DGIST 전자도서관

Elemental-Doped Catalysts for Photoelectrochemical CO2 Conversion to Solar Fuels

ACCEPTSolar RRL

Solar-driven photoelectrochemical (PEC) carbon dioxide (CO2) conversion to valuable chemicals, combining the advantages of photocatalysis and electrocatalysis, represents a promising approach toward establishing a carbon-neutral society and harnessing solar energy. Photoelectrode materials doped with metals and/or nonmetals have shown promise in achieving high CO2 reduction efficiency. Metal or nonmetal doping entails introducing a heteroelement into the semiconductor, thereby modifying the band potentials of the semiconductor through the addition of a defective state. This alteration may improve the charge transfer kinetics of the catalysis. Furthermore, doping aids in creating active CO2 adsorption offers anchoring sites for CO2 molecules and can promote product selectivity. This review aims to provide a concise summary of elemental-doped photoelectrodes for converting CO2 into fuels through PEC processes. Several key factors affecting the performance of PEC CO2 reduction are discussed, including the interaction of reactants with catalysts, reaction conditions, and the impact of the photoelectrode. Moreover, various PEC CO2 reduction systems are discussed, with a specific focus on enhancing the efficiency of CO2 reduction. Finally, a summary of key considering aspects for further development of the PEC CO2 reduction is provided. © 2024 Wiley-VCH GmbH.

A Conflict-Aware Channel Assignment in Multi-Radio Multi-Channel Wireless Mesh Networks

2024.0IEEE Access, v.12, pp.14751 - 14763

This paper proposes a theoretical model-driven channel assignment scheme designed to enhance network performance in multi-radio multi-channel wireless mesh networks. Unlike previous conflict graph-based channel assignments that addressed co-channel interference and hidden terminal problems while overlooking an exposed terminal problem, our proposed approach integrates these problems comprehensively to mitigate network performance degradation. Given a communication graph, we establish a conflict graph based on hop distance for practical implementation. The weighted conflict graph is constructed by analyzing packet collision conditions under the IEEE 802.11 standard with the CSMA/CA protocol, considering not only the transmission range and interference range but also the carrier sensing range simultaneously. Given a weighted conflict graph and available channel lists on each router, we devise a Weighted Soft List Coloring problem to address the channel assignment challenge. We prove the NP-hardness of this problem by establishing its dual problem, Max list-Cut. We present an approximation algorithm with worst-case performance at most twice the optimal solution while preserving network topology. We substantiate the performance of the proposed channel assignment algorithm through simulations in various topologies. The proposed algorithm, on average, demonstrates a network throughput increase of 162% and 174% compared to the greedy heuristic algorithm with 3 channels and 12 channels, respectively. © 2013 IEEE.

Ultrastrong and ductile steel welds achieved by fine interlocking microstructures with film-like retained austenite

2024-02Nature Communications, v.15, no.1

The degradation of mechanical properties caused by grain coarsening or the formation of brittle phases during welding reduces the longevity of products. Here, we report advances in the weld quality of ultra-high strength steels by utilizing Nb and Cr instead of Ni. Sole addition of Cr, as an alternative to Ni, has limitations in developing fine weld microstructure, while it is revealed that the coupling effects of Nb and Cr additions make a finer interlocking weld microstructures with a higher fraction of retained austenite due to the decrease in austenite to acicular ferrite and bainite transformation temperature and carbon activity. As a result, an alloying design with Nb and Cr creates ultrastrong and ductile steel welds with enhanced tensile properties, impact toughness, and fatigue strength, at 45% lower material costs and lower environmental impact by removing Ni. © The Author(s) 2024. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Progress and Perspectives on Lithium Metal Powder for Rechargeable Batteries

