Chong Min Koo

Sungkyunkwan University | SKKU · School of Advanced Materials Science and Engineering (AMSE)

Surface chemistry influences not only physicochemical properties but also safety and applications of MXene nanomaterials. Fluorinated Ti3 C2 Tx MXene, synthesized using conventional HF-based etchants, raises concerns regarding harmful effects on electronics and toxicity to living organisms. In this study, well-delaminated halogen-free Ti3 C2 Tx fla...

MXenes are an emerging class of 2D materials with unique properties including metallic conductivity, mechanical flexibility, and surface tunability, which ensure their utility for diverse applications. However, the synthesis of MXenes with high crystallinity and atomic stoichiometry in a low-cost process is still challenging because of the difficul...

Shape‐Deformable Locomotive MXene In article number 2210385, Cheolmin Park and co‐workers develop a MXene‐encapsulated magnetic liquid metal with shape deformable, locomotive, and self‐healing abilities. The liquid metal composite can be integrated as an electrical component of a device, with magnetic field‐induced performance tunability. Such char...

Lightweight electromagnetic interference (EMI) shielding materials for portable and highly compact electronics are required to have robust mechanical strength as well as excellent shielding efficiency. In the recent years, although 1D/2D nano carbons and 2D MXenes have been explored as electromagnetic shield in place of highly conductive yet dense...

Owing to their unique surface chemistry, room‐temperature pseudoliquidity, and high electrical conductivity, gallium‐based liquid metals (LMs) exhibit multifunctionality. To grant deformable and self‐flowing characteristics to LMs, magnetic particles are incorporated for precisely controlling the LM motion and shape deformability. However, LM surfa...

Ligands can control the surface chemistry, physicochemical properties, processing, and applications of nanomaterials. MXenes are the fastest growing family of two-dimensional (2D) nanomaterials, showing promise for energy, electronic, and environmental applications. However, complex oxidation states, surface terminal groups, and interaction with th...

With the rapid development of electronic technology, mobile communication and satellite communication, electromagnetic interference (EMI) or Radio Frequency Interference (RFI) has received global scientific attention to ensure unperturbed performance of electronic items and to avoid any adverse effect on human health. EMI is one of the main factors...

MXene Synthesis In article number 2203767, Chong‐Min Koo and co‐workers show that a high temperature non‐aqueous synthesis of Ti3C2Tx can significantly enhance the reaction rate and yield of delaminated MXene flakes with high quality. Additionally, Ti3C2Tx prepared by this method is covered with more F‐terminations and exhibits high tensile strengt...

Texture regulation of metal–organic frameworks (MOFs) is essential for controlling their electromagnetic wave (EMW) absorption properties. This review systematically summarizes the recent advancements in texture regulation strategies for MOFs, including etching and exchange of central ions, etching and exchange of ligands, chemically induced self‐a...

While two-dimensional (2D) Ti3C2Tx MXene in aqueous dispersions spontaneously oxidizes into titanium dioxide (TiO2) nanocrystals, the crystallization mechanism has not been comprehensively understood and the resultant crystal structures are not controlled among three representative polymorphs: anatase, rutile, and brookite. In this study, such cont...

Two-dimensional transition metal carbide/nitride (MXene) conductive inks are promising for scalable production of printable electronics, electromagnetic devices, and multifunctional coatings. However, the susceptible oxidation and poor rheological property seriously impede the printability of MXene inks and the exploration of functional devices. He...

Controlling the orientation of two-dimensional materials is essential to optimize or tune their functional properties. In particular, aligning MXene, a two-dimensional carbide and/or nitride material, has recently received much attention due to its high conductivity and high-density surface functional group properties that can easily vary based on...

2D transition metal carbides or nitrides (MXenes) have attracted considerable attention from materials scientists and engineers owing to their physicochemical properties. Currently, MXenes are synthesized from MAX‐phase precursors using aqueous HF. Here, in order to enhance the production of MXenes, an anhydrous etching solution is proposed, consis...

