Abstract:

More and more attentions have been paid to synthesize the graphene quantum dots by the biomass “bottom-up” approach because of the outstanding features, such as low-cost and environmentally friendly. Nitrogen and sulfur codoped graphene quantum dots (N, S-GQDs) were synthesized from soy protein through hydrothermal method. And ethanol precipitation was adopted as the purification method. Chemical structures and optical properties of the synthesized N, S-GQDs were carefully investigated by transmission electron microscopy (HRTEM), atomic force microscope (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and fluorescence spectrum. The N,S-GQDs showed good water dispersibility and bright blue fluorescence. When the mass ratio of the soy protein to citric acid-urea was 5%(mass), the fluorescence quantum yield of the N, S-GQDs was as high as 9.23%. A 0.34 nm crystal lattice spacing was observed and the thickness of the N, S-GQDs was around 2—5 nm. The detection limit of the N, S-GQDs for Fe³⁺ was as low as 0.95 μmol/L. This work provided a facile method to synthesize N, S-GQDs from soy protein with high quantum yield.

Key words: graphene quantum dots, soybean protein, precipitation, iron ions, biomass, hydrothermal synthesis

摘要：

以来源丰富的大豆蛋白为前体，采用水热法和乙醇沉淀的分离方法合成了氮和硫双掺杂的石墨烯量子点（N，S-GQDs）。通过红外光谱（FTIR）、X射线光电子能谱（XPS）、紫外-可见光光谱（UV-vis）、高分辨率透射电镜（HRTEM）、原子力显微镜（AFM）和荧光光谱表征了N，S-GQDs的结构，及其对铁离子的检测性能。结果表明：大豆蛋白-柠檬酸-尿素水溶液在220℃水热温度下反应10 h，获得荧光量子效率为9.23%的N，S-GQDs，其水分散液具有明亮的蓝色荧光。N， S-GQDs具有0.34 nm的石墨烯晶格并展现出清晰的快速傅里叶变换图像，其厚度为2~5 nm。N， S-GQDs对Fe³⁺的检测限为0.95 μmol/L。本工作乙醇沉淀的简便方法将是一种快速获得N，S-GQDs固体的方法。

关键词: 石墨烯量子点, 大豆蛋白, 沉淀, 铁离子, 生物质, 水热合成