Quantum dot surface mediated unprecedented reaction of Zn²⁺ and copper quinolate complex

Abstract

We report the reaction between Zn²⁺ ions, being present on the surface of ZnS quantum dot (Qdot), and copper(II) bis(8-hydroxyquinoline) (copper quinolate; CuQ₂) complex, leading to the formation of luminescent ZnQ₂ on the surface. This is contrary to the reactivity of copper complex based on Irving–William series in the liquid medium and thus indicating catalytic role of the Qdot surface. The rate of the reaction was observed to be first order with respect to the concentrations of both the reactants, with activation energy measured to be 74.3 kJ mol^–1. Further, the reaction of the Zn²⁺ ions on the Qdot was observed to be the fastest with HQ, slower with MnQ₂, and the slowest with CuQ₂, all leading to the formation of ZnQ₂ on the surface of the Qdot. The enhanced stability of the product complex on the surface, in the presence of dangling sulfide ions, indicated a new type of chemical reaction deserving special attention.