Size Quenching during Laser Synthesis of Colloids Happens Already in the Vapor Phase of the Cavitation Bubble
Size Quenching during Laser Synthesis of Colloids Happens Already in the Vapor Phase of the Cavitation Bubble
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DOI：
10.1021/acs.jpcc.6b12554
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发表时间：
2017-03-09
影响因子：
3.7
通讯作者：
Barcikowski, S.
中科院分区：
文献类型：
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作者：
Letzel, A.;Goekce, B.;Barcikowski, S.
虽然通过液体中的脉冲激光烧蚀（PLAL）的纳米颗粒合成获得了广泛的适用性，但是颗粒形成的机制，特别是溶解的阴离子的尺寸猝灭效应，尚未完全理解。众所周知，通过在激光烧蚀之前向液体中加入少量的单价电解质，可以有效地降低非原位观察到的小初级颗粒（d <10 nm）和团聚体的尺寸。在这项研究中，我们专注于粒子的形成和演变内充满水蒸气的空化泡。该气相富含来自前面添加的电解质的离子。通过小角X射线散射（SAXS）探测空化气泡的内部，我们能够检查纳米颗粒和离子之间的尺寸淬灭反应是否已经在空化气泡限制期间开始，或者这些反应是否受到液相的影响。我们发现，颗粒尺寸淬火已经发生在第一气泡振荡（约100它的激光冲击后），仍然在气相内。因此，我们表明，纳米粒子离子相互作用在PLAL实际上是一个气相现象。这些相互作用包括初级和次级颗粒的尺寸减小以及后者的丰度降低，如原位SAXS所示并通过非原位颗粒分析（例如，静态SAXS和TEM）。
Although nanoparticle synthesis by pulsed laser ablation in liquids (PLAL) is gaining wide applicability, the mechanism of particle formation, in particular size-quenching effects by dissolved anions, is not fully understood yet. It is well-known that the size of small primary particles (d 10 nm), and agglomerates observed ex situ is effectively reduced by the addition of small amounts of monovalent electrolyte to the liquid prior to laser ablation. In this study, we focus on the particle formation and evolution inside the vapor filled cavitation bubble. This vapor phase is enriched with ions from the afore added electrolyte. By probing the cavitation bubbles' interior by means of small-angle X-ray scattering (SAXS), we are able to examine whether the size quenching reaction between nanoparticles and ions starts already during cavitation bubble confinement or if these reactions are subjected to the liquid phase. We find that particle size quenching occurs already within the first bubble oscillation (approximately 100 its after laser impact), still inside the vapor phase. Thereby we demonstrate that nanoparticle ion interactions during PLAL are in fact a gas phase phenomenon. These interactions include size reduction of both primary and secondary particles and a decreased abundance of the latter as shown by in situ SAXS and confirmed by ex situ particle analysis (e.g., static SAXS and TEM).