Publications
106 results found
Ben-Jaber S, Glass D, Brick T, et al., 2023, Photo-induced enhanced Raman spectroscopy as a probe for photocatalytic surfaces., Philos Trans A Math Phys Eng Sci, Vol: 381
Photo-induced enhanced Raman spectroscopy (PIERS) has emerged as a highly sensitive surface-enhanced Raman spectroscopy (SERS) technique for the detection of ultra-low concentrations of organic molecules. The PIERS mechanism has been largely attributed to UV-induced formation of surface oxygen vacancies (Vo) in semiconductor materials, although alternative interpretations have been suggested. Very recently, PIERS has been proposed as a surface probe for photocatalytic materials, following Vo formation and healing kinetics. This work establishes comparison between PIERS and Vo-induced SERS approaches in defected noble-metal-free titanium dioxide (TiO2-x) films to further confirm the role of Vo in PIERS. Upon application of three post-treatment methods (namely UV-induction, vacuum annealing and argon etching), correlation of Vo kinetics and distribution could be established. A proposed mechanism and further discussion on PIERS as a probe to explore photocatalytic materials are also presented. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.
Jin H, Herran M, Cortés E, et al., 2023, Theory of Hot-Carrier Generation in Bimetallic Plasmonic Catalysts, ACS Photonics, ISSN: 2330-4022
Zhang H, Luo T, Chen Y, et al., 2023, Highly Efficient Decomposition of Perfluorocarbons for over 1000 Hours via Active Site Regeneration, Angewandte Chemie, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>Tetrafluoromethane (CF<jats:sub>4</jats:sub>), the simplest perfluorocarbon (PFC), has the potential to exacerbate global warming. Catalytic hydrolysis is a viable method to degrade CF<jats:sub>4</jats:sub>, but fluorine poisoning severely restricts both the catalytic performance and catalyst lifetime. In this study, Ga is introduced to effectively assists the defluorination of poisoned Al active sites, leading to highly efficient CF<jats:sub>4</jats:sub> decomposition at 600 °C with a catalytic lifetime exceeding 1,000 hours. <jats:sup>27</jats:sup>Al and <jats:sup>71</jats:sup>Ga magic‐angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the introduced Ga exists as tetracoordinated Ga sites (Ga<jats:sub>IV</jats:sub>), which readily dissociate water to form Ga−OH. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density function theory (DFT) calculations confirmed that Ga−OH assists the defluorination of poisoned Al active sites via a dehydration‐like process. As a result, the Ga/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> catalyst achieved 100 % CF<jats:sub>4</jats:sub> decomposition keeping an ultra‐long catalytic lifetime and outperforming reported results. This work proposes a new approach for efficient and long‐term CF<jats:sub>4</jats:sub> decomposition by promoting the regeneration of active sites.</jats:p>
Zhang H, Luo T, Chen Y, et al., 2023, Highly Efficient Decomposition of Perfluorocarbons for over 1000 Hours via Active Site Regeneration., Angew Chem Int Ed Engl
Tetrafluoromethane (CF4 ), the simplest perfluorocarbon (PFC), has the potential to exacerbate global warming. Catalytic hydrolysis is a viable method to degrade CF4 , but fluorine poisoning severely restricts both the catalytic performance and catalyst lifetime. In this study, Ga is introduced to effectively assists the defluorination of poisoned Al active sites, leading to highly efficient CF4 decomposition at 600 °C with a catalytic lifetime exceeding 1,000 hours. 27 Al and 71 Ga magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the introduced Ga exists as tetracoordinated Ga sites (GaIV ), which readily dissociate water to form Ga-OH. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density function theory (DFT) calculations confirmed that Ga-OH assists the defluorination of poisoned Al active sites via a dehydration-like process. As a result, the Ga/Al2 O3 catalyst achieved 100 % CF4 decomposition keeping an ultra-long catalytic lifetime and outperforming reported results. This work proposes a new approach for efficient and long-term CF4 decomposition by promoting the regeneration of active sites.
