Near-infrared driven photocatalysis by novel up-converting TiO2@NaGdF4:Yb3+,Tm3+ core/shell nano-composites
Résumé
Elaboration of lanthanide-doped NaLnF4 upconverting (UC) nanocrystals (which convert near infra-red radiation to shorter wavelength UV-visible region) via novel heterometallic Na-Ln (Ln = Y, La-Lu) trifluoroacetate complexes as single source precursors was reported for the first time by our group [1]. A study on the decomposition behaviour of the Na-Gd precursor shows that the hexagonal phase of the NaGdF4 matrix, which is many fold more efficient for the upconversion process, is easily obtained at much lower temperature than over the extensively used homometallic Ln(TFA)3(H2O)3. [2] Moreover, these molecular precursors have multiple advantages such as being anhydrous (presence of water molecules is detrimental for the up-converting properties) and containing glyme ligand, which acts as a capping-reagent during decomposition to provide controlled size and stable dispersion of nanocrystals in organic solvents.
In this presentation we will discuss the synthesis and complete characterization of TiO2@NaGdF4:Yb3+,Tm3+ core/shell nano-composites. UC nanomaterials absorb extremely weakly and within a very narrow spectral window, making very high illumination intensities often necessary. We will then present further functionalization of upconverting nanopaticles using a set of dye molecules as antenna to enhance the overall upconversion due to increased absorptivity and overall broadening of the absorption spectrum of the upconverter [3]. NIR-driven photocatalytic activity of the above obtained nano-structures will be addressed.