Publications by authors named "Taeghwan Hyeon"

280 Publications

Adaptive Self-Organization of Nanomaterials Enables Strain-Insensitive Resistance of Stretchable Metallic Nanocomposites.

Adv Mater 2022 Apr 6:e2200980. Epub 2022 Apr 6.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.

Highly conductive and stretchable nanocomposites are promising material candidates for skin electronics. However, the resistance of stretchable metallic nanocomposites highly depends on external strains, often deteriorating the performance of fabricated electronic devices. Here, a material strategy for the highly conductive and stretchable nanocomposites comprising metal nanomaterials of various dimensions and a viscoelastic block-copolymer matrix is presented. The resistance of the nanocomposites can be well retained under skin deformations (<50% strain). It is demonstrated that silver nanomaterials can self-organize inside the viscoelastic media in response to external strain when their surface is conjugated with 1-decanethiol. Distinct self-organization behaviors associated with nanomaterial dimensions and strain conditions are found. Adopting the optimum composition of 0D/1D/2D silver nanomaterials can render the resistance of the nanocomposites insensitive to uniaxial or biaxial strains. As a result, the resistance can be maintained with a variance of < 1% during 1000 stretching cycles under uniaxial and biaxial strains of <50% while a high conductivity of ≈31 000 S cm is achieved.
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http://dx.doi.org/10.1002/adma.202200980DOI Listing
April 2022

Facet-Defined Strain-Free Spinel Oxide for Oxygen Reduction.

Nano Lett 2022 May 31;22(9):3636-3644. Epub 2022 Mar 31.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Exposing facet and surface strain are critical factors affecting catalytic performance but unraveling the composition-dependent activity on specific facets under strain-controlled environment is still challenging due to the synthetic difficulties. Herein, we achieved a (001) facet-defined Co-Mn spinel oxide surface with different surface compositions using epitaxial growth on CoO nanocube template. We adopted composition gradient synthesis to relieve the strain layer by layer, minimizing the surface strain effect on catalytic activity. In this system, experimental and calculational analyses of model oxygen reduction reaction (ORR) activity reveals a volcano-like trend with Mn/Co ratios because of an adequate charge transfer from octahedral-Mn to neighboring Co. CoMn as an optimized Mn/Co ratio exhibits both outstanding ORR activity (0.894 V vs RHE in 1 M KOH) and stability (2% activity loss against chronoamperometry). By controlling facet and strain, this study provides a well-defined platform for investigating composition-structure-activity relationships in electrocatalytic processes.
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http://dx.doi.org/10.1021/acs.nanolett.2c00238DOI Listing
May 2022

Metastable hexagonal close-packed palladium hydride in liquid cell TEM.

Nature 2022 03 23;603(7902):631-636. Epub 2022 Mar 23.

Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea.

Metastable phases-kinetically favoured structures-are ubiquitous in nature. Rather than forming thermodynamically stable ground-state structures, crystals grown from high-energy precursors often initially adopt metastable structures depending on the initial conditions, such as temperature, pressure or crystal size. As the crystals grow further, they typically undergo a series of transformations from metastable phases to lower-energy and ultimately energetically stable phases. Metastable phases sometimes exhibit superior physicochemical properties and, hence, the discovery and synthesis of new metastable phases are promising avenues for innovations in materials science. However, the search for metastable materials has mainly been heuristic, performed on the basis of experiences, intuition or even speculative predictions, namely 'rules of thumb'. This limitation necessitates the advent of a new paradigm to discover new metastable phases based on rational design. Such a design rule is embodied in the discovery of a metastable hexagonal close-packed (hcp) palladium hydride (PdH) synthesized in a liquid cell transmission electron microscope. The metastable hcp structure is stabilized through a unique interplay between the precursor concentrations in the solution: a sufficient supply of hydrogen (H) favours the hcp structure on the subnanometre scale, and an insufficient supply of Pd inhibits further growth and subsequent transition towards the thermodynamically stable face-centred cubic structure. These findings provide thermodynamic insights into metastability engineering strategies that can be deployed to discover new metastable phases.
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http://dx.doi.org/10.1038/s41586-021-04391-5DOI Listing
March 2022

Manipulating Nanoparticle Aggregates Regulates Receptor-Ligand Binding in Macrophages.

J Am Chem Soc 2022 Apr 11;144(13):5769-5783. Epub 2022 Mar 11.

Department of Materials Science and Engineering, Korea University, Seoul 02841, Republic of Korea.

