Acetylsalicylic acid sensitized lasing luminescence of terbium complex in PVA: A case of energy avalanche via 1, 10-Phenanthroline

- Ternary complexes of Tb3+, ASA and Phen have been synthesized in PVA film.
- Selective excitations reveal energy transfer enhancing green luminescence of Tb3+ ion.
- Decay time of 5D4 → 7F5 transition rises from 557 μs in Tb3+ to 628 μs in Tb(ASA)3Phen.
- Phen to ASA transfers energy in Tb(ASA)3Phen, thus an energy avalanche.
- Green emission on 266 nm excitation in Tb(ASA)3Phen shows tendency towards lasing.

Ternary complexes of Terbium with acetylsalicylic acid (ASA) and 1, 10 Phenanthroline (Phen) were synthesized in PVA polymer film. The structural properties of the complex were evaluated using XRD and formation of complex was verified by FT-IR technique. The absorption, excitation and photoluminescence properties of the Tb3+ ion get improved when complexed with ASA and Phen ligands. Selective excitations of Tb3+, ASA and Phen revealed an efficient energy transfer enhancing green luminescence of Tb3+ ion on excitation with 355, 335 and 306 nm radiations respectively. The emission intensity arising from Tb(ASA)3Phen complex in PVA has been observed to be much more as compared to the one with Tb3+ ions only. The fluorescence decay time for Tb3+ (5D4 → 7F5 transition) is seen to increase from 557 μs in Tb3+ to 628 μs in presence of Tb(ASA)3Phen complex. The fluorescence decay time for Phen and ASA is seen to decrease from 4.43 ns to 1.64 ns and from 5.75 ns to 1.58 ns respectively in Tb(ASA)3Phen complex. This reflects an energy transfer from excited Phen to ASA and finally to Tb3+ is proposed as the cause of the above observations and thus an energy avalanche. The intense green luminescence on 266 nm excitation in Tb(ASA)3Phen complex in PVA with quantum yield of 0.32 shows a tendency towards lasing.