Visual and colorimetric detection of mercury(II) ion using gold nanoparticles stabilized with a dithia-diaza ligand
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We have developed a simple method for the highly selective colorimetric detection of dissolved mercury(II) ions via direct formation of gold nanoparticles (AuNPs). The dithia-diaza ligand 2-[3-(2-amino-ethylsulfanyl)-propylsulfanyl]-ethylamine (AEPE) was used as a stabilizer to protect AuNPs from aggregation and to impart highly selective recognition of Hg(II) ion over other metal ions. A solution of Au(III) ion is directly reduced by sodium borohydride in the presence of AEPE and the detergent Triton X-100. This results in the formation of AEPE-AuNPs and a red coloration of the solution. On the other hand, in the presence of Hg(II), the solution turns blue within a few seconds after the addition of borohydride. This can be detected spectrophotometrically or even visually. The method was successfully applied to quantify Hg(II) levels in water sample, with a minimum detectable concentration as low as 35 nM.
KeywordsGold nanoparticle Mercury(II) Dithia-diaza ligand Colorimetric detection Naked-eye
This study was carried out in the Environmental Analysis Research Unit (EARU) financially supported by Ratchadaphiseksomphot Endowment Fund, Chulalongkorn University (GRU 53-005-23-003 and FW002A), the program Strategic Scholarships for Frontier Research Network for the Ph.D. Program Thai Doctoral degree and the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission (FW652I). Dr. Robert Butcher, Publication Counseling Unit, Faculty of Science, Chulalongkorn University is also acknowledged for English corrections and suggestions.