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Multicolor Tuning and Temperature-Triggered Anomalous Eu3+-related Photoemission Enhancement via Interplay of Accelerated Energy Transfer and Relea…

A new interesting article has been published in ACS Appl Mater Interfaces. 2018 Sep 26. doi: 10.1021/acsami.8b13728. and titled:

Multicolor Tuning and Temperature-Triggered Anomalous Eu3+-related Photoemission Enhancement via Interplay of Accelerated Energy Transfer and Relea…

Authors of this article are:
Kang F Sun G Wang A Xiao X Li YY Lu J Huang B.

A summary of the article is shown below:
So far, a large number of rare earth (RE) and non-RE doped emission-tunable crystals based on controllable energy transfer have become available, but numerous mechanistic issues, particularly for those that involve temperature-dependent energy transfer between the well-shielded 4f RE ions, lack comprehensive theoretical and experimental investigation, limiting greatly their development and applications in the future. Here, we design and report a type of Tb3+, Eu3+ doped Sr3Al2O5Cl2 phosphors capable of multi emissions upon excitation at 376 nm, through using the orthorhombic Sr3Al2O5Cl2 as host lattice while the well-shielded 4f Tb3+ and Eu3+ ions as dual luminescent centers. Our results reveal that the energy transfer from Tb3+ to Eu3+ ions, happening via an electric dipole-quadrupole (d-q) interaction, can be controlled by the doping ratio of Tb3+ and Eu3+, leading to the tunable emissions from green (0.3159, 0.5572) to red (0.6579, 0.3046). It is found from time-resolved photoluminescence (PL) spectra that this energy transfer begins at t = 5 μs and gradually ends at t > 200 μs. Moreover, from temperature-dependent PL results, we reveal that the Eu3+ emission features an anomalous intensity enhancement at the earlier heating state. With the density functional theory (DFT) calculations, we have screened the possibilities of site preferential substitution problem. By jointly taking into account the XRD Rietveld refinement, DFT findings, PL and thermoluminescence (TL) spectra, a mechanistic profile is proposed for illustrating the PL observations. In particular, our discussions reveal that the temperature-triggered Eu3+ emission enhancement is due to the interplay of the temperature-induced accelerated energy transfer and defect-trapped electrons that are released upon the thermal stimulation. Unlike most of reported phosphor materials that are always suggested for phosphor converted wLEDs, we propose new application possibilities for Tb3+, Eu3+ doped Sr3Al2O5Cl2 phosphors, such as anti-counterfeiting, temperature-controlled fluorescence sensor, data storage, and security devices.

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