### Au@SiO2核壳结构-表面增强拉曼光谱原位检测食品中的酸性橙II

1. a 中国科学院生态环境研究中心环境化学与生态毒理学国家重点实验室 北京 100085;
b 中华人民共和国厦门出入境检验检疫局 厦门 361026
• 投稿日期:2012-05-14 发布日期:2012-08-06
• 通讯作者: 刘景富 E-mail:jfliu@rcees.ac.cn
• 基金资助:
项目受国家杰出青年科学基金(No. 21025729)和国家质检总局科技项目(No. 2012IK193)资助.

### In Situ Detection of Acid Orange II in Food Based on Shell-Isolated Au@SiO2 Nanoparticle-Enhanced Raman Spectroscopy

Zhang Zongmiana, Liu Ruia, Xu Dunmingb, Liu Jingfua

1. a State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environment Sciences, Chinese Academy of Sciences, Beijing 100085;
b Xiamen Entry-Exit Inspection and Quarantine Bureau, Xiamen 361026
• Received:2012-05-14 Published:2012-08-06
• Supported by:
Project supported by the National Science Fund for Distinguished Young Scholars (No. 21025729) and the General Administration of Quality Supervision, Inspection and Quarantine of China (No. 2012IK193).

As a strong carcinogen to humans, acid orange II is forbidden to be added as an additive into foodstuff. Because the foods colored with acid orange II showed stable and colorful appearance, acid orange II is broadly utilized by illegally producers for their low costing. Currently available analytical methods for acid orange II are mainly based on fluorescence and liquid chromatography, which are time-consuming and tedious as acid orange II has to be extracted from the samples before determination. For efficient detection and insurance of food safety, it is urgent to develop fast and low-cost in situ assay methods for field detection of acid orange II on foods. In this study, shell-isolated Au@SiO2 nanoparticles is prepared for detecting acid orange II on food. Gold colloidal solution with good size distribution (50 nm) is prepared using the standard sodium citrate reduction method, followed by coating a thin layer of SiO2 on Au nanoparticle surface. This shell-isolated Au@SiO2 is obtained by the addition of active silica to the gold colloidal solution, with the (3-aminopropyl)trimethoxysilane (APTMS) as the coupling agent at pH 8.5. By regulating the amount of the active silica, the Au@SiO2 with different silica shell thickness is synthesized. Ultraviolet-visible spectroscopy (UV-Vis) and transmission electron microscope (TEM) are employed to characterize the optical property and morphology of the as-synthesized Au@SiO2 nanoparticles. The amount of the active silica added in preparation of the Au@SiO2 is optimized through comparing the surface enhanced Raman scattering (SERS) intensity of acid orange II, using the synthetic Au@SiO2 structure as the SERS substrate. Under the optimized experimental conditions, acid orange II on the Si wafer can be detected at concentrations below 0.17 mg/L. The feasibility of the proposed method for detecting acid orange II in real samples is verified by spreading the Au@SiO2 nanoparticles on the surface of the watermelon seeds stained with acid orange II. Results showed that this novel method is capable of detecting 0.01 mg/g acid orange II stained on the watermelon seeds. This proposed method was applied to assay sunflower seeds and watermelon seeds purchased from local stores. It is expected that this proposed method is applicable for in situ detection of acid orange II on the surface of other food samples.