Systematics in the nanoparticle band gap of ZnS and Zn1-xMxS (M=Mn, Fe, Ni) for various dopant concentrations

We report a detailed study of the formation of semiconductor nanoparticles of the important compound ZnS and its Mn-doped variant Zn(1-x)MnxS inside reverse micelle microreactors, by carefully varying the size of the reverse micelles at a fixed Mn concentration with x=0.01. Dynamic light scattering techniques allow us to characterize the microreactor sizes and correlate them with the size of the resultant nanoparticles. Band gap measurements employing UV-visible spectroscopy clearly show that Mn-doped samples have higher band gaps, largely independent of the size of the vessel they were created in. This observation reflects the role of Mn as an inhibitor to the growth of the nanoparticles. This is further strengthened by the observation of inhibition by other elements of the first row transition metals. Substitution with Fe and Ni shows similar trends in band gap (and hence particle size) variation with the reaction chamber size as well as with the dopant concentration x of these elements, while such variations on substitution with Mn are distinct, possibly because the sulfides of Zn and Mn are isostructural