Publications by authors named "Pil J Yoo"

Transition metal dichalcogenides (TMDs) have received considerable attention as promising electrocatalysts for the hydrogen evolution reaction (HER), yet their potential is often constrained by the inertness of the basal planes arising from their poor hydrogen adsorption ability. Here, the relationship between the electronic structure of the WS basal plane and HER activity is systemically analyzed to establish a clear insight. The valance state of the sulfur atoms on the basal plane has been tuned to enhance hydrogen adsorption through sequential engineering processes, including direct phase transition and heterostructure that induces work function-difference-induced unidirectional electron transfer.

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With the escalating global demand for electric vehicles and sustainable energy solutions, increasing focus is placed on developing electrochemical systems that offer fast charging and high-power output, primarily governed by mass transport. Accordingly, porous carbons have emerged as highly promising electrochemically active or supporting materials due to expansive surface areas, tunable pore structures, and superior electrical conductivity, accelerating surface reaction. Yet, while substantial research has been devoted to crafting various porous carbons to increase specific surface areas, the optimal utilization of the surfaces remains underexplored.

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Despite the rapid advances in process analytical technology, the assessment of protein refolding efficiency has largely relied on off-line protein-specific assays and/or chromatographic procedures such as reversed-phase high-performance liquid chromatography and size exclusion chromatography. Due to the inherent time gap pertaining to traditional methods, exploring optimum refolding conditions for many recombinant proteins, often expressed as insoluble inclusion bodies, has proven challenging. The present study describes a novel protein refolding sensor that utilizes liquid crystals (LCs) to discriminate varying protein structures during unfolding and refolding.

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The binder is an essential component in determining the structural integrity and ionic conductivity of Li-ion battery electrodes. However, conventional binders are not sufficiently conductive and durable to be used with solid-state electrolytes. In this study, a novel system is proposed for a Li secondary battery that combines the electrolyte and binder into a unified structure, which is achieved by employing para-phenylenediamine (pPD) moiety to create supramolecular bridges between the parent binders.

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The ability to control the shape of hollow particles (, capsules or bubbles) holds great promise for enhancing the encapsulation efficiency and mechanical/optical properties. However, conventional preparation methods suffer from a low yield, difficulty in controlling the shape, and a tedious production process, limiting their widespread application. Here, we present a method for fabricating polyhedral graphene oxide (GO)-shelled microbubbles with sharp edges and vertices, which is based on the microfluidic generation of spherical compound bubbles followed by shell deformation.

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Nanophotonics relies on precise control of refractive index (RI) which can be designed with metamaterials. Plasmonic superstructures of nanoparticles (NPs) can suggest a versatile way of tuning RI. However, the plasmonic effects in the superstructures demand 1 nm-level exquisite control over the interparticle gap, which is challenging in a sub-wavelength NPs.

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Article Synopsis
  • This study explores the use of tungsten disulfide (WS) as an electrocatalyst for hydrogen evolution, enhancing its performance by introducing a nanodomain tungsten oxide (WO) interface.
  • The creation of a 1T-WS/a-WO heterointerface improves proton transfer to active sites, leading to more efficient hydrogen production due to a hydrophilic nature.
  • Results show that the optimized material (WSO-1.2) significantly enhances hydrogen evolution reaction activity with an overpotential of just 212 mV, demonstrating an effective strategy for water splitting through superior proton transport mechanics.
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Recent advances in using biological scaffolds for nanoparticle synthesis have proven to be useful for preparing various nanostructures with uniform shape and size. Proteins are significant scaffolds for generating various nanostructures partly because of the presence of many functional groups to recognize different chemistries. In this endeavor, cocosin protein, an 11S allergen, is prepared from coconut fruit and employed as a potential scaffold for synthesizing MnO materials.