Lithium metal batteries (LMBs) have attracted increasing attention owing to their high theoretical capacity and low reduction potential. However, safety concerns and their low coulombic efficiencies (CE) arising from the nonuniform and irreversible formation of Li dendrites on their anodes hinder their practical application. Here, we demonstrate th...

The development of electrodes with high conductivity, optical transparency, and reliable mechanical flexibility and stability is important for numerous solution-processed photoelectronic applications. Although transparent Ti3C2TX MXene electrodes with high conductivity are promising, their suitability for displays remains limited because of the hig...

MXenes have recently attracted significant interest owing to their outstanding properties and performance. However, their hydrophilic and metastable surfaces make most MXenes prone to oxidation, which can greatly degrade their properties and hinder their practical applications. Here, we enhanced the stability of Ti3C2Tx MXene films by coating a con...

Sendust/expanded graphite and Sendust/boron nitride binary composite fillers adhered through surface silane modification and their non-modified, simply mixed, polymer composites were fabricated for optimization of multifunctional EMI shielding and thermal conduction properties. The effect of filler type, filler content, surface modification, and di...

High-tech electronic and communication devices require advanced materials for their protection against electromagnetic interference (EMI). Electrically conductive solid materials, such as metals, are typically employed as EMI shields owing to their high shielding performance caused by their high electronic conductivity. Herein, electrically insulat...

Understanding and preventing oxidative degradation of MXene suspensions is essential for fostering fundamental academic studies and facilitating widespread industrial applications. Owing to their outstanding electrical, electrochemical, optoelectronic, and mechanical properties, MXenes, an emerging class of two-dimensional (2D) nanomaterials, show...

High-performance EMI shielding of a core-shell nanocomposite of Ni-Co MOF (core) wrapped by a heterogeneous layer of FeBTC MOF and polymeric polypyrrole (PPy) (shell) named Ni-Co/[email protected] is reported. Herein, the spherical structure Ni-Co MOF was firstly prepared and employed as nucleation sites for polymerization of pyrrole monomer utiliz...

Lightweight shielding materials that can protect devices against undesirable multispectral electromagnetic waves are critical in electronic, medical, military, and aerospace applications. However, the existing shielding materials are heavyweight and work only in a narrow frequency-range. In this work, we developed metal–metal oxide Ag-WO3 decorated...

Discover a cutting-edge reference on 2D EMI shielding materials for both industrial and academic audiences Two-Dimensional Materials for Electromagnetic Shielding delivers a thorough and comprehensive examination of all aspects of electromagnetic interference (EMI) shielding and microwave absorption, including fundamentals and applications, as wel...

The positive effects of a lithiophilic substrate on the electrochemical performance of lithium metal anodes are confirmed in several reports, while the understanding of lithiophilic substrate‐guided lithium metal nucleation and growth behavior is still insufficient. In this study, the effect of a lithiophilic surface on lithium metal nucleation and...

Lithium Metal Batteries In article number 2101261, Seon Joon Kim, Young Soo Yun, and co-workers study lithiophilic surface-guided lithium metal nucleation and growth behaviors using a large-area Ti3C2Tx MXene electrode containing a large number of oxygen and fluorine dual heteroatoms. The lithiophilic MXene substrate significantly affects the surfa...

MXenes are interesting 2D materials that have been considered as attractive frontier materials for potential applications in the fields of energy and electronic devices due to their excellent optoelectronic properties including metallic conductivity and high optical transparency. However, it is still challenging to achieve compatibility for the as‐...

In article number 2010897, Yong Jin Jeong, Tae Kyu An, Insik In, Se Hyun Kim, and co-workers propose a clever strategy of engineering MXene inks for electrohydrodynamic jet printing to produce all printed logic circuits. This work could inspire further practical printed electronics by providing an option to manufacture electrodes in complex circuit...