Vinnacombe-Willson GA, Conti Y, Stefancu A, et al., 2023, Direct Bottom-Up In Situ Growth: A Paradigm Shift for Studies in Wet-Chemical Synthesis of Gold Nanoparticles., Chem Rev, Vol: 123, Pages: 8488-8529
Plasmonic gold nanoparticles have been used increasingly in solid-state systems because of their applicability in fabricating novel sensors, heterogeneous catalysts, metamaterials, and thermoplasmonic substrates. While bottom-up colloidal syntheses take advantage of the chemical environment to control size, shape, composition, surface chemistry, and crystallography of the nanostructures precisely, it can be challenging to assemble nanoparticles rationally from suspension onto solid supports or within devices. In this Review, we discuss a powerful recent synthetic methodology, bottom-up in situ substrate growth, which circumvents time-consuming batch presynthesis, ligand exchange, and self-assembly steps by applying wet-chemical synthesis to form morphologically controlled nanostructures on supporting materials. First, we briefly introduce the properties of plasmonic nanostructures. Then we comprehensively summarize recent work that adds to the synthetic understanding of in situ geometrical and spatial control (patterning). Next, we briefly discuss applications of plasmonic hybrid materials prepared by in situ growth. Overall, despite the vast potential advantages of in situ growth, the mechanistic understanding of these methodologies remains far from established, providing opportunities and challenges for future research.
Berger LM, Duportal M, Menezes LDS, et al., 2023, Improved In Situ Characterization of Electrochemical Interfaces Using Metasurface-Driven Surface-Enhanced IR Absorption Spectroscopy, Advanced Functional Materials, Vol: 33, ISSN: 1616-301X
Electrocatalysis plays a crucial role in realizing the transition toward a zero-carbon future, driving research directions from green hydrogen generation to carbon dioxide reduction. Surface-enhanced infrared absorption spectroscopy (SEIRAS) is a suitable method for investigating electrocatalytic processes because it can monitor with chemical specificity the mechanisms of the reactions. However, it remains difficult to detect many relevant aspects of electrochemical reactions such as short-lived intermediates. Herein, an integrated nanophotonic-electrochemical SEIRAS platform is developed and experimentally realized for the in situ investigation of molecular signal traces emerging during electrochemical experiments. A platinum nano-slot metasurface featuring strongly enhanced electromagnetic near fields is implemented and spectrally targets the weak vibrational mode of the adsorbed carbon monoxide at ≈2033 cm−1. The metasurface-driven resonances can be tuned over a broad range in the mid-infrared spectrum and provide high molecular sensitivity. Compared to conventional unstructured platinum films, this nanophotonic-electrochemical platform delivers a 27-fold improvement of the experimentally detected characteristic absorption signals, enabling the detection of new species with weak signals, fast conversions, or low surface concentrations. By providing a deeper understanding of catalytic reactions, the nanophotonic-electrochemical platform is anticipated to open exciting perspectives for electrochemical SEIRAS, surface-enhanced Raman spectroscopy, and other fields of chemistry such as photoelectrocatalysis.
Nan L, Giráldez-Martínez J, Stefancu A, et al., 2023, Investigating Plasmonic Catalysis Kinetics on Hot-Spot Engineered Nanoantennae., Nano Lett, Vol: 23, Pages: 2883-2889
Strong hot-spots can facilitate photocatalytic reactions potentially providing effective solar-to-chemical energy conversion pathways. Although it is well-known that the local electromagnetic field in plasmonic nanocavities increases as the cavity size reduces, the influence of hot-spots on photocatalytic reactions remains elusive. Herein, we explored hot-spot dependent catalytic behaviors on a highly controlled platform with varying interparticle distances. Plasmon-meditated dehalogenation of 4-iodothiophenol was employed to observe time-resolved catalytic behaviors via in situ surface-enhanced Raman spectroscopy on dimers with 5, 10, 20, and 30 nm interparticle distances. As a result, we show that by reducing the gap from 20 to 10 nm, the reaction rate can be sped up more than 2 times. Further reduction in the interparticle distance did not improve reaction rate significantly although the maximum local-field was ∼2.3-fold stronger. Our combined experimental and theoretical study provides valuable insights in designing novel plasmonic photocatalytic platforms.
