Facile fabrication of AuNP-functionalized cotton sensors for colorimetric Cd2+ detection

Gold nanoparticles (AuNPs) coated with disodium ethylenediaminetetraacetic acid (Na 2 EDTA) have been created as a highly sensitive, selective, and simple colorimetric test for the detection of Cd 2+ . In this case, Na 2 EDTA serves as a stabilizing and reducing agent. When Cd 2+ coordinates with Na 2 EDTA capped-AuNPs in a colorimetric sensing method, the interparticle distances decrease, leading to aggregation. As a result, the color shifts significantly from red wine to blue. The Na 2 EDTA-AuNPs/Cd complex is created when the color changes from red-wine to purple and finally blue as the concentration of Cd 2+ increases. The Na 2 EDTA-AuNPs/Cd blue solution turns yellow when Na 2 S is added. By comparing these color changes to various metal ions (Hg 2+ , Mg 2+ , Ni 2+ , Co 2+ , Ca 2+ , K + , Ba 2+ , and Bi 2+ ), selective Cd 2+ detection can be achieved. This provided a simple and effective colorimetric sensor (no enzyme or DNA) for on-site, real-time Cd 2+ detection. With a linear fit coefficient of R 2 = 0.93929, this shows a sensitive linear relationship between 1/R values and [Cd 2+ ]. Using a cotton probe based on Na 2 EDTA-AuNPs, the estimated detection limit of Cd was 280 nM.