The present disclosure relates to detection of organophosphorus herbicides. In one aspect of the present disclosure, envisaged is a nanobiocatalyst for detecting organophosphorus herbicides. The nanobiocatalyst comprises a laccase enzyme immobilized on silica coated magnetic iron oxide nanoparticles. Also envisaged is a method for detecting organophosphorus herbicides. In an embodiment of the present disclosure, the laccase enzyme used for detecting the presence of said organophosphorus herbicides is optionally reused by separating the laccase enzyme immobilized on silica coated magnetic iron oxide nanoparticles by magnetic decantation. In an embodiment of the present disclosure, envisaged is a method for producing the nanobiocatalyst for detecting organophosphorus herbicides. Also envisaged is a test strip for detecting organophosphorus herbicides comprising a laccase enzyme immobilized on silica coated magnetic iron oxide nanoparticles.