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

Mercury(II) ions (Hg) 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 Hg 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 Hg ions. Due to the inherent difficulty in directly detecting Hg 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 Hg 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 Hg and the nitrogen of pyridine, Hg could be captured by 4-MPY to form a Hg(pyridine) complex. After adsorption of the Hg 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 Hg 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.