BaF2:Eu2+/3+,Tb3+ nanofibres achieve enhanced multicolor luminescence and white-light emission via multi-channel excitation and energy migration procedure†
Abstract
A series of BaF2:Eu2+/3+ and BaF2:Eu2+/3+,Tb3+ one-dimensional (1D) nanofibres are devised and constructed by using electrospinning and di-crucible fluorination technology without applying reducing gas and protective gas. During the formation process of 1D Eu-doped BaF2 nanofibres, partial reduction of Eu3+ is realized, resulting in the co-existence of Eu2+ and Eu3+ in the specimen, which is responsible for multicolor luminescence. In the emission spectra of BaF2:Eu2+/3+ nanofibres, the broad peak centered at 377 nm (5d → 4f) belongs to Eu2+ ions and the narrow peaks at 592 (5D0 → 7F1) and 613 nm (5D0 → 7F2) belong to Eu3+ ions. Concurrently, BaF2:Eu2+/3+ nanofibres directly emit luminous color from the blue-light to the yellow-light region by applying different wavelength excitation. Furthermore, by doping green-light-emitting Tb3+ into the BaF2:Eu2+/3+ nanofibres to acquire BaF2:Eu2+/3+,Tb3+ nanofibres, white-light emission and multicolor luminescence, covering the whole visible light area, are facilely realized via the multi-mode regulation of Eu ion valence states, Eu2+/3+ and Tb3+ concentrations, the energy transfer among Eu2+/3+ and Tb3+, and excitation wavelengths, thereby greatly improving the practicability of the neoteric luminescent material. Furthermore, the mechanisms of multicolor luminescence and white-light emission are systematically studied, and the Eu2+ → Tb3+ → Eu3+ energy transfer process in BaF2:Eu2+/3+,Tb3+ nanofibres is further improved and clarified. These new findings are helpful to design and fabricate new types of rare earth-based 1D luminescent nanostructures.