Doped Two Dimensional Metal Chalcogenides as Printable White Light Phosphors

Doping of 2D metal dichalcogenides (TMDCs) in particular, provides a facile route by which to produce new advanced composite nanomaterials that have advanced optoelectronic properties. [1] Doping of two-dimensional TMDCs with lanthanide ions provides an attractive opportunity by which to extend the latter's advanced materials properties. Lanthanide(III) ions (Ln3+) have long been investigated for their unique photophysical properties, which include long lifetimes (in ms), intense line-like emission profiles and, due to the lack of crystal field preference in each ion, the ability to tune photoluminescence or magnetic properties by judicious choice of lanthanide ion e.g. Eu3+ for red photonic emission, Tb3+ for green emission, Yb3+ for emission in the near infrared and Gd3+ for intense paramagnetism.[2]

We have recently shown that 2D molybdenum disulfide nanosheets can be functionalised with both Eu3+ and Gd3+ complexes simultaneously. The resulting nanomaterials display long photoluminescence emission lifetimes of 0.8 ms from the Eu3+ emission in the red region of the electromagnetic spectrum (570 - 720 nm), derived from the 5D0 -> 7Fj electronic f-f transitions, whilst having strong paramagnetic response in EPR spectra, and thus could be used as a bimodal optical probe / magnetic resonance imaging contrast agent. [3]
We now wish to extend the properties that we can impart to 2D materials by exploring the whole range of lanthanide elements available for doping. Doping with mixed optical emitting lanthanide complexes (e.g. Sm3+, Dy3+, Eu3+ and Tb3+) could lead to solid state phosphors which have white light emission. Printing of these new materials could lead to flexible white light phosphors for flexible lighting. The project will involve the synthesis and characterisation of Ln-doped 2D materials, the study of their photophysics by various techniques including temperature-dependent photoluminescence and absorption spectroscopy, confocal microscopy and quantum yield measurements. Transient photoluminescence and ultrafast transient absorption spectroscopy will enable carrier dynamics to be determined down to a sub-picosecond time-scale and will give us insight into the radiative and non-radiative pathways [4]. Printable inks will be developed and their properties elucidated.

References
[1] Tedstone et al Chem Mater 2016, 28, 1965. [2] Lewis et al Coord. Chem. Rev. 2014, 273, 213. [3] McAdams et al, Adv Func. Mater. 2017, 1703646 [4] Kime et al J. Phys. Chem. C 2017, 121, 22415.