High performance of colorimetric humidity sensors based on minerals

In this study, three minerals were chosen as the host of colorimetric humidity sensor, and Bromothymol blue (BTB) was used as the indicator. The BTB based on titanium dioxide (BTB-TiO 2 ), BTB based on palygorskite (BTB-palygorskite) and BTB based on mullite (BTB-mullite) exhibited the readable response to the relative humidity (RH) of 11, 43 and 75% at 1 min at 25 °C. Moreover, the BTB-palygorskite exhibited the rapid and stable color response, especially under the low humidity (11% RH). The surface area played an important role on the cover density of BTB and water adsorption which made the humidity sensor with excellent performances.