【摘要】：當(dāng)前咖啡堿、茶氨酸等茶葉功能成分的檢測(cè)技術(shù)普遍存在檢測(cè)時(shí)間長(zhǎng)、過(guò)程繁瑣、靈敏度不足等缺點(diǎn)。開(kāi)發(fā)一種實(shí)時(shí)、快速、精確的茶葉成分檢測(cè)技術(shù)對(duì)于科學(xué)研究、茶葉品質(zhì)分析以及食品安全等具有重要意義。表面增強(qiáng)拉曼光譜(Surface Enhanced Raman Spectroscopy,SERS)技術(shù)具有檢測(cè)范圍廣、靈敏度高、特征性強(qiáng)等特點(diǎn),在計(jì)量檢測(cè)領(lǐng)域具有良好的應(yīng)用前景。SERS襯底的制備是SERS技術(shù)發(fā)展及應(yīng)用的前提和基礎(chǔ),而襯底的SERS活性與其尺寸、形貌、晶型、聚集狀態(tài)等特征密切相關(guān)。本文分別研究了金納米顆粒、花狀銀納米顆粒以及GO/Ag復(fù)合納米材料等納米結(jié)構(gòu)的制備方法及SERS性質(zhì),并分別以花狀銀納米顆粒、GO/Ag復(fù)合納米材料為襯底研究了SERS技術(shù)在咖啡堿、L-茶氨酸定性及定量分析中的應(yīng)用。主要研究結(jié)果如下:1.研究了金納米顆粒合成過(guò)程中氯金酸濃度對(duì)其粒徑及分布狀態(tài)的影響;分析了金納米顆粒的粒徑及分布狀態(tài)與其SERS活性的關(guān)系。結(jié)果表明,金納米顆粒的數(shù)量隨氯金酸濃度增加而增加,但當(dāng)氯金酸濃度過(guò)高時(shí),金納米顆粒發(fā)生團(tuán)聚,而其SERS活性顯著降低。2.分別以硝酸銀,抗壞血酸,聚乙烯吡咯烷酮(PVP)為前驅(qū)物、還原劑及表面活性劑,在液相條件下合成了粒徑約為450~500 nm,表面突起大小約為10~15 nm的花狀銀納米顆粒。結(jié)果表明,PVP分子對(duì)銀晶核的包裹程度決定了銀納米顆粒的最終形貌,當(dāng)PVP分子對(duì)銀晶核的包裹處于某種特定程度時(shí),晶核發(fā)生各向異性生長(zhǎng),形成花狀結(jié)構(gòu);花狀銀納米顆粒表面可形成較多的“hot spots”,提高面感應(yīng)電磁場(chǎng)強(qiáng)度,從而產(chǎn)生更高的SERS活性;以花狀銀納米顆粒為襯底的SERS檢測(cè)技術(shù)對(duì)R6G的檢測(cè)限可達(dá)10-8 mol/L。3.通過(guò)在氧化石墨烯(GO)表面構(gòu)筑銀納米顆粒合成了一系列具有不同形貌的GO/Ag復(fù)合納米材料。結(jié)果表明,反應(yīng)體系中AgNO3的相對(duì)含量對(duì)于GO/Ag復(fù)合納米材料中銀納米顆粒的粒徑、團(tuán)聚程度及其在GO表面的分布狀態(tài)有顯著影響;GO/Ag復(fù)合納米材料同時(shí)具備電磁場(chǎng)增強(qiáng)機(jī)理和電荷轉(zhuǎn)移增強(qiáng)機(jī)理,但電磁場(chǎng)增強(qiáng)機(jī)理占據(jù)主導(dǎo)地位;以GO/Ag復(fù)合納米材料為襯底的SERS檢測(cè)技術(shù)對(duì)R6G分子的檢測(cè)限可達(dá)10-8 mol/L以下。4.對(duì)咖啡堿常規(guī)拉曼光譜和SERS光譜進(jìn)行了比較,分析了花狀銀納米顆粒對(duì)咖啡堿拉曼散射性質(zhì)的影響,并對(duì)SERS檢測(cè)技術(shù)在咖啡堿定量檢測(cè)中的應(yīng)用進(jìn)行了研究。結(jié)果表明,當(dāng)咖啡堿溶液濃度低至10-9 mol/L時(shí),位于807 cm-1,958 cm-1,1040 cm-1以及1327 cm-1等處的SERS信號(hào)依然清晰可見(jiàn),表明以花狀銀納米顆粒為襯底的SERS檢測(cè)技術(shù)對(duì)于咖啡堿有極高的敏感性,檢測(cè)限可達(dá)10-9 mol/L;咖啡堿溶液的濃度與其SERS光譜強(qiáng)度具有一定的對(duì)應(yīng)關(guān)系,回歸方程為:Y=10041.0-0.9X807-3.1X1327+1.4X1269+1.3X958,其中Y表示 log10C(C為咖啡堿濃度,單位為mmol/L),Xn表示n cm-1處SERS信號(hào)的強(qiáng)度,決定系數(shù)(R2)高達(dá)0.9997。5.對(duì)L-茶氨酸常規(guī)拉曼光譜和SERS光譜進(jìn)行了比較,分析了GO/Ag復(fù)合納米材料對(duì)L-茶氨酸拉曼散射性質(zhì)的影響,并研究了基于SERS的L-茶氨酸定量檢測(cè)技術(shù)。結(jié)果表明,當(dāng)L-茶氨酸濃度低至10-7 mol/L時(shí),位于476 cm-1,899 cm-1等處的SERS信號(hào)依然清晰可見(jiàn),表明以GO/Ag復(fù)合納米材料為襯底的SERS檢測(cè)技術(shù)對(duì)于L-茶氨酸的檢測(cè)限可達(dá)10-7 mol/L;L-茶氨酸溶液的濃度與其SERS光譜強(qiáng)度線(xiàn)性相關(guān),回歸方程為:Y=5676.5+30.7X1458-26.7X1251,決定系數(shù)(R2)高達(dá)0.9899。綜上所述,實(shí)驗(yàn)所得花狀銀納米顆粒及GO/Ag復(fù)合納米材料在基于SERS技術(shù)的茶葉品質(zhì)成分檢測(cè)中具有良好的應(yīng)用前景。本課題研究結(jié)果為SERS技術(shù)在咖啡堿、L-茶氨酸定性及定量分析中的應(yīng)用提供了實(shí)驗(yàn)基礎(chǔ)和理論依據(jù)。
[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，

本文編號(hào)：2309977