title: Label-free colorimetric sensing of cobalt(II) based on inducing aggregation of thiosulfate stabilized gold nanoparticles in the presence of ethylenediamine.
abstract: As a sensitive and selective analytical technique, gold nanoparticles-based colorimetric sensing was characterized by its simplicity and cost-effectiveness. Specific methods have been extensively developed for different targets in diverse samples. In this study, a label-free method for sensing Co(2+) in aqueous solutions was described. The target was achieved by the induced aggregation of thiosulfate (S(2)O(3)(2-)) stabilized gold nanoparticles (AuNPs) in the presence of ethylenediamine (en). Co(2+) first reacted with en and formed complexes of Co(en)(3)(2+) in aqueous solutions, which was followed by the oxidation of Co(en)(3)(2+) to Co(en)(3)(3+) by dissolved oxygen. Co(en)(3)(3+) then attacked S(2)O(3)(2-) ligands adsorbed on the AuNPs' surfaces, forming positively charged (en)(2)CoS(2)O(3)(+) on the AuNPs' surfaces, which reduced the surface charges of AuNPs and induced the aggregation of AuNPs. The process was accompanied by a red-shift in the adsorption spectrum and a visible colour change from wine red to blue. Potential effects of relevant experimental conditions, including pH, concentrations of S(2)O(3)(2-) and en, and incubation time were evaluated for optimization of the method. The proposed method is sensitive (LOD = 0.0 4 μM or 2.36 ppb) and selective (by at least 100-fold over other metal ions except for Cu(2+)) toward Co(2+) with a linear range from 0.1 to 0.7 μM. The cost-effective method allows rapid and simple determination of the concentrations of Co(2+) ions in drinking water.
authors: Key Laboratory of Coastal Environmental Processes, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, China.
authors: Zhiyang
authors: Z
authors: Zhang
authors: Jun
authors: J
authors: Zhang
authors: Tingting
authors: T
authors: Lou
authors: Dawei
authors: D
authors: Pan
authors: Lingxin
authors: L
authors: Chen
authors: Chengli
authors: C
authors: Qu
authors: Zhaopeng
authors: Z
authors: Chen
mesh_terms: D015374:Biosensing Techniques; D003035:Cobalt / Q000032:analysis*; D003124:Colorimetry; D060766:Drinking Water; D005029:Ethylenediamines / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D013885:Thiosulfates / Q000737:chemistry / Q000378:metabolism*
chemical_list: D060766:Drinking Water; D005029:Ethylenediamines; D013885:Thiosulfates; D003035:Cobalt; C031234:ethylenediamine; D006046:Gold