Rapid thermally driven color-switching in dual cation-modified InP/ZnS quantum dots for visible fluorescence thermometers

Indium phosphide (InP) quantum dots (QDs), as an environmentally benign semiconductor material, exhibit significant potential in optoelectronic devices. The incorporation of metal ions is a widely adopted strategy to modulate the optical properties of InP QDs, thereby expanding their application scope. In this study, rapid thermochromic response was achieved in InP/ZnS QDs through dual cation (Nd 3+ &Mn 2+ ) modification. The introduction of Mn 2+ endowed the QDs with dual emission characteristics, while Nd 3+ stabilized the intrinsic emission at the pure blue wavelength of 470 nm by suppressing QD growth via interface anchoring. Investigations revealed that temperature elevation activated the carrier re-excitation process, leading to enhanced intrinsic emission and enabling dynamic fluorescence color switching from orange-yellow to blue. Leveraging this property, a ratiometric fluorescence thermometer with a detection range of 293–533 K and a response time of <5 s was developed. Furthermore, variable-power excitation experiments elucidated the saturation behavior of Mn 2+ impurity emission, corroborating the competitive mechanism between intrinsic and impurity emissions. This work provides novel insights into the multifunctional fluorescence modulation of cadmium-free QDs, with significant implications for smart sensing and eco-friendly display technologies.