Lead sulfide (PbS) nanoparticles capped by dialkyldithiophosphate pyridine were synthesized with the method of ion modification. The nanoparticles were characterized by transmission electron microscope(TEM) and electron diffraction(ED). Results indicated that the DDPPbS nanoparticles were welldistributed with the average diameter of 3 ̄5 nm. The diffraction ring showed that the particles were crystalline of galean. The prepared DDPPbS nanoparticles can be well dispersed in mineral oil and the fourball ...