An optical ratiometric temperature sensor based on dopant-dependent thermal equilibrium in dual-emitting Ag&Mn:ZnInS quantum dots

Abstract

We reported an optical ratiometric temperature sensor via dopant-dependent dual emissions in Ag&Mn:ZnInS QDs. For QDs, the Ag-related emission is around 485 nm arising from the radiative recombination of the captured electrons' anion vacancies with holes trapped at the Ag dopant level. The energy level of anion vacancies is just below the conduction band, which can attain thermal equilibrium easily without further energy level adjusting. Moreover, Mn-related emission is around 585 nm via the Mn²⁺ ligand-field transition from ⁴T₁ to ⁶A₁. Mn-related thermal equilibrium is effectively suppressed due to the large energy gap between the conduction band and ⁴T₁ energy level. These features not only obtain the opportunity to use the photoluminescence temperature specificity of Ag and Mn for ratiometric temperature sensing, but also make the flash synthetic approach via a pot non-injection possible. This temperature sensor, designed with Ag&Mn:ZnInS QDs, exhibits good temperature sensitivity (∼0.227% °C⁻¹) and high QY (20%).