| Gold nanoparticles (AuNPs) has been payed attention owing to their distance-dependent optical properties such as surface effect, size effect, optoelectronic effect, favorable stabilization and biocompatibility. The AuNPs colorimetric method has payed attention because of its many advantages, such as special spectral properties, rapidly, simplicity, and no need large-scale instrument. In recent years, the rapid development of industrialization causes various degrees of pollution of water environment, especially the heavy metal pollution of drinking water, which affects the human seriously. In this paper, first of all, we conclude the properties and the synthesis methods of gold nanoparticles, then we reviewed the gold nanoparticle-based colourimetric in recent four years. At last we developed Ethylenediaminetetraacetic acid functionalized gold nanoparticles for sensitive colorimetric detection of chromium (Ⅲ) and colorimetric assays for iron (Ⅱ) via in situ synthesis of gold nanoparticles.Ethylenediaminetetraacetic acid functionalized gold nanoparticles for sensitive colorimetric detection of chromium (Ⅲ)A cost-effective, eco-friendly and sensitive colorimetric method was described for the determination of chromium (Ⅲ) by using ethylenediaminetetraacetic acid functionalized gold nanoparticles (EDTA-2Na-AuNPs). TEM indicates the diameter of particles of the EDTA-2Na-AuNPs was (6.0±1.5nm). The stable and dispersed EDTA-2Na-AuNPs were prepared by reducing HAuCl4with sodium borohydride in the presence of EDTA-2Na as a capping agent. Upon the addition of chromium (IIIⅢ), the color of EDTA-2Na-AuNPs solution changed from red to violet, which was in response to the surface plasmon absorption of dispersed and aggregated EDTA-2Na-AuNPs. The method is capable of determining chromium (Ⅲ) over the range of0.1-1.0μmol/L with a limit of detection of0.08μmol/L. The relative standard deviation was2.5%for repetitive measurements of0.2μmol/L chromium (Ⅲ) solution (n=11). The method was applied to the determination of chromium (Ⅲ) in water samples. Colorimetric assays for iron (Ⅱ) via in situ synthesis of gold nanoparticlesA fast and simple colorimetric method was described for the determination of iron (Ⅱ) by using in situ synthesis of gold nanoparticles. Hydrogen peroxide can reduction gold (Ⅲ) ions to generate gold nanoparticles in the morpholineethane sulfonic acid (MES) buffer. The concentration of hydrogen peroxide dictates the state of aggregation of gold nanoparticles. A high concentration of hydrogen peroxide can be generated dispersed state of AuNPs, the color is red; while the aggregation of AuNPs (blue) was generated at the low concentration of hydrogen peroxide. We consider of that the hydrogen peroxide can be catalytic decomposed by iron (Ⅱ). So we adition iron (Ⅱ) into the system of Au3+-MES-H2O2, we discovered that the solution is change from purple to blue in the presence of iron (Ⅱ). The concentration of iron (Ⅱ) can be detected by UV-Vis absorption spectroscopy. Based on these observations, a new colorimetric method was established for the determination of iron (Ⅱ). Under the selected experimental conditions, the absorbance of550nm was linear with the concentration of iron (Ⅱ) in the range of0.1-4.0μmol/L. |
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