title: Ion-directed assembly of gold nanorods: a strategy for mercury detection.
abstract: Water-soluble gold nanorods (Au NRs) have been functionalized with an N-alkylaminopyrazole ligand, 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (PyL), that has been demonstrated able to coordinate heavy metal ions. The N-alkylaminopyrazole functionalized Au NRs have been characterized by electron microscopy and spectroscopic investigation and tested in optical detection experiments of different ions, namely, Zn(2+), Cd(2+), Hg(2+), Cu(2+), Pb(2+), and As(3+). In particular, the exposure of the functionalized NRs to increasing amounts of Hg(2+) ions has resulted in a gradual red-shift and broadening of the longitudinal plasmon band, up to 900 nm. Interestingly, a significantly different response has been recorded for the other tested ions. In fact, no significant shift in the longitudinal plasmon band has been observed for any of them, while a nearly linear reduction in the plasmon band intensity versus ion concentration in solution has been detected. The very high sensitivity for Hg(2+) with respect to other investigated ions, with a limit of detection of 3 ppt, demonstrates that the functionalization of Au NRs with PyL is a very effective method to be implemented in a reliable colorimetric sensing device, able to push further down the detection limit achieved by applying similar strategies to spherical Au NPs.
authors.affiliation: CNR-IPCF Istituto per i Processi Chimici e Fisici, Sez. Bari, c/o Dip. Chimica Via Orabona 4, 70126, Bari, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Placido
authors.forename: Gemma
authors.initials: G
authors.lastname: Aragay
authors.forename: Josefina
authors.initials: J
authors.lastname: Pons
authors.forename: Roberto
authors.initials: R
authors.lastname: Comparelli
authors.forename: M Lucia
authors.initials: ML
authors.lastname: Curri
authors.forename: Arben
authors.initials: A
authors.lastname: Merkoçi
mesh_terms: D000327:Adsorption; D015374:Biosensing Techniques / Q000295:instrumentation*; D006046:Gold / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D008628:Mercury / Q000032:analysis*; D043942:Nanotubes / Q000737:chemistry*
chemical_list: D007477:Ions; D006046:Gold; D008628:Mercury