Long Y, He J, Zhang H, et al., 2023, Highly Selective Monomethylation of Amines with CO2 /H2 via Ag/Al2 O3 as a Catalyst., Chemistry, Vol: 29
The selective synthesis of monomethylated amines with CO2 is particularly challenging because the formation of tertiary amines is thermodynamically more favorable. Herein, a new strategy for the controllable synthesis of N-monomethylated amines from primary amines and CO2 /H2 is explored. First-principle calculations reveal that the dissociation of H2 via an heterolytic route reduces the reactivity of methylated amines and thus inhibit successive methylation. In situ DRIFTS proves the process of formation and decomposition of ammonium salt by secondary amine reversible binding with H+ on the Ag/Al2 O3 catalyst, thereby reducing its reactivity. Meanwhile, the energy barrier for the rate-determining step of monomethylation was much lower than that of overmethylation (0.34 eV vs. 0.58 eV) means amines monomethylation in preference to successive methylation. Under optimal reaction conditions, a variety of amines were converted to the corresponding monomethylated amines in good to excellent yields, and more than 90 % yield of product was obtained.
Cortés E, 2023, Light-activated catalysts point the way to sustainable chemistry, Nature, Vol: 614, Pages: 230-232, ISSN: 0028-0836
Stefancu A, Gargiulo J, Laufersky G, et al., 2023, Interface-Dependent Selectivity in Plasmon-Driven Chemical Reactions, ACS NANO, ISSN: 1936-0851
Wang J, Ni G, Liao W, et al., 2023, Subsurface Engineering Induced Fermi Level De-pinning in Metal Oxide Semiconductors for Photoelectrochemical Water Splitting, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ISSN: 1433-7851
Lin R, Chen H, Cui T, et al., 2023, Optimization of p-Type Cu<inf>2</inf>O Nanocube Photocatalysts Based on Electronic Effects, ACS Catalysis, Pages: 11352-11361
The size effect in semiconductor photocatalysis has been widely investigated but still remains elusive. Herein, employing p-type Cu2O nanocubes as the heterogeneous photocatalysts, we propose a feasible size optimization strategy to enhance the photocatalytic performance of semiconductors. With the size of Cu2O increasing from 2.5 nm (exciton Bohr radius) to 5 nm (twice the exciton Bohr radius), the corresponding calculated band gap of Cu2O decreases from 3.39 to 2.41 eV, indicating that controlling the size to above twice the exciton Bohr radius is vital for retaining the visible-light response of Cu2O. Based on the theoretical calculations and experimental measurements of the charge carrier dynamics, we found that the synthesized 30 nm Cu2O nanocubes have an electron diffusion length of 191 nm, while 229 nm Cu2O nanocubes show an electron diffusion length of 45 nm. An electron diffusion length larger than the semiconductor particle size lowers the electron-hole recombination, resulting in a visible-light CO generation rate 23.4 times higher for the smaller Cu2O nanocubes than that for the larger ones. These results verify that confining Cu2O size to within the minority carrier diffusion length and above twice the exciton Bohr radius is a promising way to enhance Cu2O photocatalytic activity.
Ezendam S, Nan L, Violi IL, et al., 2023, Anti Stokes Thermometry of Plasmonic Nanoparticle Arrays, Advanced Optical Materials
Metallic nanoparticles possess strong photothermal responses, especially when illuminated as ensembles due to collective effects. However, accurately quantifying the temperature increase remains a significant challenge, impeding progress in several applications. Anti Stokes thermometry offers a promising solution by enabling direct and non-invasive temperature measurements of the metal without the need for labeling or prior calibration. While Anti Stokes thermometry is successfully applied to individual nanoparticles, its potential to study light-to-heat conversion with plasmonic ensembles remains unexplored. In this study, the theoretical framework and the conditions that must be fulfilled for applying Anti Stokes thermometry to ensembles of nanoparticles are discussed. Then, this technique is implemented to measure the light-induced heating of square arrays of Au nanodisks. The obtained temperature measurements are validated using wavefront microscopy, demonstrating excellent agreement between the two thermometry methods. These results showcase the extension of Anti Stokes thermometry to plasmonic ensembles, highlighting its potential for implementation in the diverse photothermal applications involving these systems.
