LaF3 nanoparticles surface modified with tryptophan and their optical properties

LaF3 nanoparticles were synthesized by the double-jet precipitation technique in presence of tryptophan (Trp). The product was investigated by TEM, IR, absorption, and luminescence spectroscopies. Interaction of Trp with the nanoparticles results in formation of complexes between Trp and La3+ ions on the nanoparticle surface. Surface density of Trp was found as 0.7 molecule nm−2. It is shown that the modifier effects on LaF3 nanoparticle growth and stability of the surface modified LaF3 colloids. Luminescent properties of LaF3 nanoparticles modified with Trp (Trp@LaF3) are investigated. It is determined that Trp@LaF3 and Trp have the same profiles of excitation and photoluminescence spectra. Effects of pH, ionic strength, and Trp concentration on luminescence intensity are studied. At the same Trp amounts in the systems, Trp@LaF3 luminescence intensity is about 6 times less than Trp luminescence intensity. Such products can be used as luminescent labels.