Microfluidic-based fluorescent electronic eye with CdTe/CdS core-shell quantum dots for trace detection of cadmium ions

Cadmium ions (Cd2+) greatly threat human health and the environment due to its extremely severe toxicity. Therefore, it is of paramount importance to establish a sensitive and portable platform for monitoring Cd2+ on site. In this work, a novel microfluidic-based fluorescent electronic eye (E-eye) combined with tetrasodium iminodisuccinate (IDS)-etched CdTe/CdS quantum dots (QDs) was developed for portable and sensitive detection of trace Cd2+ in water environment. The fluorescent E-eye consists of a microfluidic chip for miniaturized flow analysis, an ultraviolet light excitation module for fluorescent excitation, an optical lens for device miniaturization and a smartphone for portable photographing and analysis. The IDS was added in the CdTe/CdS QDs to cause fluorescence quenching due to the chemical etching. Subsequently added Cd2+ will be recognized by etched QDs, thus inducing the fluorescence changes that can be directly captured by the E-eye for quantitative detection of Cd2+. With the optimization of all parameters including pH, reaction time and the concentration of IDS, the proposed platform could detect Cd2+ with a low detection limit of 0.26 μg/L in the range of 1–250 μg/L. It is worth noting that the performance of the developed fluorescent E-eye is quite comparable to a commercial microplate reader with a detailed comparison in linearity, sensitivity and detection limit. In summary, the proposed microfluidic-based fluorescent E-eye provides a promising platform for portable and high sensitive detection of trace cadmium in water environment.