Carbon Dot-Based Sensors for Food Chemical Hazard Detection: Real-Food Applications, Sample Preparation, and Portable Analysis

Carbon dots (CDs) are a heterogeneous family of fluorescent carbon nanomaterials that includes carbon quantum dots (CQDs) as a subclass. Owing to their favorable fluorescence, surface chemistry, and functionalization potential, CDs have been widely investigated for sensing analytes relevant to food chemical safety. This structured narrative review and evidence map examines a broad analytical corpus of 106 original CD-based studies published between 2016 and 29 August 2026, covering heavy metals and metalloids, pesticides, veterinary drugs and antibiotics, and food additives, adulterants, and processing contaminants. Food-matrix eligibility was then assessed separately: 68 studies experimentally applied the method to an actual food matrix and generated 98 study–food matrix combinations. This two-tier analysis shows that veterinary-drug studies focused mainly on dairy products, pesticide studies predominantly addressed fruits and vegetables, and the comparatively limited food applications for heavy metals concentrated in aquatic products. Centrifugation, filtration, organic-solvent extraction, and deproteinization remained common, indicating that rapid sensor response does not necessarily translate into rapid end-to-end food analysis. Paper-based, hydrogel, and smartphone-assisted platforms are advancing CD detection from visual observation toward calibration-based quantification; however, validation using commercial samples at native or unknown concentrations, incurred samples, cross-device consistency, and field standardization remain insufficient. The synthesis therefore identifies analytical reliability, complex-matrix compatibility, simplified pretreatment, multi-analyte detection, and standardized on-site quantification as priorities beyond the pursuit of lower detection limits.