Luminescence enhancement, spectral tunability, energy transfer of versatile and biocompatible hydroxyapatite nanocrystals toward flexible anti-counterfeiting fabric and functional devices

Hydroxyapatite (HAP) commonly undergoes doping with various dopants , leading to the emergence of new properties. In this study, HAP is co-doped by terbium (Tb) and europium (Eu) to impart HAP with photoluminescent properties. By controlling the Tb 3+ amount to 7.5 × 10 −5  mol unchanged, it is observed that when the doping amount of Eu 3+ reaches 4.0 × 10 −5  mol, the band gap measures 3.919 eV, with maximum fluorescence intensity. Notably, a dipole-dipole energy transfer type from Tb 3+ to Eu 3 was identified during this process. Concentration quenching occurs when the Eu 3+ amount exceeds 4.0 × 10 −5  mol. In addition, the Tb 3+ and Eu 3+ co-doped HAP demonstrates excellent thermal stability and a more comprehensive emission wavelength range than Tb 3+ -doped HAP or Eu 3+ -doped HAP. Considering these properties, Tb 3+ and Eu 3+ co-doped HAP phosphor and aramid/polyphenylene sulfide (ACFs/PPS) fiber paper are organically compounded, resulting in functional fabrics with excellent low-temperature stability. These available fabrics are made of luminescent crystals and fibers can be applied in fields such as high-performance textile testing. Notably, when a specific laser irradiates the damaged area of the textile, fluorescence is not detected by the detector. Moreover, Tb 3+ and Eu 3+ co-doped HAP has also been shown to be used in the light-emitting diode (LED) to produce the HAP-LED that emits warm white light without commercial phosphors. That expands the application of HAP in anti-counterfeiting, flexible wearables, high-performance textile testing, and semiconductor devices.