Rapid and sensitive analytical methods of measuring mycotoxin contamination levels in medicinal herbs are urgently needed. This paper proposes a novel immunoassay utilizing PEG-modified CdSe/CdS quantum dots (QDs) with signal enhancement by glycine for aflatoxin B1 (AFB1) detection in medicinal herbs. Special attention was paid to the stability and photoluminescence (PL) properties of these QDs in multi-compound solutions. In this work, the dual ligands of 3-mercaptopropionic acid (MPA) and thiol-terminated methoxy PEG (mPEG-HS) were used collectively to overcome baffling coagulation and allowed for the successful transfer of hydrophobic QDs to aqueous solution. To maintain excellent PL intensity of the QDs, the ingenious solution of adding glycine was suggested, and the final PL intensity increased approximately 2 times compared to the baseline. The proposed surface modification significantly improved the colloidal stability and PL intensity of the QDs, as well as simplified the procedure compared to commonly used approaches. Furthermore, this is the first report of using these modified QDs as sensitive label for rapidly screening of AFB1 in different medicinal herbs, with IC50s ranging from 0.17 to 0.35 ng mL−1. The QD labeling technique could potentially serve as a novel means of performing fast trace-detection in complex matrices. © 2018 Elsevier B.V.