Liao W, Liu K, Wang J, et al., 2022, Boosting Nitrogen Activation via Ag Nanoneedle Arrays for Efficient Ammonia Synthesis, ACS NANO, ISSN: 1936-0851
Paredes MY, Martinez LP, Barja BC, et al., 2022, Efficient method of arsenic removal from water based on photocatalytic oxidation by a plasmonic-magnetic nanosystem, ENVIRONMENTAL SCIENCE-NANO, Vol: 10, Pages: 166-177, ISSN: 2051-8153
Moretti GQ, Tittl A, Cortés E, et al., 2022, Introducing a Symmetry‐Breaking Coupler into a Dielectric Metasurface Enables Robust High‐Q Quasi‐BICs, Advanced Photonics Research, Vol: 3, ISSN: 2699-9293
<jats:sec><jats:label /><jats:p>Dielectric metasurfaces supporting quasibound states in the continuum (quasi‐BICs) exhibit very high‐quality factor resonances and electric field confinement. However, accessing the high‐Q end of the quasi‐BIC regime usually requires marginally distorting the metasurface design from a BIC condition, pushing the needed nanoscale fabrication precision to the limit. This work introduces a novel concept for generating high‐Q quasi‐BICs, which strongly relaxes this requirement by incorporating a relatively large perturbative element close to high‐symmetry points of an undistorted BIC metasurface, acting as a coupler to the radiation continuum. This approach is validated by adding a ≈100 nm diameter cylinder between two reflection‐symmetry points separated by a 300 nm gap in an elliptical disk metasurface unit cell, using gallium phosphide as the dielectric. It is found that high‐Q resonances emerge when the cylindrical coupler is placed at any position between such symmetry points. This metasurface's second harmonic generation capability in the optical range is further explored. Displacing the coupler as much as a full diameter from a BIC condition produces record‐breaking normalized conversion efficiencies >10<jats:sup>2</jats:sup> W<jats:sup>−1</jats:sup>. The strategy of enclosing a disruptive element between multiple high‐symmetry points in a BIC metasurface can be applied to construct robust high‐Q quasi‐BICs in many geometrical designs.</jats:p></jats:sec>
Mancini A, Nan L, Wendisch FJ, et al., 2022, Near-Field Retrieval of the Surface Phonon Polariton Dispersion in Free-Standing Silicon Carbide Thin Films, ACS PHOTONICS, Vol: 9, Pages: 3696-3704, ISSN: 2330-4022
Cai C, Liu B, Liu K, et al., 2022, Heteroatoms Induce Localization of the Electric Field and Promote a Wide Potential-Window Selectivity Towards CO in the CO2 Electroreduction., Angew Chem Int Ed Engl, Vol: 61
Carbon dioxide electroreduction (CO2 RR) is a sustainable way of producing carbon-neutral fuels. Product selectivity in CO2 RR is regulated by the adsorption energy of reaction-intermediates. Here, we employ differential phase contrast-scanning transmission electron microscopy (DPC-STEM) to demonstrate that Sn heteroatoms on a Ag catalyst generate very strong and atomically localized electric fields. In situ attenuated total reflection infrared spectroscopy (ATR-IR) results verified that the localized electric field enhances the adsorption of *COOH, thus favoring the production of CO during CO2 RR. The Ag/Sn catalyst exhibits an approximately 100 % CO selectivity at a very wide range of potentials (from -0.5 to -1.1 V, versus reversible hydrogen electrode), and with a remarkably high energy efficiency (EE) of 76.1 %.
