The performance of a label-free lateral flow immunoassay for pathogen detection that obviates the use of secondary antibodies and is revealed by the photoluminescent quenching ability of GO has been explored. The analyte is selectively attached onto the test line of the strip (which contains Ab-QDs) leading to a highly specific and sensitive sensing phenomenon that is clearly observable up to 10 CFU mL-1 in standard buffer and 100 CFU mL-1 in bottled water and milk. Since the estimated cost of the materials and reagents of the proposed lateral flow test is less than 0.10 Euro (see table ST1
in SI), this approach will prove valuable as a cost-effective device that is disposable and easy-to-use. Moreover, this device is appealing for portable and automated applications that may include other similar size analytes with interest for diagnostics.