The receptor-ligand interactions in cells are dynamically regulated by modulation of the ligand accessibility. In this study, we utilize size-tunable magnetic nanoparticle aggregates ordered at both nanometer and atomic scales. We flexibly anchor magnetic nanoparticle aggregates of tunable sizes over the cell-adhesive RGD ligand (Arg-Gly-Asp)-active material surface while maintaining the density of dispersed ligands accessible to macrophages at constant. Lowering the accessible ligand dispersity by increasing the aggregate size at constant accessible ligand density facilitates the binding of integrin receptors to the accessible ligands, which promotes the adhesion of macrophages. In high ligand dispersity, distant magnetic manipulation to lift the aggregates (which increases ligand accessibility) stimulates the binding of integrin receptors to the accessible ligands available under the aggregates to augment macrophage adhesion-mediated pro-healing polarization both in vitro and in vivo. In low ligand dispersity, distant control to drop the aggregates (which decreases ligand accessibility) repels integrin receptors away from the aggregates, thereby suppressing integrin receptor-ligand binding and macrophage adhesion, which promotes inflammatory polarization. Here, we present "accessible ligand dispersity" as a novel fundamental parameter that regulates receptor-ligand binding, which can be reversibly manipulated by increasing and decreasing the ligand accessibility. Limitless tuning of nanoparticle aggregate dimensions and morphology can offer further insight into the regulation of receptor-ligand binding in host cells.
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http://dx.doi.org/10.1021/jacs.1c08861DOI Listing
April 2022

Effect of polystyrene nanoplastics and their degraded forms on stem cell fate.

J Hazard Mater 2022 05 2;430:128411. Epub 2022 Feb 2.

School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea. Electronic address:

Several studies have examined the effects of micro- and nanoplastics on microbes, cells, and the environment. However, only a few studies have examined their effects-especially, those of their reduced cohesiveness-on cell viability and physiology. We synthesized surfactant-free amine-functionalized polystyrene (PS) nanoparticles (NPs) and PS-NPs with decreased crosslinking density (DPS-NPs) without changing other factors, such as size, shape, and zeta potential and examined their effects on cell viability and physiology. PS- and DPS-NPs exhibited reactive oxygen species (ROS) scavenging activity by upregulating GPX3 expression and downregulating HSP70 (ROS-related gene) and XBP1 (endoplasmic reticulum stress-related gene) expression in human bone marrow-derived mesenchymal stem cells (hBM-MSCs). Additionally, they led to upregulation of MFN2 (mitochondrial fusion related gene) expression and downregulation of FIS1 (mitochondrial fission related gene) expression, indicating enhanced mitochondrial fusion in hBM-MSCs. Cell-cycle analysis revealed that PS- and DPS-NPs increased the proportion of cells in the S phase, indicating that they promoted cell proliferation and, specifically, the adipogenic differentiation of hBM-MSCs. However, the cytotoxicity of DPS-NPs against hBM-MSCs was higher than that of PS-NPs after long-term treatment under adipogenic conditions.
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http://dx.doi.org/10.1016/j.jhazmat.2022.128411DOI Listing
May 2022

In Situ Liquid Phase TEM of Nanoparticle Formation and Diffusion in a Phase-Separated Medium.

ACS Appl Mater Interfaces 2022 Feb 7. Epub 2022 Feb 7.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Colloidal nanoparticles are synthesized in a complex reaction mixture that has an inhomogeneous chemical environment induced by local phase separation of the medium. Nanoparticle syntheses based on micelles, emulsions, flow of different fluids, injection of ionic precursors in organic solvents, and mixing the metal organic phase of precursors with an aqueous phase of reducing agents are well established. However, the formation mechanism of nanoparticles in the phase-separated medium is not well understood because of the complexity originating from the presence of phase boundaries as well as nonuniform chemical species, concentrations, and viscosity in different phases. Herein, we investigate the formation mechanism and diffusion of silver nanoparticles in a phase-separated medium by using liquid phase transmission electron microscopy and many-body dissipative particle dynamics simulations. A quantitative analysis of the individual growth trajectories reveals that a large portion of silver nanoparticles nucleate and grow rapidly at the phase boundaries, where metal ion precursors and reducing agents from the two separated phases react to form monomers. The results suggest that the motion of the silver nanoparticles at the interfaces is highly affected by the interaction with polymers and exhibits superdiffusive dynamics because of the polymer relaxation.
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http://dx.doi.org/10.1021/acsami.1c20824DOI Listing
February 2022

Enhanced Chemodynamic Therapy by Cu-Fe Peroxide Nanoparticles: Tumor Microenvironment-Mediated Synergistic Fenton Reaction.