MXenes occupy a leading position among materials capable of providing lightweight shielding against electromagnetic interference (EMI) owing to their outstanding metallic conductivity, low density, tunable surface chemistry, and easy solution processing. In this work, we demonstrate that multiple interfaces of segregated structures in MXene composi...

All electrical and electronic devices receive or transmit electromagnetic waves (EMWs), which cause a type of pollution called electromagnetic interference (EMI). This phenomenon affects the performance of electronic circuits, shortening their lifespan, and it is injurious to human health. For safe exposure limits to EMWs, different operating frequ...

The selection of appropriate instruments and measurement methods is vital for precise measurements of the electromagnetic interference (EMI) shielding effectiveness. This chapter describes common measurement techniques and standards for determining the electromagnetic shielding performance. Different measurement techniques, such as the coaxial tran...

Electromagnetic interference (EMI) shielding mechanisms and scattering parameter conversion theory are essential for understanding the shielding performance of materials. This chapter primarily discusses the basic EMI shielding mechanisms, including reflection, absorption, and multiple reflections. Moreover, scattering parameter conversion techniqu...

The large surface area, ballistic electron transport properties, and tunable surface chemistry of graphene make this material suitable for electromagnetic interference (EMI) shielding applications. In this chapter, the physical and chemical properties of graphene are discussed along with the shielding properties of graphene variants such as graphen...

Shielding materials with absorption‐dominant properties have been explored for many civilian and defense applications. Various 2D materials, including transition metal dichalcogenides (TMDCs; e.g. MoS2, WS2, and TaS2), black phosphorus (BP), hexagonal boron nitride (h‐BN), and metal–organic frameworks (MOFs), have been explored for electromagnetic...

Two‐dimensional (2D) MXenes are a newly discovered family of transition metal carbides, nitrides, and carbonitrides. Their outstanding electrical conductivities of >104 S cm−1 and 2D morphology offer an efficient alternative to highly conductive metals in applications requiring high electrical conductivity. In addition, the low density, mechanical...

Two-dimensional graphene is of great interest for electromagnetic interference (EMI) shielding owing to its inherent electrical conductivity, lightweight, and excellent mechanical flexibility even at minor thicknesses. However, the complex synthesis and quality-control difficulties limit its application. In this study, we demonstrate that electroch...

MXenes are two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides with unique intrinsic properties, including excellent electrical conductivity, 2D sheet morphology, lightweight, flexibility, tunable surface chemistry, and easy solution processability, thus attracting considerable attention as electromagnetic interference (EMI)...

A nanostructured composite composed of reduced graphene oxide (rGO) and NiO/ZnO hollow spheres was prepared via an in situ reaction involving pyrolysis and surface modification of a heterobimetallic Ni-Zn metal-organic framework with amine-functional group. The rGO sheet was successfully grafted on the surface of NiO/ZnO. The hybrid displayed excel...

Nano-hydroelectric technology utilizes hydraulic flow through electronically conducting nanomaterials to generate electricity in a simple, renewable, ubiquitous, and environmentally friendly manner. Up to date, several designs of nano-hydroelectric devices have...

A composite of reduced graphene oxide (rGO) coated with metal-organic framework (MOF) HKUST-1 was synthesized using a facile hydrothermal method. The micro-frame of HKUST-1 was retained with the well-decorated octahedral framework on the surface of rGO sheets, resulting in the production of a scabrous, thorny trunk structure. The as-prepared compos...

A novel inorganic–organic hybrid crosslinker was prepared through synthesis of a fully condensed, high molecular weight ladder-like poly(methacryloxypropyl)silsesquioxane (LPMASQ) in one pot with a facile, base-catalysed system. The fully condensed LPMASQ revealed good thermal (∼380 °C) and electrochemical stability (∼5.0 V) due to the absence of u...

