Optical thermometry based on ZnAl2O4:Eu3+ with carbon dots incorporation

In this study, red carbon dot-incorporated ZnAl2O4:Eu3+ (CDs@ZAO:Eu3+) nanophosphors were synthesized using the sol-gel method, and CDs were prepared using green approaches with leaves and synthetic chemicals as sources. The incorporation of CDs in ZAO:Eu3+ reduced the positive and negative defects in the phosphor, resulting in improved crystallinity. A large spectral overlap between the emission of CDs and the absorption of ZAO:Eu3+ was observed. A 15.4% enhancement in the luminescence intensity (I) was analyzed from CDs@ZAO:Eu3+. The energy transfer process between CDs and Eu3+ was demonstrated. The temperature (T) and I had a linear relationship that could be fitted to a function of T=1276.5−970.9I. The absolute sensitivity and relative sensitivity were 1.03 × 10−3 K−1 and 1.12 × 10−3 K−1, respectively, at 383 K. Thus, CDs@ZAO:Eu3+ is a promising material for non-contact optical thermometry applications.