Colorimetric Humidity Sensors Based on Electrospun Polyamide/CoCl(2) Nanofibrous Membranes

Humidity indicators based on composite polyamide 66/cobalt chloride (PA66/CoCl(2)) nanofibrous membranes (NFMs) were successfully fabricated by electrospinning. A series of NFMs with various weight percentage of CoCl(2) to PA66 were prepared, and their humidity sensitivity based on color changing and quartz crystal microbalance (QCM) were studied. Due to the color change property of cobalt chloride, the as-spun composite NFMs show obviously macroscopic color change from blue to pink as relative humidity (RH) increasing from 12.4 to 97.2%. Moreover, the QCM detection showed a linear dependence on the RH changing and exhibited short response/recovery time (less than 65.4 s/11 s), small hysteresis (less than 11%), good reproducibility, and stability. Owing to the above double sensitive mechanism on RH, the PA66/CoCl(2) composite NFM may show great potential applications from meticulous to coarse. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s11671-017-2139-0) contains supplementary material, which is available to authorized users.