Lignin-Derived Red-emitting Carbon Dots for Colorimetric and Sensitive Fluorometric Detection of Water in Organic Solvents
Water contained in organic solvents or products in chemical industries, as contaminants, posed an adverse risk in chemical reaction, life or environment safety. However, conventional fluorescent water sensing suffered from drawbacks, including limited organic solvents, narrow linear range, without visual detection, single detection strategy, and others. Herein, a novel type of red-emitting carbon dots (RCDs) had been created via one-step solvothermal synthesis based on biomass (e.g., lignin) as carbon source and p-phenylenediamine (PPD) as nitrogen sources. Colorimetric and fluorometric detection of water in organic solvents had been demonstrated. The RCDs showed excitation-independent photoluminescence (PL) in different solvents and solvochromitic behavior, red in water, orange in ethanol, yellow in N, N-dimethyl formamide (DMF), while green in acetone. Remarkably, detection of water content in six organic solvents, such as polar solvents (ethanol, acetone, dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), DMF) and apolar solvent (ether) were obtained. With the water content in solvents, emission colors changed from green to red, or yellow to red, offering a qualitative sensing of water. Furthermore, broad linear detection ranges (10-90%), low limit of detection (LOD) (e.g., 0.36% for ethanol, 0.082% for acetone), and good generality for various organic solvent system had been realized. Particularly, dual sensing strategies, including PL quenching and shift with water in various solvents had been achieved simultaneously, posing great potential for development of advanced optical sensors with high performance.