Detection of Mercury Ions in Water by Nitrogen and Sulfur-doped Fluorescent Carbon Quantum Dots

KeyWord:waste water  carbon quantum dots £¨CQDs£©  mercury  rapid detection

Abstract:

      Mercury is one of the toxic and harmful heavy metal pollutants in the environment£®It can enter the human body through the accumulation of food chain£¬thus damaging the human health£®Recently£¬the control of mercury pollution has attracted much attention£®The main detection methods for mercury in water involve inductively coupled plasma optical emission spectrometry£¨ICP£­OES£©£¬atomic absorption spectrometry£¨AAS£©£¬atomic fluorescence spectrometry£¨AFS£© and inductively coupled plasma mass spectrometry£¨ICP£­MS£©£®However£¬these methods generally could not meet the requirements for convenient£¬rapid and sensitive on-site detection£®Fluorescence detection method has the advantages of simple operation£¬rapid response£¬high sensitivity£¬good selectivity£¬and independent of large-scale instruments£¬which could fully meet the requirements for rapid detection of mercury in water£®Based on the fluorescence quenching mechanism of Hg2+ on carbon quantum dots£¨CQDs£©£¬a rapid method based on nitrogen and sulfur doped fluorescent CQDs was established for the detection of Hg2+ in water£®The fluorescent CQDs were synthesized by one-step hydrothermal method with sodium citrate£¬waste water and tetramethylthiuram disulfide as carbon£¬nitrogen and sulfur sources£®Effects of the spectral properties as well as pH value£¬reaction time and component content on fluorescence intensity were all investigated£®In the process of Hg2+ detection£¬the relationships of fluorescence quenching with reaction time and pH value were further investigated£¬and the kinetic mechanism of quenching reaction was analyzed£®The experimental results showed that the fluorescence quenching reaction of Hg2+ on CQDs was rapid£¬ which has a high quenching effect at pH 7.0£¬while the fluorescent CQDs had good selectivity and anti-interference ability for Hg2+£®Under the optimized conditions£¬the detection limit for Hg2+ was 0.95 ¦Ìg/L£¬and the linear range was 1£­6 ¦Ìg/L.The accuracy of this method was investigated with surface water£¬and the recoveries for actual water samples ranged from 100% to 126%£¬with relative standard deviations£¨RSD£© of 0.31%£­3.9%.This method was suitable for rapid and convenient on-site detection of Hg2+ in waste water samples.