摘要/Abstract

近年来, 由婴幼儿食品中存在非法添加剂所引起的食品安全问题已经受到了广泛的关注. 表面增强拉曼散射(SERS)技术可以对食品中被禁止添加的常用染料分子罗丹明B (RhB)进行快速无损超灵敏的检测. 通过在类石墨相氮化碳(g-C₃N₄)纳米片上组装Ag纳米粒子的方式构筑了g-C₃N₄/Ag复合材料, 并采用透射电子显微镜(TEM)、紫外可见近红外分光光度计(UV-Vis)、X射线衍射仪(XRD)、荧光光谱仪和共聚焦显微拉曼光谱仪(Raman)对复合材料的形貌和结构进行了表征. g-C₃N₄纳米片不仅具有高度的离域π共轭体系和良好的吸附染料分子的性能, 而且可以作为Ag纳米粒子的载体, 使Ag纳米粒子均匀稳定地分散在其表面. 通过控制实验条件, 优化了测试过程中的pH及基底与RhB的结合时间, 详细探究pH对基底表面等离子共振的影响和对探针分子SERS强度的影响. 由于基底与探针分子之间的静电相互作用及π-π相互作用, 基底可以对阳离子染料进行大量地富集, 从而实现对其检测. 在最佳的实验条件下, 在1.0×10 ^–9~1.0×10 ^–6 mol/L浓度范围内, SERS强度与RhB浓度之间成线性关系, 最低检测限为0.39 nmol/L. 另外这种基底也可以对婴幼儿食用的棒棒糖中添加的RhB分子实现痕量检测. 总而言之, g-C₃N₄/Ag纳米复合物是一种均一、稳定、高灵敏的SERS基底, 可以简单快速地实现对罗丹明B的痕量检测.
关键词: 表面增强拉曼光谱, g-C₃N₄/Ag纳米复合材料, 罗丹明B, 糖果, 痕量检测
In recent years, food safety problems caused by illegal additions in infant foods have received widespread attention. Surface-enhanced Raman scattering (SERS) technique is used to rapidly and non-destructively detect the banned RhB that is usually added in food. In this study, we have prepared g-C₃N₄/Ag composites via a simple method successfully, their morphology and structure were characterized by transmission electron microscope (TEM), ultraviolet-visible (UV-Vis), X-ray diffraction (XRD), fluorescence spectrophotometer and confocal micro-Raman spectrometer (Raman). The g-C₃N₄ nanosheet possesses good adsorption performance due to its highly delocalized π-conjugated system, which acts as a carrier for Ag nanoparticles. Therefore, Ag nanoparticles are more uniformly and stably distributed on the surface of g-C₃N₄ nanosheets to form g-C₃N₄/Ag nanocomposite, which can be used for rapid adsorption and trace detection of RhB. In the experiment, the pH of the test and the absorbed time between the substrate and RhB were optimized. The influence of pH on the SPR of the substrate and the SERS intensity of the probe molecule were investigated in detail. As g-C₃N₄/Ag nanocomposite shows a significant higher absorption in the visible region around 500 nm than Ag nanoparticles, g-C₃N₄/Ag nanocomposite is more favorable for SPR absorption. A wide SPR absorption range is achieved due to the synergy between g-C₃N₄ and Ag nanoparticles, providing an improved SERS enhancement performance. Under the optimal experimental conditions by using RhB as probe molecule, an enhancement factor of 7.6×10 ⁵ is achieved. Due to the electrostatic interaction and π-π interaction between the substrate and the probe molecules, the substrate can enrich in a large amount of cationic dyes, offering a detection of RhB. The g-C₃N₄/Ag SERS substrate can be used to detect RhB with a linear relationship from 1.0×10 ^–9 to 1.0×10 ^–6 mol/L and a detection limit as low as 0.39 nmol/L. In addition, the g-C₃N₄/Ag nanocomposite SERS substrate can also detect trace amounts of RhB molecules in the commercially available rainbow lollipops with a high sensitivity, and the recovery were 93.6%~95.04%. In summary, the g-C₃N₄/Ag nanocomposite is not only a SERS substrate with high sensitivity, uniformity and stability, but also can be used as a rapid trace detection method of Rhodamine B in real food and environment.
Key words: surface enhanced Raman spectroscopy (SERS), g-C₃N₄/Ag nanocomposites, Rhodamine B, candy, trace detection


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