An ultra-sensitive and colorimetric sensor for copper and iron based on glutathione-functionalized gold nanoclusters

- We developed a simple system for Fe3+ and Cu2+ sensing with low cost and easy operations.
- Fe3+ and Cu2+ are simultaneously detected via colorimetric readout and fluorescent absorbance signals.
- The sensor realized the simultaneously detection of Fe3+ and Cu2+ successively with highly sensitivity and selectivity.

Here, we report an ultra-sensitive and colorimetric sensor for the detection of Fe3+ or Cu2+ successively using glutathione-functionalized Au nanoclusters (GSH-AuNCs). For GSH-AuNCs can catalytically oxidize peroxidase substrates, such as 3, 3′, 5, 5′-tetramethylbenzidine (TMB), colored products are formed in the presence of H2O2. While upon the addition of Fe3+ or Cu2+ into the GSH-AuNCs-TMB-H2O2 system, diverse color and absorbance of the system was obtained due to the self oxidation of Fe3+ and the inhibition of peroxidase-like activity of GSH-AuNCs. With the introduction of ethylene diamine tetraacetic acid (EDTA) or ammonium fluoride (NH4F) to GSH-AuNCs-TMB-H2O2+Cu2+ system or GSH-AuNCs-TMB-H2O2+Fe3+ system respectively, a restoration of color and absorbance of system was realized. On the basis of above phenomenon, a colorimetric and quantitative approach for detecting Fe3+ and Cu2+ was developed with detection limit of 1.25 × 10−9 M and 1.25 × 10−10 M respectively. Moreover, the concentration of Fe3+ and Cu2+ in human serums was also accurate quantified by this method. So this design strategy realized the simple and simultaneous detection of Fe3+ and Cu2+, suggesting significant potential in clinical diagnosis.

We designed a novel strategy for the colorimetric and sensitive detection of Fe3+ and Cu2+ based on the peroxidase-like activity of GSH-AuNCs.