Atomistic View of Laser Fragmentation of Gold Nanoparticles in a Liquid Environment
Atomistic View of Laser Fragmentation of Gold Nanoparticles in a Liquid Environment
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DOI：
10.1021/acs.jpcc.1c03146
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发表时间：
2021-06-09
影响因子：
3.7
通讯作者：
Zhigilei, Leonid, V
中科院分区：
文献类型：
--
作者：
Huang, Hao;Zhigilei, Leonid, V
纳米颗粒胶体溶液的短脉冲激光照射是一种有效的方法，用于破碎纳米颗粒并产生具有生物学、医学和催化等各个应用领域所需性能的较小纳米颗粒和原子团簇。为了研究碎片化的机制，我们开发了一个计算模型，能够现实地处理发生在不同时间和长度尺度上的各种相互关联的过程，从激光脉冲的电子激发，到电子-声子能量转移和过热纳米颗粒的爆炸性相分解，以及在液体环境中纳米气泡的产生和崩溃。应用该模型模拟水中Au纳米颗粒的激光破碎，揭示了破碎产物形成的两个不同的通道。第一个通道涉及直接注入紧凑的纳米液滴推进的相爆炸的照射纳米粒子深入到水环境。纳米颗粒形成的第二个通道涉及通过嵌入到激光诱导的纳米气泡周围的狭窄水区域中的许多原子簇的附聚而更渐进地生长。该通道产生不规则形状的纳米颗粒，并导致原子团簇的数量在纳秒的时间尺度上迅速下降。所有的簇和纳米颗粒经历了超快淬火的水环境，并具有高密度的孪晶界和其他晶体缺陷，这可能会提高密度的活性位点的催化应用的纳米颗粒。计算预测在纳米气泡的外侧上的相对窄的壳状区域中迅速产生高浓度的碎裂产物，以及在纳米气泡形成的早期阶段原子团簇和纳米颗粒的快速固化，对于设计旨在实现对纳米气泡的尺寸、形状以及在液体中通过激光破碎产生的纳米颗粒的缺陷结构。
Short-pulse laser irradiation of a colloidal solution of nanoparticles is an effective method for fragmenting the nanoparticles and producing a population of smaller nanoparticles and atomic clusters with properties desired in various fields of applications, including biology, medicine, and catalysis. To investigate the mechanisms involved in the fragmentation, we develop a computational model capable of realistic treatment of a variety of interrelated processes occurring on different time and length scales, from the electronic excitation by the laser pulse, to the electron-phonon energy transfer and an explosive phase decomposition of the superheated nanoparticle, and to the generation and collapse of a nanobubble in a liquid environment. The application of the model to simulation of laser fragmentation of a Au nanoparticle in water has revealed two distinct channels of the formation of the fragmentation products. The first channel involves the direct injection of compact nanodroplets propelled by the phase explosion of the irradiated nanoparticle deep into the water environment. The second channel of the nanoparticle formation involves a more gradual growth through agglomeration of numerous atomic clusters embedded into a narrow region of water surrounding the laser-induced nanobubble. This channel produces irregularly shaped nanoparticles and leads to a rapid decline of the population of atomic clusters on the timescale of nanoseconds. All the clusters and nanoparticles experience an ultrafast quenching by the water environment and feature a high density of twin boundaries and other crystal defects, which may enhance the density of active sites for the catalytic applications of the nanoparticles. The computational predictions of the prompt generation of a high concentration of the fragmentation products in a relatively narrow shell-like region on the outer side of the nanobubble, as well as the rapid solidification of atomic clusters and nanoparticles at the early stage of the nanobubble formation, have important practical implications for the design of new methods aimed at achieving an improved control over the size, shape, and defect structures of nanoparticles produced by laser fragmentation in liquids.