ACS Nano 2022 02 26;16(2):2535-2545. Epub 2022 Jan 26.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

An urgent need in chemodynamic therapy (CDT) is to achieve high Fenton catalytic efficiency at small doses of CDT agents. However, simple general promotion of the Fenton reaction increases the risk of damaging normal cells along with the cancer cells. Therefore, a tailored strategy to selectively enhance the Fenton reactivity in tumors, for example, by taking advantage of the characteristics of the tumor microenvironment (TME), is in high demand. Herein, a heterogeneous CDT system based on copper-iron peroxide nanoparticles (CFp NPs) is designed for TME-mediated synergistic therapy. CFp NPs degrade under the mildly acidic conditions of TME, self-supply HO, and the released Cu and Fe ions, with their larger portions at lower oxidation states, cooperatively facilitate hydroxyl radical production through a highly efficient catalytic loop to achieve an excellent tumor therapeutic efficacy. This is distinct from previous heterogeneous CDT systems in that the synergism is closely coupled with the Cu-assisted conversion of Fe to Fe rather than their independent actions. As a result, almost complete ablation of tumors at a minimal treatment dose is demonstrated without the aid of any other therapeutic modality. Furthermore, CFp NPs generate O during the catalysis and exhibit a TME-responsive T magnetic resonance imaging contrast enhancement, which are useful for alleviating hypoxia and monitoring of tumors, respectively.
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http://dx.doi.org/10.1021/acsnano.1c09171DOI Listing
February 2022

Multifunctional Injectable Hydrogel for Diagnostic and Therapeutic Applications.

ACS Nano 2022 Jan 11. Epub 2022 Jan 11.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Injectable hydrogels show high potential for biomedical applications owing to their distinctive mode of administration into the human body. In this study, we propose a material design strategy for developing a multifunctional injectable hydrogel with good adhesiveness, stretchability, and bioresorbability. Its multifunctionality, whereupon multiple reactions occur simultaneously during its injection into the body without requiring energy stimuli and/or additives, was realized through meticulous engineering of bioresorbable precursors based on hydrogel chemistry. The multifunctional injectable hydrogel can be administered through a minimally invasive procedure, form a conformal adhesive interface with the target tissue, dynamically stretch along with the organ motions with minimal mechanical constraints, and be resorbed after a specific period. Further, the incorporation of functional nanomaterials into the hydrogel allows for various diagnostic and therapeutic applications, without compromising the original multifunctionality of the hydrogel. These features are verified through theranostic case studies on representative organs, including the skin, liver, heart, and bladder.
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http://dx.doi.org/10.1021/acsnano.1c07649DOI Listing
January 2022

Soft Bioelectronics Based on Nanomaterials.

Chem Rev 2022 03 28;122(5):5068-5143. Epub 2021 Dec 28.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Recent advances in nanostructured materials and unconventional device designs have transformed the bioelectronics from a rigid and bulky form into a soft and ultrathin form and brought enormous advantages to the bioelectronics. For example, mechanical deformability of the soft bioelectronics and thus its conformal contact onto soft curved organs such as brain, heart, and skin have allowed researchers to measure high-quality biosignals, deliver real-time feedback treatments, and lower long-term side-effects . Here, we review various materials, fabrication methods, and device strategies for flexible and stretchable electronics, especially focusing on soft biointegrated electronics using nanomaterials and their composites. First, we summarize top-down material processing and bottom-up synthesis methods of various nanomaterials. Next, we discuss state-of-the-art technologies for intrinsically stretchable nanocomposites composed of nanostructured materials incorporated in elastomers or hydrogels. We also briefly discuss unconventional device design strategies for soft bioelectronics. Then individual device components for soft bioelectronics, such as biosensing, data storage, display, therapeutic stimulation, and power supply devices, are introduced. Afterward, representative application examples of the soft bioelectronics are described. A brief summary with a discussion on remaining challenges concludes the review.
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http://dx.doi.org/10.1021/acs.chemrev.1c00531DOI Listing
March 2022

Highly Efficient Photoelectrochemical Hydrogen Production Using Nontoxic CuInSe Quantum Dots with ZnS/SiO Double Overlayers.

ACS Appl Mater Interfaces 2022 Jan 27;14(1):603-610. Epub 2021 Dec 27.

School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.

Quantum dots (QDs) are a promising material for photoelectrochemical (PEC) hydrogen (H) production because of their attractive optical properties including high optical absorption coefficient, band-gap tunability, and potential multiple exciton generation. To date, QDs containing toxic elements such as Cd or Pb have been mainly investigated for PEC H production, which cannot be utilized in practice because of the environmental issue. Here, we demonstrate a highly efficient type II heterojunction photoanode of nontoxic CuInSe (CISe) QDs and a mesoporous TiO film. In addition, ZnS/SiO double overlayers are deposited on the photoanodes to passivate surface defect sites on the CISe QDs, leading to the enhancement of both photocurrent density and photostability. Due to a combination of a wide light absorption range of the CISe QDs and the reduced interfacial charge recombination by the overlayers, a remarkable photocurrent density of 8.5 mA cm (at 0.5 V) is obtained under 1 sun illumination, which is a record for the PEC sulfite oxidation based on nontoxic QD photoanodes.
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http://dx.doi.org/10.1021/acsami.1c16976DOI Listing
January 2022

Real-space imaging of nanoparticle transport and interaction dynamics by graphene liquid cell TEM.

Sci Adv 2021 Dec 3;7(49):eabi5419. Epub 2021 Dec 3.

