Time-tunable white light emission in waterborne colloidal smart polymer-MXene quantum dots for high-level anticounterfeiting

The aqueous dispersion of MXene quantum dots (MQDs) is a precursor for white light-emitting colloidal polymer particles. This study presents a method of synthesizing Ti3C2Tx MQDs with a uniform size distribution and customizable optical properties. The MQDs-doped with ethylenediamine, sulfuric acid, and thiourea that have nitrogen, sulfur, and both of nitrogen and sulfur groups, respectively-exhibit a high-intensity emission across the blue to red spectra. The incorporation of spiropyran-doped poly(methyl methacrylate) nanoparticles (SPPMMANPs) into the MQDs-via reverse ATRP and nanoprecipitation in MQDs aqueous dispersions-leads to dynamically adjustable white light emission, controlled by the fluorescence resonance energy transfer mechanism. The emission color changed from blue to white and then to red with increased concentrations of the organic phase and duration of UV irradiation. An ink made of the SPPMMANPs/thiourea-doped MQDs displays Commission Internationale de l'Eclairage (CIE) color coordinates of (0.3234, 0.3303), a color temperature of 5450 K, a color rendering index of 87, and the highest emission overlap with the sunlight visible range. These economical and waterborne inks with dynamically adjustable white light emission have applications in secured quick response codes, tracking and tracing systems, fingerprint decryption, digital watermarks, and white light-emitting diodes.