Self-Diffusion Driven Ultrafast Detection of ppm-Level Nitroaromatic Pollutants in Aqueous Media Using a Hydrophilic Fluorescent Paper Sensor

Development of fluorescent film probes for toxic nitroaromatic compound pollutants (NACs) such as 2,4,6-trinitrotoluene (TNT) in real water samples implies broad applications in environmental and industrial safety control. Despite many recent advances, there are still some difficult challenges facing this area, for example, the restricted sensitivity and long response time caused by hindered and slow diffusion of aqueous NACs samples inside a dense, solid film. Hence, we report herein a robust fluorescent paper sensor with improved sensing abilities, which is prepared by absorbing hydrophilic pyrene-functionalized polymer uniformly into cellulose-based filter papers. Thanks to the numerous oxygen-containing groups grafted on cellulose papers, they allow passive and ultrafast capillary force driving diffusion of aqueous NACs samples into their hydrophilic matrix. Specifically speaking, these paper sensors can offer efficient self-diffusion paths inside the test strips and immediately bring the pyrene fluorophores and NACs quenchers into close proximity. Therefore, the developed paper-based test strips enable both naked-eye detection of low-ppm-level TNT and ultrafast fluorescence quenching with a response time of only a few seconds, which are difficult to be achieved by conventional film probes.