Protein-conjugated PbS nanocrystals with the average sizes of 15, 25, and 35 nm have been synthesized by adjusting the concentration of the bovine serum albumin (BSA) solution at room temperature. The obtained BSA-conjugated PbS nanoparticles have been characterized by powder X-ray diffraction, transmission electron microscopy, selected-area electron diffraction, high-resolution transmission electron microscopy, thermal analyses and photoluminescence. The quantum-confined effect of the BSA-conjugated PbS nanoparticles has been confirmed by the UV-vis spectra. The results indicated that the BSA not only induced the nucleation, but inhibited the further growth of PbS nanocrystals. The effect of Pb2+ on BSA and the change of BSA conformation were studied through Fourier transform infrared spectroscopy and circular dichroism spectroscopy. The possible mechanism of BSA-conjugated PbS nanoparticles growth was also discussed. (C) 2009 Elsevier B.V. All rights reserved.