“On-off–on” fluorescent probes based on amino-modified zinc oxide quantum dots for Cu2+ detection in snail meat

A fluorescent probe comprising amino-modified zinc oxide quantum dots (NH 2 –ZQDs) with stable fluorescent properties was prepared using the sol–gel method. Based on the photoinduced electron transfer (PET) and electrostatic adsorption (ESA) quenching effects of copper ions (Cu 2+ ) on the NH 2 –ZQDs and the mechanism of competitive binding of Cu 2+ and the NH 2 –ZQDs to L-methionine (L-Met), an NH 2 –ZQDs + Cu 2+ + L-Met fluorescence quenching–recovery sensing system was designed to efficiently exclude Fe 3+ interference. Thus, a novel “on-off-on” fluorescent probe was developed to specifically recognize Cu 2+ . The probe showed good linearity (y = 0.03102x − 0.1156, R 2  = 0.9953) over 5–25 μmol/L, with a limit of detection of 0.039 μmol/L. It exhibited good selectivity and was successfully applied to the quantitative determination of Cu 2+ in snail meat and tap water, with spiked recoveries in the range of 98.04 %–109.53 %.