title: Colorimetric response of dithizone product and hexadecyl trimethyl ammonium bromide modified gold nanoparticle dispersion to 10 types of heavy metal ions: understanding the involved molecules from experiment to simulation.
abstract: A new kind of analytical reagent, hexadecyl trimethyl ammonium bromide (CTAB), and dithizone product-modified gold nanoparticle dispersion, is developed for colorimetric response to 10 types of heavy metal ions (M(n+)), including Cr(VI), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change of the modified gold nanoparticle dispersion is instantaneous and distinct for Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change results from the multiple reasons, such as electronic transitions, cation-π interactions, formation of coordination bonds, and M(n+)-induced aggregation of gold nanoparticles (AuNPs). The different combining capacity of heavy metal ions to modifiers results in the different broadening and red-shifting of the plasmon peak of modified AuNPs. In addition, Cr(VI), Cu(2+), Co(2+), Ni(2+), and Mn(2+) cause the new UV-vis absorption peaks in the region of 360-460 nm. The interactions between the modifiers and AuNPs, and between the modifiers and M(n+), are investigated by using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results confirm that AuNPs are modified by CTAB and dithizone products through electrostatic interactions and Au-S bonds, respectively, and the M(n+)-N bonds form between M(n+) and dithizone products. Furthermore, the experimental and density functional theory calculated IR spectra prove that dithizone reacts with NaOH to produce C6H5O(-) and [SCH2N4](2-). The validation of this method is carried out by analysis of heavy metal ions in tap water.
authors.affiliation: Key Laboratory of Magnetic Materials and Devices, and Division of Functional Materials and Nanodevices, and New Energy Institute, Ningbo Institute of Materials Technology & Engineering (NIMTE), Chinese Academy of Sciences (CAS), Ningbo 315201, China.
authors.forename: Yumin
authors.initials: Y
authors.lastname: Leng
authors.forename: Yonglong
authors.initials: Y
authors.lastname: Li
authors.forename: An
authors.initials: A
authors.lastname: Gong
authors.forename: Zheyu
authors.initials: Z
authors.lastname: Shen
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Aiguo
authors.initials: A
authors.lastname: Wu
mesh_terms: D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D004230:Dithizone / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D019216:Metals, Heavy; D004230:Dithizone; D006046:Gold; D000077286:Cetrimonium