Er 2 O 3 nanospheres with fast response to humidity for non-contact sensing

a kind of lanthanide oxide functional material, Er 2 O 3 has aroused widespread scientific interest due to its exceptional properties; however, its humidity sensing performance remains to be explored. Herein, the rational designed Er 2 O 3 nanospheres were prepared by one-step solvothermal and high-temperature calcined method. The structure and morphology of the samples were analyzed by X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM), and the effect of calcination temperatures on humidity sensing characteristics was also investigated. It can be found that the Er 2 O 3 -600 sample (with a sintering temperature of 600 °C) exhibited favorable humidity sensing performance, including an ultra-fast response time (1 s), high sensitivity value (403), good linearity ( R 2 = 0.994) and low humidity hysteresis (2.4%). In addition, the non-contact skin moisture test indicated that the Er 2 O 3 -600 sensor could evaluate the proximity of human finger, which might widen its further potential application of human–machine interaction. Graphical abstract