A recyclable colorimetric sensor made of waste cotton fabric for the detection of copper ions

A large quantity of waste cotton fabric (WCF) generated every year in the world is either incinerated or buried leading to pollution and resource wastes. Here, in order to develop a recycling avenue for WCF, a simple, easy-to-use, and portable sensor was designed for the colorimetric detection of toxic Cu 2+ in water and food. The sensor (WCF-CPZ) was prepared by coating the surface of WCF with the chromogenic copper chelator cuprizone (CPZ). The results showed that the naked-eye detection limit of the WCF-CPZ sensor for Cu 2+ in drinking water was 0.5 mg/L. With image analysis by a smartphone, the quantitative limit of detection of the WCF-CPZ sensor was improved to 0.13 mg/L, which is well below the maximum Cu 2+ concentration allowed by the World Health Organization in drinking water of 2.0 mg/L. The WCF-CPZ sensor was also successfully employed for the detection of Cu 2+ in lake water and milk samples with an accuracy of more than 92%. Moreover, the robust and sustainable WCF support could be stripped and reused multiple times for colorimetric assays without sensitivity losses. Graphical abstract