Temperature sensing in Tb 3+ /Eu 3+ -based tetranuclear silsesquioxane cages with tunable emission.

New luminescent cage-like tetranuclear silsesquioxanes [NEt 4 ][(Ph 4 Si 4 O 8 ) 2 (Tb 3 Eu)(NO 3 ) 4 (OH)(EtOH) 3 (H 2 O)]·4(EtOH) (1) and [NEt 4 ] 2 [(Ph 4 Si 4 O 8 ) 2 (Tb 2 Eu 2 )(NO 3 ) 6 (EtOH) 2 (MeCN) 2 ]·4(MeCN) (2) present a tunable thermosensitive Tb 3+ -to-Eu 3+ energy transfer driven by Tb 3+ and Eu 3+ emission and may be used as temperature sensors operating in the range 41-100 °C with excellent linearity ( R 2 = 0.9990) and repeatability (>95%). The thermometer performance was evidenced by the maximum relative sensitivity of 0.63% °C -1 achieved at 68 °C.