Reduced Graphene Oxide Based Turn-On Fluorescence Sensor for Highly Reproducible and Sensitive Detection of Small Organic Pollutants

Although the turn-on fluorescence-based detection approach has been widely used in diverse fields, its implementation in graphene-based organic pollutant detection is challenging. Water samples having a low quantity of organic pollutants poses appreciable challenges in its sensitive and reproducible detection. We have developed a dextran-fluorescein functionalized graphene composite which can reproducibly detect organic pollutants like bisphenol A, 1-napthol, phenol, and picric acid in nanomolar to picomolar concentration via a turn-on fluorescence approach. In this approach, dextran-fluorescein has been used as a fluorescent probe whose fluorescence remains quenched on the graphene surface. In presence of organic pollutants, the fluorescent probe detaches itself from the graphene surface due to competitive interaction with the organic molecules for the graphene surface. Recovered fluorescence is measured as the positive signal of organic pollutants. This detection approach is reproducible, sensitive, and requires a small amount of sample volume. We have extended this approach for on-field detection of organic pollutants. For this purpose, the composite material is coated on a silica-based plate (thin layer chromatography plate) and exposed to organic pollutants. Under a hand-held UV lamp (365 nm excitation), recovered fluorescence can be seen by the naked eye as a signal of the presence of organic pollutants in the sample of interest. This approach is simple, reproducible, sensitive, and reusable.