Films of AOT-capped (AOT = dioctyl sulfosuccinate) lead sulfide nanoparticles (Q-PbS) were prepared by incorporation into a self-assembled monolayer of hexanethiol on Au. The Q-PbS particles showed either cathodic or anodic photocurrents, depending on the existence of a hole scavenger or an electron scavenger in the contacting solution, on the state of the surface, and on the electrode potential. The electrochemistry of Q-PbS indicated that the anodic dissolution of Q-PbS occurred at about 0.25 V vs SCE and was not particle size dependent, while the cathodic corrosion potentials of Q-PbS ranged from -1.1 V vs SCE to beyond the hydrogen evolution potential and depended on the size of the Q-PbS particles.