Nanotech 2010

Increasing PbSe Optical Stability Through Shell Formation

Y. Zhang, Q. Dai, W.W. Yu
Worcester Polytechnic Institute, US

Keywords: PbSe, nanocrystal


Infrared-emitting semiconductor nanocrystals (NCs) are of increasing interest in potential applications such as telecommunication, photoelectronic device, and biomedical labeling. Lead chalcogenide NCs, especially PbSe, provide strong confinement effect and high quantum yield in a wide spectral range of near infrared. However, the applications of PbSe NCs have been limited by their instability of optical properties under ambient conditions. Therefore, several approaches have been developed to stabilize it. PbSe/PbS and PbSe/SiO2 core/shell structures have been developed but with excessive loss of quantum yield. Hollingsworth group has developed an ion exchange method using Cd to replace Pb in outlayer of large PbSe plain NCs to form PbSe/CdSe core/shell structures. The limitation of this method is that it is difficult to growth thick CdSe layer and it damages lattice structure of PbSe NCs. In our lab, the successive ion layer adsorption and reaction was employed to form the air-stable PbSe/CdSe NCs. The thickness of the CdSe layer could be well controlled. The nanocrystal surface was treated with a small amount of sodium borohydride in hexanes at room temperature. After the surface treatment, the PbSe/CdSe NCs showed higher quantum yield than the PbSe plain core. Further, these NCs could also be covered with another ZnSe shells and became biocompatible optical labels for near infrared wavelength.
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