以天然生物质去皮的蓖麻为碳源, 采用一步水热法合成了荧光性能优良的绿色荧光蓖麻碳量子点(CO-CQDs), 对其形貌和发光性能进行了表征。通过将该CO-CQDs与荧光极强的卤代荧光素染料曙红Y(EY)复合, 二者可形成荧光发射峰相距较远的新型CO-CQDs/EY复合物。在pH=4.00的Na2HPO4-柠檬酸缓冲溶液中, 在320 nm的激发波长下, CO-CQDs/EY复合物于405 nm和540 nm处显示出两个独立的荧光发射峰。在该体系中加入Cr(Ⅵ), 405 nm和540 nm两处的荧光信号均显著猝灭。L-抗坏血酸(L-ascorbic acid,AA)的加入可使复合物于540 nm的荧光信号恢复, 而405 nm处的荧光强度基本不变。据此建立了一种以CO-CQDs/EY复合物为比率型荧光探针测定AA的新方法。实验测定了荧光信号恢复的最佳条件和影响荧光恢复的因素, 初步探讨了反应机理。在优化的实验条件下, 该探针于540 nm/405 nm两处的荧光强度比值与AA的浓度在5.0×10-8~4.0×10-6 mol/L范围内呈良好线性关系, 检出限为3.7×10-8 mol/L。该探针用于检测药物、水果和蔬菜中AA的含量, 结果满意。

Green fluorescent castor carbon quantum dots(CO-CQDs) with excellent fluorescence properties were synthesized by one-step hydrothermal method with natural biomass peeled castor. By combining the as-synthesized CO-CQDs with eosin Y(EY), a novel ratiometric fluorescence probe CO-CQDs/EY was formed. In the Na2HPO4-citric acid buffer solution of pH=4.00, under the excitation wavelength of 320 nm, the CO-CQDs/EY complex showed two independent fluorescence emission peaks at 405 nm and 540 nm. The fluorescence signals of 405 nm and 540 nm could be both quenched by Cr(Ⅵ). In the presence of L-ascorbic acid, the fluorescence signal at 540 nm was significantly increased, while the fluorescence intensity at 405 nm still remained unchanged. Therefore, a novel method for L-ascorbic acid analysis was developed based on this fluorescence ratiometric probe CO-CQDs/EY. This ratiometric method showed excellent specificity, sensitivity and accuracy. The optimum conditions of experiment were investigated and the mechanism of interaction was discussed. Under the optimized experimental conditions, the linear range of this method was 5.0×10-8-4.0×10-6 mol/L, and the detection limit was calculated to be 3.7×10-8 mol/L. Moreover, this method has been successfully applied to L-ascorbic acid analysis in drugs, vegetables and fruits, showing great potential in real sample analysis.