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  1. Article ; Online: Synthesis and Structure-Activity Characterization of a Single-Site MoO

    Liu, Yiqi / Li, Jiaqi / Das, Anusheela / Kim, Hacksung / Jones, Leighton O / Ma, Qing / Bedzyk, Michael J / Schatz, George C / Kratish, Yosi / Marks, Tobin J

    Journal of the American Chemical Society

    2021  Volume 143, Issue 51, Page(s) 21532–21540

    Abstract: Molecularly derived single-site heterogeneous catalysts can bridge the understanding and performance gaps between conventional homogeneous and heterogeneous catalysis, guiding the rational design of next-generation catalysts. While impressive advances ... ...

    Abstract Molecularly derived single-site heterogeneous catalysts can bridge the understanding and performance gaps between conventional homogeneous and heterogeneous catalysis, guiding the rational design of next-generation catalysts. While impressive advances have been made with well-defined oxide supports, the structural complexity of other supports and the nature of the grafted surface species present an intriguing challenge. In this study, single-site Mo(═O)
    Language English
    Publishing date 2021-12-16
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.1c07236
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Synthesis and Structure–Activity Characterization of a Single-Site MoO₂ Catalytic Center Anchored on Reduced Graphene Oxide

    Liu, Yiqi / Li, Jiaqi / Das, Anusheela / Kim, Hacksung / Jones, Leighton O. / Ma, Qing / Bedzyk, Michael J. / Schatz, George C. / Kratish, Yosi / Marks, Tobin J.

    Journal of the American Chemical Society. 2021 Dec. 16, v. 143, no. 51

    2021  

    Abstract: Molecularly derived single-site heterogeneous catalysts can bridge the understanding and performance gaps between conventional homogeneous and heterogeneous catalysis, guiding the rational design of next-generation catalysts. While impressive advances ... ...

    Abstract Molecularly derived single-site heterogeneous catalysts can bridge the understanding and performance gaps between conventional homogeneous and heterogeneous catalysis, guiding the rational design of next-generation catalysts. While impressive advances have been made with well-defined oxide supports, the structural complexity of other supports and the nature of the grafted surface species present an intriguing challenge. In this study, single-site Mo(═O)₂ species grafted onto reduced graphene oxide (rGO/MoO₂) are characterized by XPS, DRIFTS, powder XRD, N₂ physisorption, NH₃-TPD, aqueous contact angle, active site poisoning assay, Mo EXAFS, model compound single-crystal XRD, DFT, and catalytic performance. NH₃-TPD reveals that the anchored MoO₂ moiety is not strongly acidic, while Mo 3d₅/₂ XPS assigns the oxidation state as Mo(VI), and XRD shows little rGO periodicity change on MoO₂ grafting. Contact angle analysis shows that MoO₂ grafting consumes rGO surface polar groups, yielding a more hydrophobic surface. The rGO/MoO₂ DRIFTS assigns features at 959 and 927 cm–¹ to the symmetric and antisymmetric Mo═O stretching modes, respectively, of an isolated cis-(O═Mo═O) moiety, in agreement with DFT computation. Moreover, the Mo EXAFS rGO/MoO₂ structural data are consistent with isolated (C–O)₂–Mo(═O)₂ species having two Mo═O bonds and two Mo–O bonds at distances of 1.69(3) and 1.90(3) Å, respectively. rGO/MoO₂ is also more active than the previously reported AC/MoO₂ catalyst, with reductive carbonyl coupling TOFs approaching 1.81 × 10³ h–¹. rGO/MoO₂ is environmentally robust and multiply recyclable with 69 ± 2% of the Mo sites catalytically significant. Overall, rGO/MoO₂ is a structurally well-defined and versatile single-site Mo(VI) dioxo heterogeneous catalytic system.
    Keywords active sites ; catalysts ; catalytic activity ; contact angle ; graphene oxide ; hydrophobicity ; moieties ; oxidation ; periodicity
    Language English
    Dates of publication 2021-1216
    Size p. 21532-21540.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.1c07236
    Database NAL-Catalogue (AGRICOLA)

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  3. Article ; Online: Gallstone-Formation-Inspired Bimetallic Supra-nanostructures for Computed-Tomography-Image-Guided Radiation Therapy.

