Synthesis and Cytotoxicity of Luminescent InP Quantum Dots Yuxuan Wang 1 , Chai Hoon Quek 2 , Kam W. Leong* 2,3 and Jiye Fang* 1,4 1 Materials Science & Engineering Program, State University of New York at Binghamton, Binghamton, New York 13902 2 Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708 3 Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708 4 Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902 ABSTRACT As a potential biological imaging probe with a long-wavelength of emission, InP quantum dots were prepared via a high-temperature organic solution approach, and successfully transferred into an aqueous system through a ligand-exchange process using various functional surfactants. Photoluminescence and X-ray characterizations confirmed the desired properties of the InP quantum dots. The cytotoxicity of the water-soluble InP quantum dots against phaeochromocytoma PC12 cells as evaluated by the MTS cell viability assay was low relative to a positive control, poly(ethyleneimine). This study suggests a bright potential for this new type of InP quantum dots in bioimaging applications. INTRODUCTION Semiconductor quantum dots (QDs) attract great attention due to their unique size- dependent optical properties and many possible applications such as LED and lasers [1-5]. Recently, QDs are increasingly being used as a new class of luminescence probes for biological detection and labeling. For in vivo imaging applications, the QDs should ideally emit in the long wavelength region to minimize background interference. However, the frequently used II-VI CdSe and CdTe QDs often exhibit emission properties too close to the optimal biological window of transmission. In addition, toxicity derived from Cd diminishes the potential of these series of QDs in biological applications. As a result, non-cadmium-based QDs have attracted interest from many research groups in recent years. Among III-V semiconductor QDs, InP has become the most extensively studied system [6-10] due to its relative ease of synthesis and appropriate emission region, offering comparable or even better optical properties than CdSe QDs. Moreover, bulk InP generally exhibits low toxicity, and the structural robustness of InP can also confer optical stability [11, 12]. However, toxicity information of InP QDs has been lacking. Another issue is the unavailability of aqueous solution-based synthesis of InP QDs. The latter would require the development of a robust processing by which the high emission efficiency, narrow size- Mater. Res. Soc. Symp. Proc. Vol. 1241 © 2010 Materials Research Society 1241-XX02-04