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All Publications


  • In-situ observation of plasmon-controlled photocatalytic dehydrogenation of individual palladium nanoparticles NATURE COMMUNICATIONS Vadai, M., Angell, D. K., Hayee, F., Sytwu, K., Dionne, J. A. 2018; 9
  • In-situ observation of plasmon-controlled photocatalytic dehydrogenation of individual palladium nanoparticles. Nature communications Vadai, M., Angell, D. K., Hayee, F., Sytwu, K., Dionne, J. A. 2018; 9 (1): 4658

    Abstract

    Plasmonic nanoparticle catalysts offer improved light absorption and carrier transport compared to traditional photocatalysts. However, it remains unclear how plasmonic excitation affects multi-step reaction kinetics and promotes site-selectivity. Here, we visualize a plasmon-induced reaction at the sub-nanoparticle level in-situ and in real-time. Using an environmental transmission electron microscope combined with light excitation, we study the photocatalytic dehydrogenation of individual palladium nanocubes coupled to gold nanoparticles with sub-2 nanometer spatial resolution. We find that plasmons increase the rate of distinct reaction steps with unique time constants; enable reaction nucleation at specific sites closest to the electromagnetic hot spots; and appear to open a new reaction pathway that is not observed without illumination. These effects are explained by plasmon-mediated population of excited-state hybridized palladium-hydrogen orbitals. Our results help elucidate the role of plasmons in light-driven photochemical transformations, en-route to design of site-selective and product-specific photocatalysts.

    View details for PubMedID 30405133

  • Visualizing Facet-Dependent Hydrogenation Dynamics in Individual Palladium Nanoparticles. Nano letters Sytwu, K., Hayee, F., Narayan, T. C., Koh, A. L., Sinclair, R., Dionne, J. A. 2018

    Abstract

    Surface faceting in nanoparticles can profoundly impact the rate and selectivity of chemical transformations. However, the precise role of surface termination can be challenging to elucidate because many measurements are performed on ensembles of particles and do not have sufficient spatial resolution to observe reactions at the single and subparticle level. Here, we investigate solute intercalation in individual palladium hydride nanoparticles with distinct surface terminations. Using a combination of diffraction, electron energy loss spectroscopy, and dark-field contrast in an environmental transmission electron microscope (TEM), we compare the thermodynamics and directly visualize the kinetics of 40-70 nm {100}-terminated cubes and {111}-terminated octahedra with approximately 2 nm spatial resolution. Despite their distinct surface terminations, both particle morphologies nucleate the new phase at the tips of the particle. However, whereas the hydrogenated phase-front must rotate from [111] to [100] to propagate in cubes, the phase-front can propagate along the [100], [110], and [111] directions in octahedra. Once the phase-front is established, the interface propagates linearly with time and is rate-limited by surface-to-subsurface diffusion and/or the atomic rearrangements needed to accommodate lattice strain. Following nucleation, both particle morphologies take approximately the same time to reach equilibrium, hydrogenating at similar pressures and without equilibrium phase coexistence. Our results highlight the importance of low-coordination number sites and strain, more so than surface faceting, in governing solute-driven reactions.

    View details for PubMedID 30148640

  • Plasmonic approaches for visualizing and controlling intercalation-driven phase transformations Dionne, J., Hayee, F., Vadai, M., Angell, D., Sytwu, K. AMER CHEMICAL SOC. 2018
  • In-situ visualization of plasmon-induced hydrogenation reactions in individual palladium nanocubes Vadai, M., Angell, D., Hayee, F., Sytwu, K., Dionne, J. AMER CHEMICAL SOC. 2018
  • In-situ observation of plasmon-driven hydrogenation reactions within Au@Pd coreshell nanoparticles Sytwu, K., Vadai, M., Hayee, F., Koh, A., Sinclair, R., Dionne, J. AMER CHEMICAL SOC. 2018
  • In-situ visualization of solute-driven phase coexistence within individual nanorods. Nature communications Hayee, F., Narayan, T. C., Nadkarni, N., Baldi, A., Koh, A. L., Bazant, M. Z., Sinclair, R., Dionne, J. A. 2018; 9 (1): 1775

    Abstract

    Nanorods are promising components of energy and information storage devices that rely on solute-driven phase transformations, due to their large surface-to-volume ratio and ability to accommodate strain. Here we investigate the hydrogen-induced phase transition in individual penta-twinned palladium nanorods of varying aspect ratios with ~3 nm spatial resolution to understand the correlation between nanorod structure and thermodynamics. We find that the hydrogenated phase preferentially nucleates at the rod tips, progressing along the length of the nanorods with increasing hydrogen pressure. While nucleation pressure is nearly constant for all lengths, the number of phase boundaries is length-dependent, with stable phase coexistence always occurring for rods longer than 55 nm. Moreover, such coexistence occurs within individual crystallites of the nanorods and is accompanied by defect formation, as supported by in situ electron microscopy and elastic energy calculations. These results highlight the effect of particle shape and dimension on thermodynamics, informing nanorod design for improved device cyclability.

    View details for PubMedID 29720644

    View details for PubMedCentralID PMC5932065

  • Direct visualization of hydrogen absorption dynamics in individual palladium nanoparticles NATURE COMMUNICATIONS Narayan, T. C., Hayee, F., Baldi, A., Koh, A. L., Sinclair, R., Dionne, J. A. 2017; 8