Quantitative remote and on-site Hg²⁺ detection using the handheld smartphone based optical fiber fluorescence sensor (SOFFS)

In order to detect Hg²⁺ in remote and on-site mode, we design a smartphone based optical fiber fluorescence sensor (SOFFS), which is composed of a semiconductor laser for fluorescence signal excitation, a quantum dot modified fiber probe for Hg²⁺ sensing, a smartphone with a filter for fluorescence signal collection, and a fiber coupler for connecting fiber probe, laser and smartphone. With the evanescent wave on the optimized combination tapered fiber probe surface, SOFFS has an ultra-low detection limit of 1 nM and a wide detection range between 1 nM to 1000 nM. Besides, it is handheld with a small size of 79×57×154 mm³ and inner power supply, and the combination tapered fiber probe can be easily replaced, supporting the remote and on-site applications. Additionally, a smartphone application is designed for automatically quantifying the fluorescence signals for accurate and rapid Hg²⁺ detection. Since SOFFS is compact and cost-effective, moreover, it can measure Hg²⁺ in fast speed, excellent selectivity, high accuracy and sensitivity, it is a potential tool for remote and on-site applications.