A smartphone sensing fluorescent detection of mercury ion based on silicon quantum dots in environment water

Mercury ion (Hg²⁺) pose a significant hazard to the natural environment. Conventional techniques like Inductively coupled plasma mass spectrometry, X-ray absorption spectroscopy, among others, pose some disadvantages as they demand a lot of money, need trained employees, and cannot provide on-site detection in real-time. A smartphone sensing technique based on silicon quantum dots (Si-QDs) was presented to detect Hg²⁺ in the environment without the usage of sophisticated equipment. Meanwhile, the technology was built by utilizing a smartphone to capture gray values of fluorescent images of the Si-QDs-Hg²⁺ system. Microwave-assisted Si-QDs with tiny particle size, high fluorescence, and good optical stability were created. The fluorescence of the Si-QDs was gradually quenched by raising the Hg²⁺ concentration from 0.5 μmol/L to 5.0 μmol/L for fluorescent detection with a detection limit of 28 nmol/L. The 94.8-97.1 % recovery demonstrated the viability of the Si-QDs approach for detecting Hg²⁺. Meanwhile, a smartphone sensing strategy was built by recording the gray value of the fluorescent images of the Si-QDs-Hg²⁺ systems using a smartphone, and the detection limit of the established approach was 3 nmol/L. The accuracy and reliability of the smartphone strategy were verified with the recovery rates of 80.3-92.5 % in tap water and 87.6-109 % in river water. Electron transfer quenching mechanism between Si-QDs and Hg²⁺ was evidenced by ultraviolet-visible spectroscopy, fluorescent decay curves, cyclic voltammetry, and Zeta potential. Finally, the suggested approach was used to detect Hg²⁺ in water samples from various environments.