Gold nanoparticles-enhanced hollow fiber surface plasmon resonance sensor for highly sensitive detection of mercury(II) ions

Mercury(II) ions (Hg2+) are one of the most common and highly toxic heavy metal ions, which can contaminate the environment and damage the human health. Therefore, the precise detection of trace Hg2+ concentration is particularly important. Herein, gold nanoparticles-enhanced silver-coated hollow fiber (HF) surface plasmon resonance (SPR) sensor was developed for the highly sensitive detection of Hg2+ ions. Due to the inherent difficulty in directly detecting Hg2+ ions on the sensing surface, the advantages of gold nanoparticles (AuNPs) as signal amplification labels were exploited to improve the sensitivity of the sensor. In the presence of Hg2+ ions, we chemically modified the sensing silver film of the sensor with 4-mercaptopyridine (4-MPY) and 4-mercaptopyridine-functionalized gold nanoparticles (AuNPs/4-MPY). Owing to the specific coordination between Hg2+ and the nitrogen of pyridine, Hg2+ could be captured by 4-MPY to form a Hg(pyridine)2 complex. After adsorption of the Hg2+ ions, the strong electromagnetic coupling between the AuNPs and the silver film led to a wavelength shift of the SPR resonance peak. Experiments for the detection of Hg2+ ions were performed in the concentration range of 5 nM to 1 μM to investigate the performance of the present sensor. The sensor achieved a limit of detection (LOD) as low as 5 nM. Moreover, the developed fiber sensor exhibited excellent performance in terms of sensitivity and repeatability. Our results show this strategy has widespread applications in the field of on-site heavy metal detection and biomedical monitoring.