Stereological estimation of the morphology distribution of ZnS clusters for photonic crystal applications

A novel application of stereological methods is presented for the down selection of synthesis conditions to produce dimer building blocks for photonic crystals. Scanning electron microscopy (SEM) images of ZnS clusters were analyzed to determine the cluster population distribution for mixtures of spheres, dimers, trimers, tetramers, and other complex clusters. The volume fraction of each particle species was estimated from the average fraction of test points falling within the cluster type of interest. For example, quantitative microscopy of a particle population prepared at 29 °C for 6 h and 85 °C for 22 min yielded a composition of 59±3% spheres, 31±2% dimers, 7±1% trimers, 0.4±0.2% tetramers, and 2.5±0.8% complex clusters. Images from systematically selected experimental conditions were analyzed to determine the optimal conditions for obtaining dimer building blocks from solution precipitation. This condition was determined to be 29 °C for 5 h and 85 °C for 20 min and yielded a monodispersed dimer population of 23±2%.