Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Q17: Chemical Physics of Plasmonic Nanostructures: Catalysis and SynthesisFocus
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Sponsoring Units: DCP Chair: Matthew Sheldon, Texas A&M University Room: Room 209 |
Wednesday, March 8, 2023 3:00PM - 3:36PM |
Q17.00001: Using Photons to Influence Catalysis on Supported Metal Catalysts Invited Speaker: Phillip Christopher Supported metal catalysts, consisting of transition metal nanoparticles and single atoms on high surface area, insulating oxide supports, are ubiquitously used in the manufacturing of chemicals and fuels. Efforts by industrial and academic researchers focus on improving catalytic process efficiency (higher rates and/or selectivity at lower temperature and pressure) by tuning the composition of the catalytic materials. Alternatively, we (and others) have recently observed that visible photon illumination of metal nanoparticle and single atom catalysts (Pt, Cu, Ag, Rh etc.) on insulating oxide supports (Al2O3, SiO2) can cause significant changes to catalytic reaction selectivity, rate, and apparent kinetic parameters. Mechanistic studies suggest that photons influence catalytic processes by redistributing charge within adsorbate-metal bonds, thereby changing elementary step energetics. Further, we have observed that using pulsed photons, rather than a continuous photon flux, allows for promoted catalytic rates with higher photon utilization efficiency. Given that modern LEDs are efficient, cheap, and programmable with on-times of sub-ms to sec and frequencies > 100 MHz, this work suggests that photon promoted or mediated chemistry may offer interesting opportunities for promoting the sustainability of chemical conversion processes. In this talk I will highlight some of our work in this area and provide some thoughts on opportunities and challenges with using light to promote or drive chemistry on supported metal catalysts. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q17.00002: Monitoring Nanoscale Optical Excitation and Energy Transfer with Optically Coupled Electron Microscopy Dayne F Swearer, Haihua Liu Transmission electron microscopes (TEM) have evolved beyond tools for atomic-scale imaging and diffraction. Modern TEMs are now integrated instruments capable of witnessing the dynamic material behavior at the nanoscale. One notable advance is the combination of the TEM with ultrafast lasers for the development of ultrafast electron microscopy (UEM) to investigate the light-matter interactions with a time resolution of hundreds of femtoseconds and a spatial resolution at the nanometer scale. Recent work will be presented on on understanding the optical excitation on earth-abundant plasmonic aluminum nanocrystals based on photon-induced near-field electron microscopy (PINEM) results on UEM. Using a visible pump pulse and a time-gated electron wave-packet probe the dynamics of photon-induced near-fields can be measured in space and time. This presentation will detail recent experimental results and theoretical insights into the behaviors observed on aluminum nanocrystals with an intrinsic aluminum oxide layer and nanocrystals modified with insulating silicon dioxide and semiconducting titanium dioxide shells. Oxide modification of plasmonic aluminum nanoparticles is hypothesized to influence energy transfer mechanisms associated with carrier excitations and extraction during plasmon excitation and decay. The results presented in this talk are expected to yield insight into other applications of modified plasmonic nanomaterials, namely photocatalysis. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q17.00003: Plasmon-Generated Hot Holes for Water Oxidation Wei David Wei Plasmon-generated hot electrons in metal/oxide heterostructures have been used extensively for driving photochemistry. However, little is known about the origin of plasmon-generated hot holes in promoting photochemical reactions. Herein, we discover that during the non-radiative plasmon decay, the interband excitation rather than the intraband excitation generates energetic hot holes that enable to drive the water oxidation at the Au/TiO2 interface. Distinct from lukewarm holes via the intraband excitation that only remain on Au, hot holes from the interband excitation are found to be transferred from Au into TiO2 and stabilized by surface oxygen atoms on TiO2, making them available to oxidize adsorbed water molecules. Taken together, our studies clarify the underlying photophysical process for exciting plasmon-generated hot holes and maintaining their strong oxidizing power in metal/oxide heterostructures, and affirm their crucial functions in governing photocatalytic oxidation reactions. |
Wednesday, March 8, 2023 4:00PM - 4:12PM Author not Attending |