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Article Synopsis
  • Researchers developed aqueous dispersions of conjugated polymer nanowires (CPNWs) that show improved light absorption for use in water-based applications.
  • They created films using a donor-acceptor conjugated polymer and a liquid crystal, then transformed these films into CPNWs with a high aspect ratio by ultrasonication at basic pH.
  • The CPNWs exhibited a significant red shift in absorption maximum and demonstrated organized molecular structures, which could enhance their performance in energy conversion processes like photocatalysis.
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MXenes have received much attention as promising candidates for noble metal-free hydrogen evolution reaction (HER) electrocatalysts due to their high electrical conductivity, surface hydrophilicity, abundant surface functional groups, and great potential for rational hybridization with other materials. Herein, a novel porous monolayered-TiCT@NiCoP (P-TiCT@NiCoP) nanostructure was synthesized with uniform distribution of bimetallic compounds for improved charge transfer capability and electrocatalytic activity. In experiments, HO-utilized oxidation formed a highly mesoporous structure with a maximized surface area of monolayered MXenes as the support.

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Opal-structured thin-film hydrogel materials with micropatterns hold great potential for utility in a wide range of sensing applications. Micropatterning offers key advantages such as ready addressability, high throughput assay, and multiplexing. However, controlled fabrication of such films in a rapid, inexpensive, and reliable manner remains a challenge.

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Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted considerable attention owing to their synergetic effects with other 2D materials, such as graphene and hexagonal boron nitride, in TMD-based heterostructures. Therefore, it is important to understand the physical properties of TMD-TMD vertical heterostructures for their applications in next-generation electronic devices. However, the conventional synthesis process of TMD-TMD heterostructures has some critical limitations, such as nonreproducibility and low yield.

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Carbon nanotubes (CNTs) have attracted considerable attention because of their high electrical conductivity and outstanding mechanical properties. As such, there have been numerous attempts to form CNTs into diverse structures for use in a wide range of applications. However, the intrinsic high aspect ratios of CNTs and resulting deformability have prevented the fabrication of sophisticated CNT-based structures, especially for three-dimensional (3D) cellular architectures.

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Although self-assembled nanoparticles (SNPs) have been used extensively for targeted drug delivery, their clinical applications have been limited since most of the drugs are released into the blood before they reach their target site. In this study, metal-phenolic network (MPN)-coated SNPs (MPN-SNPs), which consist of an amphiphilic hyaluronic acid derivative, were prepared to be a pH-responsive nanocarrier to facilitate drug release in tumor microenvironments (TME). Due to their amphiphilic nature, SNPs were capable of encapsulating doxorubicin (DOX), chosen as the model anticancer drug.

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Transition metal oxide (TMO)-based anode materials for Li-ion batteries (LIBs) have generally suffered from limitations of intrinsically severe pulverization upon lithiation and reduced electrical conductivity. To address these issues, an approach of generating hollow nanostructures of TMOs complexed with highly conductive species has been attempted. As a novel means to implement highly electrochemically active TMO-based hollow nanostructures, a pre-synthesized template of a metal organic framework, zeolitic imidazolate framework (ZIF-8), was sequentially treated with partial carbonization and oxidation processes, whereby a hollow, nanocage-like structure of ZnO was obtained while preserving the carbonaceous frame as the electroconductive matrix.

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Large volumetric expansion and structural pulverization have been major problems in Si-based anode materials for Li-ion batteries. To overcome this limitation, yolk-shell structured Si-carbon structures have been proposed to allow for the reversible structural breathing of Si nanoparticles confined inside the carbon shell. However, initial coulombic efficiency (ICE) of the yolk-shell structured anodes is highly decreased mainly due to their extremely high specific surface area (SSA) and the resulting excessive formation of solid electrolyte interphase (SEI) over the carbon shell.

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Smart textiles based on conjugated polymers have been highlighted as promising fabrics that can intelligently respond to environmental stimuli based on the electrical properties of polymer semiconductors. However, there has been limited interest in the photothermal properties of conjugated polymers that can be applied to smart textiles. We prepared nanoparticles by assembling a conjugated polymer with a fatty acid via an emulsion process and nanocomposite fibers by distributing the conjugated polymer nanoparticles in a polyacrylonitrile matrix.

