Self‐Referenced Temperature Imaging with Dual Light Emitting Diode Excitation and Single‐Band Emission of AVO 4 :Eu 3+ (A=Y, La, Lu, Gd) Nanophosphors

Luminescence thermometers exhibiting ratiometric response in their emission spectrum are widely investigated but to obtain two‐dimensional measurements, either the emission spectrum must be slowly scanned over the area of interest or the emission decomposed using two separate detector arrays with spectral filters. Here, the authors propose to exploit instead an excitation‐spectrum based ratiometric response. In AVO 4 (A = Lu, Y, Gd, La) nanocrystals doped with Eu 3+ , the 1 E ( 1 T 1 )→ 1 B 2 ( 1 T 2 ) absorption band is thermally enhanced with respect to the 1 A 2 ( 1 T 1 )→ 1 B 2 ( 1 T 2 ) of the V 5+ ion. When observing the Eu 3+ emission as a result of (VO 4 ) 3− to Eu 3+ charge transfer, the ratio of intensities recorded upon two different excitation wavelengths is temperature dependent. This response is exploited for transient 2‐dimensional temperature imaging using two ultraviolet light emitting diodes (LEDs) for excitation, which are subsequently pulsed, while recording the emission on a single camera. As a demonstration, a YVO 4 :Eu 3+ coated metal plate is subjected to localised heating by a flame. Thanks to the efficient excitation and signal collection, an accuracy of 0.6 °C and a precision of 1.5 °C are achieved at a resolution of 160 μm and a repetition rate of 2.5 Hz, all with peak LED powers below 1 mW and a single low‐frame‐rate camera.