一步水热法合成荧光碳点检测锰(Ⅶ)

One-Step Hydrothermal Synthesis of Carbon Dots for Detection of Manganese(Ⅶ)

以苦杏仁酸和脯氨酸为碳源和氮掺杂剂,采用一步水热法合成氮掺杂的蓝色荧光水溶性碳点(CDs),通过透射电镜、红外光谱、X射线光电子能谱、紫外可见吸收光谱和荧光光谱法等手段进行表征。合成的CDs粒径均匀,尺寸约为(2.62±0.20) nm,表面存在氨基、羟基、羧基、CC等官能团。最大激发和发射波长分别为360和450 nm,具有典型的激发波长依赖性,相对量子产率为7.86%,稳定性好。基于荧光共振能量转移(FRET)原理,CDs的荧光可被MnⅦ有效猝灭。在1～100μmol/L (即0.055～5.500 mg/L)范围内,MnⅦ浓度与CDs的荧光猝灭程度呈线性关系,相关系数(R^2)为0.9986,检出限为0.04μmol/L (2.20μg/L),具有高灵敏度和良好的选择性。此CDs可进入HepG2细胞内,发出蓝光,且胞内荧光强度与MnⅦ浓度大致呈线性关系。将此碳点用于环境水样和细胞内MnⅦ含量的检测,结果良好。

A convenient and green strategy was developed for the synthesis of water-soluble carbon dots (CDs) with blue fluorescence by one-step hydrothermal synthesis method using mandelic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet visible spectroscopy (UV) and fluorescence, respectively. The CDs were quasi spherical nano-particles with perfect monodispersity, and the average size was 2.62 ± 0.20 nm. They possessed crystal structures and the distinct lattice spacing was 0.21 nm. Abundant groups like C C, hydroxyl, carboxylic and amine groups, etc, were linked on the surface of the synthesized CDs. The CDs showed typical excitation-dependent photoluminescent behavior with the maximum excitation and emission wavelengths of 360 nm and 450 nm, respectively. The effects of ionic strength, pH and storage time on the fluorescence intensity of the CDs were slight, which demonstrated the perfect fluorescence stability of the CDs. Based on fluorescence resonance energy transfer (FRET) mechanism between donor CDs and acceptor Mn , the fluorescence of CDs could be effectively quenched by Mn . On the basis of this, a method was developed for detection of Mn . The method showed a linear range of 1-100 μmol/L (i.e., 0.055-5.500 mg/L) with a correlation coefficient ( R 2) of 0.9986. The limit of detection was 0.04 μmol/L (i.e., 2.20 μg/L), showing excellent sensitivity and selectivity. Due to low toxicity and excellent biocompatibility of CDs, HepG2 cells emitted blue fluorescence after incubated with CDs, and intracellular fluorescence intensities were roughly linear with Mn concentration, which enabled the potential applications of CDs in Mn biosensing. In brief, the CDs were designed as successful fluorescent sensors for direct determination of Mn content in aqueous solution and living cell.