title: Synthesis of polyethyleneimine capped carbon dots for preconcentration and slurry sampling analysis of trace chromium in environmental water samples.
abstract: Carbon dots capped with polyethyleneimine (CD-PEI) were synthesized and applied in selective separation and preconcentration of trace Cr(VI). Dispersed particle extraction (DPE) slurry sampling with flame atomic absorption spectrometry (FAAS) was used to selectively and sensitively determine Cr(VI) in water samples. The as-synthesized CD-PEI was confirmed by Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, elemental analysis, fluorescence and zeta potential measurement. The adsorption of Cr(VI) on CD-PEI was evaluated. Its isothermal adsorption was studied and fitted in the Langmuir model. Nearly 85% of Cr(VI) was adsorbed within 10 min showed that the CD-PEI exhibited fairly fast kinetics for the sorption of Cr(VI). Experimental conditions, including the content and size of CD-PEI, sample pH, adsorption time, sample volume, slurry volume and interfering ions, were further optimized to obtain efficient preconcentration and high-precision determination of Cr(VI). CD-PEI with small size turned to be a good candidate for the preparation of slurry. CD-PEI served not only as a promising adsorbent for separation and preconcentration of Cr, but also a signal-enhancing agent in FAAS. The method achieved an enhancement factor of 30 and a detection limit (S/N=3) of 0.21 µg L(-1) Cr(VI) with a consumption of 14.0 mL sample and an adsorption time of 5 min, which provided two times of signal enhancement. The RSD for 11 replicate measurements of 5.0 µg L(-1) Cr(VI) was 2.8%. The possible signal enhancement mechanism was proposed. The developed method has been applied to determine trace Cr(VI) in a variety of water samples.
authors.affiliation: Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, China. Electronic address: nkcmliu@yahoo.com.
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Beijing Guodian Futong Science and Technology Development CO., LTD, Beijing 100070, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Chemistry, Nankai University, Tianjin 300071, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, China.
authors.forename: Hai-Ping
authors.initials: HP
authors.lastname: Wei
authors.affiliation: Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, China.
authors.forename: Xiao-Shuang
authors.initials: XS
authors.lastname: Li
authors.affiliation: Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, China.
authors.forename: Xi-Hua
authors.initials: XH
authors.lastname: Zhang
authors.affiliation: Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, China.
authors.forename: Shi-Min
authors.initials: SM
authors.lastname: Chen
authors.affiliation: Tianjin Guangfu Fine Chemical Research Institute, Tianjin 300384, China.
authors.forename: Xiao-Qin
authors.initials: XQ
authors.lastname: Chen
keywords: Carbon dots capped with polyethyleneimine; Chromium (VI); Dispersed particle extraction; Slurry sampling