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

Abstract 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 Tb 3+ ion get improved when complexed with ASA and Phen ligands. Selective excitations of Tb 3+ , ASA and Phen revealed an efficient energy transfer enhancing green luminescence of Tb 3+ ion on excitation with 355, 335 and 306 nm radiations respectively. The emission intensity arising from Tb(ASA) 3 Phen complex in PVA has been observed to be much more as compared to the one with Tb 3+ ions only. The fluorescence decay time for Tb 3+ ( 5 D 4  →  7 F 5 transition) is seen to increase from 557 μs in Tb 3+ to 628 μs in presence of Tb(ASA) 3 Phen 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) 3 Phen complex. This reflects an energy transfer from excited Phen to ASA and finally to Tb 3+ 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) 3 Phen complex in PVA with quantum yield of 0.32 shows a tendency towards lasing.