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  1. Article ; Online: Shaping Copper Oxide Layers on Gold Nanoparticle Ensembles by Controlled Electrodeposition with Single Particle Scatterometry.

    Hwang, Hyunsik / Oh, Hyuncheol / Song, Hyunjoon

    Small (Weinheim an der Bergstrasse, Germany)

    2023  Volume 19, Issue 32, Page(s) e2301241

    Abstract: Electrodeposition of copper on gold nanoelectrode ensembles result in the formation of uniform copper oxide layers on individual nanoparticles. A linear sweep of voltammetric change induces three distinct morphologies dependent upon particle density. Ex ... ...

    Abstract Electrodeposition of copper on gold nanoelectrode ensembles result in the formation of uniform copper oxide layers on individual nanoparticles. A linear sweep of voltammetric change induces three distinct morphologies dependent upon particle density. Ex situ imaging and in situ scatterometry at a single-particle level identifies multi-step electrochemical growth sequences that deviated from classical nucleation and growth pathways. In addition, the study demonstrated the possibility of synthesizing sophisticated structures based on the symmetry of nanoelectrodes. This result guides the nanoscale morphology control of electrode ensembles with potential application in electrocatalysis and sensing.
    Language English
    Publishing date 2023-04-22
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2168935-0
    ISSN 1613-6829 ; 1613-6810
    ISSN (online) 1613-6829
    ISSN 1613-6810
    DOI 10.1002/smll.202301241
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Convergent paired electrolysis for zinc-mediated diastereoselective cinnamylation of α-amino esters.

    Park, Hahyoun / Kim, Minjun / Kang, Jungtaek / Song, Hyunjoon / Kim, Hyunwoo

    Chemical communications (Cambridge, England)

    2023  Volume 59, Issue 36, Page(s) 5447–5450

    Abstract: A paired electrochemical method is presented for the one-pot synthesis of γ,δ-unsaturated α-amino esters. The method involves ... ...

    Abstract A paired electrochemical method is presented for the one-pot synthesis of γ,δ-unsaturated α-amino esters. The method involves the
    Language English
    Publishing date 2023-05-02
    Publishing country England
    Document type Journal Article
    ZDB-ID 1472881-3
    ISSN 1364-548X ; 1359-7345 ; 0009-241X
    ISSN (online) 1364-548X
    ISSN 1359-7345 ; 0009-241X
    DOI 10.1039/d3cc01197f
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Metal hybrid nanoparticles for catalytic organic and photochemical transformations.

    Song, Hyunjoon

    Accounts of chemical research

    2015  Volume 48, Issue 3, Page(s) 491–499

    Abstract: In order to understand heterogeneous catalytic reactions, model catalysts such as a single crystalline surface have been widely studied for many decades. However, catalytic systems that actually advance the reactions are three-dimensional and commonly ... ...

    Abstract In order to understand heterogeneous catalytic reactions, model catalysts such as a single crystalline surface have been widely studied for many decades. However, catalytic systems that actually advance the reactions are three-dimensional and commonly have multiple components including active metal nanoparticles and metal oxide supports. On the other hand, as nanochemistry has rapidly been developed and been applied to various fields, many researchers have begun to discuss the impact of nanochemistry on heterogeneous catalysis. Metal hybrid nanoparticles bearing multiple components are structurally very close to the actual catalysts, and their uniform and controllable morphology is suitable for investigating the relationship between the structure and the catalytic properties in detail. In this Account, we introduce four typical structures of metal hybrid nanoparticles that can be used to conduct catalytic organic and photochemical reactions. Metal@silica (or metal oxide) yolk-shell nanoparticles, in which metal cores exist in internal voids surrounded by thin silica (or metal oxide) shells, exhibited extremely high thermal and chemical stability due to the geometrical protection of the silica layers against the metal cores. The morphology of the metal cores and the pore density of the hollow shells were precisely adjusted to optimize the reaction activity and diffusion rates of the reactants. Metal@metal oxide core-shell nanoparticles and inverted structures, where the cores supported the shells serving an active surface, exhibited high activity with no diffusion barriers for the reactants and products. These nanostructures were used as effective catalysts for various organic and gas-phase reactions, including hydrogen transfer, Suzuki coupling, and steam methane reforming. In contrast to the yolk- and core-shell structures, an asymmetric arrangement of distinct domains generated acentric dumbbells and tipped rods. A large domain of each component added multiple functions, such as magnetism and light absorption, to the catalytic properties. In particular, metal-semiconductor hybrid nanostructures could behave as effective visible photocatalysts for hydrogen evolution and CO oxidation reactions. Resulting from the large surface area and high local concentration of the reactants, a double-shell hollow structure showed reaction activities higher than those of filled nanoparticles. The introduction of plasmonic Au probes into the Pt-CdS double-shell hollow particles facilitated the monitoring of photocatalytic hydrogen generation that occurred on an individual particle surface by single particle measurements. Further development of catalysis research using well-defined metal hybrid nanocatalysts with various in situ spectroscopic tools provides a means of maximizing catalytic performances until they are comparable to or better than those of homogeneous catalysts, and this would have possibly useful implications for industrial applications.
    Language English
    Publishing date 2015-03-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1483291-4
    ISSN 1520-4898 ; 0001-4842
    ISSN (online) 1520-4898
    ISSN 0001-4842
    DOI 10.1021/ar500411s
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Nanoparticle design and assembly for p-type metal oxide gas sensors.

