A facile and stable colorimetric sensor based on three-dimensional graphene/mesoporous Fe3O4 nanohybrid for highly sensitive and selective detection of p-nitrophenol

•Fabricating a novel and convenient colorimetric nanosensor for sensitive and selective detection of p-nitrophenol.•3D GF/m-Fe3O4 exhibits highly peroxidase mimicking activity as a novel heterogeneous nanozymes.•The sensor was based on the switching off the nanozyme activity of 3D GF/m-Fe3O4.•The selectivity was due to the π-stacking interaction.•3D GF/m-Fe3O4 nanohybrid sensor possesses good reusability and stability.