ACCEPTSmall Structures

The increasing demand for batteries with high-energy densities for applications such as electric vehicles necessitates a paradigm shift from the use of conventional graphite as anodes. Li metal is spotlighted as a replacement for graphite due to its ultrahigh theoretical capacity (3860 mAh g−1). However, Li metal foil is plagued with limited cycle life and safety concerns due to poor Coulombic efficiency and uncontrollable growth of Li dendrites. To overcome these challenges, utilizing Li metal in powder form instead of the conventional foil proves to be advantageous. The anode consisting of spherical-shaped Li metal powders (LMPs) has a larger surface area than Li metal foil, resulting in a lower effective current density. Furthermore, using the powder-based slurry process facilitates the fabrication of large-area and thin-film (≤20 μm) Li anodes. In this review, the various fabrication methods and surface stabilization techniques of LMPs are summarized with their associated patents. Also, research trends with regard to LMP-based anodes toward high-performance Li metal batteries (LMBs) are carefully presented. Additionally, the application of LMPs as prelithiation agents in electrode active materials for batteries and capacitors is outlined. Finally, perspectives are suggested regarding the future of LMPs to accelerate the commercialization of advanced LMBs. © 2024 The Authors. Small Structures published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Ferroelectric 2D SnS2 Analog Synaptic FET

ACCEPTAdvanced Science

In this study, the development and characterization of 2D ferroelectric field-effect transistor (2D FeFET) devices are presented, utilizing nanoscale ferroelectric HfZrO2 (HZO) and 2D semiconductors. The fabricated device demonstrated multi-level data storage capabilities. It successfully emulated essential biological characteristics, including excitatory/inhibitory postsynaptic currents (EPSC/IPSC), Pair-Pulse Facilitation (PPF), and Spike-Timing Dependent Plasticity (STDP). Extensive endurance tests ensured robust stability (107 switching cycles, 105 s (extrapolated to 10 years)), excellent linearity, and high Gmax/Gmin ratio (>105), all of which are essential for realizing multi-level data states (>7-bit operation). Beyond mimicking synaptic functionalities, the device achieved a pattern recognition accuracy of ≈94% on the Modified National Institute of Standards and Technology (MNIST) handwritten dataset when incorporated into a neural network, demonstrating its potential as an effective component in neuromorphic systems. The successful implementation of the 2D FeFET device paves the way for the development of high-efficiency, ultralow-power neuromorphic hardware which is in sub-femtojoule (48 aJ/spike) and fast response (1 µs), which is 104 folds faster than human synapse (≈10ms). The results of the research underline the potential of nanoscale ferroelectric and 2D materials in building the next generation of artificial intelligence technologies. © 2024 The Authors. Advanced Science published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Influence of Solvents on Catalytic C-H Bond Oxidation by a Copper(II)-Alkylperoxo Complex

2024-02ACS Catalysis, v.14, no.5, pp.3524 - 3532

Oxidation of unactivated alkanes, which requires substantial energy for conversion to valuable organic chemicals, is a major challenge in both industry and academia. Herein, we describe how solvents affect and improve the catalytic oxidation ability of a mononuclear copper(II)-alkylperoxo complex, [CuII(iPr3-tren)(OOC(CH3)2Ph)]+ (1, iPr3-tren = tris[2-(isopropylamino)ethyl]amine), toward hydrocarbon substrates. 1 was prepared by adding cumene hydroperoxide and triethylamine to the solution of [Cu(iPr3-tren)(CH3CN)]2+, which was characterized using various physicochemical methods. Product analyses, along with theoretical calculations, indicate that homolytic O-O bond cleavage occurs during the thermal decomposition of 1 at 60 °C in various solvents such as CH3CN, CH3COCH3, C6H5CF3, and C6H6. Both experimental results and density functional theory (DFT) calculations supported variations in the catalytic activity of 1 depending on solvents. In CH3CN and CH3COCH3, 1 activates weak C-H bonds (bond dissociation energy (BDE) ≤ ∼81.6 kcal mol-1), while 1 in C6H5CF3 and C6H6 can oxidize slightly stronger C-H bonds with a BDE of up to 84.5 kcal mol-1. In supercritical carbon dioxide (SC-CO2), 1 can oxidize alkanes with strong C-H bonds, such as cyclohexane (99.5 kcal mol-1). The enhanced C-H bond oxidation of 1 in C6H5CF3, C6H6, and SC-CO2 was generally attributed to two different factors: (a) the nonpolarity of the solvent and (b) the absence of C(sp3)-H bonds in the solvent. Interestingly, in CH2Cl2, a nonpolar solvent with C(sp3)-H bonds, 1 exhibited similar reactivity to that in C6H5CF3, indicating that nonpolar solvents enhance the catalytic ability of copper(II)-cumylperoxo complex to abstract hydrogen atoms from substrates, regardless of the presence of C(sp3)-H bonds in solvent molecules. DFT calculations employing an implicit solvent model further supported the enhanced reactivity, without the need to account for the presence of a C(sp3)-H bond. The reactivity of the different possible reactive intermediates arising from the catalytic oxidation was also explored using DFT calculations. This study provides a perspective on how solvents can be utilized to modulate the catalytic effects on C-H bond activation. © 2024 American Chemical Society

