Ultrasensitive and Label-Free Detection of Mercury Ions Using a Highly Efficient Solid-Liquid Triboelectric Nanosensor

Abstract

The mercury pollution in the world have increased tremendously due to both natural and anthropogenic reasons. The mercury ions (Hg2+) after being released from the industrial wastes into the environment is transformed into the highly toxic form of methylmercury (CH3Hg+) by the microorganisms present, which further accumulates in the human body via drinking water and food, ultimately causing irreversible damage to reproductive, immune and nervous system. Currently, analytical tools such as ICPMS, X-ray fluorescence spectroscopy, AES etc are employed for detection of the Hg2+ions but their utility is overshadowed by certain limitations like complicated sample preparation steps, time-consuming protocol, non-portable nature, requirement of trained professionals etc. Therefore, in this work we propose a highly sensitive and selective sensing method for Hg2+ions using the concept of solid-liquid contact electrification. This triboelectric nanosensor was developed employing modified Copper(II) oxide nanowires (CuO NWs) as the solid-triboelectric layer and deionized water as the liquid-triboelectric layer. Due to the highly specific reaction between the modified CuO NWs surface and Hg2+ions, the as-developed sensor can detect the Hg2+ion concentrations as low as 0.1 nM with a good linear range of 1nM-10 μM. In addition, the unrivalledly flexible nanosensor is coupled with the robotic fingertips for highly automated on-site monitoring of Hg2+ions, making it possible to track the heavy metal pollution in inaccessible and remote locations. We believe that this work will be a stepping stone towards designing a reusable, portable, low-cost and stand-alone sensing systems.