Cheap and green deep eutectic solvents with favorable physical properties for significantly improved near-infrared light detection

Cheap and highly thermal-sensitive liquid media with favorable physical properties is one of the key parameters for achieving the efficient near-infrared light (NIR) photothermal sensor with high potential application. However, the reported liquid media for photothermal sensor is expensive or non-efficient. Herein, several deep eutectic solvents (DESs) composed by DBU and LiNO 3 with different mole ratio are utilized as liquid media and DBU:LiNO 3 (3:1) shows the best thermal-sensitive ability. After doping photothermal agents polydopamine (PDA) with DBU:LiNO 3 (3:1), the efficiency of photothermal sensor could reach 1100.25%, much higher than the highest value of the previous report (ca. 379.91%) at the same NIR light power. Cycle investigation on the NIR photothermal sensor could be recycled at least five times with negligible loss of efficiency. Most importantly, the price of DBU:LiNO 3 (3:1) in this work is also about one third of the previous report. This work broadens the design strategy for highly efficient NIR photothermal sensor through selecting appropriate component and regulating suitable mole ratio of DESs with low cost and high sustainability.