Lead sulfide (PbS) nanoparticles are currently being investigated as potential candidates for increasing the efficiency of polymeric solar cells. The current, most popular synthesis of PbS nanoparticles ultimately gives a product capped by oleic acid, however the oleic acid is not an ideal ligand for use in solar cell applications due to its length and insulating nature. Therefore, we employ the use of biphasic ligand exchange reactions on the PbS nanoparticles to afford surface-modified nanoparticles. The first biphasic reaction produces the water-soluble 3-mercaptopropane sulfonate (MPS) nanoparticles, and the second biphasic reaction gives a variety of shorter, thiol-capped nanoparticles that are solution processable. Because of the solution stability of the ligand-exchanged particles, they can be characterized through IR, NMR and UV-vis techniques. Both linear and aromatic thiols have been investigated as potentially appropriate ligands for solar devices.
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