Since the first report on electromagnetic interference (EMI) shielding of 2D Ti3C2Tx in 2016, MXenes have captured the leadership position among lightweight shielding materials due to many advantages, including their excellent shielding performance, outstanding metallic conductivity, low density, large specific surface area, tunable surface chemist...

In article number 2000883, Chong Min Koo, Aamir Iqbal, and Pradeep Sambyal comprehensively review the recent advancements in MXene‐based electromagnetic interference shielding materials with different structural morphologies and provides an insight into future challenges and guideline for finding material solutions for the next‐generation shielding...

2-dimensional (2D) MXene has enlightened enormous potentials in scientific fields, including energy storage and electromagnetic interference (EMI) shielding. Unfortunately, MXene based material structures generally suffer from mechanical fragility and vulnerability to oxidation. Herein, mussel-inspired dopamine successfully addresses those weakness...

MXenes (Ti3C2) are 2D transition‐metal carbides and carbonitrides with high conductivity and optical transparency. However, transparent MXene electrodes suitable for polymer light‐emitting diodes (PLEDs) have rarely been demonstrated. With the discovery of the excellent electrical stability of MXene under an alternating current (AC), herein, PLEDs...

In article number 2001224, Chong Min Koo, Cheolmin Park, and co‐workers demonstrate a solution‐processed, large‐area, flexible, transparent MXene electrode suitable for a high‐performance polymer light emitting diode (PLED). The PLED with the MXene electrode exhibits a light‐emission performance superior to that of previously reported flexible PLED...

Lightweight, ultrathin, and flexible electromagnetic interference (EMI) shielding materials are needed to protect electronic circuits and portable telecommunication devices and to eliminate cross-talk between devices and device components. Here, we show that a two-dimensional (2D) transition metal carbonitride, Ti3CNT x MXene, with a moderate elec...

New ultrathin and multifunctional electromagnetic interference (EMI) shielding materials are required for protecting electronics against electromagnetic pollution in the fifth-generation networks and Internet of Things era. Micrometer-thin Ti3C2T x MXene films have shown the best EMI shielding performance among synthetic materials so far. Yet, the...

Miniaturization of electronics demands electromagnetic interference (EMI) shielding of nanoscale dimension. The authors report a systematic exploration of EMI shielding behavior of 2D Ti3C2Tx MXene assembled films over a broad range of film thicknesses, monolayer by monolayer. Theoretical models are used to explain the shielding mechanism below ski...

In article number 1906769, Yury Gogotsi, Sang Ouk Kim, Chong Min Koo, and co‐workers report systematic experimental and theoretical exploration of the electromagnetic interference (EMI) shielding behavior of two‐dimensional Ti3C2Tx MXene assembled films over a broad range of film thicknesses, monolayer by monolayer. A monolayer assembled film offer...

Herein, we demonstrate a simple and versatile way for preparing stable Ti3C2T x MXene dispersions in nonpolar organic solvents through a simultaneous interfacial chemical grafting reaction and phase transfer method. Alkylphosphonic acid ligands were chemically grafted on the hydroxyl terminal groups of Ti3C2T x flakes at the liquid-liquid interface...

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE)/Nylon 66 blends have been considered as the potential heat resistant engineering plastics with high mechanical toughness and flame retardancy, suitable for high temperature applications. However, incompatibility between PPE and Nylon 66 and poor thermal stability of Nylon 66 degrade mechanical toughness...

The problems associated with electromagnetic interference (EMI) have grown up rapidly due to the large usage of electronic gadgets and telecommunication devices. Thus, it is extremely important to understand the EMI shielding mechanisms and develop such materials that can mitigate the harmful effects of EMI arising due to advancement of telecommuni...

Lightweight materials with high electrical conductivity and robust mechanical properties are highly desirable for electromagnetic interference (EMI) shielding in modern portable and highly integrated electronics. Herein, a three-dimensional (3D) porous Ti3C2T x /carbon nanotube (CNT) hybrid aerogel was fabricated via a bidirectional freezing method...

