Colorimetric detection of Cd2+ using gold nanoparticles cofunctionalized with 6-mercaptonicotinic acid and L-Cysteine

• Published in: Analyst (London) 2011-09, Vol.136 (18), p.3725-3730
• Main Authors: Xue, Ying, Zhao, Hong, Wu, Zhijiao, Li, Xiangjun, He, Yujian, Yuan, Zhuobin
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Applied sciences; Cadmium - analysis; Cations - chemistry; Chemistry; Colorimetry; Cysteine - chemistry; Exact sciences and technology; Global environmental pollution; Gold - chemistry; Hydrogen-Ion Concentration; Metal Nanoparticles - chemistry; Picolinic Acids - chemistry; Pollution; Sodium Chloride - chemistry; Spectrometric and optical methods; Water Pollutants, Chemical - analysis
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c1an15238f

We have developed a colorimetric assay for the highly sensitive and selective detection of Cd(2+) using gold nanoparticles (AuNPs) cofunctionalized with 6-mercaptonicotinic acid (MNA) and L-Cysteine (L-Cys) through the formation of an Au-S bond. In the presence of Cd(2+), the aggregation of functionalized AuNPs occurred by means of a metal-ligand interaction that led to visible color changes. Most importantly, cofunctionalized AuNPs had better responses for Cd(2+) than that functionalized by either MNA or L-Cys. Cd(2+) could be detected by the colorimetric response of AuNPs that could be detected by the naked eye or a UV-vis spectrophotometer. The absorbance ratio (A(620)/A(523)) was linear with the Cd(2+) concentration in the range of 2.0 × 10(-7) to 1.7 × 10(-6) M. Under optimum conditions (2.0 × 10(-5) M MNA, 2.0 × 10(-6) M L-Cys and 0.020 M NaCl at pH 10.0), the detection limit (3σ) of Cd(2+) could be as low as 1.0 × 10(-7) M. Interference experiments showed that Pb(2+) and Cu(2+) caused a slight interference for Cd(2+) determination while other metal ions caused no interference. The proposed method was successfully applied to determine the concentration of Cd(2+) in environmental samples (lake water).