title: A label-free colorimetric detection of lead ions by controlling the ligand shells of gold nanoparticles.
abstract: We have developed a simple, colorimetric and label-free gold nanoparticle (Au NP)-based probe for the detection of Pb(2+) ions in aqueous solution, operating on the principle that Pb(2+) ions change the ligand shell of thiosulfate (S(2)O(3)(2-))-passivated Au NPs. Au NPs reacted with S(2)O(3)(2-) ions in solution to form Au(+).S(2)O(3)(2-) ligand shells on the Au NP surfaces, thereby inhibiting the access of 4-mercaptobutanol (4-MB). Surface-assisted laser desorption/ionization time-of-flight ionization mass spectrometry (SALDI-TOF MS) and inductively coupled plasma mass spectrometry (ICP-MS) measurements revealed that PbAu alloys formed on the surfaces of the Au NPs in the presence of Pb(2+) ions; these alloys weakened the stability of the Au(+).S(2)O(3)(2-) ligand shells, enhancing the access of 4-MB to the Au NP surfaces and, therefore, inducing their aggregation. As a result, the surface plasmon resonance (SPR) absorption of the Au NPs red-shifted and broadened, allowing quantitation of the Pb(2+) ions in the aqueous solution. This 4-MB/S(2)O(3)(2-)-Au NP probe is highly sensitive (linear detection range: 0.5-10 nM) and selective (by at least 100-fold over other metal ions) toward Pb(2+) ions. This cost-effective sensing system allows the rapid and simple determination of the concentrations of Pb(2+) ions in real samples (in this case, river water, Montana soil and urine samples).
authors.affiliation: Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan.
authors.forename: Yu-Lun
authors.initials: YL
authors.lastname: Hung
authors.forename: Tung-Ming
authors.initials: TM
authors.lastname: Hsiung
authors.forename: Yi-You
authors.initials: YY
authors.lastname: Chen
authors.forename: Chih-Ching
authors.initials: CC
authors.lastname: Huang
mesh_terms: D003124:Colorimetry / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D006801:Humans; D007854:Lead / Q000032:analysis* / Q000737:chemistry / Q000652:urine; D008024:Ligands; D057230:Limit of Detection; D053768:Metal Nanoparticles / Q000737:chemistry*; D008956:Models, Chemical; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D008024:Ligands; D014867:Water; D007854:Lead; D006046:Gold