### Session APS2: APS II - Condensed Matter and Nanomaterials

3:30 PM–5:42 PM, Friday, March 23, 2007
Foster Science Building Room: 458

Chair: Tikhon Bykov, McMurry University

Abstract ID: BAPS.2007.TSS07.APS2.7

### Abstract: APS2.00007 : Structural and Magnetic Characterizations of Gold and Silica Doubly Coated $\gamma$-Fe$_{2}$O$_{3}$ Nanoparticles

4:42 PM–4:54 PM

Preview Abstract MathJax On | Off   Abstract

#### Authors:

Gan Liang
(Sam Houston State University)

Keeseong Park
(University of Texas at Austin)

John Markert
(University of Texas at Austin)

Zhi-Ping Luo
(Texas A\&M University)

Mark Croft
(Rutgers University)

Xiaojun Ji
(University of Texas M.D. Anderson Cancer Center)

Chun Li
(University of Texas M.D. Anderson Cancer Center)

An extensive structural and magnetic characterization has been carried out on the gold (Au) and silica (SiO$_{2})$ doubly coated $\gamma$-Fe$_{2}$O$_{3}$ nanoparticles. The phase of the uncoated and Au/SiO$_{2}$ coated nanoparticles were studied by powder x-ray diffraction (XRD) and x-tray absorption spectroscopy (XAS), which show that the iron oxide particles before and after coating have the phase of $\gamma$-Fe$_{2}$O$_{3. }$The transmission electron microscopy (TEM) results indicate that the average sizes of the $\gamma$-Fe$_{2}$O$_{3.}$cores, the Au/SiO$_{2}$ coated Fe$_{2}$O$_{3 }$ nanoparticles, and the Au nanoparticles in the Au nanoshells are about 12 nm, 92 nm, and 7 nm, respectively. We have the following observations from the magnetization measurements: (i) both the uncoated and coated nanoparticles are superparamagnetic at room temperature (T), and the Au nanoparticles are diamagnetic at all temperatures, (ii) the blocking temperature is decreased by the Au/SiO$_{2}$ double coating, and (iii) the coercivity for both the uncoated and coated nanoparticles decreases almost linearly with T$^{ \raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} }$ with the latter decreasing faster than the former.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.TSS07.APS2.7