Excitonic absorption of spherical PbS nanoparticles in zeolite A

We report the optical and structural properties of PbS nanoparticles in zeolite A. The samples were obtained by sulfidation of the Pb2+ ion-exchanged zeolite in a thiourea solution at 50 °C. The optical properties of the samples were studied by diffuse reflectance spectroscopy. Their crystalline structure and morphology were studied by electron diffraction and by transmission and scanning electron microscopy. The results show that the nanoparticles are not inside the zeolite cages but outside, embedded in the zeolite matrix. Exciton absorption peaks at much higher energy than the fundamental absorption edge of bulk PbS indicate quantum confinement effects in the spherical shape nanoparticles as a consequence of their small size.