    Cho, Soojeong / Park, Wooram / Kim, Hacksung / Jokisaari, Jacob R / Roth, Eric W / Lee, Sungsik / Klie, Robert F / Lee, Byeongdu / Kim, Dong-Hyun

    ACS applied nano materials

    2018  Volume 1, Issue 9, Page(s) 4602–4611

    Abstract: Inspired by the gallstone formation mechanism, we report a fast one-pot synthesis of high-surface-area bimetallic hierarchical supra-nanostructures. As gallstones are generated from metal cholate complexes, cholate bile acid molecules with Au/Ag metal ... ...

    Abstract Inspired by the gallstone formation mechanism, we report a fast one-pot synthesis of high-surface-area bimetallic hierarchical supra-nanostructures. As gallstones are generated from metal cholate complexes, cholate bile acid molecules with Au/Ag metal precursors formed stable nanocomplexes aggregated with metal Au ions and preformed ~2 nm silver halide nanoparticles before reduction. When a reducing agent was added, the metal cholate nanocomplexes quickly formed noble bimetallic hierarchical supra-nanostructures. The morphology of bimetallic supra-nanostructures could be tailored by changing the feeding ratio of each metal precursor. In situ synchrotron small-angle X-ray scattering measurement with a custom-designed reaction cell showed two-step growth and attachment behavior toward hierarchical supra-nanostructures from the gallstone-formation-inspired metal cholate nanocomplexes in a 60 s reaction. Additional wide-angle X-ray scattering, X-ray absorption near-edge structure, in situ Fourier transform infrared, and high-resolution scanning transmission electron microscopy investigations subsequently revealed the mechanism for the evolution of bimetallic hierarchical supra-nanostructures. The gallstone-formation-inspired synthesis mechanism can be universally applied to other metals, for example, Pt-Ag and Pd-Ag bimetallic nanostructures. Finally, the synthesized high-surface-area bimetallic supra-nanostructures demonstrated significantly enhanced X-ray computed tomography imaging contrast and radiosensitizing effect for a potential image-guided nanomedicine application. We believe that our synthetic method inspired by gallstone formation and understanding represents an important step toward the development of hierarchical nanoparticles for various applications.
    Language English
    Publishing date 2018-08-06
    Publishing country United States
    Document type Journal Article
    ISSN 2574-0970
    ISSN (online) 2574-0970
    DOI 10.1021/acsanm.8b00908
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Targeted multimodal nano-reporters for pre-procedural MRI and intra-operative image-guidance.

    Lee, Joonseok / Gordon, Andrew C / Kim, Hacksung / Park, Wooram / Cho, Soojeong / Lee, Byeongdu / Larson, Andrew C / Rozhkova, Elena A / Kim, Dong-Hyun

    Biomaterials

    2016  Volume 109, Page(s) 69–77

    Abstract: Multimodal-imaging probes offer a novel approach, which can provide detail diagnostic information for the planning of image-guided therapies in clinical practice. Here we report targeted multimodal ... ...

    Abstract Multimodal-imaging probes offer a novel approach, which can provide detail diagnostic information for the planning of image-guided therapies in clinical practice. Here we report targeted multimodal Nd
    MeSH term(s) Animals ; Carcinoma, Hepatocellular/diagnostic imaging ; Cell Line ; Cell Survival ; Contrast Media/administration & dosage ; Contrast Media/chemistry ; Fluorescent Dyes/administration & dosage ; Fluorescent Dyes/chemistry ; Humans ; Infusions, Intra-Arterial ; Intraoperative Period ; Liver/diagnostic imaging ; Liver Neoplasms/diagnostic imaging ; Magnetic Resonance Imaging/methods ; Male ; Multimodal Imaging/methods ; Nanoparticles/administration & dosage ; Nanoparticles/chemistry ; Neodymium/chemistry ; Optical Imaging/methods ; Particle Size ; Rats, Sprague-Dawley ; Spectrometry, Fluorescence/methods ; Surface Properties ; Tissue Distribution
    Chemical Substances Contrast Media ; Fluorescent Dyes ; Neodymium (2I87U3734A)
    Language English
    Publishing date 2016-09-19
    Publishing country Netherlands
    Document type Journal Article ; Research Support, U.S. Gov't, Non-P.H.S. ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 603079-8
    ISSN 1878-5905 ; 0142-9612
    ISSN (online) 1878-5905
    ISSN 0142-9612
    DOI 10.1016/j.biomaterials.2016.09.013
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Resolution of Electronic and Structural Factors Underlying Oxygen-Evolving Performance in Amorphous Cobalt Oxide Catalysts.