School of Chemical and Biological Engineering, and Institute of Chemical Process, Seoul National University, Seoul 08826, Republic of Korea.

Thermal motion of colloidal nanoparticles and their cohesive interactions are of fundamental importance in nanoscience but are difficult to access quantitatively, primarily due to the lack of the appropriate analytical tools to investigate the dynamics of individual particles at nanoscales. Here, we directly monitor the stochastic thermal motion and coalescence dynamics of gold nanoparticles smaller than 5 nm, using graphene liquid cell (GLC) transmission electron microscopy (TEM). We also present a novel model of nanoparticle dynamics, providing a unified, quantitative explanation of our experimental observations. The nanoparticles in a GLC exhibit non-Gaussian, diffusive motion, signifying dynamic fluctuation of the diffusion coefficient due to the dynamically heterogeneous environment surrounding nanoparticles, including organic ligands on the nanoparticle surface. Our study shows that the dynamics of nanoparticle coalescence is controlled by two elementary processes: diffusion-limited encounter complex formation and the subsequent coalescence of the encounter complex through rotational motion, where surface-passivating ligands play a critical role.
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http://dx.doi.org/10.1126/sciadv.abi5419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8641935PMC
December 2021

Recent Advances and Prospects in Colloidal Nanomaterials.

JACS Au 2021 Nov 23;1(11):1849-1859. Epub 2021 Sep 23.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Colloidal nanomaterials of metals, metal oxides, and metal chalcogenides have attracted great attention in the past decade owing to their potential applications in optoelectronics, catalysis, and energy conversion. Introduction of various synthetic routes has resulted in diverse colloidal nanostructured materials with well-controlled size, shape, and composition, enabling the systematic study of their intriguing physicochemical, optoelectronic, and chemical properties. Furthermore, developments in the instrumentation have offered valuable insights into the nucleation and growth mechanism of these nanomaterials, which are crucial in designing prospective materials with desired properties. In this perspective, recent advances in the colloidal synthesis and mechanism studies of nanomaterials of metal chalcogenides, metals, and metal oxides are discussed. In addition, challenges in the characterization and future direction of the colloidal nanomaterials are provided.
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http://dx.doi.org/10.1021/jacsau.1c00339DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8611664PMC
November 2021

Structural Insights into Multi-Metal Spinel Oxide Nanoparticles for Boosting Oxygen Reduction Electrocatalysis.

Adv Mater 2022 Feb 11;34(8):e2107868. Epub 2022 Jan 11.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.

Multi-metal oxide (MMO) materials have significant potential to facilitate various demanding reactions by providing additional degrees of freedom in catalyst design. However, a fundamental understanding of the (electro)catalytic activity of MMOs is limited because of the intrinsic complexity of their multi-element nature. Additional complexities arise when MMO catalysts have crystalline structures with two different metal site occupancies, such as the spinel structure, which makes it more challenging to investigate the origin of the (electro)catalytic activity of MMOs. Here, uniform-sized multi-metal spinel oxide nanoparticles composed of Mn, Co, and Fe as model MMO electrocatalysts are synthesized and the contributions of each element to the structural flexibility of the spinel oxides are systematically studied, which boosts the electrocatalytic oxygen reduction reaction (ORR) activity. Detailed crystal and electronic structure characterizations combined with electrochemical and computational studies reveal that the incorporation of Co not only increases the preferential octahedral site occupancy, but also modifies the electronic state of the ORR-active Mn site to enhance the intrinsic ORR activity. As a result, nanoparticles of the optimized catalyst, Co Mn Fe -MMO, exhibit a half-wave potential of 0.904 V (versus RHE) and mass activity of 46.9 A g (at 0.9 V versus RHE) with promising stability.
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http://dx.doi.org/10.1002/adma.202107868DOI Listing
February 2022

Noble Metal-Based Multimetallic Nanoparticles for Electrocatalytic Applications.

Adv Sci (Weinh) 2022 01 17;9(1):e2104054. Epub 2021 Nov 17.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.

Noble metal-based multimetallic nanoparticles (NMMNs) have attracted great attention for their multifunctional and synergistic effects, which offer numerous catalytic applications. Combined experimental and theoretical studies have enabled formulation of various design principles for tuning the electrocatalytic performance through controlling size, composition, morphology, and crystal structure of the nanoparticles. Despite significant advancements in the field, the chemical synthesis of NMMNs with ideal characteristics for catalysis, including high activity, stability, product-selectivity, and scalability is still challenging. This review provides an overview on structure-based classification and the general synthesis of NMMN electrocatalysts. Furthermore, postsynthetic treatments, such as the removal of surfactants to optimize the activity, and utilization of NMMNs onto suitable support for practical electrocatalytic applications are highlighted. In the end, future direction and challenges associated with the electrocatalysis of NMMNs are covered.
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http://dx.doi.org/10.1002/advs.202104054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8728832PMC
January 2022

In Vivo Sol-Gel Reaction of Tantalum Alkoxide for Endovascular Embolization.

