Design of dual-emission fluorescence sensor based on Cu nanoclusters with solvent-dependent effects: Visual detection of water via a smartphone

The visual detection of water in organic solvents by ratiometric fluorescence probes has attracted much attention because they can reduce environmental interference and differentiate color readily. Herein, a fast, convenient, and low-cost method of detecting water was developed based on a ratiometric fluorescence probe composed of fluorescent Cu nanoclusters (CuNCs) and carbon dots (CDs). CuNCs with solvent-dependent effects have different responses to water in various solvents while CDs are ideal fluorescence reference because of their excellent fluorescence stability. With the increase of water content in organic solvents, the ratiometric fluorescence probe exhibited an obvious color change from orange to blue and was employed for the sensitive detection of water contents via fluorescence intensity ratios (orange/blue). Smartphone as a portable tool was introduced to quantitatively analyze the visual results by acquire images, read colors, and analyze data. Moreover, the developed water sensing platform was applied to the detection of water contents in white wine and medical alcohol samples, proving its great potential in practical applications.