A portable fluorescence probe-based sensor for rapid field detection of zinc ions in water.

Excessive Zn2+ in water poses a threat to aquatic ecosystems and human health. Conventional methods for Zn2+ detection either rely on bulky instrumentation or suffer from poor quantification capability, limiting their suitability for field analysis. Recent integration of three-dimensional (3D)-printed platforms and smartphone imaging presents an opportunity for field analysis. Therefore, a small molecule fluorescent probe (SWJT-K1) was combined with a 3D-printed homemade portable device and a smartphone for field analysis of Zn2+ in water. SWJT-K1 undergoes a rapid green-to-blue fluorescence color change upon Zn2+ coordination, enabling quantification by RGB readings directly from smartphone images. The system exhibited good linearity for Zn2+ in the range of 0.3-7.0 μM with a detection limit of 0.23 μM. The results obtained for real water samples (river water, lake water, tap water, precipitation and oilfield water) showed satisfactory agreement with inductively coupled plasma mass spectrometry (ICP-MS) results, and spiked recoveries ranged from 94.6% to 107.2%. This work provides a low-cost, easy-to-operate, and portable solution for routine Zn2+ monitoring in resource-limited settings, enabling rapid field water quality assessment where conventional analytical infrastructure is unavailable or impractical to deploy.