Green Synthetic Fluorescent Carbon Quantum Dot as pH Sensor Applied to Real Water Samples Determination

Abstract

Willow, a common tree species, is mainly distributed in temperate regions of the Northern Hemisphere. Catkins are the seeds of willow. In addition to propagating new willows, it is of great significance to study its application in other areas. Carbon quantum dots (CQDs) have attracted extensive attention owing to their excellent luminescence properties, low toxicity and water solubility. The use of CQDs for accurate measurement of pH is of great significance in environmental, medical and other fields. Based on this, blue-emission fluorescent CQDs with 4.93% quantum yield (Q.Y.) are prepared via natural product catkins as the only raw material by one-step hydrothermal method. The prepared CQDs exhibit excellent water solubility, narrow particle size distribution, excitation-dependent photoluminescence properties and sensitive pH response behavior. The fluorescence intensity of CQDs has a good linear relationship with pH in the range of 6–12, and the correlation coefficient is 0.994. In addition, the CQDs have good stability, and the response to pH displays excellent reversibility, which can be developed as a pH sensor to quantitatively monitor the pH values in real water samples. Thereby, the potential practical application is promising.