Wang Q, Liu K, Hu K, et al., 2022, Attenuating metal-substrate conjugation in atomically dispersed nickel catalysts for electroreduction of CO2 to CO., Nat Commun, Vol: 13
Atomically dispersed transition metals on carbon-based aromatic substrates are an emerging class of electrocatalysts for the electroreduction of CO2. However, electron delocalization of the metal site with the carbon support via d-π conjugation strongly hinders CO2 activation at the active metal centers. Herein, we introduce a strategy to attenuate the d-π conjugation at single Ni atomic sites by functionalizing the support with cyano moieties. In situ attenuated total reflection infrared spectroscopy and theoretical calculations demonstrate that this strategy increases the electron density around the metal centers and facilitates CO2 activation. As a result, for the electroreduction of CO2 to CO in aqueous KHCO3 electrolyte, the cyano-modified catalyst exhibits a turnover frequency of ~22,000 per hour at -1.178 V versus the reversible hydrogen electrode (RHE) and maintains a Faradaic efficiency (FE) above 90% even with a CO2 concentration of only 30% in an H-type cell. In a flow cell under pure CO2 at -0.93 V versus RHE the cyano-modified catalyst enables a current density of -300 mA/cm2 with a FE above 90%.
Chen S, Luo T, Li X, et al., 2022, Identification of the Highly Active Co-N-4 Coordination Motif for Selective Oxygen Reduction to Hydrogen Peroxide, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 144, Pages: 14505-14516, ISSN: 0002-7863
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- Citations: 8
Hu H, Weber T, Bienek O, et al., 2022, Catalytic metasurfaces empowered by bound states in the continuum, ACS Nano, Vol: 16, Pages: 13057-13068, ISSN: 1936-0851
Photocatalytic platforms based on ultrathin reactive materials facilitate carrier transport and extraction but are typically restricted to a narrow set of materials and spectral operating ranges due to limited absorption and poor energy-tuning possibilities. Metasurfaces, a class of 2D artificial materials based on the electromagnetic design of nanophotonic resonators, allow optical absorption engineering for a wide range of materials. Moreover, tailored resonances in nanostructured materials enable strong absorption enhancement and thus carrier multiplication. Here, we develop an ultrathin catalytic metasurface platform that leverages the combination of loss-engineered substoichiometric titanium oxide (TiO2–x) and the emerging physical concept of optical bound states in the continuum (BICs) to boost photocatalytic activity and provide broad spectral tunability. We demonstrate that our platform reaches the condition of critical light coupling in a TiO2–x BIC metasurface, thus providing a general framework for maximizing light–matter interactions in diverse photocatalytic materials. This approach can avoid the long-standing drawbacks of many naturally occurring semiconductor-based ultrathin films applied in photocatalysis, such as poor spectral tunability and limited absorption manipulation. Our results are broadly applicable to fields beyond photocatalysis, including photovoltaics and photodetectors.
Yao K, Li J, Wang H, et al., 2022, Mechanistic insights into OC-COH coupling in CO2 electroreduction on fragmented copper, Journal of the American Chemical Society, Vol: 144, Pages: 14005-14011, ISSN: 0002-7863
The carbon–carbon (C–C) bond formation is essential for the electroconversion of CO2 into high-energy-density C2+ products, and the precise coupling pathways remain controversial. Although recent computational investigations have proposed that the OC–COH coupling pathway is more favorable in specific reaction conditions than the well-known CO dimerization pathway, the experimental evidence is still lacking, partly due to the separated catalyst design and mechanistic/spectroscopic exploration. Here, we employ density functional theory calculations to show that on low-coordinated copper sites, the *CO bindings are strengthened, and the adsorbed *CO coupling with their hydrogenation species, *COH, receives precedence over CO dimerization. Experimentally, we construct a fragmented Cu catalyst with abundant low-coordinated sites, exhibiting a 77.8% Faradaic efficiency for C2+ products at 300 mA cm–2. With a suite of in situ spectroscopic studies, we capture an *OCCOH intermediate on the fragmented Cu surfaces, providing direct evidence to support the OC–COH coupling pathway. The mechanistic insights of this research elucidate how to design materials in favor of OC–COH coupling toward efficient C2+ production from CO2 reduction.