Q17.00004: Magnetic and Plasmonically Active Supports for Singlet Oxygen Photocatalysis Audrey Moores Our group has worked on the design of novel nanoplasmonic systems for their use as photocatalysts applied to organic transformations,1 including the use of Ag nanocubes for hydrogen activation and hydrogenation of ketones and aldehydes,2 and Ru decorated Au nanoparticles able to tackle the difficult arene hydrogenation under mild conditions.3 Plasmonic nanomaterials are also powerful antennae for other types of photocatalysts. In this talk I will focus on the work we did towards enhancing the properties of photocatalysts in the context of organic transformation. We designed a silica-covered Ag nanosupport to enhance the performance of tris(bipyridine)ruthenium in singlet oxygen triggered C=C oxidation.4 The excitation of the surface plasmon resonance of the Ag core enables an enhancement of both the catalytic activity as well as fluorescence of the dye, which is dependant on the distance between them. Transmission Electron Microscopy - Electron Energy Loss Spectroscopy allowed to gain insight into the intensity of the surface plasmon resonance around the plasmonic metal in this system. In an effort to understand the generality of such systems, we have also explored the effect of this support onto two other dyes: Rose Bengal and methylene Blue.5 This study has allowed us to better understand the effect of plasmonic enhancement as a function of the dye excitation wavelength (and its overlap with the surface plasmon resonance of the support) and of the quantum yield of the free dyes. This work will help expand the use of these strategies in the context of organic transformations. Finally, we have also work on magnetic supports for such dyes, as this approach could help their recovery. In this example, we studied how magnetic materials, such as iron nanoparticles, who strongly absorb light and compete with the dye for photons, have been modified to improve their efficacy.6 |
Wednesday, March 8, 2023 4:12PM - 4:48PM |
Q17.00005: The Light Stuff: Enabling Sustainable Chemical Manufacturing with Atomically-Optimized Photocatalysts Invited Speaker: Jennifer Dionne
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Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q17.00006: Promoting Plasmonic Photocatalysis with Ligand-Induced Charge Separation Wei-Shun Chang, Ben Roche, Tamie Vo, Vidhi Singla Plasmonic nanoparticles have been demonstrated to enhance photocatalysis due to strong photon absorption and efficient hot-carrier generation. The intraband Landau damping creates hot electrons and warm holes by exciting surface plasmon resonances, while the d-sp interband transition yields hot d-band holes and warm electrons. However, plasmonic photocatalysts suffer a short lifetime of plasmon-generated hot carriers that decays through internal relaxation pathways before being harnessed for chemical reactions. Here, we demonstrate an enhancement of the photocatalytic reduction reaction of gold ions on gold nanorods coated with Polyvinylpyrrolidone (PVP). The catalytic activities of the reaction are quantified by in-situ monitoring the spectral evolution of single nanorods using dark-field spectro-microscopy. We observed an increased reduction rate by a factor of five with the excitation of d-sp interband transition compared to the dark condition and a negligible increase in reduction rate when excited with the intraband transition. Additionally, the hole scavenger only plays a minor role in the photocatalytic reduction reaction with the interband transition. We attribute the enhanced photocatalysis to an efficient charge separation at the gold-PVP interface where a photogenerated d-band hole at gold transfers to the HOMO of PVP, leading to the prolonged lifetime of the warm electrons that subsequently reduce gold ions to gold atoms. These results provide new insight into the design of plasmonic photocatalysts with capping ligands. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q17.00007: The Role of Surfactants in Colloidal and Electrochemical Syntheses of Palladium Tetrahexahedra Gabriel C Halford Shape-controlled noble metal nanoparticles show great promise for the development of selective catalysts. The development of robust syntheses for novel nanoparticle shapes and compositions is therefore of interest . We have developed a colloidal synthesis of monometallic palladium tetrahexahedra (THH) in a cetyltrimethylammonium bromide (CTAB) surfactant and have observed that the successful formation of THH is dependent on the type and lot number of the CTAB. Subtle differences in these surfactants lead to various effects on reaction rate, driving the formation of different kinetic products. As well as investigating these colloidal reactions via more traditional approaches such as electron microscopy, we electrochemically monitor reaction potentials in situ for the different CTAB conditions to gain a better understanding of the reaction kinetics. Additionally, we translate these colloidal syntheses for palladium THH and other shaped palladium particles of interest to electrochemical growth on a carbon electrode surface. Merging colloidal and electrochemical approaches allows us to attain a fuller understanding of the kinetics of this system and the mechanisms of formation for shaped palladium nanoparticles in general. