Designing Dual Emissions via Co-doping or Physical Mixing of Individually Doped ZnO and Their Implications in Optical Thermometry.

Here, we report on the novel design of dual emission via defect state engineering in codoped oxide microstructures and its implication in fluorescence intensity ratio (FIR) based optical temperature sensing. Eu- and Er-co-doped ZnO (EuEr:ZnO) microrods prepared by hydrothermal method. The emission peaks corresponding to Eu3+ and Er3+ are observed suggesting dual emission from codoped ZnO. Interestingly, Er3+ peak intensity decreases and that of Eu3+ increases with increase of temperature as is the case of individual doped cases and dual emission is also achieved via phyical mixing of the individual doped ZnO. The opposite trend is due to the electron transfer from the defect levels of host ZnO to Eu3+ and not to Er3+. Overall, our results pave the way in designing dual emission that can be exploited in FIR based temperature sensing. As an example, we probe temperature dependency of congo-red and polyvinyle alcohol (PVA) composite using EuEr:ZnO as optical probe for temperature sensing.