Hu Xuetao, Zhang Xinai, Li Yanxiao, Shi Jiyong, Huang Xiaowei, Li Zhihua, Zhang Junjun, Li Wenting, Xu Yiwei, Zou Xiaobo
School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, China.
Analyzing and Test Center, Jiangsu University, Zhenjiang 212013, China.
Foods. 2022 Jun 23;11(13):1855. doi: 10.3390/foods11131855.
This study established a flexible and eye-readable sensing system for the easy-to-use, visual detection of milk freshness, using acidity-responsive N-doped carbon quantum dots (N-CQDs). N-CQDs, rich in amino groups and with characteristic acidity sensitivity, exhibited high relative quantum yields of 25.2% and an optimal emission wavelength of 567 nm. The N-CQDs fluorescence quenching upon the dissociated hydrogen ions (H) in milk and their reacting with the amino groups produced an excellent linear relation (R = 0.996) between the fluorescence intensity and the milk acidity, which indicated that the fluorescence of the N-CQDs was highly correlated with milk freshness. Furthermore, a fluorescence sensor was designed by depositing the N-CQDs on filter-papers and starch-gel films, to provide eye-readable signals under UV light. A fluorescence colorimetric card was developed, based on the decrease in fluorescence brightness as freshness deteriorated. With the advantages of high sensitivity and eye readability, the proposed sensor could detect spoiled milk in advance and without any preprocessing steps, offering a promising method of assessing food safety.
本研究利用对酸度有响应的氮掺杂碳量子点（N-CQDs）建立了一种灵活且肉眼可读的传感系统，用于方便地对牛奶新鲜度进行视觉检测。N-CQDs富含氨基且具有独特的酸度敏感性，其相对量子产率高达25.2%，最佳发射波长为567nm。牛奶中解离出的氢离子（H⁺）与N-CQDs的氨基发生反应，导致N-CQDs荧光猝灭，荧光强度与牛奶酸度之间呈现出良好的线性关系（R = 0.996），这表明N-CQDs的荧光与牛奶新鲜度高度相关。此外，通过将N-CQDs沉积在滤纸和淀粉凝胶膜上设计了一种荧光传感器，以便在紫外光下提供肉眼可读的信号。基于新鲜度下降时荧光亮度的降低，开发了一种荧光比色卡。该传感器具有高灵敏度和肉眼可读性的优点，无需任何预处理步骤就能提前检测出变质牛奶，为评估食品安全提供了一种很有前景的方法。
