In this work, fluorescent carbon dots were synthesized from polyethylene glycol. The carbon dots are of sizes below 10 nm as confirmed through dynamic light scattering studies and transmission electron microscope images. Carbon dot was further conjugated with Ca to form metal-ion-conjugated polyethylene glycol carbon dot. The metal-ion-conjugated polyethylene glycol carbon dot exhibits enhanced photoluminescence properties. Fluorescence of the Ca-modified carbon dots was quenched in the presence of Trifluralin. The practical utility of the system was demonstrated by using it to detect Trifluralin contaminated soil sample. Also, an array of sensor plates prepared using the drop-casting method on glass plates showed visual changes in fluorescence in the presence of Trifluralin. Development of such fluorescent-based detection system will lead to visual detection kits for detecting herbicides in general.Graphical AbstractWe developed a fluorescent-based metal conjugated polyethylene glycol carbon dot (Ca-PEG-CD) that was used to detect Trifluralin herbicide.