    Choi, Byeonghoon / Shin, Dongwoo / Lee, Hee-Seung / Song, Hyunjoon

    Nanoscale

    2022  Volume 14, Issue 9, Page(s) 3387–3397

    Abstract: Metal oxide semiconductors have wide band gaps with tailorable electrical properties and high stability, suitable for chemiresistive gas sensors. p-Type oxide semiconductors generally have less sensitivity than their n-type counterparts but provide ... ...

    Abstract Metal oxide semiconductors have wide band gaps with tailorable electrical properties and high stability, suitable for chemiresistive gas sensors. p-Type oxide semiconductors generally have less sensitivity than their n-type counterparts but provide unique functionality with low humidity dependence. Among various approaches to enhance the p-type characteristics, nanostructuring of active materials is essential to exhibit high sensing performances comparable to n-type materials. Moreover, p-n heterojunction formation can achieve superior sensitivity at low operating temperatures. The representative examples are hollow and urchin-like particles, mesoporous structures, and nanowire networks. These morphologies can generate abundant active surface sites with a high surface area and induce rapid gas diffusion and facile charge transport. For growing interests in environmental and healthcare monitoring, p-type oxide semiconductors and their heterojunctions with well-designed nanostructures gain much attention as advanced gas sensing materials for practical applications. In addition to precise nanostructure design, the combination with other strategies,
    Language English
    Publishing date 2022-03-07
    Publishing country England
    Document type Journal Article ; Review
    ZDB-ID 2515664-0
    ISSN 2040-3372 ; 2040-3364
    ISSN (online) 2040-3372
    ISSN 2040-3364
    DOI 10.1039/d1nr07561f
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Structural complexity induced by {110} blocking of cysteine in electrochemical copper deposition on silver nanocubes.

    Oh, Hyuncheol / Hwang, Hyunsik / Song, Hyunjoon

    Nanoscale

    2021  Volume 13, Issue 3, Page(s) 1777–1783

    Abstract: Morphology evolution into intricate structures at the nanoscale is hard to understand, but we can get critical information from the combination of ex situ and in situ spectroelectrochemical techniques. In this study, we investigated the structural ... ...

    Abstract Morphology evolution into intricate structures at the nanoscale is hard to understand, but we can get critical information from the combination of ex situ and in situ spectroelectrochemical techniques. In this study, we investigated the structural complexity generated during electrochemical Cu deposition on individual Ag nanocubes, which was driven by surface regulating cysteine molecules. During the deposition process, selective nucleation occurred on the Ag nanocubes by underpotential deposition, and then sequential structural evolution to a windmill morphology was observed. By adjusting the cysteine coverage, diverse structures were yielded, including face-overgrown, four-leaf clover, and octapod-like structures. Structural analysis along the crystallographic directions demonstrated that cysteine molecules exclusively blocked the growth along 110 and relatively promoted the growth along 100 and 111, respectively. Interestingly, all morphologies maintained a highly symmetric nature from the pristine cube, despite being diverse and sophisticated. These findings would be essential to design complex morphologies and achieve desirable optical and catalytic properties.
    Language English
    Publishing date 2021-01-12
    Publishing country England
    Document type Journal Article
    ZDB-ID 2515664-0
    ISSN 2040-3372 ; 2040-3364
    ISSN (online) 2040-3372
    ISSN 2040-3364
    DOI 10.1039/d0nr07470e
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Grain Boundary-Rich Copper Nanocatalysts Generated from Metal-Organic Framework Nanoparticles for CO

    Kim, Sungjoo / Shin, Dongwoo / Park, Jonghyeok / Jung, Jong-Yeong / Song, Hyunjoon

    Advanced science (Weinheim, Baden-Wurttemberg, Germany)

    2023  Volume 10, Issue 9, Page(s) e2207187

    Abstract: Due to severe contemporary energy issues, generating ... ...

