Paper-Like Visual Indicator Films for Harmful Hydrophilic Liquids and Vapors

Even a small amount of harmful liquid/gas leakage is hazardous and probably leads to extraordinarily dangerous situations. To effectively control the storage of harmful liquids/gases, the monitoring of leakage is thus highly important. Herein, we develop an indicator film that can easily respond to harmful hydrophilic liquids and gases and allow for the visual recognition of a transparency transformation involving hydrated poly­(N-isopropylacrylamide). The normalized transparency of the indicator film is 100% when it is wet and below 10% when it is triggered by hydrophilic liquids and gases. The pH paper-like indicator film responds to some harmful hydrophilic liquids and gases in the chemical laboratory, including alcohols, ketones, aldehydes, acid solutions, their corresponding vapors, and some gases. The response to hydrophilic liquids and gases by the indicator film is attributed to competition between hydrophilic molecules and poly­(N-isopropylacrylamide) in absorbing water. This work not only provides an understanding of the adsorption and diffusion of gases and liquids on surfaces but also affords promising applications for monitoring chemical industry and chemical laboratory environments, general pollution levels, and indoor air quality.