Synthesis of lead chalcogenide nanoparticles in block copolymer micelles: investigation of optical properties and fabrication of 2-D arrays of nanoparticles

Narrow band gap PbS and PbSe semiconductor nanocrystals were prepared in the poly(4-vinyl pyridine) core of self assembled polystyrene-block-poly(4-vinyl pyridine) copolymer micelles in toluene at room temperature, and characterized by high resolution-transmission electron microscopy and X-ray diffractograms. Optical absorption and photoluminescence (PL) studies of the nanocrystals showed the quantized phenomena. The PL intensity of the PbSe nanocrystals was strongly enhanced, with a slight red shift in the peak position, by treating with aqueous Na2S solution. Interestingly, the inclusion of ZnS amorphous nanoparticles into the P4VP/PbSe core leads to a large red shift in the peak position, which covers the technologically important range (1.3 to 1.55 mu m), with strong enhancement of the emission intensity. We fabricated a monolayer thin film of PbSe nanocrystals by spin coating on a silicon wafer, and it showed similar PL behavior to that in solution.