薄荷叶源荧光碳点制备及其光催化降解有机染料性能

Preparation of fluorescent carbon dots from mint leaves and its performance of photocatalytic degradation of organic dyes

以薄荷叶作为碳源,采用一步水热法制备出N掺杂碳点(N-CDs)和B,N共掺杂碳点(B,N-CDs)绿色荧光碳点。通过TEM,XRD,FT-IR,XPS,UV-Vis,XRF表征了CDs的形貌结构、元素成分、表面官能团及荧光性质。结果表明:制备的CDs尺寸均匀,表面有亲水的―OH,―COOH等基团。两种CDs均是典型的芳香体系,最大荧光发射峰分别在490 nm和440 nm,且表现出激发光依赖特性。经过在模拟太阳光光照120 min,N-CDs和B,N-CDs的对亚甲基蓝(MB)降解率分别为84%和67%。在活性物质捕获剂捕获实验中发现N-CDs在光催化过程产生活性物质主要是h^(+),·O_(2)^(-)和e^(-),而B,N-CDs在光催化过程中产生的活性物质主要是h^(+)和·O_(2)^(-)。采用电子自旋共振谱(ESR)验证活性氧的类型和强度,两种碳点都检测出·O_(2)^(-),而N-CDs光催化过程还产生的1O2要多于B,N-CDs,进而使得N-CDs太阳光光催化降解MB的效率高于B,N-CDs。

The green fluorescent N-doped carbon dots(N-CDs)and(B,N)-doped carbon dots(B,NCDs)were prepared from mint leaves by one-step hydrothermal method.The morphology structure,elementary composition,surface functional groups,and fluorescence properties of CDs were characterized by TEM,XRD,FT-IR,XPS,UV-Vis,and XRF.The results show that CDs are uniform in size and have hydrophilic groups such as—OH and—COOH on the surface.N-CDs and B,N-CDs are typical aromatic systems,with the maximum fluorescence emission peaks at 490 nm and 440 nm,respectively,exhibiting excitation light-dependent characteristics.After 120 min of simulated solar light,the degradation rate of methylene blue by N-CDs and B,N-CDs are 84%and 67%.The capture experiment result shows that h^(+),·O_(2)^(-),and e-are the main active substances produced by N-CDs,and h^(+)and·O_(2)^(-)are the main active substances produced by B,N-CDs in the photocatalytic process.The type and intensity of reactive oxygen species are verified using electron spin resonance(ESR)spectroscopy,and·O_(2)^(-)is detected in both carbon dots.The photocatalytic process of N-CDs also produced more 1O2 than B,N-CDs,which resulted in a higher efficiency of N-CDs in photocatalytic degradation of MB than that of B,N-CDs.