    Kwon, Gihan / Jang, Hoyoung / Lee, Jun-Sik / Mane, Anil / Mandia, David J / Soltau, Sarah R / Utschig, Lisa M / Martinson, Alex B F / Tiede, David M / Kim, Hacksung / Kim, Jungho

    Journal of the American Chemical Society

    2018  Volume 140, Issue 34, Page(s) 10710–10720

    Abstract: Non-noble-metal, thin-film oxides are widely investigated as promising catalysts for oxygen evolution reactions (OER). Amorphous cobalt oxide films electrochemically formed in the presence of borate (CoBi) and phosphate (CoPi) share a common cobaltate ... ...

    Abstract Non-noble-metal, thin-film oxides are widely investigated as promising catalysts for oxygen evolution reactions (OER). Amorphous cobalt oxide films electrochemically formed in the presence of borate (CoBi) and phosphate (CoPi) share a common cobaltate domain building block, but differ significantly in OER performance that derives from different electron-proton charge transport properties. Here, we use a combination of L edge synchrotron X-ray absorption (XAS), resonant X-ray emission (RXES), resonant inelastic X-ray scattering (RIXS), resonant Raman (RR) scattering, and high-energy X-ray pair distribution function (PDF) analyses that identify electronic and structural factors correlated to the charge transport differences for CoPi and CoBi. The analyses show that CoBi is composed primarily of cobalt in octahedral coordination, whereas CoPi contains approximately 17% tetrahedral Co(II), with the remainder in octahedral coordination. Oxygen-mediated 4 p-3 d hybridization through Co-O-Co bonding was detected by RXES and the intersite dd excitation was observed by RIXS in CoBi, but not in CoPi. RR shows that CoBi resembles a disordered layered LiCoO
    Language English
    Publishing date 2018-08-01
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.8b02719
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Nuclearity effects in supported, single-site Fe(ii) hydrogenation pre-catalysts.

    Langeslay, Ryan R / Sohn, Hyuntae / Hu, Bo / Mohar, Jacob S / Ferrandon, Magali / Liu, Cong / Kim, Hacksung / Jeremy Kropf, A / Yang, Ce / Niklas, Jens / Poluektov, Oleg G / Ercan Alp, E / Ignacio-de Leon, Patricia / Sattelberger, Alfred P / Hock, Adam S / Delferro, Massimiliano

    Dalton transactions (Cambridge, England : 2003)

    2018  Volume 47, Issue 32, Page(s) 10842–10846

    Abstract: Dimeric and monomeric supported single-site Fe(ii) pre-catalysts on SiO2 have been prepared via organometallic grafting and characterized with advanced spectroscopic techniques. Manipulation of the surface hydroxyl concentration on the support influences ...

    Abstract Dimeric and monomeric supported single-site Fe(ii) pre-catalysts on SiO2 have been prepared via organometallic grafting and characterized with advanced spectroscopic techniques. Manipulation of the surface hydroxyl concentration on the support influences monomer/dimer formation. While both pre-catalysts are highly active in liquid-phase hydrogenation, the dimeric pre-catalyst is ∼3× faster than the monomer. Preliminary XAS experiments on the H2-activated samples suggest the active species are isolated Fe(ii) sites.
    Language English
    Publishing date 2018-07-25
    Publishing country England
    Document type Journal Article
    ZDB-ID 1472887-4
    ISSN 1477-9234 ; 1364-5447 ; 0300-9246 ; 1477-9226
    ISSN (online) 1477-9234 ; 1364-5447
    ISSN 0300-9246 ; 1477-9226
    DOI 10.1039/c8dt02720j
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Resolution of Electronic and Structural Factors Underlying Oxygen-Evolving Performance in Amorphous Cobalt Oxide Catalysts

    Kwon, Gihan / Hoyoung Jang / Jun-Sik Lee / Anil Mane / David J. Mandia / Sarah R. Soltau / Lisa M. Utschig / Alex B. F. Martinson / David M. Tiede / Hacksung Kim / Jungho Kim

    Journal of the American Chemical Society. 2018 July 20, v. 140, no. 34

    2018  

    Abstract: Non-noble-metal, thin-film oxides are widely investigated as promising catalysts for oxygen evolution reactions (OER). Amorphous cobalt oxide films electrochemically formed in the presence of borate (CoBi) and phosphate (CoPi) share a common cobaltate ... ...

