A fluorescence sensor probe based on porous carbon, molecularly imprinted polymer and graphene quantum dots for the detection of trace sulfadimethoxine

•A composite nanoprobe was fabricated and used to detect sulfadimethoxine.•We embedded graphene quantum dots and porous carbon in molecularly imprinted polymer.•Sulfadimethoxine was detected by the quenched fluorescence of the probe.•The nanoprobe exhibited high specificity and sensitivity toward sulfadimethoxine.•The developed optosensor accurately detected sulfadimethoxine in milk (86.8–98.9%).