Lanthanide doped ZnS quantum dots dispersed in silica glasses: an easy one pot sol-gel synthesis for obtaining novel photonic materials

Silica glasses containing both ZnS quantum dots (QDs) and luminescent lanthanide ions are attractive candidates to develop new lighting displays, sensor devices or laser emitters. This work reports an easy sol-gel method to prepare Eu3+-doped and Eu3+, Mn2+-codoped ZnS nanocrystals dispersed in a transparent silica matrix. Semiconductor nanocrystals with an average size of 5-6 nm and exhibiting both cubic and hexagonal phases were obtained at low temperature. The luminescent interactions between ZnS QDs, Eu3+ and Mn2+ ions provided materials with different optical responses but also gave information about the organization of the different species in the nanocomposite. Indeed, Eu ions were found to be both dispersed within the silica and located at the surface of the nanochalcogenide, the latter providing a ZnS -> Eu3+ energy transfer. Incorporation of Mn2+ into the ZnS lattice induced the appearance of defect states that enhance the blue luminescence of the nanocomposite. These results underline the sensitivity of optical processes to the nature and organization of the active species, which is of vital importance for the design of photonic materials.