cobalt chloride system in weather indicator devices

In order to ensure the colors of PA66/cobalt chloride NFM exposed to different relative humidity conditions, visible absorption spectra (380–780 nm) of the 50 wt% CoCl 2♶H 2O-doped NFM following exposure to variable RH were examined as displayed in Fig. b Humidity dependence of visible absorption spectra (380–780 nm) of PA66/CoCl 2♶H 2O (50 wt%) The results showed that the electrospun PA66/cobalt chloride NFM sensors exhibiting high humidity sensitivity with obviously color change, rapid response/recovery performance, small hysteresis, excellent reproducibility, and good stability.Ī The photographs of PA66/CoCl 2♶H 2O NFMs containing different concentrations of CoCl 2♶H 2O: 0, 10, 30, and 50 wt% in different RH. In this work, we fabricated PA66/cobalt chloride NFMs by electrospinning and investigated its humidity sensing properties by extensive color change and both fine quartz crystal microbalance (QCM).

However, colorimetric humidity sensor based on electrospun fibers was rarely investigated. Typical colorimetric RH indicator such as silica gel self indicator and CoCl 2-based optical humidity sensor have been presented. In addition, cobalt chloride has been applied as colorimetric RH indicator for its color changes when contaminated by water. At present, several intermediate agents have been adapted to realize colorimetric indicator for humidity including photonic crystal, polymer electrolyte thin films, doped cholesteric liquid crystal, and crystalline covalent organic framework nanofibers. Since RH do not have measurable intrinsic optical properties, some intermediate agent will be introduced to show a change in optical property. Optical humidity sensors will be a possible solution. While the sensitivity of the above humidity sensors based on electrospun fibers were detected by precise instrument, it may do not work in practical application limits to conditions.

Moreover, ceramic LiCl-doped ZnO electrospun fibers were also fabricated as humidity sensor, with response time and recovery time about 3 and 6 s. It shows high sensitivity and the response and recover times are 120 and 50 s, respectively, with RH changing from 2 to 35%. For example, electrospun polyamide 6 nano-fiber/net modified by polyethyleneimine was investigated as RH indicator detected by quartz crystal microbalance (QCM). It is now believed that RH sensors based on the electrospun nanofibrous membranes (NFMs) show improved sensor sensitivity due to their large surface area to volume ratio, providing an increased number of sites for analyte interaction or signal transduction. Among these types of sensors, the optical type has attracted a lot of interests since it is supplying a change in optical properties, easily detectable with the naked eye (visual) which is suitable for applications in daily life. Until now, various types of humidity sensors have been reported, such as resistance type, capacitor type, field-effect-transistor type, optical type, and so on. Relative humidity (RH) sensor is mainly used for monitoring atmospheric humidity environment and shows important applications in warehousing, environmental monitoring, instruments and meters, and meteorology.

Cobalt chloride system in weather indicator devices