New ligand selection rule for quantum dot functionalization

Hard Soft Acid Base (HSAB) theory is introduced as a new tool to select ligands (molecules) for quantum dot covalent functionalization. According to HSAB, only soft acid-soft base bond is covalent. Since most of the transition metal semiconductor cations on the surface of the quantum dots are soft acids, the approach we propose is to select anchors which are soft bases. Following this strategy, the suitable anchors for surface modification of the quantum dots are selected. Moreover, a plethora of bifunctional ligands for assembling quantum dots onto the surface of titania are identified among the existing molecules. The functionalization of a semiconducting organic polymer backbone with HSAB-adequate anchors for the design of polymer-quantum dot hybrid interface is presented. In addition, our new approach coherently explains the heuristic approaches described in the literature.