Green upconversion fluorescence in terbium coordination complexes

Three terbium coordination complexes have been synthesized. Bright green emission from these compounds can be obtained under infrared pulsed laser pumping. The detail photophysics demonstrates it is due to two-photon absorption of the ligand. In addition, the effect of different ligands on upconversion efficiency was compared and discussed. This study demonstrates that enhanced two-photon induced lanthanide emission can be achieved when it is sensitized with suitable organic ligands. The estimated upconversion efficiency was 1% with an excitation energy of 1.2 W/cm2 under nanosecond pulse excitation, suggesting their potential applications in two-photon area.