All-in-one thermometer-heater up-converting platform YF3:Yb3+,Tm3+ operating in the first biological window

Achieving the combination of real-time diagnosis and therapy in one up-converting platform with sensitive thermometry and efficient heat production is a critical step towards photo-thermal therapy (PTT). Here, the potentiality of truncated octahedral YF3:Tm3+/Yb3+ micro-crystals as thermometers operating in the first biological window (BW-I) was evaluated on the basis of a thermo-responsive fluorescence intensity ratio (FIR) of far-red to NIR emission from completely separated F-3(2,3)/H-3(4) -> H-3(6) transitions. The probabilities of cross-relaxation (CR) processes related to F-3(2,3)/H-3(4) levels were greatly enhanced by increasing the Yb3+ content, leading to an increase of more than three times in the absolute sensitivity within the physiological temperature range. Photo-thermal effects were also assessed by monitoring the variation of temperature around the samples as functions of the Yb3+ dosage, excitation time and density of 980 nm laser diodes. These results offer a promising strategy to optimize the thermal sensitivity and optical heating ability, which indicates that the present UC platform has great potential applications in PTT as real-time thermometers and photo-thermal agents.