Solid-state fluorescent Se QD-Tb³⁺-doped SiO₂for multimodal anti-counterfeiting applications

In this work, multicolor and near white-light-emitting Se-Tb³⁺-doped SiO₂is synthesized via the sol-gel method. Due to the phase shift from cubic (c-Se) to amorphous (a-Se) in Se quantum dots (QDs), the absorption spectrum of the annealed Se-Tb³⁺-doped SiO₂exhibits a broad absorption in the lower wavelength region. Due to the combined effect of excitation-dependent blue emissions [c-Se QDs] and enhanced multiple emission bands (Tb³⁺ions), fluorescent c-Se-Tb³⁺-doped SiO₂is color-tunable from blue to near white to green under different excitations. While Se QDs sensitize and boost Tb³⁺fluorescence in their cubic phase, they quench Tb³⁺emission in their amorphous phase. Under 340 nm UV excitation, cool white emission (0.3040, 0.4074) with a correlated color temperature value of 6426 K is obtained for c-Se-Tb³⁺-doped SiO₂(c37). Excitation-dependent photoluminescence color tuning, shifting from blue to near white at a lower c-Se QD content and white to green at a higher c-Se QD content is observed in c-Se-Tb³⁺-doped SiO₂. The dependence of fluorescence emission from Se-Tb³⁺-doped SiO₂on the crystallinity of Se QDs, Se concentration and excitation wavelength is beneficial in realizing anti-counterfeiting and advanced solid color tunable lighting devices.