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Advancing Plasmon-Induced Selectivity in Chemical Transformations with Optically Coupled Transmission Electron Microscopy
Accounts of Chemical Research ( IF 18.3 ) Pub Date : 2021-09-07 , DOI: 10.1021/acs.accounts.1c00309
Dayne F Swearer 1 , Briley B Bourgeois 1 , Daniel K Angell 1 , Jennifer A Dionne 1, 2
Affiliation  

Nanoparticle photocatalysts are essential to processes ranging from chemical production and water purification to air filtration and surgical instrument sterilization. Photochemical reactions are generally mediated by the illumination of metallic and/or semiconducting nanomaterials, which provide the necessary optical absorption, electronic band structure, and surface faceting to drive molecular reactions. However, with reaction efficiency and selectivity dictated by atomic and molecular interactions, imaging and controlling photochemistry at the atomic scale are necessary to both understand reaction mechanisms and to improve nanomaterials for next-generation catalysts. Here, we describe how advances in plasmonics, combined with advances in electron microscopy, particularly optically coupled transmission electron microscopy (OTEM), can be used to image and control light-induced chemical transformations at the nanoscale. We focus on our group’s research investigating the interaction between hydrogen gas and Pd nanoparticles, which presents an important model system for understanding both hydrogenation catalysis and hydrogen storage. The studies described in this Account primarily rely on an environmental transmission electron microscope, a tool capable of circumventing traditional TEM’s high-vacuum requirements, outfitted with optical sources and detectors to couple light into and out of the microscope. First, we describe the H2 loading kinetics of individual Pd nanoparticles. When confined to sizes of less than ∼100 nm, single-crystalline Pd nanoparticles exhibit coherent phase transformations between the hydrogen-poor α-phase and hydrogen-rich β-phase, as revealed through monitoring the bulk plasmon resonance with electron energy loss spectroscopy. Next, we describe how contrast imaging techniques, such as phase contrast STEM and displaced-aperture dark field, can be employed as real-time techniques to image phase transformations with 100 ms temporal resolution. Studies of multiply twinned Pd nanoparticles and high aspect ratio Pd nanorods demonstrate that internal strain and grain boundaries can lead to partial hydrogenation within individual nanoparticles. Finally, we describe how OTEM can be used to locally probe nanoparticle dynamics under optical excitation and in reactive chemical environments. Under illumination, multicomponent plasmonic photocatalysts consisting of a gold nanoparticle “antenna” and a Pd “reactor” show clear α-phase nucleation in regions close to electromagnetic “hot spots” when near plasmonic antennas. Importantly, these hot spots need not correspond to the traditionally active, energetically preferred sites of catalytic nanoparticles. Nonthermal effects imparted by plasmonic nanoparticles, including electromagnetic field enhancement and plasmon-derived hot carriers, are crucial to explaining the site selectivity observed in PdHx phase transformations under illumination. This Account demonstrates how light can contribute to selective chemical phenomena in plasmonic heterostructures, en route to sustainable, solar-driven chemical production.

中文翻译:

使用光耦合透射电子显微镜提高化学转化中等离子体诱导的选择性

纳米粒子光催化剂对于从化学生产和水净化到空气过滤和手术器械消毒等过程至关重要。光化学反应通常由金属和/或半导体纳米材料的照射介导,这些材料提供必要的光吸收、电子能带结构和表面刻面以驱动分子反应。然而,由于原子和分子相互作用决定了反应效率和选择性,因此在原子尺度上成像和控制光化学对于理解反应机制和改进用于下一代催化剂的纳米材料是必要的。在这里,我们描述了等离子体激元的进步与电子显微镜的进步,特别是光耦合透射电子显微镜 (OTEM) 的进步,可用于在纳米尺度上成像和控制光诱导的化学转化。我们专注于我们小组的研究,研究氢气和 Pd 纳米粒子之间的相互作用,它为理解加氢催化和储氢提供了一个重要的模型系统。本帐户中描述的研究主要依赖于环境透射电子显微镜,这是一种能够规避传统 TEM 高真空要求的工具,配备有光源和探测器以将光耦合进出显微镜。首先,我们描述 H 它为理解加氢催化和储氢提供了一个重要的模型系统。本帐户中描述的研究主要依赖于环境透射电子显微镜,这是一种能够规避传统 TEM 高真空要求的工具,配备有光源和探测器以将光耦合进出显微镜。首先,我们描述 H 它为理解加氢催化和储氢提供了一个重要的模型系统。本帐户中描述的研究主要依赖于环境透射电子显微镜,这是一种能够规避传统 TEM 高真空要求的工具,配备有光源和探测器以将光耦合进出显微镜。首先,我们描述 H2单个 Pd 纳米粒子的加载动力学。当尺寸限制在小于 100 nm 时,单晶 Pd 纳米粒子在贫氢 α 相和富氢 β 相之间表现出相干相变,如通过用电子能量损失光谱监测体等离子体共振所揭示的那样。接下来,我们将描述对比成像技术,例如相位对比 STEM 和位移孔径暗场,如何用作实时技术,以 100 毫秒的时间分辨率对相变进行成像。多重孪晶 Pd 纳米粒子和高纵横比 Pd 纳米棒的研究表明,内部应变和晶界会导致单个纳米粒子内的部分氢化。最后,我们描述了 OTEM 如何用于在光激发和反应化学环境中局部探测纳米粒子动力学。在光照下,由金纳米粒子“天线”和 Pd“反应器”组成的多组分等离子体光催化剂在靠近等离子体天线时在靠近电磁“热点”的区域显示出清晰的 α 相成核。重要的是,这些热点不需要对应于催化纳米颗粒的传统活性、能量优选位点。等离子体纳米粒子赋予的非热效应,包括电磁场增强和等离子体衍生的热载流子,对于解释在 PdH 中观察到的位点选择性至关重要 由金纳米粒子“天线”和 Pd“反应器”组成的多组分等离子体光催化剂在靠近等离子体天线时在靠近电磁“热点”的区域显示出清晰的 α 相成核。重要的是,这些热点不需要对应于催化纳米颗粒的传统活性、能量优选位点。等离子体纳米粒子赋予的非热效应,包括电磁场增强和等离子体衍生的热载流子,对于解释在 PdH 中观察到的位点选择性至关重要 由金纳米粒子“天线”和 Pd“反应器”组成的多组分等离子体光催化剂在靠近等离子体天线时在靠近电磁“热点”的区域显示出清晰的 α 相成核。重要的是,这些热点不需要对应于催化纳米颗粒的传统活性、能量优选位点。等离子体纳米粒子赋予的非热效应,包括电磁场增强和等离子体衍生的热载流子,对于解释在 PdH 中观察到的位点选择性至关重要x光照下的相变。本报告展示了光如何促进等离子体异质结构中的选择性化学现象,从而实现可持续的、太阳能驱动的化学生产。
更新日期:2021-10-06
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