Fabrication of In 2 O 3 Oxide Semiconductor Nano-Particles Using Apoferritin
- PDF / 139,617 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 44 Downloads / 198 Views
K3.13.1
Fabrication of In2O3 oxide semiconductor nano-particles using apoferritin Mitsuhiro OKUDA, Ichiro YAMASHITA, Kenji IWAHORI1 and Hideyuki YOSHIMURA2 Advanced Technology Research Laboratories, Matsushita Electric Industrial Co., Ltd., Hikaridai, Seika, Kyoto 619-0237 1 CREST, Japan Science and Technology Agency, Honcho 4-1-8, Kawaguchi 332-0012 2 Meiji University, Higashimita 1-1-1, Tama Kawasaki Kanagawa 214-8571 ABSTRACT In2O3 nanoparticles were fabricated in the cavity of the cage-shaped protein, apoferritin by utilizing a quick chemical reaction of indium oxide. Horse spleen apoferritin in the solution of indium ions buffered at pH 9.5 was incubated for 30 minutes. The transmission electron microscopy (TEM) observation with aurothioglucose staining showed that cores were formed in the apoferritin cavity. The sizes of cores were regulated by the cavity size and their diameters were below 7nm. Energy dispersion X-ray analysis (EDX) indicated that indium was contained in the cores. The high-resolution TEM (HR-TEM) revealed that cores are single or poly crystalline and the lattice space was consistent with that of In2O3. These results confirmed that the In2O3 cores were successfully formed in the apoferritin cavity.
INTRODUCTION Inorganic materials of nanometer order attract researchers’ attention from application point of view. Many methods for fabricating nano-inorganic materials, especially nanoparticles (NPs) were developed including physical and chemical methods. It is also attracting researchers’ interest for nano-inorganic materials to be ordered as two-dimensional crystal as a first step to make nanometric functional structures [1,2]. Based on such context, we propose biological method to synthesize nano-inorganic materials and make two- or three-dimensional crystal of them on flat substrate [3]. Ferritin is a spherical protein with a diameter of 12 nm. It has a cavity, 7 nm in diameter, surrounded by 24 polypeptide subunits (Figure 1). It is known that there are eight hydrophilic channels which penetrate the protein shell and are considered to be the pathways of Fe(II). Natural apoferritins consists of two types of polypeptide subunits, H- and L-subunit, the relative ratio of which varies with the type of biological species and organ. The H-subunit has a “ferroxidase” catalytic site at the interior of subunit where Fe(II) is oxidized to Fe(III), whereas the L-subunit shows no ferroxidase activity. Under physiological conditions, apoferritin stores iron in the cavity as ferrihydrite (5Fe2O3·9H2O) [4]. Artificial biomineralization of some other materials in the cavity were also reported [5-12]. Here we report that Horse spleen (Natural) apoferritin can accumulate nanosize In2O3 in the cavity.
K3.13.2
a
b Fe3+ or In3+
12nm
6nm
Figure 1. (a) The schematic drawing of the ferritin viewed down from three fold axis. (b) The cross section of apoferritin and the supposed way of iron or indium nanoparticle formation in ferritin. EXPERIMENTAL DETAILS The indium cores are formed in the apoferritin cavitie
Data Loading...
