Highly-sensitive optical thermometer developed based on an intervalence charge transfer mashup.

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Optical thermometers using lanthanide thermal-coupled levels are crucial for public health, biology, and integrated circuits.
• Lanthanide properties like shielded 4f configurations and non-radiative relaxation limit sensing performance and relative temperature sensitivity (S_R).

Purpose of the Study:

• To overcome limitations in lanthanide-based optical thermometers.
• To enhance relative temperature sensitivity (S_R) using a novel material design strategy.

Main Methods:

• Incorporation of d⁰ electron configured transition metals (Ta⁵⁺) into Tm³⁺/Eu³⁺:LiNbO₃.
• Validation of the strategy on other oxide crystals like NaY(Mo_1-zW_zO₄)₂.
• Density Functional Theory (DFT) calculations to understand electron transfer mechanisms.

Main Results:

• The intervalence charge transfer strategy significantly improved S_R from 5.30 to 11.16% K^-1 in Tm³⁺/Eu³⁺:LiNbO₃.
• The observed improvement was consistent across different oxide crystal systems.
• DFT calculations confirmed that the d-orbit component at the valence band minimum is key to electron transfer.

Conclusions:

• The proposed intervalence charge transfer strategy effectively enhances optical thermometer performance.
• Relating S_R to the band structure of luminescence carriers offers a new approach for designing lanthanide materials.
• This work provides a novel perspective for the rational design of lanthanide configurations for advanced sensing applications.