Abstract

Water sources in rural areas are exposed to harmful Organophosphorus pesticides (OP) that should be detected before human consumption [1], and biosensors have emerged as an alternative [2]. The application of nanomaterials, including carbon quantum dots (CD), can significantly improve the performance of optical biosensors. In this work, naturally fluorescent and non- toxic CD synthesized previously [3] from African-oil palm biochar were integrated with Acetylcholinesterase enzyme (AChE) as a bioreceptor, to produce a fluorescent biosensor. This system is modulated with graphene oxide (OG), showing a fluorescence recovery in the presence of the OP. The biosensor was evaluated under pure chlorpyrifos, but also under a commercial formulation called Lorsban®. We obtained a limit of detection (LOD) as low as 0.13 ppb and 2.14 ppb for chlorpyrifos and Lorsban® respectively. The system also shows a good selectivity against proteins and other organic substances usually present in drinking water, even in tests with tap water. The specificity was also evaluated against two types of pesticides: cypermethrin (pyrethroid type) and methomyl (carbamate type), showing expected behavior. As far as we know, this is one of the few works reporting the integration of CD-AChE in optical systems and the detection of commercial pesticide formulations with promising results.