Bright green emission from f-MWCNT embedded co-doped Bi3+ + Tb3+: polyvinyl alcohol polymer nanocomposites for photonic applications

A bright, dazzling green emission has been obtained from functionalized multi walled carbon nanotube (fMWCNTs)- embedded Bi3+ + Tb3+: PVA polymer nanocomposites under UV excitation. We successfully synthesized Tb3+: PVA, Bi3+ + Tb3+: PVA and Bi3+ + Tb3+ + f-MWCNTs: PVA polymer films by a solution casting method. For these polymer films, their XRD and FTIR spectral profiles were analyzed for structural details and ion-polymer interaction mechanism. Tb3+ doped at different concentrations in PVA polymer films displayed a green emission at 546 nm ((5)D4 -> F-7(5)) under 370 nm (F-7(6) -> L-5(10)) excitation. Upon co-doping with Bi3+ in the Tb3+: PVA polymer film, the film exhibits enriched green emission compared to single Tb3+: PVA under 320 nm excitation due to the energy transfer from Bi3+ to Tb3+. Surprisingly, a common excitation band was found at 320 nm for Tb3+, Bi3+ and f-MWCNTs. After dispersion of the f-MWCNTs in the co-doped Bi3++ Tb3+: PVA polymer films, the photoluminescence properties were remarkably enhanced, and a prominent green emission was observed at 546 nm. The green emission of Tb3+ is significantly enhanced though an efficient energy transfer process from Bi3+ to Tb3+ and f-MWCNTs to Tb3+. The possible energy transfer mechanism was clearly demonstrated via several fluorescent methods. The energy transfer mechanism was substantiated with fluorescence lifetime decay dynamics. From these results, these f-MWCNTs-embedded Bi3++ Tb3+: PVA polymer films could be suggested as promising candidates for green luminescent materials for photonic devices.