Rethinking Assumptions:\nAssessing the Impact of Strong\nMagnetic Fields on Luminescence Thermometry

Luminescence (nano)thermometry has exploded in popularity,\noffering\na remote detection way to measure temperature across diverse fields\nlike nanomedicine, microelectronics, catalysis, and plasmonics. A\nkey advantage is its supposed immunity to strong electromagnetic fields,\na crucial feature in many environments. However, this assumption lacks\ncomprehensive experimental verification as most of the proposed luminescent\nthermometers rely on magnetic ions, such as lanthanides. Here, we\naddress this gap by critically examining the thermometric response\nof the luminescent molecular thermometer [Tb<sub>0.93</sub>Eu<sub>0.07</sub>(bpy)<sub>2</sub>(NO<sub>3</sub>)<sub>3</sub>] (bpy = 2,2′-bipyridine)\nunder high magnetic fields (up to 58 T). Our findings reveal that\nthe conventional intensity-based method for Tb/Eu luminescent thermometers\nfails even under weak magnetic fields. However, careful data analysis\nidentified specific transitions with minimal magnetic correlation,\nenabling the thermometer to operate across the entire temperature\nrange up to 20 T, and with larger fields for temperatures exceeding\n120 K. This study highlights the strong dependence of thermometric\nperformance on material properties, urging caution, but also offers\na path forward for developing robust luminescent thermometers in such\nenvironments.