Size-dependent optical nonlinearities and scattering properties of PbS nanoparticles

Abstract

We report the size-dependent optical nonlinearities of PbS nanoparticles both in solution and as a composite film. Different sizes of PbS nanoparticles were synthesized by chemical methods, with the sizes controlled by varying reaction temperature and time. Transparent PbS/polystyrene thin films deposited on glass slides were successfully prepared by a simple imprinting-thermal cross-linking method. We found that smaller nanoparticles show higher nonlinear absorption and refraction of photoexcited free carriers, as well as larger optical Kerr nonlinearity. Our studies also revealed that nonlinear scattering is strongly dependent on size and plays a dominant role in the case of bigger nanoparticles in solution at higher excitation energy. © 2009 American Chemical Society.