基于SERS技术的茶叶咖啡碱和茶氨酸快速检测方法研究

发布时间：2018-11-04 13:37

【摘要】：当前咖啡碱、茶氨酸等茶叶功能成分的检测技术普遍存在检测时间长、过程繁琐、灵敏度不足等缺点。开发一种实时、快速、精确的茶叶成分检测技术对于科学研究、茶叶品质分析以及食品安全等具有重要意义。表面增强拉曼光谱(Surface Enhanced Raman Spectroscopy,SERS)技术具有检测范围广、灵敏度高、特征性强等特点,在计量检测领域具有良好的应用前景。SERS衬底的制备是SERS技术发展及应用的前提和基础,而衬底的SERS活性与其尺寸、形貌、晶型、聚集状态等特征密切相关。本文分别研究了金纳米颗粒、花状银纳米颗粒以及GO/Ag复合纳米材料等纳米结构的制备方法及SERS性质,并分别以花状银纳米颗粒、GO/Ag复合纳米材料为衬底研究了SERS技术在咖啡碱、L-茶氨酸定性及定量分析中的应用。主要研究结果如下:1.研究了金纳米颗粒合成过程中氯金酸浓度对其粒径及分布状态的影响;分析了金纳米颗粒的粒径及分布状态与其SERS活性的关系。结果表明,金纳米颗粒的数量随氯金酸浓度增加而增加,但当氯金酸浓度过高时,金纳米颗粒发生团聚,而其SERS活性显著降低。2.分别以硝酸银,抗坏血酸,聚乙烯吡咯烷酮(PVP)为前驱物、还原剂及表面活性剂,在液相条件下合成了粒径约为450~500 nm,表面突起大小约为10~15 nm的花状银纳米颗粒。结果表明,PVP分子对银晶核的包裹程度决定了银纳米颗粒的最终形貌,当PVP分子对银晶核的包裹处于某种特定程度时,晶核发生各向异性生长,形成花状结构;花状银纳米颗粒表面可形成较多的“hot spots”,提高面感应电磁场强度,从而产生更高的SERS活性;以花状银纳米颗粒为衬底的SERS检测技术对R6G的检测限可达10-8 mol/L。3.通过在氧化石墨烯(GO)表面构筑银纳米颗粒合成了一系列具有不同形貌的GO/Ag复合纳米材料。结果表明,反应体系中AgNO3的相对含量对于GO/Ag复合纳米材料中银纳米颗粒的粒径、团聚程度及其在GO表面的分布状态有显著影响;GO/Ag复合纳米材料同时具备电磁场增强机理和电荷转移增强机理,但电磁场增强机理占据主导地位;以GO/Ag复合纳米材料为衬底的SERS检测技术对R6G分子的检测限可达10-8 mol/L以下。4.对咖啡碱常规拉曼光谱和SERS光谱进行了比较,分析了花状银纳米颗粒对咖啡碱拉曼散射性质的影响,并对SERS检测技术在咖啡碱定量检测中的应用进行了研究。结果表明,当咖啡碱溶液浓度低至10-9 mol/L时,位于807 cm-1,958 cm-1,1040 cm-1以及1327 cm-1等处的SERS信号依然清晰可见,表明以花状银纳米颗粒为衬底的SERS检测技术对于咖啡碱有极高的敏感性,检测限可达10-9 mol/L;咖啡碱溶液的浓度与其SERS光谱强度具有一定的对应关系,回归方程为:Y=10041.0-0.9X807-3.1X1327+1.4X1269+1.3X958,其中Y表示 log10C(C为咖啡碱浓度,单位为mmol/L),Xn表示n cm-1处SERS信号的强度,决定系数(R2)高达0.9997。5.对L-茶氨酸常规拉曼光谱和SERS光谱进行了比较,分析了GO/Ag复合纳米材料对L-茶氨酸拉曼散射性质的影响,并研究了基于SERS的L-茶氨酸定量检测技术。结果表明,当L-茶氨酸浓度低至10-7 mol/L时,位于476 cm-1,899 cm-1等处的SERS信号依然清晰可见,表明以GO/Ag复合纳米材料为衬底的SERS检测技术对于L-茶氨酸的检测限可达10-7 mol/L;L-茶氨酸溶液的浓度与其SERS光谱强度线性相关,回归方程为:Y=5676.5+30.7X1458-26.7X1251,决定系数(R2)高达0.9899。综上所述,实验所得花状银纳米颗粒及GO/Ag复合纳米材料在基于SERS技术的茶叶品质成分检测中具有良好的应用前景。本课题研究结果为SERS技术在咖啡碱、L-茶氨酸定性及定量分析中的应用提供了实验基础和理论依据。
[Abstract]:The detection technology of tea functional components such as caffeine, theanine and the like has the defects of long detection time, complex process, low sensitivity and the like. It is of great significance to develop a real-time, fast and accurate tea composition detection technology for scientific research, tea quality analysis and food safety. Surface Enhanced Raman Spectroscopy (SERS) has the characteristics of wide detection range, high sensitivity and strong specificity, and has a good application prospect in the field of measurement and detection. SERS substrate preparation is the premise and foundation of SERS technology development and application, and SERS activity of substrate is closely related to its size, morphology, crystal form and aggregation state. The preparation methods and SERS properties of nano-structures such as gold nanoparticles, flower-shaped silver nanoparticles and GO/ Ag composite nano-materials were studied in this paper. Application of L-theanine in qualitative and quantitative analysis. The main results are as follows: 1. The influence of chlorogold acid concentration on its particle size and its distribution state during the synthesis of gold nanoparticles was studied. The relationship between the particle size and its distribution state of gold nanoparticles and its SERS activity was analyzed. The results showed that the number of gold nanoparticles increased with the increase of chlorogold acid concentration, but when the concentration of chlorogold was too high, the gold nanoparticles were agglomerated and their SERS activity decreased significantly. With silver nitrate, ascorbic acid and polyethylene (PVP) as the precursor, the reducing agent and the surfactant, the flower-shaped silver nanoparticles with the particle size of about 450-500 nm and the size of the surface projection of about 10-15 nm were synthesized under the liquid phase condition. The results show that the degree of inclusion of PVP molecules on silver crystal nucleus determines the final morphology of silver nanoparticles. When the package of PVP molecules on silver crystal nucleus is in some specific degree, the crystal nucleus undergoes anisotropic growth to form a flower-shaped structure, and the surface of flower-like silver nanoparticles can be formed more. 鈥渉ot spots鈥，

本文编号：2309977