7th ISF

CHEM035 - Enhanced Gold Amalgamation Catalysis in Paper-Based Analytical Device for Fluorometric Mercury Detection in Environmental Samples

In this work, a selective and sensitive mercury (Hg²⁺) determination in environmental samples based on enhanced catalytic activity of gold amalgamation (Au-Hg) using a paper-based analytical device (PAD) was developed. The developed peroxidase-mimicking activity of Au-Hg towards H₂O₂-mediated oxidation of o-phenylenediamine dihydrochloride (non-fluorescence structure, OPD) to produce an orange-yellow fluorescence product of 2,3-diamino phen (DAP) was investigated. The detection zone was coated with gold nanoparticles (AuNPs) solution and added the OPD substrate. During the analysis step, Hg²⁺ in the samples interacts with AuNPs to form the Au-Hg amalgam products through the amalgamation. Next, the generated Au-Hg amalgam species oxidized the OPD fluorescence substrate in the presence of H₂O₂, subsequently increasing the fluorescent intensity (DAP) on the PAD corresponding to Hg²⁺ concentrations. For quantitative analysis of Hg²⁺, the detection zone on the PAD was captured by a camera attached to a smartphone under a homemade UV-controlled lightbox. The fluorescence intensities were then analyzed using the ImageJ software to establish a calibration curve for further quantification. Importantly, this developed approach can offer advantages over the conventional method in terms of ease of use, low cost, and small volumes of reagents.

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