The conjugation of luminescent nano-sized doped ZnS or ZnO particles with various polymeric and biochemical substrates requires particle surfaces with well defined chemical characteristics and covalently bonded anchor groups. Huge progress has been made in this respect recently, but still the interplay between luminescent properties and surface chemistry remains a delicate theoretical and preparational task. In this work, the ratio of room temperature luminescence from (bulk) defect sites and Mn2+ sites (bulk and surface) has been used in a series of particles with varying particle size to study the influence of ligands present on the surface. Coupling of the ligands to the particle surface has been achieved by thio groups. Although most of the preparation of the nano-particles has been performed in aqueous solution, redispersability and transfer into non-aqueous solvents has been investigated as well.