Yanling Huang,Guiyin Yue,Fang Luo,Longhua Guo,Bin Qiu,Zhenyu Lin
Hydrogen sulfide (H2S) is a dramatically toxic gas molecule; long term exposure to H2S environment poses a serious threat to human health. It is highly imperative to develop sensitive and selective methods for H2S detection. In this study, a signal-on fluorescence biosensor for the H2S (used to represent the total amount of H2S, HS− and S2−) detection was developed based on silver-mediated base pairs (C–Ag+–C). Two separate C-rich single-stranded DNAs (ssDNAs) were synthesized, namely, one was labeled with fluorescein (6-carboxyfluorescein, FAM) and the other was labeled with quencher (black hole quencher, BHQ1). The two ssDNAs were in a flexible single strand owing to the mismatch of the ssDNA, and hence, significant fluorescence intensity was observed. In the presence of Ag+, DNA probes could selectively capture Ag+ to form double stranded DNA (dsDNA) via the C–Ag+–C base pairs, which made the quench of FAM by BHQ1 and low fluorescence signal was detected. With the addition of H2S to the system, the dsDNA was decomposed into ssDNA since Ag+ could be released from C–Ag+–C by the formation of a more stable complex Ag2S, which resulted in the recovery of the fluorescence intensity. The enhanced fluorescence intensity had a linear relationship with H2S concentration in the range from 0.5 to 20 μM with a detection limit (LOD) of 0.16 μM (S/N = 3). The proposed system was applied to detect H2S (used to represent the total amount of H2S, HS− and S2−) in air near a garbage station with satisfying results.
It is highly desirable and a popular topic in scientific research to develop a highly sensitive and selective detection and quantitative analysis method of determining trace silver ions (Ag + ) in aqueous media since Ag + ions are recognized as one of the most hazardous metal pollutants. Three-dimensional graphene oxide (3D-GO) was decorated with Fe 3 O 4 to form nanocomposites of Fe 3 O 4 @3D-GO, which were further used as electrode materials in an electrochemical DNA sensor for detecting Ag + . Because of the chemical functionality and porous structure of the developed nanocomposites, single-stranded and cytosine-rich oligonucleotides could be anchored onto their surfaces or interior, followed by selective detection of Ag + through formation of C–Ag + –C complex forms. The results of electrochemical measurement showed that the Fe 3 O 4 @3D-GO nanocomposites exhibits high sensitivity for detecting Ag + with a detection limit of 2.0 pM within the range of 0.01–100 nM Ag + (S/N = 3). The developed electrochemical biosensor based on Fe 3 O 4 @3D-GO exhibits highly selectivity, good repeatability, and stability for detecting Ag + ions. The results of this work demonstrate that Fe 3 O 4 @3D-GO nanocomposites could be used as a promising tool to detect heavy metal ions in water or the environment.
Chenhui Hao,Jinxiu Wei,Shenfei Zong,Zhuyuan Wang,Hong Wang,Yiping Cui
Ag+ ions are widely used in various fields of human life due to their unique properties and they threaten the environment and human health. The traditional methods for Ag+ detection commonly suffer from disadvantages including limited sensitivity, expensive equipment and complicated operating steps. Herein, we developed a highly specific dual-color fluorescence co-localization (DFC) strategy based on the C–Ag+–C structure for Ag+ detection. In this strategy, Ag+ ions can be captured to form C–Ag+–C base pairs, and these ions enable single-stranded DNAs to form double strands. The DFC strategy can exclude nonspecific interaction sites and greatly improve the sensitivity and specificity. By DFC of the QDs and Cy5 linked to the DNA strands, highly sensitive Ag+ detection was achieved in the concentration range from 0.14 pM to 200 nM, with a limit of detection (LOD) of 0.14 pM. Moreover, this method has been applied for the detection of Ag+ ions in real environmental samples with satisfactory recoveries. We believe that the DFC strategy is promising for Ag+ detection.
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