Optical and\nStructural Properties of Anisotropic ZnS\nNanoparticle Suspensions

We studied the optical and structural properties of highly\nordered\narrays of surfactant-capped ZnS nanowires (NWs) and nanorods (NRs)\nin organic suspensions. The photoluminescence (PL) emission measured\nunder different concentrations and postsynthesis washing cycles interestingly\nshowed increasing emission upon decreasing nanoparticle (NP) concentration.\nSynchrotron small angle X-ray scattering measurements elucidated the\nliquid-crystal-like structure of the NPs in suspension under different\nconcentrations and temperatures. The NWs are stacked in a simple structure\nwith a hexagonal cross-section, whereas the structure of the NRs is\nmore complex, resembling a smectic-c liquid crystal, and shows unusual\nthermal expansion versus temperature. The results point out that a\ncertain amount of bound surfactant must be present on the NP surface\nto maximize the PL intensity.