    Abstract Due to severe contemporary energy issues, generating C
    Language English
    Publishing date 2023-01-22
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2808093-2
    ISSN 2198-3844 ; 2198-3844
    ISSN (online) 2198-3844
    ISSN 2198-3844
    DOI 10.1002/advs.202207187
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Tracking Underpotential Deposition of Copper on Individual Silver Nanocubes by Real-Time Single-Particle Plasmon Scattering Imaging

    Oh, Hyuncheol / Park, Youngchan / Song, Hyunjoon

    Journal of physical chemistry. 2020 Aug. 25, v. 124, no. 37

    2020  

    Abstract: Spectroelectrochemical analysis using surface plasmon scattering can provide a great deal of information on nucleation and growth mechanisms for nanoscale materials. In this study, we combined a transparent electrochemical thin-layer cell with dark-field ...

    Abstract Spectroelectrochemical analysis using surface plasmon scattering can provide a great deal of information on nucleation and growth mechanisms for nanoscale materials. In this study, we combined a transparent electrochemical thin-layer cell with dark-field spectroscopy to resolve the Cu deposition process on individual Ag nanocubes. During the deposition process, both electrochemical responses and plasmon scattering images were obtained, which were directly correlated with reduction kinetics and morphological evolution, respectively. By applying linear sweep potentials with variable sweep rates, three distinct morphologies, atop tetrapods, dendritic spheres, and multiple cubes, were uniformly generated. The atop tetrapods were formed at the bulk deposition potential, −0.34 V. At lower potential sweep rates, however, the maximum scattering peak wavelength and intensity, converted from the plasmon scattering images, significantly changed in the low potential region of −0.23 to −0.33 V. The plasmon scattering simulation and scanning electron microscopy images at the fixed potentials provided evidence that nucleation occurred on the Ag surface in this potential range. Such an underpotential deposition of Cu on Ag was hardly observed in bulk but was critical to induce the distinct morphology in the nanoscale. Based on these observations, the deposition mechanism was understood in detail: the atop tetrapods were generated by selective bulk deposition, whereas the dendritic spheres and multiple cubes were formed by underpotential nucleation and growth aided by a surfactant. This spectroelectrochemical tool with dark-field spectroscopy provides real-time and in situ analysis under the actual reaction conditions and therefore, would be versatile to analyze various heterogeneous reaction systems.
    Keywords electrochemistry ; physical chemistry ; spectroscopy ; surfactants ; wavelengths
    Language English
    Dates of publication 2020-0825
    Size p. 20398-20409.
    Publishing place American Chemical Society
    Document type Article
    Note NAL-AP-2-clean
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.0c05258
    Database NAL-Catalogue (AGRICOLA)

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  8. Article: Pt cocatalyst morphology on semiconductor nanorod photocatalysts enhances charge trapping and water reduction.

    Park, Bumjin / Park, Won-Woo / Choi, Ji Yong / Choi, Woong / Sung, Young Mo / Sul, Soohwan / Kwon, Oh-Hoon / Song, Hyunjoon

    Chemical science

    2023  Volume 14, Issue 27, Page(s) 7553–7558

    Abstract: In photocatalysis, metal-semiconductor hybrid structures have been proposed for ideal photocatalytic systems. In this study, we investigate the effect of morphology and surface nature of Pt cocatalysts on photocatalytic hydrogen evolution activity in Pt- ... ...

    Abstract In photocatalysis, metal-semiconductor hybrid structures have been proposed for ideal photocatalytic systems. In this study, we investigate the effect of morphology and surface nature of Pt cocatalysts on photocatalytic hydrogen evolution activity in Pt-tipped CdSe nanorods. Three distinct morphologies of Pt cocatalysts were synthesized and employed as visible light photocatalysts. The rough tips exhibit the highest activity, followed by the round and cubic tips. Kinetic investigations using transient absorption spectroscopy reveal that the cubic tips exhibit lower charge-separated states feasible for reacting with water and water reduction rates due to their defectless surface facets. In contrast, the rough tips show a similar charge-separation value but a two-fold higher surface reaction rate than the round tips, resulting in a significant enhancement of hydrogen evolution. These findings highlight the importance of rational design on metal cocatalysts in addition to the main semiconductor bodies for maximizing photocatalytic activities.
    Language English
    Publishing date 2023-06-23
    Publishing country England
    Document type Journal Article
    ZDB-ID 2559110-1
    ISSN 2041-6539 ; 2041-6520
    ISSN (online) 2041-6539
    ISSN 2041-6520
    DOI 10.1039/d3sc01429k
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: Bimetallic Gold–Silver Nanostructures Drive Low Overpotentials for Electrochemical Carbon Dioxide Reduction

    Park, Joon Woo / Choi, Woong / Noh, Juhwan / Park, Woonghyeon / Gu, Geun Ho / Park, Jonghyeok / Jung, Yousung / Song, Hyunjoon

    ACS applied materials & interfaces. 2022 Jan. 25, v. 14, no. 5

    2022  

    Abstract: Alloy formation is an advanced approach to improve desired properties that the monoelements cannot achieve. Alloys are usually designed to tailor intrinsic natures or induce synergistic effects by combining materials with distinct properties. Indeed, ... ...

