I’m from Wales, so I’m used to using an umbrella on a regular basis. But in the future, umbrellas could be used to do more than just protect us from getting a soaking. Researchers in China are hoping that they’ll be used to monitor environmental conditions - more specifically, acid rainfall.
Hong-Wen Gao and Xin-Hui Xu from Tongji University in Shanghai painted a dye that changes colour in acidic rain onto an umbrella, mixed with acrylic-based emulsion paint, as reported in Chemical Communications.
— The umbrella before and after five minutes’ exposure to simulated acid rain: (A) before rain; (B to E) pH 5.6, 5.0, 4.5 and 4.0
The dye is made from a Congo red dye–barium sulfate hybrid that changes from red to blue if the rain has a pH less than 5 (the opposite to school lab staple litmus paper). When it dries, the material changes back to red. Congo red is used in labs as an acid–base indicator and in textile, print and paper making. Barium sulfate is usually used to increase hardness and whiteness in paint, paper, rubber and plastic. Here, the researchers have bound barium sulfate to Congo red, which transforms the dye into a thick semi-fluid and prevents the dye leaching in water.
Acid rain is caused by large amounts of sulfur dioxide and nitrogen dioxide gases released into the atmosphere during industrial processes. The areas most affected are eastern and north-western Europe, northern and eastern America and south-eastern Canada. The rain itself isn’t harmful, but the gases have been linked to asthma and bronchitis.
Gao and Xu had thought about painting the dye onto buildings, but when they tested it in strong sunshine for 18 hours, the dye decomposed under the ultraviolet rays.
The researchers say that the umbrellas would provide the public with a way to detect acid rain as a form of personal protection. But then they conclude their article with: ‘Surely, with every citizen all over the world acting forcefully, air pollution and acid rain problems may eventually be solved.’ Perhaps there’s a more ambitious plan for these umbrellas?
Elinor Richards
