等离激元诱导光催化反应的微观机制

发布时间：2018-04-28 11:29

本文选题：表面等离激元 + 水分解　；参考：《中国科学院大学(中国科学院物理研究所)》2017年博士论文

【摘要】：本文致力于研究等离激元诱导的光化学反应。等离激元金属纳米颗粒可以有效地利用太阳能,提高光催化反应的能源转化效率。在等离激元参与的反应中,蕴含着丰富的物理现象,如电荷转移,电场增强和非线性效应等。实验已经证实了等离激元纳米颗粒可以增强反应效率,而复杂的反应机制还不清楚。我们从第一性原理出发,研究等离激元诱导化学反应的超快过程与微观机理。基于含时密度泛函理论,本文首先研究了银原子链末端氢分解的电子-离子动力学。在超短脉冲作用下,银链等离激元产生的热电子转移到氢分子的反键态,导致氢分解。增加激光强度与原子链长可以提高反应速率。然后,我们研究了金纳米颗粒在超快激光作用下分解水的动力学过程。模拟表明反应速率线性地依赖于激光强度,表明该反应是单光子过程,与实验结果一致。更重要的是,我们首次发现反应速率具有量子模式的选择性:奇等离激元模式比偶模式更加有效。这种选择性来源于奇模式衰减产生的热电子与水分子的反键态有更好的能量匹配。进一步,我们把体系扩展到实际的金属团簇在液态水环境下光解水,观察到超快产氢过程:两个水分子各贡献一个氢原子形成氢分子。此外,我们发现局域场增强极大地影响反应速率。最后,在银链体系中,我们观察到隧穿电流谱的非线性响应,并确定这种非线性效应来源于等离激元衰减产生的热电子。本文通过研究金属等离激元与分子体系的电荷转移与电子激发态动力学,更深入的理解了等离激元诱导光化学反应的微观机制。我们发现调节激光参数,纳米颗粒尺寸以及体系的能级匹配可以改善反应速率。这些结果为等离激元诱导光催化的发展提供新的思路。
[Abstract]:This paper is devoted to the study of photochemical reactions induced by isopherons. The isobaric metal nanoparticles can effectively utilize solar energy and improve the energy conversion efficiency of photocatalytic reaction. There are abundant physical phenomena such as charge transfer, electric field enhancement and nonlinear effect. It has been proved by experiments that the isobaric nanoparticles can enhance the reaction efficiency, but the complex reaction mechanism is not clear. Based on the first principle, we study the ultrafast process and the microscopic mechanism of the chemical reaction induced by the isobaric element. Based on the time-dependent density functional theory, the electron ion dynamics of hydrogen decomposition at the end of the silver atom chain is studied. Under the action of ultrashort pulses, the hot electrons produced by the iso-excitons of silver chains transfer to the anti-bonding states of the hydrogen molecules, leading to the decomposition of hydrogen. The reaction rate can be increased by increasing laser intensity and atomic chain length. Then, we studied the kinetic process of gold nanoparticles decomposing water under the action of ultrafast laser. The simulation results show that the reaction rate is linearly dependent on the laser intensity, which indicates that the reaction is a single photon process, which is consistent with the experimental results. More importantly, we found for the first time that the reaction rate has the selectivity of quantum mode: the odd ionization mode is more efficient than the even mode. This selectivity comes from a better energy match between the hot electrons produced by the odd mode decay and the antibonding states of water molecules. Furthermore, we extend the system to the actual metal clusters photolysis of water in liquid water environment, and observe the ultrafast hydrogen production process: two water molecules contribute one hydrogen atom to form hydrogen molecule. In addition, we find that local field enhancement greatly affects the reaction rate. Finally, we observe the nonlinear response of tunneling current spectrum in the silver chain system, and determine that the nonlinear effect originates from the hot electrons produced by the decay of the isophernion. By studying the charge transfer and electron excited state dynamics of metal isophosphoric and molecular systems, the microscopic mechanism of the photochemical reaction induced by isoexcitations has been further understood in this paper. We find that adjusting laser parameters, particle size and energy level matching can improve the reaction rate. These results provide new ideas for the development of isobaric induced photocatalysis.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O469

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