A Smartphone-Based Sensing for Portable and Sensitive Visual Detection of Hg (II) via Nitrogen Doped Carbon Quantum Dots Modified Paper Strip.

The development of portable and cost-effective sensing system for Hg²⁺ quantitation is highly demanded for environmental monitoring. Herein, an on-site, rapid and portable smartphone readout device based Hg²⁺ sensing system integrating nitrogen-doped carbon quantum dots (NCDs) modified paper strip was proposed, and the physicochemical properties of NCDs were characterized by high resolution TEM, FTIR, UV–vis absorption spectrum and fluorescence spectral analysis. The modified paper strip was prepared via "ink-jet" printing technology and exhibits sensitive fluorescence response to Hg²⁺ with fluorescence color of bright blue (at the excitation/emission wavelength of 365/440 nm). This portable smartphone-based sensing platform is highly selective and sensitive to Hg²⁺ with the limit of detection (LOD) of 10.6 nM and the concentration range of 0–130 nM. In addition, the recoveries of tap water and local lake water were in the range of 89.4% to 109%. The cost-effective sensing system based on smartphone shows a great potential for trace amounts of Hg²⁺ monitoring in environmental water samples. [ABSTRACT FROM AUTHOR]