纳米银增强基底制备及分子的拉曼光谱解析

【作者】 董鹍；

【导师】 张鹏翔；

【作者基本信息】 昆明理工大学 ， 材料学， 2011， 博士

【摘要】 拉曼光谱学是现代分析检测科学中十分重要的学科。应用拉曼光谱检测技术可以直接对固体或液体进行检测,无需对样品进行预先处理,检测过程不会对样品造成损伤。采用光纤激光头设计的拉曼光谱仪可以适用于各种体积和外形的样品,极大的方便了分析检测工作。但是由于拉曼散射光本身信号就较弱,并且经常受到荧光干扰,在实际检测过程中有时难以获得样品的拉曼光谱；另外就是当样品浓度较低时,也很难以检测到有效的拉曼信号,从而有可能造成错误的判断。表面增强拉曼光谱技术(SERS)可以有效的抑制荧光,极大的提高拉曼散射光的强度。因此应用表面增强拉曼光谱技术可以广泛应用于实际检测工作。表面增强拉曼的基底主要有粗糙金属电极、金属胶体、金属岛膜、金属纳米颗粒等。人们对于SERS增强基底的研究不断深入,已期获得更好的材料表面性质,从而进一步提高SERS的增强因子。采用纳米阵列自主装技术制备的贵金属材料,是目前最为热门的SERS增强基底。但是由于该方法制备过程难以控制,增强因子有限。因此在此基础上进一步对金属纳米结构进行研究,从而制备出增强因子更大的SERS基底显得尤其重要。本文第二章利用金属铝表面氧化后形成的特殊纳米凹坑阵列,进行纳米银增强基底的制备。通过试验发现：选用铬酸和磷酸的混合溶液可以去除阳极氧化铝模板纳米管道结构,在金属铝基底表面形成纳米凹坑阵列,该凹坑阵列有利于银纳米颗粒的生长。使用交流电沉积的方法可以在已形成的纳米凹坑阵列中生长银纳米颗粒。在不同的沉积时间下可以制备出不同形貌的纳米银结构,沉积时间较短时,生成球形纳米银阵列,这种银纳米结构的增强效果有限,与在氧化铝纳米管道中生长银纳米线所获得增强因子相似,当探针分子的浓度低于10-3mg/L时,将不能获得SERS增强光谱；沉积时间适中时,将生成树枝状纳米银结构,这种结构的纳米银具有极强的拉曼增强效应,即使当探针分子的浓度低至10-12mg/L时,依然能够得到该探针分子的拉曼光谱,该增强基底已经达到了单分子检测水平；当沉积时间较长时,将生成结复杂结构的薄膜,因其本身具有较强的拉曼振动峰,因此不适合作为SERS增强基底。通过新型纳米银增强基底可以有效的解决难检分子的检测问题,随后需要对检测所获得的拉曼光谱进行振动解析,以获取其有用的分子光谱信息。由于拉曼光谱技术真正应用于实际检测仅有近三十年的历史,加上高性能电子计算的发展也是近二十年才有的事情。因此一直缺乏分子拉曼光谱的系统性解析。量子化学中密度泛函理论是解释拉曼光谱的有效途径,通过构建分子模型并模拟计算,可以获得分子中各原子的振动信息,从对拉曼光谱给予合理的解释。本文第三章简要介绍了密度泛函理论的基本原理,泛函数与原子轨道价键计算基组的基本概念,通过对乙腈分子计算光谱与实验光谱的比较,确定了最终的计算参数选择。本文第四章对有机分子中卤代烷、醇类分子、醛类分子、有机酸类分子、苯及其衍生物、二甲苯异构体、氨基苯甲酸异构体、领苯二甲酸类分子、杂环化合物、食品添加剂中乙基麦芽酚、“一滴香”等物质,约三十八种分子,进行了实验检测,并通过量子化学理论进行了模拟计算,计算光谱与实验光谱获得了很好的吻合。拉曼光谱对于同分异构体的研究具有较大的优势,另外拉曼光谱关于环状化合物的研究发现环张力在分子光谱中具有重要的影响。本文第五章对无机分子中盐酸、硝酸、硫酸、磷酸、硼酸、高氯酸几种酸类分子进行了检测和振动解析；对氢氧化锂、氢氧化钠、氢氧化钾、氢氧化镁、氢氧化钙、氢氧化铜、氢氧化铝、氢氧化铁等碱类分子进行了检测和振动解析；对硝酸盐、碳酸盐、硫酸盐、磷酸盐四大类盐类分子进行了检测和振动解析,其中硝酸盐包括：硝酸钠、硝酸钾、硝酸镁、硝酸钙、硝酸铜、硝酸锌、硝酸钡、硝酸锶、硝酸镍、硝酸铅、硝酸钴、硝酸铝、硝酸铁、硝酸铋、硝酸铬、硝酸镧、硝酸锆。碳酸盐包括：碳酸锂、碳酸钠、碳酸钾、碳酸镁、碳酸钙、碳酸锌、碳酸锶、碳酸钡。硫酸盐包括：硫酸钠、硫酸钾、硫酸镁、硫酸钙、硫酸锌、硫酸铜、硫酸铁、硫酸铝。磷酸盐包括：磷酸钠、磷酸钾、磷酸铝、磷酸钙、磷酸铁、磷酸锌。总计共约六十三种分子,在进行大量实验检测的基础上,同时我们对结构相似的同类物质进行了实验拉曼光谱的横向比较从中分析总结出一定的规律性。更多还原

