title: "Turn-on" fluorescent sensor for Hg2+ based on single-stranded DNA functionalized Mn:CdS/ZnS quantum dots and gold nanoparticles by time-gated mode.
abstract: An ultrasensitive "turn-on" fluorescent sensor was presented for determination of Hg(2+). This method is mainly based on Hg(2+)-induced conformational change of a thymine-rich single-stranded DNA. The water-soluble long-lifetime fluorescence quantum dot (Mn:CdS/ZnS) acted as the fluorophore, which was labeled on a 33-mer thymine-rich single-stranded DNA (strand A). The gold nanoparticles (GNPs) functionalized 10-mer single-stranded DNA (strand B) is selected as the quencher to quench the fluorescence of Mn:CdS/ZnS. Without Hg(2+) in the sample solution, strands A and B could form hybrid structures, resulting in the fluorescence of Mn:CdS/ZnS being decreased sharply. When Hg(2+) is present in the sample solution, Hg(2+)-mediated base pairs induced the folding of strand A into a hairpin structure, leading to the release of GNPs-tagged strand B from the hybrid structures. The fluorescence signal is then increased obviously compared with that without Hg(2+). The sensor exhibits two linear response ranges between fluorescence intensity and Hg(2+) concentration. Meanwhile, a detection limit of 0.18 nM is estimated based on 3α/slope. Selectivity experiments reveal that the fluorescent sensor is specific for Hg(2+) even with interference by high concentrations of other metal ions. This sensor is successfully applied to determination of Hg(2+) in tap water and lake water samples. This sensor offers additional advantage to efficiently reduce background noise using long-lifetime fluorescence quantum dots by a time-gated mode. With excellent sensitivity and selectivity, this sensor is potentially suitable for monitoring of Hg(2+) in environmental applications.
authors.affiliation: College of Environmental Science and Engineering, Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082, China.
authors.forename: Dawei
authors.initials: D
authors.lastname: Huang
authors.forename: Chenggang
authors.initials: C
authors.lastname: Niu
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wang
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Lv
authors.forename: Guangming
authors.initials: G
authors.lastname: Zeng
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D004277:DNA, Single-Stranded / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry; D008628:Mercury / Q000032:analysis*; D053768:Metal Nanoparticles / Q000737:chemistry*; D045663:Quantum Dots; D013440:Sulfides / Q000737:chemistry; D013997:Time Factors; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D004277:DNA, Single-Stranded; D005456:Fluorescent Dyes; D013440:Sulfides; D017967:Zinc Compounds; C034939:cadmium sulfide; D008345:Manganese; D006046:Gold; D008628:Mercury; C031238:zinc sulfide