Formation and luminescence phenomena of LaF₃:Ce³⁺ nanoparticles and lanthanide-organic compounds in dimethyl sulfoxide

LaF₃:Ce³⁺-doped nanoparticles were synthesized at different temperatures in dimethyl sulfoxide (DMSO) by the chemical reaction of lanthanum nitrate hydrate and cerium nitrate hexahydrate with ammonium fluoride. The formation of Ce³⁺-doped LaF₃ nanoparticles is confirmed by X-ray diffraction and high-resolution transmission electron microscopy. An intense emission at around 310 nm from the d-f transition of Ce³⁺ was observed from the LaF₃:Ce³⁺ powder samples. However, in solution samples, the ultraviolet emission from Ce ³⁺ is mostly absent, but intense luminescence is observed in the visible range from blue to red. The emission wavelength of the solution samples is dependent on the reaction time and temperature. More interestingly, the emission wavelength varies with the excitation wavelength. Most likely, this emission is from metal organic compounds of Ce³⁺ or La³⁺ and DMSO as similar phenomena are also observed when lanthanum nitrate hydrate or cerium nitrate hexahydrate are heated in DMSO.