    Abstract Non-noble-metal, thin-film oxides are widely investigated as promising catalysts for oxygen evolution reactions (OER). Amorphous cobalt oxide films electrochemically formed in the presence of borate (CoBi) and phosphate (CoPi) share a common cobaltate domain building block, but differ significantly in OER performance that derives from different electron–proton charge transport properties. Here, we use a combination of L edge synchrotron X-ray absorption (XAS), resonant X-ray emission (RXES), resonant inelastic X-ray scattering (RIXS), resonant Raman (RR) scattering, and high-energy X-ray pair distribution function (PDF) analyses that identify electronic and structural factors correlated to the charge transport differences for CoPi and CoBi. The analyses show that CoBi is composed primarily of cobalt in octahedral coordination, whereas CoPi contains approximately 17% tetrahedral Co(II), with the remainder in octahedral coordination. Oxygen-mediated 4p–3d hybridization through Co–O–Co bonding was detected by RXES and the intersite dd excitation was observed by RIXS in CoBi, but not in CoPi. RR shows that CoBi resembles a disordered layered LiCoO₂-like structure, whereas CoPi is amorphous. Distinct domain models in the nanometer range for CoBi and CoPi have been proposed on the basis of the PDF analysis coupled to XAS data. The observed differences provide information on electronic and structural factors that enhance oxygen evolving catalysis performance.
    Keywords X-radiation ; X-ray absorption spectroscopy ; X-ray scattering ; borates ; catalysts ; catalytic activity ; chemical bonding ; cobalt ; cobalt oxide ; electrochemistry ; models ; oxygen ; oxygen production ; phosphates
    Language English
    Dates of publication 2018-0720
    Size p. 10710-10720.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.8b02719
    Database NAL-Catalogue (AGRICOLA)

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  8. Article: Targeted multimodal nano-reporters for pre-procedural MRI and intra-operative image-guidance

    Lee, Joonseok / Andrew C. Gordon / Hacksung Kim / Wooram Park / Soojeong Cho / Byeongdu Lee / Andrew C. Larson / Elena A. Rozhkova / Dong-Hyun Kim

    Biomaterials. 2016 Dec., v. 109

    2016  

    Abstract: Multimodal-imaging probes offer a novel approach, which can provide detail diagnostic information for the planning of image-guided therapies in clinical practice. Here we report targeted multimodal Nd3+-doped upconversion nanoparticle (UCNP) imaging ... ...

    Abstract Multimodal-imaging probes offer a novel approach, which can provide detail diagnostic information for the planning of image-guided therapies in clinical practice. Here we report targeted multimodal Nd3+-doped upconversion nanoparticle (UCNP) imaging reporters, integrating both magnetic resonance imaging (MRI) and real-time upconversion luminescence imaging (UCL) capabilities within a single platform. Nd3+-doped UCNPs were synthesized as a core–shell structure showing a bright visible emission upon excitation at the near infrared (minimizing biological overheating and increasing tissue penetration depth) as well as providing strong MRI T2 contrast (high r2/r1 ratio). Transcatheter intra-arterial infusion of Nd3+-doped UCNPs conjugated with anti-CD44-monoclonal antibody allowed for high performance in vivo multimodal UCL and MR imaging of hepatocellular carcinoma (HCC) in an orthotopic rat model. The resulted in vivo multimodal imaging of Nd3+ doped core-shell UCNPs combined with transcatheter intra-arterial targeting approaches successfully discriminated liver tumors from normal hepatic tissues in rats for surgical resection applications. The demonstrated multimodal UCL and MRI imaging capabilities of our multimodal UCNPs reporters suggest strong potential for in vivo visualization of tumors and precise surgical guidance to fill the gap between pre-procedural imaging and intraoperative reality.
    Keywords animal models ; antibodies ; hepatoma ; image analysis ; luminescence ; magnetic resonance imaging ; nanoparticles ; planning ; rats ; resection ; tissues
    Language English
    Dates of publication 2016-12
    Size p. 69-77.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 603079-8
    ISSN 0142-9612
    ISSN 0142-9612
    DOI 10.1016/j.biomaterials.2016.09.013
    Database NAL-Catalogue (AGRICOLA)

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  9. Article: Role of Cr3+/Cr6+ redox in chromium-substituted Li2MnO3·LiNi1/2Mn1/2O2 layered composite cathodes: electrochemistry and voltage fade

    Lee, Eungje / Johnson, Christopher S / Kim, Hacksung / Lu, Jun / Park, Joong Sun / Stair, Peter C / Sun, Cheng-Jun / Wu, Tianpin / Zhou, Dehua

    Journal of materials chemistry A. 2015 Apr. 28, v. 3, no. 18

    2015  

    Abstract: The effect of redox-active Cr substitution on the electrochemistry and voltage fade of a lithium-rich “layered–layered” composite cathode material has been investigated. A series of Cr-substituted 0.5Li2MnO3·0.5LiNi1/2Mn1/2O2 powder samples (i.e., Li1 ... ...

