Ultrasensitive label-free ratiometric colorimetric sensor for free chlorine detection in tap water based on a novel brilliant blue-Au NCs

In this work, Au nanoclusters was prepared under the guidance of a synthetic colorant brilliant blue (BB-Au NCs). The microstructure and crystal structure of the resulting products were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The absorbance of BB-Au NCs at 247 nm was enhanced while the absorbance at 308 and 630 nm was reduced by free chlorine, an unavoidable and ubiquitous disinfection byproduct. The optical properties of BB-Au NCs and the influence of free chlorine were analyzed using computational chemistry methods based on density functional theory (DFT). The ratio of absorbance of BBAu NCs at 247 and 630 nm was used for accurate quantitative determination of free chlorine in a range from 5 to 50 mu M, with the detection limit is 1 mu M. This method demonstrates potential application for simple and environmentally friendly detection of free chlorine in water samples.