Up- and downconversion emission studies in Er3+/Yb3+: Ca3 (PO4)2 phosphor for thermometry

Up- and downconversion emission and sensing sensitivity is studied in Er3+/Yb3+ co-doped biocompatible Ca-3(PO4)(2) phosphor synthesized via co-precipitation (CPT) and hydrothermal (HYDT) methods. The emission bands are observed at 523, 549 & 656 nm due to the H-2(11/2)-> I-4(15/2), S-4(3/2)-> I-4(15/2), and F-4(9/2)-> I-4(15/2) transitions, respectively on excitation under 980 nm diode laser. The sample prepared via hydrothermal method has shown higher upconversion emission as compared to the sample prepared via co-precipitation method. The temperature sensing performance on green upconverted-emission from two thermally coupled H-2(11/2) and S-4(3/2) levels of Er3+ ion was measured in the 300-473 K temperature range and maximum sensor sensitivity of 0.34 %/K for HYDT and 0.26 %/K for CPT sample at 300 K is observed. Cell survivability at various sample concentrations (0 mu M to 100 mu M) was studied and finally, no significant toxicity on WI-38 cells was assessed by the MTT assay method. (C) 2020 Elsevier B.V. All rights reserved.