1D-Zigzag Eu3+/Tb3+ Coordination Chains as Luminescent Ratiometric Thermometers Endowed with Multicolor Emission.

Luca Bellucci,Lidia Armelao,Simona Samaritani,Daniela Belli Dell'Amico,Luca Labella,Gregorio Bottaro,Fabio Marchetti

doi:10.3390/ma14216445

Abstract

Two homometallic Coordination Polymers (CPs) with composition [Ln(hfac)3bipy]n (Ln3+ = Eu3+, 1, and Tb3+, 2; hfac = hexafluoroacetylacetonato, bipy = 4,4′-bipyridine) were used to develop a family of ratiometric luminescent thermometers containing Eu3+ and Tb3+ as red and green emitters, respectively. The thermometric properties of pure CPs and of their mixtures having an Eu3+/Tb3+ molar ratio of 1:1, 1:3, 1:5, and 1:10 (samples: Eu1Tb1, Eu1Tb3, Eu1Tb5, and Eu1Tb10) were studied in the 83–383 K temperature range. Irrespective of the chemical composition, we observed similar thermometric responses characterized by broad applicative temperature ranges (from 100 to 165 K wide), and high relative thermal sensitivity values (Sr), up to 2.40% K−1, in the physiological temperature range (298–318 K). All samples showed emissions endowed with peculiar and continuous color variation from green (83 K) to red (383 K) that can be exploited to develop a colorimetric temperature indicator. At fixed temperature, the color of the emitted light can be tuned by varying composition and excitation wavelength.

Highlights

Nowadays, luminescence thermometry plays a relevant role due to its high importance in many societal needs
We carefully described the synthesis of monodimensional lanthanide β-diketonate coordination polymers based on bipy as connector ligand [33]
The two homometallic compounds were used to prepare a family of Eu3+/Tb3+ ratiometric thermometers in which terbium acts as probe and europium as reference

Summary

Introduction

Luminescence thermometry plays a relevant role due to its high importance in many societal needs. Among the different types of luminescent thermometers, intensity-based ones are useful for many applications such as real-time measurements on large moving systems [4,5]. The stated drawbacks can be overcome using the intensity ratio of different emission bands of a given luminescent material, creating self-referencing thermometers [6,7,9,10]. These thermometers, called “ratiometric thermometers”, have been developed using a variety of luminescent probes [7,8,11]. Europium and terbium complexes have been extensively used due to their peculiar luminescent properties [6,12,13,14,15,16,17]

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