Smartphone-Enabled Fluorescence and Colorimetric Platform for the On-Site Detection of Hg2+ and Cl− Based on the Au/Cu/Ti3C2 Nanosheets

Smartphone-assisted fluorescence and colorimetric methods for the on-site detection of Hg2+and Cl−were established based on the oxidase-like activity of the Au–Hg alloy on the surface of Au/Cu/Ti3C2NSs. The Au nanoparticles (NPs) were constructed via in-situ growth on the surface of Cu/Ti3C2NSs and characterized by different characterization techniques. After the addition of Hg2+, the formation of Hg–Au alloys could promote the oxidization of o-phenylenediamine (OPD) to generate a new fluorescence emission peak of 2,3-diaminopenazine (ADP) at 570 nm. Therefore, a turn-on fluorescence method for the detection of Hg2+was established. As the addition of Cl−can influence the fluorescence of ADP, the fluorescence intensity was constantly quenched to achieve the continuous quantitative detection of Cl−. Therefore, a turn-off fluorescence method for the detection of Cl−was established. This method had good linear ranges for the detection of Hg2+and Cl−in 8.0–200.0 nM and 5.0–350.0 µM, with a detection limit of 0.8 nM and 27 nM, respectively. Depending on the color change with the detection of Hg2+and Cl−, a convenient on-site colorimetric method for an analysis of Hg2+and Cl−was achieved by using digital images combined with smartphones (color recognizers). The digital picture sensor could analyze RGB values in concentrations of Hg2+or Cl−via a smartphone app. In summary, the proposed Au/Cu/Ti3C2NSs-based method provided a novel and more comprehensive application for environmental monitoring.Keywords:Au/Cu/Ti3C2NS;Au–Hg alloy;oxidase-like activity;smartphone;colorimetric detection