Quantum-dot-functionalized paper-based device for simultaneous visual detection of Cu(II), Mn(II), and Hg(II)

In this work, a new paper-based device (PAD) was developed for the colorimetric detection of multiple heavy metals. The sensing principle of this PAD is based on the analyte-regulated photocatalytic activity of quantum dots (QDs) to certain substrates. The PAD consisted of three filter paper layers, defining a sample area, three channels, and three testing areas. Three photocatalytic reactions between different QDs and their corresponding substrates could be performed in one device, achieving the simultaneous detection of Cu(II), Mn(II), and Hg(II). The detection limits are 7.3 nM for Cu(II), 5.4 nM for Mn(II), and 8.1 nM for Hg(II), respectively. This PAD was applied to analyze real samples and the results were consistent with those obtained by inductively coupled plasma-optical emission spectrometer. This approach may provide a promising colorimetric sensing platform for multi-target analysis.