Novel Visual Detection of Mercury(II) Ion Based on <i>In Situ </i>Deposited Gold Nanoparticles

Abstract

In this report, we present a new method for visual and colorimetric detection of Hg (II) ion by using in-situ composited gold nanoparticle (GNP). GNP was formed in one step at room temperature, using NaBH4 as reducing agent incorporated with 2-[5-(2-aminoethylsulfanyl)-pentylsulfanyl]-ethylamine (5-AEPE) as a stabilizer. A 5-AEPE ligand displayed an effective stabilizer for preventing the aggregation of gold nanoparticle in the absence of Hg (II) ion, showing a rose-red color. On the other hand, in the presence of Hg (II) ion, reduced Hg (0) can also deposit on the surface of gold nanoparticle, resulting solution turn to purple and blue immediately. Based on naked eye detection optimization, 125 μM Au (III), 0.6 mM 5-AEPE, 0.8 mM NaBH4 and 0.1%(v/v) Triton X-100 was achieved. By measuring at a wavelength of 680 nm, absorbance values increased linearly as two levels of concentration of Hg (II) ion range of 0.125-2.5 μM (low) and 2.5-15 μM (high). This method offer advantage of simplicity, rapidity, cost effectiveness and no requirement of any sophisticated instruments. Moreover, this method has several potential advantages as optical sensor, especially no as-prepared gold nanoparticle synthesis and shorter observation time.