Engineering a ratiometric-sensing platform based on a PTA-NH2@GSH-AuNCs composite for the visual detection of copper ions via RGB assay

This work involved the development of a smartphone-assisted ratiometric-sensing platform for the convenient detection of copper ions (Cu2+). The ratiometric fluorescence sensor was fabricated by the formation of a complex between 2-aminoterephthalic acid (PTA-NH2) and glutathione-stabilized gold nanoclusters (GSH-AuNCs). Within 30 s after adding different concentrations of Cu2+, the fluorescence intensity of GSH-AuNCs decreased dramatically at 595 nm, whereas the fluorescence intensity of PTA-NH2 at 445 nm remained constant. Accordingly, a clear linear relationship was found to exist between the fluorescence intensity ratio (F595/F445) and a wide range of Cu2+ concentrations (1–150 μM), and the detection limit (LOD) for Cu2+ sensing was 0.275 μM. The recoveries of spiked samples from real samples ranged from 94.4 % to 105.2 %, proving that the sensing platform could be successfully utilized to detect Cu2+ in real samples. Moreover, the fluorescence images that were captured with a smartphone were uploaded and analyzed by the desktop software Photoshop (PS). The channel values of red (R), green (G), and blue (B) of the generated images were rapidly determined, and the R/B values were suitable for the semi-quantitative analysis of Cu2+ in real samples without any expensive equipment or complicated operation. Therefore, the as-proposed strategy offers great potential prospects for visually monitoring environmental pollution, particularly in resource-limited areas.