Temperature- and humidity-sensing properties of ZnO:Yb/Er nanocrystal clusters synthesized by a facile microwave-assisted approach

In this paper, we synthesized monodispersed ZnO:Yb/Er nanocrystal clusters (NCs) by a facile microwave-assisted approach. The fluorescence intensity ratio technique based on the two green upconversion emissions of ZnO:Yb/Er NCs was studied as a function of temperature with the maximum temperature sensitivity of 0.00323 K−1 in the range of 300-625 K. The ZnO:Yb/Er NCs also exhibited excellent impedance-dependent humidity sensing behavior with fast response and recovery characteristics time and dynamic response at a wide range of 11-95% relative humidity. It is anticipated that the present rare-earth doped ZnO NCs can furnish a simple, inexpensive and facile multifunctional application both in temperature and humidity sensing.