Adv Healthc Mater 2022 02 23;11(4):e2101908. Epub 2021 Nov 23.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.

Liquid embolic agents are considered the most promising for various embolization procedures because they enable deep penetration. For realizing effective procedures, the delivery of liquid embolic agents should be guided under X-ray imaging systems and the solidification time should be optimized for the specific indication. The biocompatibility of embolic agents is also crucial because they remain in the vessel after embolization. In this study, new biocompatible embolic agents based on tantalum ethoxide is synthesized. Tantalum alkoxide liquid embolics (TALE) possess the radiopacity for fluoroscopy and can control the penetration depth by modifying the sol-gel kinetics. Furthermore, TALE can serve as drug carriers for synergistic treatment. Using these excellent characteristics, it is demonstrated that TALE agents can be used in various situations including the transarterial chemoembolization of hepatocellular carcinoma and embolotherapy of massive bleeding from the femoral artery.
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http://dx.doi.org/10.1002/adhm.202101908DOI Listing
February 2022

Slow oxidation of magnetite nanoparticles elucidates the limits of the Verwey transition.

Nat Commun 2021 Nov 4;12(1):6356. Epub 2021 Nov 4.

Center for Quantum Materials, Seoul National University, Seoul, 08826, Republic of Korea.

Magnetite (FeO) is of fundamental importance for the Verwey transition near T = 125 K, below which a complex lattice distortion and electron orders occur. The Verwey transition is suppressed by chemical doping effects giving rise to well-documented first and second-order regimes, but the origin of the order change is unclear. Here, we show that slow oxidation of monodisperse FeO nanoparticles leads to an intriguing variation of the Verwey transition: an initial drop of T to a minimum at 70 K after 75 days and a followed recovery to 95 K after 160 days. A physical model based on both doping and doping-gradient effects accounts quantitatively for this evolution between inhomogeneous to homogeneous doping regimes. This work demonstrates that slow oxidation of nanoparticles can give exquisite control and separation of homogeneous and inhomogeneous doping effects on the Verwey transition and offers opportunities for similar insights into complex electronic and magnetic phase transitions in other materials.
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http://dx.doi.org/10.1038/s41467-021-26566-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8568917PMC
November 2021

Wafer-Scale Production of Transition Metal Dichalcogenides and Alloy Monolayers by Nanocrystal Conversion for Large-Scale Ultrathin Flexible Electronics.

Nano Lett 2021 Nov 22;21(21):9153-9163. Epub 2021 Oct 22.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Two-dimensional (2D) transition metal dichalcogenide (TMD) layers are unit-cell thick materials with tunable physical properties according to their size, morphology, and chemical composition. Their transition of lab-scale research to industrial-scale applications requires process development for the wafer-scale growth and scalable device fabrication. Herein, we report on a new type of atmospheric pressure chemical vapor deposition (APCVD) process that utilizes colloidal nanoparticles as process-scalable precursors for the wafer-scale production of TMD monolayers. Facile uniform distribution of nanoparticle precursors on the entire substrate leads to the wafer-scale uniform synthesis of TMD monolayers with the controlled size and morphology. Composition-controlled TMD alloy monolayers with tunable bandgaps can be produced by simply mixing dual nanoparticle precursor solutions in the desired ratio. We also demonstrate the fabrication of ultrathin field-effect transistors and flexible electronics with uniformly controlled performance by using TMD monolayers.
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http://dx.doi.org/10.1021/acs.nanolett.1c02991DOI Listing
November 2021

Dynamic Ligand Screening by Magnetic Nanoassembly Modulates Stem Cell Differentiation.

Adv Mater 2022 Jan 14;34(2):e2105460. Epub 2021 Nov 14.

Department of Materials Science and Engineering, Korea University, Seoul, 02841, Republic of Korea.

In native microenvironment, diverse physical barriers exist to dynamically modulate stem cell recruitment and differentiation for tissue repair. In this study, nanoassembly-based magnetic screens of various sizes are utilized, and they are elastically tethered over an RGD ligand (cell-adhesive motif)-presenting material surface to generate various nanogaps between the screens and the RGDs without modulating the RGD density. Large screens exhibiting low RGD distribution stimulate integrin clustering to facilitate focal adhesion, mechanotransduction, and differentiation of stem cells, which are not observed with small screens. Magnetic downward pulling of the large screens decreases the nanogaps, which dynamically suppress the focal adhesion, mechanotransduction, and differentiation of stem cells. Conversely, magnetic upward pulling of the small screens increases the nanogaps, which dynamically activates focal adhesion, mechanotransduction, and differentiation of stem cells. This regulation mechanism is also shown to be effective in the microenvironment in vivo. Further diversifying the geometries of the physical screens can further enable diverse modalities of multifaceted and safe unscreening of the distributed RGDs to unravel and modulate stem cell differentiation for tissue repair.
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http://dx.doi.org/10.1002/adma.202105460DOI Listing
January 2022

Oxygen-Vacancy-Driven Orbital Reconstruction at the Surface of TiO Core-Shell Nanostructures.

