title: Colorimetric detection of Cd2+ using gold nanoparticles cofunctionalized with 6-mercaptonicotinic acid and L-cysteine.
abstract: 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).
authors.affiliation: College of Chemistry and Chemical Engineering, Graduate University of Chinese Academy of Sciences, 19A YuQuan Road, 100049 Beijing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xue
authors.forename: Hong
authors.initials: H
authors.lastname: Zhao
authors.forename: Zhijiao
authors.initials: Z
authors.lastname: Wu
authors.forename: Xiangjun
authors.initials: X
authors.lastname: Li
authors.forename: Yujian
authors.initials: Y
authors.lastname: He
authors.forename: Zhuobin
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D002104:Cadmium / Q000032:analysis*; D002412:Cations / Q000737:chemistry; D003124:Colorimetry; D003545:Cysteine / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D010848:Picolinic Acids / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D002412:Cations; D010848:Picolinic Acids; D014874:Water Pollutants, Chemical; D002104:Cadmium; C045255:6-mercaptopicolinic acid; D012965:Sodium Chloride; D006046:Gold; D003545:Cysteine