Silver nanocubes-based sensor for mercury detection in water samples

Mercury is a commonly known environmental pollutant that can cause severe harm to humans and animals. One of the main sources of chronic low-level mercury exposure is fish and shellfish consumption. Mercury is metabolized by... [ view full abstract ]

Mercury is a commonly known environmental pollutant that can cause severe harm to humans and animals. One of the main sources of chronic low-level mercury exposure is fish and shellfish consumption. Mercury is metabolized by the bacteria or algae and enters the food chain, to be consumed by water organisms and finally by humans. Due to potential danger of mercury poisoning, it is very important to monitor this element concentration in water samples.

Various classical analytical methods have been proposed for mercury detection. However, most of them are usually complex and need time consuming pre-treatment, pre-concentration and separation steps. Many systems utilizes mercury’s unique capability to form amalgams with gold and silver. The amalgamation process significantly influences localized surface plasmon resonance (LSPR) spectrum of the nanostructures. Since the measurements require only a spectrophotometer as an instrument, LSPR-based methods have been developed as fast, simple, and low cost technology.

In our work a new, selective AgNCs-based mercury sensor have been developed. The silver nanocubes were synthesized by polyol reduction. Addition of aqueous NaBH₄ is necessary to reduce Hg²⁺ to Hg(0). Aqueous solutions of HgCl₂ were added to AgNCs in the presence of NaBH₄ and the UV-vis spectra have been measured. The HgCl₂ concentration range was1×10^-17 – 1×10^-5 M. The detection limit of AgNCs-sensor was 1×10^-16 M, which is significantly lower comparing to the others already published silver nanoparticles-based mercury sensors.

The new sensor has been demonstrated to be selective against Fe²⁺, Cu²⁺, Co²⁺, Zn²⁺, Ni²⁺ and Mg²⁺. The potential application of AgNCs-sensor may be investigation of Hg²⁺ in natural waters e.g. Baltic Sea. We have also investigated mercury detection by silver nanocubes suspended in NaCl water solutions. The silver nanocubes did not precipitate at the high concentration of NaCl and the shape of peaks remained the same as in water. After addition of HgCl₂ to AgNCs/NaBH₄ the sensor was still sensitive to the mercury also in the low concentration of HgCl₂.