Nano Lett 2021 Oct 29;21(19):7953-7959. Epub 2021 Sep 29.

Pohang Accelerator Laboratory, Pohang 37673, Republic of Korea.

Oxygen vacancies and their correlation with the electronic structure are crucial to understanding the functionality of TiO nanocrystals in material design applications. Here, we report spectroscopic investigations of the electronic structure of anatase TiO nanocrystals by employing hard and soft X-ray absorption spectroscopy measurements along with the corresponding model calculations. We show that the oxygen vacancies significantly transform the Ti local symmetry by modulating the covalency of titanium-oxygen bonds. Our results suggest that the altered Ti local symmetry is similar to the , which implies that the Ti exists in two local symmetries ( and ) at the surface. The findings also indicate that the Ti distortion is a short-range order effect and presumably confined up to the second nearest neighbors. Such distortions modulate the electronic structure and provide a promising approach to structural design of the TiO nanocrystals.
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http://dx.doi.org/10.1021/acs.nanolett.1c01995DOI Listing
October 2021

Nanocomplex-Mediated In Vivo Programming to Chimeric Antigen Receptor-M1 Macrophages for Cancer Therapy.

Adv Mater 2021 Oct 12;33(43):e2103258. Epub 2021 Sep 12.

Interdisciplinary Program for Bioengineering, Seoul National University, Seoul, 08826, Republic of Korea.

Chimeric antigen receptor-T (CAR-T) cell immunotherapy has shown impressive clinical outcomes for hematologic malignancies. However, its broader applications are challenged due to its complex ex vivo cell-manufacturing procedures and low therapeutic efficacy against solid tumors. The limited therapeutic effects are partially due to limited CAR-T cell infiltration to solid tumors and inactivation of CAR-T cells by the immunosuppressive tumor microenvironment. Here, a facile approach is presented to in vivo program macrophages, which can intrinsically penetrate solid tumors, into CAR-M1 macrophages displaying enhanced cancer-directed phagocytosis and anti-tumor activity. In vivo injected nanocomplexes of macrophage-targeting nanocarriers and CAR-interferon-γ-encoding plasmid DNA induce CAR-M1 macrophages that are capable of CAR-mediated cancer phagocytosis, anti-tumor immunomodulation, and inhibition of solid tumor growth. Together, this study describes an off-the-shelf CAR-macrophage therapy that is effective for solid tumors and avoids the complex and costly processes of ex vivo CAR-cell manufacturing.
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http://dx.doi.org/10.1002/adma.202103258DOI Listing
October 2021

Highly conductive and elastic nanomembrane for skin electronics.

Science 2021 08;373(6558):1022-1026

School of Mechanical Engineering, Pusan National University, Busan 46241, Republic of Korea.

Skin electronics require stretchable conductors that satisfy metallike conductivity, high stretchability, ultrathin thickness, and facile patternability, but achieving these characteristics simultaneously is challenging. We present a float assembly method to fabricate a nanomembrane that meets all these requirements. The method enables a compact assembly of nanomaterials at the water-oil interface and their partial embedment in an ultrathin elastomer membrane, which can distribute the applied strain in the elastomer membrane and thus lead to a high elasticity even with the high loading of the nanomaterials. Furthermore, the structure allows cold welding and bilayer stacking, resulting in high conductivity. These properties are preserved even after high-resolution patterning by using photolithography. A multifunctional epidermal sensor array can be fabricated with the patterned nanomembranes.
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http://dx.doi.org/10.1126/science.abh4357DOI Listing
August 2021

Recent Development of Flexible and Stretchable Supercapacitors Using Transition Metal Compounds as Electrode Materials.

Small 2021 09 29;17(36):e2101974. Epub 2021 Jul 29.

Program in Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, 145 Gwanggyo-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, 16229, Republic of Korea.

Flexible and stretchable supercapacitors (FS-SCs) are promising energy storage devices for wearable electronics due to their versatile flexibility/stretchability, long cycle life, high power density, and safety. Transition metal compounds (TMCs) can deliver a high capacitance and energy density when applied as pseudocapacitive or battery-like electrode materials owing to their large theoretical capacitance and faradaic charge-storage mechanism. The recent development of TMCs (metal oxides/hydroxides, phosphides, sulfides, nitrides, and selenides) as electrode materials for FS-SCs are discussed here. First, fundamental energy-storage mechanisms of distinct TMCs, various flexible and stretchable substrates, and electrolytes for FS-SCs are presented. Then, the electrochemical performance and features of TMC-based electrodes for FS-SCs are categorically analyzed. The gravimetric, areal, and volumetric energy density of SC using TMC electrodes are summarized in Ragone plots. More importantly, several recent design strategies for achieving high-performance TMC-based electrodes are highlighted, including material composition, current collector design, nanostructure design, doping/intercalation, defect engineering, phase control, valence tuning, and surface coating. Integrated systems that combine wearable electronics with FS-SCs are introduced. Finally, a summary and outlook on TMCs as electrodes for FS-SCs are provided.
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http://dx.doi.org/10.1002/smll.202101974DOI Listing
September 2021

[PtCu(PET)Cl]: An Atomically Precise, 10-Electron PtCu Bimetal Nanocluster with a Direct Pt-Pt Bond.

