Driving energetically unfavorable dehydrogenation dynamics with plasmonics

Abstract

Nanoparticle surface structure and geometry generally dictate where chemical transformations occur, with higher chemical activity at sites with lower activation energies. Here, we show how optical excitation of plasmons enables spatially modified phase transformations, activating otherwise energetically unfavorable sites. We have designed a crossed-bar Au-PdHx antenna-reactor system that localizes electromagnetic enhancement away from the innately reactive PdHx nanorod tips. Using optically coupled in situ environmental transmission electron microscopy, we track the dehydrogenation of individual antenna-reactor pairs with varying optical illumination intensity, wavelength, and hydrogen pressure. Our in situ experiments show that plasmons enable new catalytic sites, including dehydrogenation at the nanorod faces. Molecular dynamics simulations confirm that these new nucleation sites are energetically unfavorable in equilibrium and only accessible through tailored plasmonic excitation.

Advancing Plasmon-Induced Selectivity in Chemical Transformations with Optically Coupled Transmission Electron Microscopy

“…By carefully positioning the scanning TEM (STEM) detector, this lattice parameter change can be visualized as an intensity contrast (since the diffracted beam moves out of the STEM detector). Because STEM contrast imaging is temporally limited by slow raster speeds, we later utilized displaced aperture dark field (DADF) imaging to probe the same phenomenon with 100 ms temporal resolution, limited only by the frame rate of the attached camera . In DADF imaging, a 10 μm objective aperture is carefully placed over the diffracted electron beam pattern and results in a dark-field image where lattice expansion and contraction (i.e., from phase transformations or another type of lattice strain) can be visualized directly.…”

“…The concept of spatially modified phase transformations was further explored by Sytwu et al using a crossed-bar Au–Pd antenna–reactor geometry . Importantly, the work by Sytwu explored whether plasmonic hotspots could drive reactions at locations separated from the energetically preferred reaction sites in the dark.…”

“…All scale bars correspond to 100 nm. Adapted with permission from ref . Copyright 2021 American Association for the Advancement of Science.…”

“…In the Dionne laboratory, we have taken advantage of rapidly developing advances in transmission electron microscopy (TEM) to visualize catalytic and photocatalytic phase transformations at the nanoscale, with a particularly relevant focus on Pd nanoparticles when exposed to hydrogen gas. − ,, We take advantage of environmental TEM (ETEM: a specialized electron microscope with the capability to introduce low-pressure gases around the sample) and capitalize on our group’s advancement of optically coupled transmission electron microscopy (OTEM) to illuminate samples in situ . With these techniques, we have been able to monitor how Pd nanocrystals interact with hydrogen with nanometer-to-atomic-scale resolution in response to light.…”

Anisotropic plasmonic Pd-tipped Au nanorods for near-infrared light-activated photoacoustic imaging guided photothermal–photodynamic cancer therapy

“…[18][19][20] Plasmonic metals combined with other noble metal materials are emerging as potent application platforms, especially in the field of catalysis. [21][22][23][24][25][26] Metal plasma heterostructures can promote the generation of energetic hot electrons and the enhancement of the electromagnetic field in plasmonic nanostructures under stimulation by an external light. 18,27 The generated hot electrons could release heat energy by the electron-phonon relaxation process, [28][29][30] and promote reactive oxygen species (ROS) generation by energy and electron transfer processes.…”