CdTe QDs based fluorescent sensor for the determination of gallic acid in tea.

A new fluorescent light switch method, which based on N‑acetyl‑l‑cysteine capped CdTe QDs (NALC-CdTe QDs), was developed for the detection of gallic acid (GA). The QDs possess a fluorescence emission wavelength at 520nm and with symmetric fluorescence. When KMnO4 is added, the high fluorescence of QDs could be effectively quenched for the electron transfer process between KMnO4 and QDs. But with the addition of GA, the fluorescence of KMnO4-QDs system could recover for the reason that redox reaction of GA and KMnO4. Therefore, a fluorescent light switch method could be used for GA with a detection range of 0.6-12.6μg·mL-1 and a detection limit of 0.56ng·mL-1. Furthermore, the feasibility of the proposed fluorescence biosensor in tea was also studied and satisfactory results were obtained.