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

Abstract Up- and downconversion emission and sensing sensitivity is studied in Er3+/Yb3+ co-doped biocompatible Ca3(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 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 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 2H11/2 and 4S3/2 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 μM to 100 μM) was studied and finally, no significant toxicity on WI-38 cells was assessed by the MTT assay method.