J Am Chem Soc 2021 Aug 27;143(31):12100-12107. Epub 2021 Jul 27.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Heteroatom-doped metal nanoclusters (NCs) are highly desirable to gain fundamental insights into the effect of doping on the electronic structure and catalytic properties. Unfortunately, their controlled synthesis is highly challenging when the metal atomic sizes are largely different (e.g., Cu and Pt). Here, we design a metal-exchange strategy that enables simultaneous doping and resizing of NCs. Specifically, [PtCu(PET)Cl] NC, the first example of a Pt-doped Cu NC, is synthesized by utilizing the unique reactivity of [Cu(PET)ClH] NC with Pt ions. The single-crystal X-ray structure reveals that two directly bonded Pt atoms occupy the two centers of an unusually interpenetrating, incomplete biicosahedron core (PtCu), which is stabilized by a Cu(PET)Cl shell. The molecular structure and composition of the NC are validated by combined experimental and theoretical results. Electronic structure calculations, using the density functional theory, show that the PtCu NC is a 10-electron superatom. The computed absorption spectrum matches well with the measured data and allows for assignment of the absorption peaks. The calculations also rationalize energetics for ligand exchange observed in the mass spectrometry data. The synergistic effects induced by Pt doping are found to enhance the catalytic activity of Cu NCs by ∼300-fold in silane to silanol conversion under mild conditions. Furthermore, our synthetic strategy has potential to produce Ni-, Pd-, and Au-doped Cu NCs, which will open new avenues to uncover their molecular structures and catalytic properties.
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http://dx.doi.org/10.1021/jacs.1c04002DOI Listing
August 2021

High photoluminescence from self-assembled AgCl(dppe) clusters through metallophilic interactions.

J Chem Phys 2021 Jul;155(1):014307

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, South Korea.

Ligand protected metal nanoclusters (NCs) are an emerging class of functional materials with intriguing photophysical and chemical properties. The size and molecular structure play an important role in endowing NCs with characteristic optical and electronic properties. Modulation of these properties through the chemical reactivity of NCs is largely unexplored. Here, we report on the synthesis of self-assembled AgCl(dppe) clusters through the ligand-exchange-induced transformation of [PtAgCl(PPh)] NCs [(dppe): 1,2-bis(diphenylphosphino)ethane; (PPh): triphenylphosphine]. The single crystal x-ray structure reveals that two Ag atoms are bridged by one dppe and two Cl ligands, forming a AgCl(dppe) cluster, which is subsequently self-assembled through dppe ligands to form [AgCl(dppe)]. Importantly, the AgCl(dppe) cluster assembly exhibits high photoluminescence quantum yield: ∼18%, which is attributed to the metallophilic interactions and rigidification of the ligand shell. We hope that this work will motivate the exploitation of the chemical reactivity of NCs as a new path to attain cluster assemblies endowed with enhanced photophysical properties.
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http://dx.doi.org/10.1063/5.0057356DOI Listing
July 2021

Tissue-like skin-device interface for wearable bioelectronics by using ultrasoft, mass-permeable, and low-impedance hydrogels.

Sci Adv 2021 05 7;7(19). Epub 2021 May 7.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Hydrogels consist of a cross-linked porous polymer network and water molecules occupying the interspace between the polymer chains. Therefore, hydrogels are soft and moisturized, with mechanical structures and physical properties similar to those of human tissue. Such hydrogels have a potential to turn the microscale gap between wearable devices and human skin into a tissue-like space. Here, we present material and device strategies to form a tissue-like, quasi-solid interface between wearable bioelectronics and human skin. The key material is an ultrathin type of functionalized hydrogel that shows unusual features of high mass-permeability and low impedance. The functionalized hydrogel acted as a liquid electrolyte on the skin and formed an extremely conformal and low-impedance interface for wearable electrochemical biosensors and electrical stimulators. Furthermore, its porous structure and ultrathin thickness facilitated the efficient transport of target molecules through the interface. Therefore, this functionalized hydrogel can maximize the performance of various wearable bioelectronics.
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http://dx.doi.org/10.1126/sciadv.abd3716DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8104866PMC
May 2021

Localized Delivery of Theranostic Nanoparticles and High-Energy Photons using Microneedles-on-Bioelectronics.