    Abstract The effect of redox-active Cr substitution on the electrochemistry and voltage fade of a lithium-rich “layered–layered” composite cathode material has been investigated. A series of Cr-substituted 0.5Li2MnO3·0.5LiNi1/2Mn1/2O2 powder samples (i.e., Li1.2Ni0.2−2/xMn0.6−2/xCrxO2, where x = 0, 0.05, 0.1, and 0.2) was synthesized via the sol–gel method. X-ray diffraction data confirmed the incorporation of Cr ions into the lattice structure. While similar initial charge capacities (∼300 mA h g−1) were obtained for all of the cathode samples, the capacity contribution from the Li2MnO3 activation plateau (at 4.5 V vs. Li) decreased with increasing Cr content. This finding suggests suppressed oxygen loss that triggers cation migration and voltage fade in subsequent cycles. Continued investigation revealed that the Cr substitution mitigates the voltage fade on charge but not discharge. The resulting insignificant effect of Cr substitution on mitigating voltage fade, in spite of decreased Li2MnO3 activation, is attributed to the additional instability caused by Cr6+ migration to a tetrahedral site, as evidenced by ex situ X-ray absorption spectroscopy. Our results provide the framework for a future redox active cation substitution strategy by highlighting the importance of the structural stability of the substituent itself.
    Keywords cathodes ; cations ; chromium ; electric potential difference ; electrochemistry ; oxygen ; sol-gel processing ; X-ray absorption spectroscopy ; X-ray diffraction
    Language English
    Dates of publication 2015-0428
    Size p. 9915-9924.
    Publishing place The Royal Society of Chemistry
    Document type Article
    ZDB-ID 2702232-8
    ISSN 2050-7496 ; 2050-7488
    ISSN (online) 2050-7496
    ISSN 2050-7488
    DOI 10.1039/c5ta01214g
    Database NAL-Catalogue (AGRICOLA)

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  10. Article: Resonance Raman and surface- and tip-enhanced Raman spectroscopy methods to study solid catalysts and heterogeneous catalytic reactions

    Kim, Hacksung / Kosuda, Kathryn M / Van Duyne, Richard P / Stair, Peter C

    Chemical Society reviews. 2010 Nov. 16, v. 39, no. 12

    2010  

    Abstract: Resonance Raman (RR) spectroscopy has several advantages over the normal Raman spectroscopy (RS) widely used for in situ characterization of solid catalysts and catalytic reactions. Compared with RS, RR can provide much higher sensitivity and selectivity ...

    Abstract Resonance Raman (RR) spectroscopy has several advantages over the normal Raman spectroscopy (RS) widely used for in situ characterization of solid catalysts and catalytic reactions. Compared with RS, RR can provide much higher sensitivity and selectivity in detecting catalytically-significant surface metal oxides. RR can potentially give useful information on the nature of excited states relevant to photocatalysis and on the anharmonic potential of the ground state. In this critical review a detailed discussion is presented on several types of RR experimental systems, three distinct sources of so-called Raman (fluorescence) background, detection limits for RR compared to other techniques (EXAFS, PM-IRAS, SFG), and three well-known methods to assign UV-vis absorption bands and a band-specific unified method that is derived mainly from RR results. In addition, the virtues and challenges of surface-enhanced Raman spectroscopy (SERS) are discussed for detecting molecular adsorbates at catalytically relevant interfaces. Tip-enhanced Raman spectroscopy (TERS), which is a combination of SERS and near-field scanning probe microscopy and has the capability of probing molecular adsorbates at specific catalytic sites with an enormous surface sensitivity and nanometre spatial resolution, is also reviewed (300 references).
    Keywords Raman spectroscopy ; X-ray absorption spectroscopy ; active sites ; catalysts ; detection limit ; fluorescence ; oxides ; photocatalysis ; scanning probe microscopy ; ultraviolet-visible spectroscopy
    Language English
    Dates of publication 2010-1116
    Size p. 4820-4844.
    Publishing place The Royal Society of Chemistry
    Document type Article
    ZDB-ID 1472875-8
    ISSN 1460-4744 ; 0306-0012
    ISSN (online) 1460-4744
    ISSN 0306-0012
    DOI 10.1039/c0cs00044b
    Database NAL-Catalogue (AGRICOLA)

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