Structure, Luminescence and Temperature Detection Capability of [C(NH₂)₃]M(HCOO)₃ (M = Mg²⁺, Mn²⁺, Zn²⁺) Hybrid Organic–Inorganic Formate Perovskites Containing Cr³⁺ Ions

• Published in: Sensors
• Main Authors: Dagmara Stefańska, Adam Kabański, Thi Hong Quan Vu, Marek Adaszyński, Maciej Ptak
• Format: Article
• Language: English
• Published: MDPI AG 2023-07-01
• Subjects: MOF; hybrid perovskite; luminescence; thermometry; chromium(III) ions; temperature sensing
• Online Access: https://www.mdpi.com/1424-8220/23/14/6259
• ISSN: 1424-8220

Metal-organic frameworks are of great interest to scientists from various fields. This group also includes organic–inorganic hybrids with a perovskite structure. Recently their structural, phonon, and luminescent properties have been paid much attention. However, a new way of characterization of these materials has become luminescence thermometry. Herein, we report the structure, luminescence, and temperature detection ability of formate organic–inorganic perovskite [C(NH₂)₃]M(HCOO)₃ (Mg²⁺, Mn²⁺, Zn²⁺) doped with Cr³⁺ ions. Crystal field strength (Dq/B) and Racah parameters were determined based on diffuse reflectance spectra. It was shown that Cr³⁺ ions are positioned in the intermediate crystal field or close to it with a Dq/B range of 2.29–2.41. The co-existence of the spin-forbidden and spin-allowed transitions of Cr³⁺ ions enable the proposal of an approach for remote readout of the temperature. The relative sensitivity (S_r) can be easily modified by sample composition and Cr³⁺ ions concentration. The luminescent thermometer based on the ²E/⁴T_2g transitions has the relative sensitivity S_r of 2.08%K⁻¹ at 90 K for [C(NH₂)₃]Mg(HCOO)₃: 1% Cr³⁺ and decrease to 1.20%K⁻¹ at 100 K and 1.08%K⁻¹ at 90 K for Mn²⁺ and Zn²⁺ analogs, respectively.