Metal-coated polymer bead based composites are promising as electromagnetic interference (EMI) shielding and thermally conductive materials because they form a percolation 3D metal shell network at very low filler content. Herein, we fabricated 3D Cu/Ag shell network composites through electroless plating of metal on polymer beads and a simple hot...

Non-aqueous lithium-ion redox flow batteries (Li-RFBs) have recently garnered much interest because of their high operating voltage and energy density. Albeit these outstanding advantages, challenges, such as poor cyclability and efficiency, still remain in employing the practical application. In an attempt to address these problems, a series of 2,...

Solution-processed nanostructured mesoporous rutile phase titanium dioxides (TiO2) are a fascinating class of materials for energy applications owing to their remarkable properties, including thermal stability. The unique lattice structure of rutile TiO2 (R-TiO2) leads to multifaceted physicochemical properties, which influence its performances. We...

Mixture of ionic liquid, 1,3-dimethylimidazolium 2-methoxy(2-ethoxy(2-ethoxy(2-ethoxy)))ethylphosphite ([DMIm][MPEGP]), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), which forms an ionic liquid crystal with a superior ionic conductivity, evolves a smectic struc-ture through ion–ion interactions as a function of LiTFSI concentration. Nucl...

Herein, we demonstrate the selective sensing of Dopamine (DA), an important neurotransmitter, by using Nafion-stabilized two-dimensional transition metal carbides (Ti3C2Tx MXenes). Ti3C2Tx was deposited on a glassy carbon electrode followed by Nafion coating to achieve a robust sensitivity (∼3 nM), good selectivity, wide detection window (0.015–10...

Grafting nanotechnology on thermoelectric materials leads to significant advances in their performance. Creation of structural defects including nano-inclusion and interfaces via nanostructuring achieves higher thermoelectric efficiencies. However, it is still challenging to optimize the nanostructure via conventional fabrication techniques. The th...

Prior to the advent of the next-generation heater for wearable/on-body electronic devices, various properties are required, including conductivity, transparency, mechanical reliability, and conformability. Expansion to two dimensional (2D) structure of metallic nanowires based on network- and mesh- type geometries has been widely exploited for real...

Herein, for the first time, FeSiAl (sendust)/metal hybrid materials were synthesized with a magnetic core and a highly electrically conductive metal shell for shielding electromagnetic interference (EMI) pollution. Soft magnetic sendust flakes were electroless-plated with electrically conductive Ag or Ni metal to form Ag-plated and Ni-plated sendus...

Lightweight and mechanically flexible materials that can provide efficient electromagnetic interference (EMI) shielding are highly desirable for protecting portable and smart electronic devices against electromagnetic pollution. Here, the authors report a tunable design of a three‐dimensional (3D) porous aerogel structure made of 2D transition meta...

Metals, due to their extremely large electrical conductivity, have been a natural choice for electromagnetic interference (EMI) protection. Polymers can generally be classified into two types of insulating and intrinsically conducting polymers (ICPs). Metallic nanowires were initially used as filler to impart the metallic conduction character to in...

Silica nanoparticles were chemically grafted onto a porous polyethylene separator to improve the adhesion strength, thermal stability, and electrochemical performance of a polyolefin separator. A surface activation via UVO plasma treatment, followed by silane hybridization yielded a polymeric binder-free, thin coating of SiO2 nanoparticles onto the...

The fatigue resistance of piezoelectric PVDF has been under question in recent years. While some report that a significant degradation occurs after 106 cycles of repeated voltage input, others report that the reported degradation originates from the degraded metal electrodes instead of the piezoelectric PVDF itself. Here, we report the piezoelectri...

Herein, we report the synthesis of a graphene/polymer composite via a facile and straightforward approach for electromagnetic interference (EMI) shielding applications. Polystyrene (PS) beads were added in graphene oxide (GO)/water solution followed by the addition of hydroiodic acid (HI) for in situ reduction of GO. The composite solution (rGO/PS)...