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

Abstract

A bright, dazzling green emission has been obtained from functionalized multi walled carbon nanotube (f-MWCNTs)-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 (⁵D₄ → ⁷F₅) under 370 nm (⁷F₆ → ⁵L₁₀) 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.