A general procedure is described for the synthesis and conversion of dispersible core/shell LaF3:Tm/LaF3 nanoparticles to highly dispersible thulium-doped lanthanum disilicate nanoparticles (La2Si2O7:Tm) with an average diameter of 7 nm that show emission at a wavelength of 1.47 μm. Measurement of the citrate-stabilized precursor nanoparticles in a KBr pellet shows a 1.47 μm emission with an effective lifetime of only 3 μs and an estimated quantum yield of ≪ 1 %. However, significant improvements to the emission properties are obtained by forming a ca. 1 nm thick silica shell around the nanoparticles via a modified Stöber method, followed by baking at 900 °C for 12 h to convert the LaF3 matrix to La2Si2O7. Excitation with a 785 nm continuous wave (CW) diode laser results in the luminescence of the 3H4–3F4 transition at 1.47 μm with an effective lifetime of 56 μs and an estimated quantum yield of 4 %. High-resolution measurements at 77 K are carried out in order to improve the resolution of the crystal-field splitting observed from the 3H4 level.