Synergistic Integration of Nanogenerators and Solar Cells: Advanced Hybrid Structures and Applications

2024-02Advanced Energy Materials

The rapid growth of global energy consumption and the increasing demand for sustainable and renewable energy sources have urged vast research into harnessing energy from various sources. Among them, the most promising approaches are nanogenerators (NGs) and solar cells (SCs), which independently offer innovative solutions for energy harvesting. This review paper presents a comprehensive analysis of the integration of NGs and SCs, exploring advanced hybrid structures and their diverse applications. First, an overview of the principles and working mechanisms of NGs and SCs is provided for seamless hybrid integrations. Then, various design strategies are discussed, such as piezoelectric and triboelectric NGs with different types of SCs. Finally, a wide range of applications are explored that benefit from the synergistic integration of NGs and SCs, including self-powered electronics, wearable devices, environmental monitoring, and wireless sensor networks. The potential for these hybrid systems is highlighted to address real-world energy needs and contribute to developing sustainable and self-sufficient technologies. In conclusion, this review provides valuable insights into the state-of-the-art developments in NGs and SCs integration, shedding light on advanced hybrid structures and their diverse applications. © 2024 Wiley-VCH GmbH.

Attention guided multi-scale cluster refinement with extended field of view for amodal nuclei segmentation

2024-03Computers in Biology and Medicine, v.170

Nuclei segmentation plays a crucial role in disease understanding and diagnosis. In whole slide images, cell nuclei often appear overlapping and densely packed with ambiguous boundaries due to the underlying 3D structure of histopathology samples. Instance segmentation via deep neural networks with object clustering is able to detect individual segments in crowded nuclei but suffers from a limited field of view, and does not support amodal segmentation. In this work, we introduce a dense feature pyramid network with a feature mixing module to increase the field of view of the segmentation model while keeping pixel-level details. We also improve the model output quality by adding a multi-scale self-attention guided refinement module that sequentially adjusts predictions as resolution increases. Finally, we enable clusters to share pixels by separating the instance clustering objective function from other pixel-related tasks, and introduce supervision to occluded areas to guide the learning process. For evaluation of amodal nuclear segmentation, we also update prior metrics used in common modal segmentation to allow the evaluation of overlapping masks and mitigate over-penalization issues via a novel unique matching algorithm. Our experiments demonstrate consistent performance across multiple datasets with significantly improved segmentation quality. © 2024 Elsevier Ltd

Regenerating native surface of lithium-metal electrodes via hydrohalic acid-assisted pre-halogenation

2024-03Chemical Engineering Journal, v.483

Building a uniform and homogeneous solid-electrolyte interphase (SEI) at the initial stage is critical for achieving a long, stable cycling performance in lithium (Li) metal batteries (LMBs). Typically, the majority of Li metal anodes (LMAs) are pre-passivated by inherently heterogeneous native oxide layers, which adversely induce spatially irregular Li+ ion fluxes and sporadic Li dendrite growth, thereby resulting in uncontrollable SEI evolution and poor cycling stability. Although halogenated SEI can offer superior mechanical strength, insulation, and thermodynamic stability, the most suitable Li halides for the halogenation of the LMA surface remain in ongoing debates. This study presents the pre-halogenation of an LMA surface via a simple chemical reaction using hydrohalic acids (HXs, X = F, Cl, Br, and I) dissolved in aprotic solutions. With different halide anions (X−), LiX compounds can be selectively enriched and homogenized on the entire LMA surface. Among the pre-halogenated LMAs (HX-Li), it is experimentally revealed that LiCl-enriched pre-passivation (HCl-Li) can enhance Li electroplating kinetics, facilitating uniform Li nucleation and leading to dendrite-less compact Li plating. HCl-Li effectively mitigates the volume expansion of the reacted Li/SEI layer, leading to longer cycling of the LMBs. © 2024 Elsevier B.V.