Adv Mater 2021 Jun 6;33(24):e2100425. Epub 2021 May 6.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.

The low delivery efficiency of light-responsive theranostic nanoparticles (NPs) to target tumor sites, particularly to brain tumors due to the blood-brain barrier, has been a critical issue in NP-based cancer treatments. Furthermore, high-energy photons that can effectively activate theranostic NPs are hardly delivered to the target region due to the strong scattering of such photons while penetrating surrounding tissues. Here, a localized delivery method of theranostic NPs and high-energy photons to the target tumor using microneedles-on-bioelectronics is presented. Two types of microneedles and flexible bioelectronics are integrated and mounted on the edge of surgical forceps. Bioresorbable microneedles containing theranostic NPs deliver the NPs into target tumors (e.g., glioblastoma, pituitary adenoma). Magnetic resonance imaging can locate the NPs. Then, light-guiding/spreading microneedles deliver high-energy photons from bioelectronics to the NPs. The high-energy photons activate the NPs to treat tumor tissues by photodynamic therapy and chemotherapy. The controlled thermal actuation by the bioelectronics accelerates the diffusion of chemo-drugs. The proposed method is demonstrated with mouse tumor models in vivo.
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http://dx.doi.org/10.1002/adma.202100425DOI Listing
June 2021

Durable and Fatigue-Resistant Soft Peripheral Neuroprosthetics for In Vivo Bidirectional Signaling.

Adv Mater 2021 May 19;33(20):e2007346. Epub 2021 Mar 19.

Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea.

Soft neuroprosthetics that monitor signals from sensory neurons and deliver motor information can potentially replace damaged nerves. However, achieving long-term stability of devices interfacing peripheral nerves is challenging, since dynamic mechanical deformations in peripheral nerves cause material degradation in devices. Here, a durable and fatigue-resistant soft neuroprosthetic device is reported for bidirectional signaling on peripheral nerves. The neuroprosthetic device is made of a nanocomposite of gold nanoshell (AuNS)-coated silver (Ag) flakes dispersed in a tough, stretchable, and self-healing polymer (SHP). The dynamic self-healing property of the nanocomposite allows the percolation network of AuNS-coated flakes to rebuild after degradation. Therefore, its degraded electrical and mechanical performance by repetitive, irregular, and intense deformations at the device-nerve interface can be spontaneously self-recovered. When the device is implanted on a rat sciatic nerve, stable bidirectional signaling is obtained for over 5 weeks. Neural signals collected from a live walking rat using these neuroprosthetics are analyzed by a deep neural network to predict the joint position precisely. This result demonstrates that durable soft neuroprosthetics can facilitate collection and analysis of large-sized in vivo data for solving challenges in neurological disorders.
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http://dx.doi.org/10.1002/adma.202007346DOI Listing
May 2021

Designing Atomically Dispersed Au on Tensile-Strained Pd for Efficient CO Electroreduction to Formate.

J Am Chem Soc 2021 Apr 16;143(14):5386-5395. Epub 2021 Mar 16.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Pd is one of the most effective catalysts for the electrochemical reduction of CO to formate, a valuable liquid product, at low overpotential. However, the intrinsically high CO affinity of Pd makes the surface vulnerable to CO poisoning, resulting in rapid catalyst deactivation during CO electroreduction. Herein, we utilize the interaction between metals and metal-organic frameworks to synthesize atomically dispersed Au on tensile-strained Pd nanoparticles showing significantly improved formate production activity, selectivity, and stability with high CO tolerance. We found that the tensile strain stabilizes all reaction intermediates on the Pd surface, whereas the atomically dispersed Au selectively destabilizes CO* without affecting other adsorbates. As a result, the conventional COOH* versus CO* scaling relation is broken, and our catalyst exhibits 26- and 31-fold enhancement in partial current density and mass activity toward electrocatalytic formate production with over 99% faradaic efficiency, compared to Pd/C at -0.25 V versus RHE.
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http://dx.doi.org/10.1021/jacs.0c12696DOI Listing
April 2021

Self-supported mesoscopic tin oxide nanofilms for electrocatalytic reduction of carbon dioxide to formate.

Chem Commun (Camb) 2021 Apr 1;57(28):3445-3448. Epub 2021 Mar 1.

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.

Here we report a self-supported SnO nanofilm prepared by a robust electrochemical process as an electrocatalyst for the CO reduction reaction. The SnO film had a large surface area originating from its nano-architecture and manifested high selectivity toward formate (over 60%), which resulted in CO-to-formate current density up to 33.66 mA cm that is among the state-of-the-art. We unveiled that the high performance of the SnO nanofilm is attributable to the presence of a metastable oxide under reductive conditions in addition to the abovementioned advantages.
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http://dx.doi.org/10.1039/d1cc00927cDOI Listing
April 2021
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