Tunable emission properties and energy transfer of Tb3+/Eu3+ co-activated glasses for anti-counterfeiting

A range of color-tunable tellurite glasses co-doped with Tb³⁺/Eu³⁺ ions were fabricated using the melt quenching technique, then analyzed their structural properties, luminescent behavior, energy transfer dynamics, and potential anti-counterfeiting uses. When excited at 487 nm, the 542 nm emission intensity and fluorescence lifetime of Tb³⁺ ions gradually decreased as the Eu³⁺ doping concentrations rose, while the characteristic 615 nm emission of Eu³⁺ intensified. This shift resulted in a corresponding change in chromaticity coordinates from yellow-green to orange-red hues. The team conducted detailed investigations into the energy transfer mechanisms using selective excitation at 495 nm (Tb³⁺-specific absorption) and 395 nm (Eu³⁺-specific absorption). Their findings revealed not only the expected energy transfer from Tb³⁺ to Eu³⁺ but also an unexpected, albeit weaker, reverse transfer from Eu³⁺ back to Tb³⁺. Furthermore, the emitted light from these glasses exhibited tunable coloration depending on both the excitation wavelength and Eu³⁺ concentration. These results demonstrate that Tb³⁺/Eu³⁺ co-doped tellurite glasses hold significant promise for advanced security and anti-counterfeiting applications due to their controllable optical properties.