Precursor-directed synthesis of upconverting LiYF4:Yb3+, Tm3+ nanoparticles and their composites designed for near infra-red driven photocatalysis
Résumé
Titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) are among the most promising
photocatalysts due to their low cost, non-toxicity and high catalytic activity. However, these
photocatalysts also have certain limitations in terms of low efficiency of visible light utilization and high recombination rate of the photo-generated electron-hole pairs. Coupling of these photocatalysts with lanthanide-based upconverting nanoparticles (UCNPs) can lead to utilization of near-infrared part of the solar spectrum and, therefore, enhance the photocatalytic efficiency many folds.1 In this context, upconverting nanomaterials LiYF4: Tm3+/Yb3+ have great potential as they show intense upconverted emissions in the deep-UV region,2 which would greatly facilitate efficiency of above photocatalysts. However, in comparison to the more thoroughly investigated NaLnF4-based systems, the studies on upconverting nanomaterials based on the LiYF4 host matrix remain in its nascent state.3
Here we describe bottom-up synthesis of a series of LiYF4 nanocrystals (NCs) co-doped with varying amount of Yb3+ and Tm3+ ions using new molecular precursors [Ln(TFA)3(monoglyme)] [Ln = Y, Tm, Yb] and [Li(TFA)(monoglyme)] (where TFA = trifluoroacetate, and monoglyme = dimethoxyethane). These precursors, synthesized in a simple one-pot reaction and characterized by spectroscopy, single crystal X-ray structures and thermogravimetric studies, are advantageous in terms of being anhydrous. The multicolour up-conversion fluorescence studies of the obtained LiYF4:Tm3+/Yb3+ NCs established them to be promising UC nanophosphors, which were further used to prepare composites with earlier-mentioned photocatalysts to realize near IR-driven photocatalysis.
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