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Nano-particles (NPs) have been attracting researchers' interest because of their potential to be used as nanotechnology key component. Various NPs are used or expect to be used in many applications such as magnetic recording materials, catalytic materials, fluorescent markers, drug delivery systems, and quantum electronics. A lot of methods to produce NPs have been studied including physical methods, chemical method and biological methods. Recently, a biological method using protein cages as the bio-template has become used for the uniform synthesis of metal and semiconductor NPs. We have adopted two kinds of cage-shaped protein, apoferritin from horse spleen (HsAfr) and Dps (DNA binding protein from starved cells) from Listeria innocua (LiDps) to synthesize metal oxide or semiconductor NPs for some electronics devices. Apoferritin, the cellular iron-storage protein, is a spherical hollow shell composed of 24 polypeptide subunits. The inner and outer diameters of the protein shell are about 7 nm and 12 nm respectively. LiDps is composed of 12 polypeptide subunits. The inner and outer diameters of the protein shell are about 5 nm and 9 nm. Recently, semiconductor NPs are anticipated to be good quantum nano-electronics device components. The electron energy levels of semiconductor NPs are strongly dependent on the NP size. Our method using protein cages is the most suitable to synthesize uniform NPs, because inner cavity of protein-shell restricts the growth of NPs. Therefore, we have designed a slow chemical reaction system that the cadmium ions were stabilized by the excess ammonium ions for CdS NPs synthesis. We report the successful synthesis of two kinds of homogeneous CdS semiconductor NPs with 7 or 5 nm at diameter in the cavities of HsAFr or LiDps and we compare to the characteristics of their NPs. Both structures of synthesized CdS NPs were analyzed by X-ray powder diffraction (XRD) and energy-dispersive spectrometry (EDS), resulting that the both of CdS NPs showed the cubic crystal. In addition, the photo luminescent from synthesized CdS NPs were observed. These CdS NPs with different diameter will be used as quantum dots or fluorescence marker. The possible of biomineralization mechanism of these semiconductor NPs are now under investigate. |