    Abstract Alloy formation is an advanced approach to improve desired properties that the monoelements cannot achieve. Alloys are usually designed to tailor intrinsic natures or induce synergistic effects by combining materials with distinct properties. Indeed, unprecedented properties have emerged in many cases, superior to a simple sum of pure elements. Here, we present Au–Ag alloy nanostructures with prominent catalytic properties in an electrochemical carbon dioxide reduction reaction (eCO₂RR). The Au–Ag hollow nanocubes are prepared by galvanic replacement of Au on Ag nanocubes. When the Au-to-Ag ratio is 1:1 (Au₁Ag₁), the alloy hollow nanocubes exhibit maximum Faradaic efficiencies of CO production in a wide potential range and high mass activity and CO current density superior to those of the bare metals. In particular, overpotentials are estimated to be similar to or lower than that of the Au catalyst under various standard metrics. Density functional theory calculations, machine learning, and a statistical consideration demonstrate that the optimal configuration of the *COOH intermediate is a bidentate coordination structure where C binds to Au and O binds to Ag. This active Au–Ag neighboring configuration has a maximum population and enhanced intrinsic catalytic activity on the Au₁Ag₁ surface among other Au-to-Ag compositions, in good agreement with the experimental results. Further application of Au₁Ag₁ to a membrane electrode assembly cell at neutral conditions shows enhanced CO Faradaic efficiency and current densities compared to Au or Ag nanocubes, indicating the possible extension of Au–Ag alloys to larger electrochemical systems. These results give a new insight into the synergistic roles of Au and Ag in the eCO₂RR and offer a fresh direction toward a rational design of bimetallic catalysts at a practical scale.
    Keywords alloys ; carbon dioxide ; catalysts ; catalytic activity ; density functional theory ; electrochemistry ; electrodes
    Language English
    Dates of publication 2022-0125
    Size p. 6604-6614.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1944-8252
    DOI 10.1021/acsami.1c20852
    Database NAL-Catalogue (AGRICOLA)

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  10. Article: Abnormal Hypsochromic Shifts of Surface Plasmon Scattering by Atomic Ordering in Gold–Copper Intermetallic Nanoparticles

    Oh, Hyuncheol / Kim, Minjun / Park, Youngchan / Ryu, Seol / Song, Hyunjoon

    Journal of physical chemistry. 2021 Sept. 01, v. 125, no. 36

    2021  

    Abstract: Alloy nanoparticles are of importance to tailor their physical and chemical characteristics, which can overcome the limits of monometallic materials. In particular, the plasmonic properties of metal alloys are primarily tuned by varying their alloy ... ...

    Abstract Alloy nanoparticles are of importance to tailor their physical and chemical characteristics, which can overcome the limits of monometallic materials. In particular, the plasmonic properties of metal alloys are primarily tuned by varying their alloy composition and electronic structure. The alloys tend to be described as a linear combination of the constituent elements, and their plasmonic characteristics are also expected to follow Vegard’s rule. In this study, we demonstrated the importance of atomic ordering in Au–Cu alloy nanoparticles, which exhibited a rather opposite trend of photophysical properties against such rough estimation for random alloys. The intermetallic Au₃Cu, AuCu, and AuCu₃ nanoparticles with a diameter of 20 nm were synthesized using a modified co-reduction method under identical aqueous environments. The alloys were characterized by X-ray spectroscopic techniques precisely, confirming their compositions and atomic arrangements in crystals. Notably, plasmon light scattering on intermetallic nanoparticles collected by single-particle dark-field spectroscopy exhibited unexpected abnormal hypsochromic shifts with the Cu content increase, in contrast to linear bathochromic shifts of random alloys. Density functional theory calculations considered the combined effect of both intraband and interband transitions in the intermetallic compounds and successfully confirmed the hypsochromic shifts of the plasmon bands by atomic ordering in the Au–Cu alloys. Our findings suggest that atomic engineering in alloy nanoparticles, by modulating their intrinsic complex permittivities, provide a new way for regulating plasmonic optical properties and developing various alloy systems with desired photophysical properties.
    Keywords X-radiation ; alloy nanoparticles ; alloys ; density functional theory ; physical chemistry ; spectroscopy
    Language English
    Dates of publication 2021-0901
    Size p. 19936-19946.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.1c06555
    Database NAL-Catalogue (AGRICOLA)

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