LAUSR

Abstract Lanthanide doped upconversion nanocrystals with remarkable optical properties have been utilized for many emerging applications. Here, solid solution Na(GdxLa1-x)(MoO4)2 nanocrystals are synthesized hydrothermally, and their upconversion photoluminescent and photothermal properties as luminescent host matrix for Yb3+/Er3+ activators are systematically studied. The effect of La3+ doping content on the phase, crystal structure, upconversion luminescence and photothermal conversion are investigated. Rietveld refinements based on XRD data indicate that La3+ occupy Gd3+ sites substitutionally, and pure phase solid solution Na(GdxLa1-x)(MoO4)2 is formed. Due to lattice distortion, lower lanthanide site symmetry and augmented odd-parity crystal field interactions after La3+ doping, the 4f-4f transition probabilities of the lanthanide ions are effectively increased. Na(Gd/La)(MoO4)2 solid solution hosts exhibit enhanced upconversion luminescence from Er3+/Yb3+, compared with single-component NaGd(MoO4)2 counterparts. What's more, based on the calculated temperatures of the samples derived from the luminescence intensity ratio of states 2H11/2 and 4S3/2 for Er3+, enhanced photothermal conversion efficiency is speculated in solid solution Na(GdxLa1-x)(MoO4)2:Yb3+/Er3+ nanocrystals, which is further confirmed by infrared thermographic images. The underling mechanisms of simultaneously enhanced photothermal effects and luminescence intensity in Na(GdxLa1-x)(MoO4)2 solid solution nanocrystals are elucidated. Modulation of composition in solid solution hosts may be an effective method for combating luminescent thermal quenching and/or regulating photothermal conversion and photoluminescence properties simultaneously. Multifunctional solid solution upconversion nanocrystals could be potential for photoluminescent and photothermal applications.