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q17.00008: Plasmon Enhanced Deposition of Single Atom Catalysts Sanchari Chowdhury, Pabitra Choudhury, Keeniya-Gamalage-Gehan C. De Silva, Naomi Helsel, Tucker Burnett We developed a noble method to synthesize single atom nickel catalysts using the plasmon enhanced photo-deposition method. Single-atom catalysts (SACs) provide superior efficiency, selectivity, and tunability for catalysis. So far most of the synthesis methods of SACs required complex chemical steps, extreme conditions, or sophisticated instruments. SACs deposition under mild conditions using visible light can encourage their wide-scale applications. Plasmonic nanomaterials can efficiently absorb and concentrate light at the nanoscale to generate intense electromagnetic fields. The photoexcited electrons can undergo nonradiative decay, generating highly energetic electrons which can reduce metal cations adsorbed on the surface to deposit metal atoms on the surface. The reduction rate of metal cations can be easily controlled by varying light intensities and wavelengths to efficiently deposit single atoms. Here we deposited nickel single atoms on refractory plasmonic titanium nitride (TiN) nanomaterials which exhibit high-temperature stability, strong surface plasmon resonance, and can absorb a broad spectrum of solar light. We studied the Ni deposition on TiN nanoparticles by varying the light intensities, reaction time, and metal precursor concentration. SACs deposition is enhanced with the increase in light intensities (576 mW cm-2). Both XPS data and DFT calculations suggested Ni single atoms favorably deposit on N-vacancies sites and then on N sites on the TiN surface. |
Wednesday, March 8, 2023 5:24PM - 5:36PM |
Q17.00009: Modulating Plasmon-mediated Chemical Reaction by Electrode Potential on Copper Nanoelectrode Govinda Ghimire, Jin He Plasmon-mediated chemical reaction (PMCRs) is a promising approach for facilitating light-driven chemical reactions by utilizing solar energy. PMCR is an emerging field of research whereby the chemical reactions are triggered by the plasmonic metals which facilitate the conversion and redistribution of the photon energy into hot electrons and/or thermal energy. The molecular fingerprint of the PMCR-derived surface species can be characterized by Surface-enhanced Spectroscopy (SERS) in situ and in real-time with a sensitivity down to a single molecule. Plasmonic noble metals such as gold (Au) or silver (Ag) are typically used as SERS substrates owing to their extraordinary plasmonic properties associated with their high chemical stability. However, due to their limited amount in the continental crust, there’s a constant need to develop an alternative SERS substrate. Copper (Cu) is an attractive and cheaper alternative with its high catalytic activities combined with its strong plasmonic properties. In this talk, I will present the SERS studies of PMCRs on electrochemically etched copper nanoelectrodes (CuNE) as tunable, reliable, and efficient electrochemical SERS (EC-SERS) substrates. The catalytic reactions on the CuNE surface can be tuned by three factors: (i) the surface plasmons, (ii) the electrode potential, and (iii) the redox states of Cu. By using the time-resolved EC-SERS, the reversible conversion of 4-aminothiophenol(4-ATP)/4-nitrothiophenol(4-NTP) to 4,4′-dimercaptoazobenzene (DMAB) is studied. |
Wednesday, March 8, 2023 5:36PM - 5:48PM |
Q17.00010: Plasmon-Driven Reconfiguration of Metal Nanoparticle Defect Structure Michelle Personick, Gianna Argento, Dylan Judd, Leila Etemad We report a visible light-driven approach for converting planar-twinned Ag triangular prisms into multiply twinned Ag icosahedra. To our knowledge, this is the first demonstration of a post-synthetic reconfiguration of nanoparticle twin structure using light and it is one of the only post-synthetic methods for reconfiguring nanoparticles with one defect structure into another. Crystalline defect structure influences catalytic reactivity and selectivity, and thus the ability to reconfigure defect structure provides a promising handle for tuning catalyst performance. In addition, we have developed a method for further reconfiguring the defect structure of these multiply twinned Ag icosahedra back to planar-twinned Ag prisms through subsequent light-induced steps and pH control. To do so, we first determined the mechanism of the initial Ag prism to Ag icosahedra conversion and then used insight from that mechanism to overcome challenges in further material transformations. This interconversion of Ag nanoparticle shape and defect structure between prisms, icosahedra, and spheres using visible light opens opportunities for the reuse and recycling of Ag nanomaterials and provides a pathway to the synthesis of shape-reconfigurable nanocatalysts with light-tunable reactivity. |
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