表面等离激元调制含氮芳香化合物氧化还原反应理论研究

发布时间：2018-04-26 07:30

本文选题：表面等离激元共振 + 密度泛函理论(DFT)　；参考：《西南大学》2017年硕士论文

【摘要】：近年来,基于等离激元增强的光催化反应成为了研究热点。金或者银纳米粒子在一定波长的激发光照射下其表面的自由电子在外界光电场的扰动下会发生集体振荡。当入射光电场的频率与金属纳米结构电子振荡的固有频率匹配时就会产生共振现象,这种现象称为表面等离激元共振。表面等离激元共振因其独特性质而对表面化学具有多种促进作用,因而等离激元增强表面催化反应有望成为一种高效的太阳能转化途径。大量的文献报道了芳香族分子吸附在金属表面或者金属电极上,其拉曼信号会显著增强。至今为止,人们就芳香族分子吸附在金属表面后其拉曼信号增强的机理仍然缺乏全面理解。对于拉曼信号的增强机理,科学家们普遍持两种观点:化学增强机理和电磁场增强机理。人们对于电磁增强机理研究的较为透彻,而对于化学增强机理局限于光驱电荷转移机理而忽略了表面等离激元的化学效应。因此本论文以表面等离激元的化学效应为出发点,从等离激元增强拉曼光谱(PERS)和等离激元增强化学反应(PECR)两个方面开展研究。相应的研究内容和结果如下:(1)采用密度泛函理论(DFT)计算模拟PNA的常规拉曼光谱和表面拉曼光谱,并对其振动模式进行指认。提出PNA分别在溶液中和空气中的光诱导催化偶联反应合理的反应路线并计算反应微观机理路径上的各物质。理论研究证实PNA在溶液中发生还原偶合反应生成DAAB,在空气中发生氧化偶合反应生成DNAB。(2)利用SERS技术结合DFT研究对苯二胺以及对二硝基苯是否可以发生等离激元光聚合反应。这部分工作包括DNB和PDA的常规拉曼谱和表面拉曼谱和对应的实验谱图以及相关的反应机理。实验和理论证明DNB和PDA分别在溶液中和空气中发生还原偶合和氧化偶合反应生成对应的N-N偶联寡聚物。(3)采用密度泛函理论方法分别研究了在暗场和光照条件下偶氮苯和对苯乙烯在纳米银粒子作用下的反顺异构化反应。我们计算了偶氮苯和对苯乙烯的反顺异构化反应的反应势能曲线以及他们和金属相互作用的光驱电荷转移跃迁能和分子轨道图。结果表明空穴氧化反式偶氮苯和对苯乙烯使其转化成对应的顺式构型是Ag NPs辅助偶氮苯以及对苯乙烯的反顺异构化最可能的方式。本课题工作不仅帮助我们弄清楚了目标分子吸附在金属表面后信号增强的原因而且还为我们获得偶氮苯类化合物提供了一种新的绿色方法。此外,对于偶氮苯以及对苯乙烯的研究可以进一步帮助我们将偶氮苯和对苯乙烯应用于实际光学分子开关。
[Abstract]:In recent years, the photocatalytic reaction based on the enhancement of isophosphors has become a hot topic. The free electrons on the surface of gold or silver nanoparticles under the excitation light of a certain wavelength will oscillate collectively under the disturbance of the external photoelectric field. Resonance occurs when the frequency of the incident photoelectric field matches the natural frequency of the electron oscillation of the metal nanostructure. This phenomenon is called surface isoexciton resonance. Due to its unique properties, surface isoexciton resonance can promote surface chemistry. Therefore, it is expected that the surface catalytic reaction enhanced by isophosphors will become an efficient way of solar energy conversion. A large number of literatures have reported that the Raman signal of aromatic molecules adsorbed on metal surface or on metal electrode will be significantly enhanced. Up to now, there is still a lack of comprehensive understanding of the mechanism of Raman signal enhancement of aromatic molecules adsorbed on metal surface. Scientists generally hold two views on the enhancement mechanism of Raman signal: chemical enhancement mechanism and electromagnetic field enhancement mechanism. The study of electromagnetic enhancement mechanism is more thorough, while the chemical enhancement mechanism is limited to the charge transfer mechanism of optical drive and neglects the chemical effect of surface isoexcitators. Therefore, based on the chemical effect of surface isophosphors, this thesis studies on the two aspects of isophosphorus enhanced Raman spectroscopy (PERS) and isophoric enhanced chemical reaction (PECR). The corresponding research contents and results are as follows: (1) the conventional Raman spectra and surface Raman spectra of simulated PNA are calculated by density functional theory (DFT) and the vibrational modes are identified. A reasonable route for photo-induced coupling reaction of PNA in solution and in air was proposed, and the substances in the path of micro-mechanism of the reaction were calculated. It is proved that PNA can be synthesized by reductive coupling reaction in solution and oxidative coupling reaction in air to form DNAB.t2) the isobaric photopolymerization of p-phenylenediamine and p-dinitrobenzene can be studied by SERS and DFT. This work includes the conventional Raman spectra and surface Raman spectra of DNB and PDA, the corresponding experimental spectra and the related reaction mechanisms. Experimental and theoretical results show that DNB and PDA have reduced coupling and oxidative coupling reactions in solution and air respectively to form corresponding N-N coupling oligomers. (3) the density functional theory (DFT) method has been used to study the coupling under dark and light conditions, respectively. The transisomerization of azobenzene and p-styrene under the action of silver nanoparticles. We have calculated the potential energy curves of the transisomerization of azobenzene and styrene, the charge transfer transition energy and molecular orbital diagram of their interaction with metal. The results show that hole oxidation of trans-azobenzene and p-styrene into the corresponding cis-configuration is the most likely way of Ag NPs assisted azobenzene and p-styrene trans-cis-isomerization. This work not only helps us to find out the cause of signal enhancement of target molecules adsorbed on metal surface, but also provides us a new green method for obtaining azobenzene compounds. In addition, the study of azobenzene and p-styrene can further help us to apply azobenzene and p-styrene to practical optical molecular switches.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O621.254

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