In this work we propose Eu3+-doped YVO4 as a model compound of a multimodal photoenergy converter that shows photoluminescence and photocatalytic activity and discuss the relation between these two photoenergy conversion modes. YVO4:Eu3+ nanoparticles with different Eu3+ concentrations and distributions were prepared by coprecipitation and ion exchange methods. The obtained samples consisted of elliptical nanoparticles of 20-25 nm in mean size, irrespective of the Eu3+ concentration and distribution. The nanoparticles showed two photoenergy converting functions under UV irradiation: (i) Red photoluminescence corresponding to a 4f → 4f transition of Eu3+ and (ii) photocatalytic decomposition of methyl orange. Increase in the Eu3+ concentration increased the photoluminescence quantum yield but decreased the photocatalytic activity. Localizing Eu3+ ions at the particle surface increased the photocatalytic activity but decreased the photoluminescence quantum yield. These results imply a competitive relation between photoluminescence and photocatalytic activity for the compositional range used in this work.
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