title: Highly selective and sensitive detection of mercuric ion based on a visual fluorescence method.
abstract: The instant and on-site detection of trace aqueous mercuric ion still remains a challenge for environmental monitoring and protection. This work demonstrates a new analytical method and its utility for visual detection of aqueous Hg(2+) on the basis of a novel water-soluble CdSe-ZnS quantum dots (QDs) functionalized with a bidentate ligand of 2-hydroxyethyldithiocarbamate (HDTC). The fluorescence of the aqueous HDTC modified QDs (HDTC-QDs) could be selectively and efficiently quenched by Hg(2+) through a surface chelating reaction between HDTC and Hg(2+), and the detection limit was measured to be 1 ppb. Most interestingly, the orange fluorescence of the HDTC-QDs gradually changes to red upon the increasing amount of Hg(2+) added besides the decreasing of the fluorescence intensity. By taking advantage of this optical phenomenon, a paper-based sensor for aqueous Hg(2+) detection has been developed by immobilizing the HDTC-QDs on cellulose acetate paper which has low background fluorescence in the wavelength range. The paper-based sensor showed high sensitivity and selectivity for Hg(2+) visual detection. When Hg(2+) was dropped onto the paper-sensor, an obviously distinguishable fluorescence color evolution (from orange to red) could be clearly observed depending on the concentration of Hg(2+). The limit of detection of the visual method for aqueous Hg(2+) detection was as low as 0.2 ppm. The very simple and effective strategy reported here should facilitate the development of portable and reliable fluorescence chemosensors for mercuric pollution control.
authors.affiliation: Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Yuan
authors.forename: Kui
authors.initials: K
authors.lastname: Zhang
authors.forename: Zhongping
authors.initials: Z
authors.lastname: Zhang
authors.forename: Suhua
authors.initials: S
authors.lastname: Wang
mesh_terms: D003116:Color; D004050:Ditiocarb / Q000031:analogs & derivatives / Q000737:chemistry; D057230:Limit of Detection; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D010209:Paper; D045663:Quantum Dots; D013050:Spectrometry, Fluorescence; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D004050:Ditiocarb; D008628:Mercury; C039353:dihydroxyethyldithiocarbamate