Physical insights into the facilitation of an unprecedented complexation reaction on the surface of a doped quantum dot leading to white light generation

Abstract

Herein, we report a complexation reaction between Zn²⁺ ions present on the surface of an orange-red-emitting environmentally sustainable Mn²⁺-doped ZnS QD and a non-emitting copper quinolate (CuQ₂) complex, which leads to the formation of a greenish blue-emitting surface zinc quinolate (ZnQ₂) complex. The synchronous contribution of the surface ZnQ₂ complex and Mn²⁺-doped ZnS QD is directed towards the generation of photostable bright white light (at λ_ex – 355 nm) with chromaticity coordinates of (0.34, 0.42), color rendering index (CRI) of 71 and color-correlated temperature (CCT) of 5046 K. The ZnQ₂ complexed Mn²⁺-doped ZnS QD is herein called as quantum dot complex (QDC). The excitation- and time-dependent tunability in emission, chromaticity, CRI and CCT of QDC revealed their futuristic applications in light-emitting devices with an anticipated color output. The current work also shows the catalytic behavior of Mn²⁺-doped ZnS QDs towards facilitating the formation of surface ZnQ₂ from CuQ₂, which is not feasible with regard to the reactivity of CuQ₂ under normal conditions according to the Irving–William series. The rate of the reaction was observed to be first order with respect to CuQ₂ at 20 °C, and the complexation constant for the formation of ZnQ₂ was estimated to be 8.3 × 10⁵ M⁻¹. This is important for understanding the surface chemistry of metal chalcogenide QDs towards complexation reactions.