Heterogeneity effects of Tm upconversion emission in Mo, Tm codoped rare-earth garnets
- Journal Article
Co-doping with transition metals, such as Mo6+ has been intensively used to optimize the emission colour and intensity of the lanthanide (Ln) such as Tm in Yb-based upconversion (UC) nanomaterials. Mo addition allegedly enhances the Tm UC emission intensity by orders of magnitude, shifts the emission colour dramatically from red to blue and reduces the photon order of blue emission from three to two. Here, we investigate the effects of Mo co-doping on Tm UC emission properties, such as intensity, colour and photon order of the relevant emissions involved. Unlike fixed cw excitation used exclusively till now, we employ pulsed and tunable laser excitation spanning the complete Yb absorption. Such an experimental approach is generally more appropriate for investigating heterogeneity effects due to the multisite, dopant, or phase segregation effects induced by Mo, which may alter the Ln luminescence intensity, colour, and dynamics. We found that the overall optical behaviour of Tm upconversion emission induced by Mo is most likely related to minor, foreign phase impurity, which remains unnoticed by X-ray diffraction, transmission electron microscopy or optical absorption. In this impurity phase, Tm upconversion emission is characterized by a relatively strong intensity, distinct colour and dynamics being induced by distinct Yb absorption relative to the Mo-free counterpart. The upconversion mechanism is explained by a classical Yb-Tm energy transfer, with no involvement of Yb-Mo dimer sensitization as currently accepted. Show more
Journal / seriesJournal of Alloys and Compounds
Pages / Article No.
SubjectUpconversion emission; Variable, pulsed excitation; Mo co-doping; Sequential Yb-Tm energy transfer; Yb-Mo dimer sensitization; Upconversion excitation spectra
Organisational unit02891 - ScopeM / ScopeM
MoreShow all metadata