Paper-Based, Hand-Drawn Free Chlorine Sensor with\nPoly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)

Abstract

The\nconcentration of free chlorine used for disinfecting drinking water,\nrecreational water, and food processing water is critical for environmental\nand human health conditions, and should be controlled within stipulated\nranges. This report, for the first time, describes a paper-based electrochemical\nfree chlorine sensor fabricated by hand-drawing. The electrical resistivity\nof a poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS)\nchemoresistor increases when it is exposed to free chlorine in water\ndue to oxidation reactions. Because the relative change of the electrical\nresistance represents the sensor’s response, the sensor can\nbe fabricated by hand-drawing with different shapes and dimensions.\nThe fabrication steps are all at room temperature, require no instrumentation\nor equipment, and can be carried out by untrained personnel. The fabricated\nsensor is mechanically stable, reusable, has a wide sensing range,\nand can accurately measure free chlorine concentrations in real water\nsamples. Therefore, the low-cost, hand-drawn free chlorine sensor\nis of great significance for water quality monitoring in less developed\nareas where fabrication facilities, analytical equipment, and trained\npersonnel are limited, but the need for analytical devices is critical.\nIn addition to the free chlorine sensor demonstrated in this study,\nother types of PEDOT:PSS-based sensors and electronic devices can\nbe fabricated by the developed hand-drawing process.