Photoluminescence properties of SrF₂:3Tb@BaF₂ nanoparticles and improved hyperthermia temperature achieved by core-shell nanohybrid SrF₂:3Tb@BaF₂/Fe₃O₄ materials

SrF₂:3Tb and SrF₂:3Tb@BaF₂ core-shell were synthesized by using ethylene glycol as solvent medium and capping agent. Both phases of SrF₂ and BaF₂ were observed from the XRD patterns which indicate the presence of these phases in their pure states. Since small size Tb³⁺ is incorporated into larger size Sr²⁺ lattice, there is peak shifts in the larger 2θ in SrF₂:3Tb. Intensity of the XRD peaks of SrF₂ was decreased when SrF₂:3Tb formed core-shell with BaF₂ due to the decrease of penetration depth of x-ray. There is twofold increase in the luminescence properties of Tb³⁺ ion in SrF₂:3Tb when it formed core-shell with BaF₂. Increases in luminescence intensity were also further supported by increase in weighted average lifetime values. Weighted average life time values attained for SrF₂:3Tb, SrF₂:3Tb@BaF₂ (1:0.5), SrF₂:3Tb@BaF₂ (1:1), and SrF₂:3Tb@BaF₂ (1:2) were 6.75, 6.94, 7.42, and 7.75 ms, respectively. Further, these luminescent materials were combined with magnetic nanoparticles to form luminescent-magnetic materials which are very useful in hyperthermia applications. Hyperthermia temperature (HT) attained by 6 mg of Fe₃O₄, SrF₂:3Tb/Fe₃O₄ and SrF₂:3Tb@BaF₂ (1:1)/Fe₃O₄ nanohybrid with time at fixed currents 400 A are 70, 54, and 65 °C. Thus, hyperthermia temperatures could be tuned by core-shell formation. This improvement in HT after core-shell formation can be exploited in cancer therapy. Moreover, this nanohybrid (luminescence-magnetic) material can also be detected through luminescence techniques since it contained luminescent parts also.