【Abstract】 Raman spectroscopy is an important subject in modern analysis and detection science. The solid or liquid samples can be directly tested application of Raman spectroscopy technology without any pretreatment operation, and the samples won’t be damaged with the test process. Raman spectrometer which is designed with optical fiber laser head can be applied to all kinds samples with any sizes and shapes. The analysis and test work became great convenience.But because of the Raman scattering signal is very weak, and it’s often interfered by fluorescence, It’s hard to get the samples’ Raman spectra in actual testing process; On the other hand is very difficult to detect the samples Raman signals when the concentration samples is too low, which may result in the wrong judgment. Surface-Enhanced Raman Spectroscopy (SERS) technique can restrain fluorescence, increase the intensity of Raman scattering light greatly. So Surface-Enhanced Raman Spectroscopy can be widely used in the actual testing work.The substrate which used for Surface-Enhanced Raman Spectroscopy include rough metal electrodes, metal colloid, metal island film, metal nanoparticles. With the development of SERS substrate research, we want to get more better material surface properties in order to improve SERS enhancement factor furtherly. The precious metallic material which prepared by nanometer array technology is the most popular SERS enhancement base at present. But this method is very difficult to control in the preparation process and the enhance factor is limited. So it’s very important to do further research on metallic nano material on the basis of previous research results, so the enhance factor of the SERS substrate can be improved further moreIn the second chapter, we prepared nano silver SERS substrate with the nano pits array which were formed by aluminium surface oxidation. Through the experiments we found that:The anodic alumina template nanotubes structure can be removed bu the mixed solution of chromium acid and phosphoric acid, the nano pits array will be remained on the surface of the aluminium. These nano pits array were beneficial to the growth of the silver nanoparticles. The silver nano particles will be formed in the nano pits array using alternating current(AC) electrodeposition method. Different shapes of silver nanoparticles can be prepared under different electrodeposition time, when the electrodeposition time was short, the shape of the silver nanoparticles were spherical, The enhancement effect of this kind of silver nano array structure was limited, its enhancement factor was similar with the nanowires which were grew in the aluminum oxide nanotubes, when the concentration of the probe molecules was below 10"3 mg/L we would not get SERS enhancement spectrum; When the electrodeposition time was appropriate the shapes of silver nanoparticles like trees, and this structure of the silver nanoparticles has strong Raman enhancement effects, even when the concentration of the probe molecules was low to 10-12 mg/L, we still can get the Raman spectra of the probe molecules, the enhancement substrate has reached the single molecule detection level; When electrodeposition time was too long, the film with complex structure will be formed, Due to this kind of substrate has strong Raman signals itself, therefore it is not applicable for SERS enhancement substrate.The problem of some molecules which were difficult to detect can be effective solved by using the trees like nano silver enhance substrate. After we got the Raman spectra of molecules, the next work is vibration analysis in order to get useful information from the spectroscopy. Because Raman spectroscopy technology was really applied in practical detection work only has nearly thirty years history, and the development of high performance electronic computers was only 20 years time. So ithere were no systemic analysis of Raman spectra. Quantum chemical theory is most effective way for explaining Raman spectra, By building the molecular model and simulation computation Quantum chemical theory can get all the atoms vibration information of the molecular, and give reasonable explanation with the Raman spectra. The third chapter of this paper briefly introduced the basic principle of quantum chemistry theory, and the basic concepts of function and the atom valence bond orbital, By comparing the computing calculation spectrum and experimental spectrum of acetonitrile molecular, and calculated parameters was finally choiced.In the fourth chapter, various organic molecules included halogenated monosilane, alcohols, aldehydes, organic acids, benzene and its derivatives, xylene isomers, aminobenzoic acid, phthalate, heterocyclic compounds,some food additives like ethyl maltol, "one drops delicious" and other material, about 38 kinds of molecules had been detected, These molecules have been all simulate calculated by quantum chemical theory, and the calculation spectrum was coincided with their experimental spectrum. Raman spectra has many advantages at isomers research, and we found that the ring tension has great influence in Raman spectroscopy with ring compounds molecular.In the chapter 5 of this paper, Some inorganic molecules included sulphuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, high chlorine acid several acids molecules were tested and vibration analysed; Some kinds of alkali molecules include lithium hydroxide monohydrate, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, copper hydroxide, aluminum hydroxide, ferric hydroxide were tested and vibration analysed; Four categories salts molecules include nitrate, carbonate, sulfate and phosphate were tested and vibration analysed, nitrate including:sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, copper nitrate, zinc nitrate, lead nitrate, barium nitrate, strontium nitrate, nickel nitrate, cobalt nitrate, aluminum nitrate, iron nitrate, bismuth nitrate, chromium nitrate, lanthanum nitrate, zirconium nitrate. Carbonate included:lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, zinc carbonate, strontium carbonate, barium carbonate. Sulfate included: sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, copper sulfate, ferric sulfate, alumina sulfate. Phosphate included:potassium phosphate, sodium phosphate, aluminum phosphate, calcium phosphate, iron phosphate, zinc phosphate. A total kinds of these molecules was sixty-three. On the basis of lots of experiment testing, also we analysed certain laws by comparing the Raman spectra of the similar material molecules.更多还原