Smartphone-Enabled Fluorescence and Colorimetric Platform for the On-Site Detection of Hg and Cl Based on the Au/Cu/TiC Nanosheets.

Smartphone-assisted fluorescence and colorimetric methods for the on-site detection of Hg and Cl were established based on the oxidase-like activity of the Au-Hg alloy on the surface of Au/Cu/TiC NSs. The Au nanoparticles (NPs) were constructed via in-situ growth on the surface of Cu/TiC NSs and characterized by different characterization techniques. After the addition of Hg, 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 Hg 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 Hg 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 Hg and Cl, a convenient on-site colorimetric method for an analysis of Hg and Cl was achieved by using digital images combined with smartphones (color recognizers). The digital picture sensor could analyze RGB values in concentrations of Hg or Cl via a smartphone app. In summary, the proposed Au/Cu/TiC NSs-based method provided a novel and more comprehensive application for environmental monitoring.