Chen Q, Liu K, Zhou Y, et al., 2022, Ordered Ag Nanoneedle Arrays with Enhanced Electrocatalytic CO2 Reduction via Structure-Induced Inhibition of Hydrogen Evolution, NANO LETTERS, Vol: 22, Pages: 6276-6284, ISSN: 1530-6984
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- Citations: 3
Herran M, Sousa-Castillo A, Fan C, et al., 2022, Tailoring Plasmonic Bimetallic Nanocatalysts Toward Sunlight-Driven H-2 Production, ADVANCED FUNCTIONAL MATERIALS, Vol: 32, ISSN: 1616-301X
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- Citations: 3
Cortes E, Wendisch FJ, Sortino L, et al., 2022, Optical Metasurfaces for Energy Conversion, CHEMICAL REVIEWS, ISSN: 0009-2665
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- Citations: 8
Rosenberger P, Dagar R, Zhang W, et al., 2022, Imaging elliptically polarized infrared near-fields on nanoparticles by strong-field dissociation of functional surface groups, European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, Vol: 76, Pages: 1-9, ISSN: 0011-4626
We investigate the strong-field ion emission from the surface of isolated silica nanoparticles aerosolized from an alcoholic solution, and demonstrate the applicability of the recently reported near-field imaging at 720 nm [Rupp et al., Nat. Comm., 10(1):4655, 2019] to longer wavelength (2 μm) and polarizations with arbitrary ellipticity. Based on the experimental observations, we discuss the validity of a previously introduced semi-classical model, which is based on near-field driven charge generation by a Monte-Carlo approach and classical propagation. We furthermore clarify the role of the solvent in the surface composition of the nanoparticles in the interaction region. We find that upon injection of the nanoparticles into the vacuum, the alcoholic solvent evaporates on millisecond time scales, and that the generated ions originate predominantly from covalent bonds with the silica surface rather than from physisorbed solvent molecules. These findings have important implications for the development of future theoretical models of the strong-field ion emission from silica nanoparticles, and the application of near-field imaging and reaction dynamics of functional groups on isolated nanoparticles.
Zhang W, Dagar R, Rosenberger P, et al., 2022, All-optical nanoscopic spatial control of molecular reaction yields on nanoparticles, OPTICA, Vol: 9, Pages: 551-560, ISSN: 2334-2536
Stefancu A, Nan L, Zhu L, et al., 2022, Controlling Plasmonic Chemistry Pathways through Specific Ion Effects, ADVANCED OPTICAL MATERIALS, Vol: 10, ISSN: 2195-1071
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- Citations: 3
Cortes E, Grzeschik R, Maier SA, et al., 2022, Experimental characterization techniques for plasmon-assisted chemistry, NATURE REVIEWS CHEMISTRY, Vol: 6, Pages: 259-274
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- Citations: 11
Chen K, Cao M, Lin Y, et al., 2022, Ligand Engineering in Nickel Phthalocyanine to Boost the Electrocatalytic Reduction of CO<inf>2</inf>, Advanced Functional Materials, Vol: 32, ISSN: 1616-301X
Designing and synthesizing efficient molecular catalysts may unlock the great challenge of controlling the CO2 reduction reaction (CO2RR) with molecular precision. Nickel phthalocyanine (NiPc) appears as a promising candidate for this task due to its adjustable Ni active-site. However, the pristine NiPc suffers from poor activity and stability for CO2RR owing to the poor CO2 adsorption and activation at the bare Ni site. Here, a ligand-tuned strategy is developed to enhance the catalytic performance and unveil the ligand effect of NiPc on CO2RR. Theoretical calculations and experimental results indicate that NiPc with electron-donating substituents (hydroxyl or amino) can induce electronic localization at the Ni site which greatly enhances the CO2 adsorption and activation. Employing the optimal catalyst—an amino-substituted NiPc—to convert CO2 into CO in a flow cell can achieve an ultrahigh activity and selectivity of 99.8% at current densities up to −400 mA cm−2. This work offers a novel strategy to regulate the electronic structure of active sites by ligand design and discloses the ligand-directed catalysis of the tailored NiPc for highly efficient CO2RR.
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