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When multiple intermolecular interactions occur simultaneously, complexed molecules undergo gelation by inter-cohesive bonding, inducing a pseudo-crosslinking effect to form a supramolecular gel. Among the number of substances that can induce supramolecular assembly, phenolic species such as 3,4-dihydroxy-l-phenylalanine (DOPA) are widely utilized for synthesizing adhesive materials. However, despite the strong adhesion capability of monomeric phenol, it lacks cohesive strength and rarely forms a supramolecular gel to secure its mechanical properties.

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Objective: Quantitative ventilation monitoring and respiratory event detection are needed for the diagnosis of sleep apnea and hypoventilation. We developed a portable device with a chest belt, nasal cannula and finger sensor to continuously acquire multi-channel signals including tidal volume, nasal pressure, respiratory effort, body position, snoring sound, ECG and SpO. The unique feature of the device is the continuous tidal volume signal obtained from real-time lung ventilation images produced by the electrical impedance tomography (EIT) technique.

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The design and synthesis of cellular structured materials are of both scientific and technological importance since they can impart remarkably improved material properties such as low density, high mechanical strength, and adjustable surface functionality compared to their bulk counterparts. Although reducing the density of porous structures would generally result in reductions in mechanical properties, this challenge can be addressed by introducing a structural hierarchy and using mechanically reinforced constituent materials. Thus, precise control over several design factors in structuring, including the type of constituent, symmetry of architectures, and dimension of the unit cells, is extremely important for maximizing the targeted performance.

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Pt, a representative electrocatalyst for the oxygen reduction reaction (ORR), has suffered from high cost and poor stability, and thus it is essential to develop alternative electrocatalyst with a high catalytic activity comparable to Pt. Herein, we propose a rationally designed metal-free electrocatalyst with exposed active sites using an N, P, and S ternary-doped and graphene-incorporated porous carbon foam. We developed a novel template-free synthetic approach wherein the electrostatically-mediated complexation of graphene oxide (GO) with 2-aminothiazole (2AT) and branched polyethylenimine (PEI) in the presence of phytic acid (PA) was first induced, followed by a carbonization process to drive the formation of a three-dimensionally interconnected porous carbon foam.

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Advanced materials with low density and high strength impose transformative impacts in the construction, aerospace, and automobile industries. These materials can be realized by assembling well-designed modular building units (BUs) into interconnected structures. This study uses a hierarchical design strategy to demonstrate a new class of carbon-based, ultralight, strong, and even superelastic closed-cellular network structures.

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With the advent of the era of consumer-oriented displays and mobile devices, the importance of barrier film coatings for securing devices from oxygen or moisture penetration has become more salient. Recently developed approaches to generate gas barrier films in a combination of polyelectrolyte multilayer matrices and incorporated inorganic nanosheets have shown great potential in outperforming conventional gas barrier films. However, these films have the intrinsic drawback of vulnerability to brittleness and inability to stretch for flexible device applications.

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Exploring new single, active photocatalysts for solar-water splitting is highly desirable to expedite current research on solar-chemical energy conversion. In particular, Z-scheme-based composites (ZBCs) have attracted extensive attention due to their unique charge transfer pathway, broader redox range, and stronger redox power compared to conventional heterostructures. In the present report, we have for the first time explored CuP, a new, single photocatalyst for solar-water splitting applications.

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Wrinkling is a well-known example of instability-driven surface deformation that occurs when the accumulated compressive stress exceeds the critical value in multilayered systems. A number of studies have investigated the instability conditions and the corresponding mechanisms of wrinkling deformation. Force balance analysis of bilayer systems, in which the thickness of the capping layer is importantly considered, has offered a useful approach for the quantitative understanding of wrinkling.

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