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0959-M03-03

Synthesis of Water Soluble PbSe Quantum Dots Lioz Etgar1, Efrat Lifshitz2, and Rina Tannenbaum3,4 1 Nanoscience and Nanotechnology, Technion, Israel Institute of Technology, Haifa, 32000, Israel 2 Chemistry, Technion, Israel Institute of Technology, Haifa, 32000, Israel 3 Chemical Engineering, Technion, Israel Institute of Technology, Haifa, 32000, Israel 4 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332 ABSTRACT Water-soluble PbSe semiconductor quantum dots (QDs) with near-infrared absorption of 1100-2520 nm (corresponding to a diameter of 3-13 nm) were synthesized using 2-aminoethanthiol. The oleic acid stabilizing ligands used in the traditional synthesis of PbSe were exchanged with the 2-aminoethanethiol (AET) ligands, which promoted the solubilization of the QDs in an aqueous medium. This occurred due to the attraction of the surrounding water molecules to the exposed amino-group, thus allowing the particles to reside in the water environment. The water-soluble PbSe QDs have very narrow size distribution (σ ≈ 4.5-5.5%). Transmission electron microscopy (TEM), spectrophotometric measurements, and Fourier transform infrared (FTIR) spectroscopy indicate that the morphology, size, size distribution and chemical composition of the PbSe QDs remained unchanged during the transfer to an aqueous medium. In conclusion, the ability to synthesize water soluble PbSe QDs with stable properties and uniform size distribution will allow them to have substantial advantages for biological applications such as biosensors and drug delivery. INTRODUCTION The synthesis and use of nanoparticles constitute a major research area that attracts both academic and industrial interest1, 2. Due to quantum confinement effects, semiconductor nanocrystals (NCs) exhibit special physical and chemical properties which are greatly different from those of their corresponding bulk materials3,4,5,6. Over the past two decades, great efforts have been put into the synthesis of highly fluorescent II-VI semiconductor nanocrystals7,8,9,10. One of the multitude of synthesis methods, the TOP/TOPO (TOPO = trioctylphosphine oxide) synthetic approach has become one of the most successful and mature methods for preparing highly fluorescent II-VI NCs to date7,8. However, the direct product of the TOP/TOPO synthetic approach is insoluble in water, which to some extent limits applications of TOP-stabilized NCs as bio-labeling materials11. Many applications require these particles to be water-dispersible and to remain suspended in water with no loss of physical or chemical properties over extended periods of time2. Hence, to overcome this difficulty, the main strategy employed here is to replace the surface binding TOP with molecules that have either strong polar groups such as 2-aminoethanthiol (AET).

Unfortunately, water-based syntheses of nanoparticles are fraught with problems as a result of ionic interactions, which are typically overcome by using low reactant concentrations (about 5·10-4 M) 12, or