Disodium EDTA-capped AuNP-engineered cotton pad as a colorimetric probe for formalin detection

Formalin, an organic chemical containing a mixture of carbon, hydrogen, and oxygen, is a formaldehyde solution in water that is widely used as a preservative because of its antibacterial qualities. Despite being used to extend the shelf life and conceal product deterioration, it may be harmful to customers. In light of these factors, a portable, sensitive, accurate, and user-friendly platform for formalin detection is suggested here. The present study utilizes a colorimetric approach that involves the use of disodium ethylenediaminetetraacetic acid (EDTA)-capped gold nanoparticles (AuNPs) and a smartphone. A cotton pad with AuNa₂EDTA integrated served as the substrate for formalin adsorption. The colorimetric image is then converted into RGB values using the graphical editor software, GNU Image Manipulation Program (GIMP), to detect formalin. A noticeable color shift was seen during the detection process: the hue changed from red-wine to purplish-blue as the formalin content rose, indicating the development of the AuNa₂EDTA-HCHO complex. This result provides a low detection limit of 0.11 μM and a sensitive linear correlation between 1/R values and various formalin concentrations, with a linear fit coefficient of 0.99607. The present study represents the first attempt, to the best of our knowledge, to report on the experimental activation energy of gold nanoparticles capped with Na₂EDTA as well as the application of this nanostructure as a formalin detection platform. The developed system has a great potential of being used in clinical settings for the detection of formalin.