are mainly caused by their surface roughness, and the hollow nature of these particles plays only a minor role [17]. The simulation results show that SPR peaks for hollow particles are only slightly red-shifted compared to solid particles with the same outer diameter (100 nm). For particles with a roughness of 5 nm, SPR peak shifts to longer wavelength (~630 nm). As the roughness increases to 8 nm which is the average grain size in the shell, a much greater red-shift (to 720 nm) is observed. This roughness effect is due to the strong interaction of electric fields from adjacent bumps on the surface, similar to the plasmonic properties of the aggregates of several nanoparticles. The simulated results are in good agreement with experimental results. This unique SPR tuning mechanism makes it possible to maintain the optical properties of PHAuNPs even after the loading of iron oxide.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Synthesis of the core/shell-structured Fe3O4/Au nanoparticles by trapping Fe3O4 inside hollow Au nanoparticles is described. The produced composite nanoparticles are strongly magnetic with their surface plasmon resonance peaks in the near infrared region (wavelength from 700 to 800 nm), combining desirable magnetic and plasmonic properties into one nanoparticle. They are particularly suitable for in vivo diagnostic and therapeutic applications. The intact Au surface provides convenient anchorage sites for attachment of targeting molecules, and the particles can be activated by both near infrared lights and magnetic fields. As more and more hollow nanoparticles become available, this synthetic method would find general applications in the fabrication of core–shell multifunctional nanostructures.

No MeSH data available.