Abstract
Mercury ion (Hg2+) is considered to be one of the most toxic heavy metal ions. Once the content of Hg2+ exceeds the quality standard in drinking water, the living environment and health of human beings will be threatened and destroyed. Therefore, the establishment of simple and efficient methods for Hg2+ ion detection has important practical significance. In this paper, we present a highly sensitive and selective fiber-optic surface plasmon resonance (SPR) Hg2+ ion chemical nanosensor by designing thymine (T)-modified gold nanoparticles (Au NPs/T) as the signal amplification tags. Thymine-1-acetic acid (T-COOH) was covalently coupled to the surface of 2-aminoethanethiol (AET)-modified Au NPs and Au film by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride/N-Hydroxysuccinimide (EDC/NHS) activation effect, respectively. In the presence of Hg2+ ions, the immobilized thymine combines specifically with Hg2+ ions, and forms an Au/thymine-Hg2+-thymine/Au (Au/T-Hg2+-T/Au) complex structure, leading to a shift in SPR wavelength due to the strong electromagnetic couple between Au NPs and Au film. Under optimal conditions, the proposed sensor was found to be highly sensitive to Hg2+ in the range of 80 nM–20 µM and the limit of detection (LOD) for Hg2+ was as low as 9.98 nM. This fiber-optic SPR sensor afforded excellent selectivity for Hg2+ ions against other heavy metal ions such as Fe3+, Cu2+, Ni2+, Ba2+, K+, Na+, Pb2+, Co2+, and Zn2+. In addition, the proposed sensor was successfully applied to Hg2+ assay in real environmental samples with excellent recovery. Accordingly, considering its simple advantages, this novel strategy provides a potential platform for on-site determination of Hg2+ ions by SPR sensor.
Highlights
Introduction published maps and institutional affilHeavy metals are characterized by natural stability, biological toxicity, activity and persistency, non-biodegradation, and bioaccumulation, etc. [1,2,3,4]
Au NPs/T tags were injected into the sensing system; it was found that the surface plasmon resonance (SPR) resonant wavelength showed a significant shift
This result clearly demonstrates that our proposed sensor has a high selectivity for Hg2+ ion detection (Figure 10). Such high selectivity is due to the special combination between T and Hg2+ ions, which forms a relatively stable Au/T-Hg2+ -T/Au complex structure. These results demonstrated that the present SPR sensor possesses a high potential application in environmental pollution detection
Summary
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), chloroauric acid (HAuCl4 ·4H2 O), thymine-1-acetic acid (T-COOH), N-Hydroxysuccinimide (NHS), and 2-aminoethanethiol (AET) were purchased from Sigma-Aldrich (Shanghai, China). The T-modified fiber-optic SPR surface was achieved by immersing the stand for 15 min. The T-modified fiber-optic SPR surface was achieved by immersing the AET-functionalized optic fiber in the carboxyl-activated T-COOH solution for 3 h. For the preparation of thymine-functionalized Au NPs (Au NPs/T), 0.1 mM T-COOH was activated by 10 mM EDC/NHS solution (MES buffer solution, 1 mM, pH 6) for 15 min at 25 ◦ C with constant stirring. For the preparation of thymine-functionalized Au NPs (Au NPs/T), 0.1 mM T-COOH was activated by 10 mM EDC/NHS solution (MES buffer solution, 1 mM, pH 6) for 15 min at of 12. 0.3 mL of carboxyl-activated T-COOH was added into 5 mL Au NPs/AET solution with stirring at room temperature for 4 h. Ter was used for demonstration of Hg2+ ion detection in real water samples
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