Direct surface modification of semiconductor quantum dots with metal–organic frameworks

Abstract

Robust surface protective materials for practical applications of luminescent semiconductor quantum dots (QDs) that differ from conventional organic ligands are required for long-term QD stability. Among the alternatives, metal–organic frameworks (MOFs) are expected to act as functional stabilizers because of their insulating or semiconducting properties and the versatility of material design. Here, a new strategy for developing a QD@MOF composite is proposed without any bonding materials between the QD and MOF-like polymers. Forming a direct bond between QDs and MOFs is desirable for exploiting the synergistic effects of both materials. The dropwise addition of MOF precursors into QD solutions, ligands of which have been exchanged to easily detach pyridine derivatives, demonstrates the growth of MOFs on the direct surface of QDs. How these QDs are incorporated in MOFs is investigated in relation to the manner of MOF precursor introduction during the synthesis reaction. The resulting QD@MOF composite emits intense photoluminescence in the solid state, and complete coverage of the MOF on the QD surface was demonstrated by the unresponsiveness of the composite to photoluminescence quenching tests.