Browsing by Author "Christopher, Phillip"

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    Impact of chemical interface damping on surface plasmon dephasing
    (Royal Society of Chemistry, 2019) Therrien, Andrew J.; Kale, Matthew J.; Yuan, Lin; Zhang, Chao; Halas, Naomi J.; Christopher, Phillip; Laboratory for Nanophotonics; Smalley-Curl Institute
    The excellent light harvesting ability of plasmonic nanoparticles makes them promising materials for a variety of technologies that rely on the conversion of photons to energetic charge carriers. In such applications, including photovoltaics and photocatalysis, the excitation of surface plasmons must induce charge transfer across the metal–adsorbate or metal–semiconductor interface. However, there is currently a lack of molecular level understanding of how the presence of a chemical interface impacts surface plasmon dephasing pathways. Here, we report an approach to quantitatively measure the influence of molecular adsorption on the spectral shape and intensity of the extinction, scattering, and absorption cross-sections for nanostructured plasmonic surfaces. This is demonstrated for the case of thiophenol adsorption on lithographically patterned gold nanodisk arrays. The results show that the formation of a chemical interface between thiophenol and Au causes surface plasmons to decay more prominently through photon absorption rather than photon scattering, as compared to the bare metal. We propose that this effect is a result of the introduction of adsorbate-induced allowable electronic transitions at the interface, which facilitate surface plasmon dephasing via photon absorption. The results suggest that designed chemical interfaces with well-defined electronic structures may enable engineering of hot electron distributions, which could be important for understanding and controlling plasmon-mediated photocatalysis and, more generally, hot carrier transfer processes.
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    Impact of Surface Enhanced Raman Spectroscopy in Catalysis
    (American Chemical Society, 2024) Stefancu, Andrei; Aizpurua, Javier; Alessandri, Ivano; Bald, Ilko; Baumberg, Jeremy J.; Besteiro, Lucas V.; Christopher, Phillip; Correa-Duarte, Miguel; de Nijs, Bart; Demetriadou, Angela; Frontiera, Renee R.; Fukushima, Tomohiro; Halas, Naomi J.; Jain, Prashant K.; Kim, Zee Hwan; Kurouski, Dmitry; Lange, Holger; Li, Jian-Feng; Liz-Marzán, Luis M.; Lucas, Ivan T.; Meixner, Alfred J.; Murakoshi, Kei; Nordlander, Peter; Peveler, William J.; Quesada-Cabrera, Raul; Ringe, Emilie; Schatz, George C.; Schlücker, Sebastian; Schultz, Zachary D.; Tan, Emily Xi; Tian, Zhong-Qun; Wang, Lingzhi; Weckhuysen, Bert M.; Xie, Wei; Ling, Xing Yi; Zhang, Jinlong; Zhao, Zhigang; Zhou, Ru-Yu; Cortés, Emiliano
    Catalysis stands as an indispensable cornerstone of modern society, underpinning the production of over 80% of manufactured goods and driving over 90% of industrial chemical processes. As the demand for more efficient and sustainable processes grows, better catalysts are needed. Understanding the working principles of catalysts is key, and over the last 50 years, surface-enhanced Raman Spectroscopy (SERS) has become essential. Discovered in 1974, SERS has evolved into a mature and powerful analytical tool, transforming the way in which we detect molecules across disciplines. In catalysis, SERS has enabled insights into dynamic surface phenomena, facilitating the monitoring of the catalyst structure, adsorbate interactions, and reaction kinetics at very high spatial and temporal resolutions. This review explores the achievements as well as the future potential of SERS in the field of catalysis and energy conversion, thereby highlighting its role in advancing these critical areas of research.
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    Monitoring Chemical Reactions with Terahertz Rotational Spectroscopy
    (American Chemical Society, 2018) Swearer, Dayne F.; Gottheim, Samuel; Simmons, Jay G.; Phillips, Dane J.; Kale, Matthew J.; McClain, Michael J.; Christopher, Phillip; Halas, Naomi J.; Everitt, Henry O.
    Rotational spectroscopy is introduced as a new in situ method for monitoring gas-phase reactants and products during chemical reactions. Exploiting its unambiguous molecular recognition specificity and extraordinary detection sensitivity, rotational spectroscopy at terahertz frequencies was used to monitor the decomposition of carbonyl sulfide (OCS) over an aluminum nanocrystal (AlNC) plasmonic photocatalyst. The intrinsic surface oxide on AlNCs is discovered to have a large number of strongly basic sites that are effective for mediating OCS decomposition. Spectroscopic monitoring revealed two different photothermal decomposition pathways for OCS, depending on the absence or presence of H2O. The strength of rotational spectroscopy is witnessed through its ability to detect and distinguish isotopologues of the same mass from an unlabeled OCS precursor at concentrations of <1 nanomolar or partial pressures of <10 μTorr. These attributes recommend rotational spectroscopy as a compelling alternative for monitoring gas-phase chemical reactants and products in real time.