Optical temperature sensing behavior of enhanced green upconversion emissions from Er–Mo:Yb2Ti2O7 nanophosphor

The Er–Mo:Yb2Ti2O7 nanocrystalline phosphor has been prepared by sol–gel method and used as an optical thermometry. By Mo codoping, the green upconversion (UC) emission intensity increased about 250 times than that of Er:Yb2Ti2O7 under a 976 nm laser diode excitation. It indicates that such green enhancement arises from the high excited state energy transfer (HESET) with the |2F7/2, 3T2> state of Yb3+–MoO42− dimer to the 4F7/2 level of Er3+. The fluorescence intensity ratio (FIR) of the two green UC emissions bands was studied as a function of temperature in a range of 290–610 K, and the maximum sensitivity and the temperature resolution were approximately 0.0074 K−1 and 0.1 K, respectively. It suggests that the Er–Mo:Yb2Ti2O7 nanophosphor with a higher green UC emissions efficiency is a promising prototype for applications in optical temperature sensing.