High-detectivity silver telluride nanoparticle-based near-infrared photodetectors functionalized with surface-plasmonic gold nanoparticles

2024-05Applied Surface Science, v.654

Herein, the performance of near-infrared (NIR) photodetectors fabricated through a combination of AgxTe films comprising colloidal AgxTe nanoparticles (NPs) with plasmonic Au NPs was investigated. The surface-plasmonic Au NPs on low-bandgap AgxTe considerably enhanced the detectivity of NIR photodetectors. The Au NPs formed on the AgxTe surface triggered localized surface-plasmon resonance and increased light absorption, hot-carrier injection, and silver telluride crystallinity during an additional annealing process, which was required to form Au NPs from thermally deposited thin Au layers. Under illumination using an 808-nm laser, the detectivity of the as-fabricated Au NP–decorated AgxTe photodetectors was 7.17 × 1011 cmHz1/2 W−1. Compared with that of pristine AgxTe photodetectors, the detectivity of the prepared photodetectors was seven-fold higher; this detectivity was superior to those of devices based on MoS2, arsenic phosphorus, and SnTe nanoplates and commercial photosensors at room temperature. Thus, the proposed strategy of combining AgxTe films with surface-plasmonic Au NPs for enhanced performance of NIR photodetectors provides a new approach for realizing next-generation optoelectronic devices for detection in the NIR region. © 2024

Full-dry flipping transfer method for van der waals heterostructure

2024-03Current Applied Physics, v.59, pp.165 - 168

We present a novel flipping transfer method for van der Waals heterostructures, offering a significant advancement over previous techniques by eliminating the need for polymers and solvents. Here, we utilize commercially available gel film and control its stickiness through oxygen plasma and UV-Ozone treatment, also effectively removing residues from the gel film surface. The cleanliness of the surface is verified through atomic force microscopy. We investigate the quality of our fabricated devices using magnetotransport measurements on graphene/hBN and graphene/α-RuCl3 heterostructures. Remarkably, graphene/hBN devices produced with the flipping method display quality similar to that of fully encapsulated devices. This is evidenced by the presence of a symmetry-broken state at 1 T. Additionally, features of the Hofstadter butterfly were also observed in the second devices. In the case of graphene/α-RuCl3, we observe quantum oscillations with a beating mode and two-channel conduction, consistent with fully encapsulated devices. © 2023 Korean Physical Society

Revolutionizing Cancer Treatment: The Promising Horizon of Zein Nanosystems

ACCEPTACS Biomaterials Science and Engineering

Various nanomaterials have recently become fascinating tools in cancer diagnostic applications because of their multifunctional and inherent molecular characteristics that support efficient diagnosis and image-guided therapy. Zein nanoparticles are a protein derived from maize. It belongs to the class of prolamins possessing a spherical structure with conformational properties similar to those of conventional globular proteins like ribonuclease and insulin. Zein nanoparticles have gained massive interest over the past couple of years owing to their natural hydrophilicity, ease of functionalization, biodegradability, and biocompatibility, thereby improving oral bioavailability, nanoparticle targeting, and prolonged drug administration. Thus, zein nanoparticles are becoming a promising candidate for precision cancer drug delivery. This review highlights the clinical significance of applying zein nanosystems for cancer theragnostic─moreover, the role of zein nanosystems for cancer drug delivery, anticancer agents, and gene therapy. Finally, the difficulties and potential uses of these NPs in cancer treatment and detection are discussed. This review will pave the way for researchers to develop theranostic strategies for precision medicine utilizing zein nanosystems. © 2024 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0.