Hyunho Kim

Drexel University | DU · A.J. Drexel Nanotechnology Institute (DNI)

MXenes have been widely investigated in energy storage, electromagnetic interference shielding, sensing, electronic, and photonic applications. Some MXenes have been predicted to have outstanding thermoelectric (TE) properties, but relevant explorations are very limited. Herein, the TE performance of Mo2TiC2Tx and Nb2CTx MXenes are carefully contro...

Wafer-scale growth has become a critical bottleneck for scaling up applications of van der Waal (vdW) layered two-dimensional (2D) materials in high-end electronics and optoelectronics. Most vdW 2D materials were initially obtained through top-down synthesis methods, such as exfoliation, which can only prepare small flakes on a micrometer scale. Bo...

It is very challenging to employ solution-processed conducting films in large-area ultrathin nanoelectronics. In this manuscript, spray-coated Ti3C2Tx MXene films as metal contacts are successfully integrated into sub-10 nm gate oxide two-dimensional (2D) MoS2 transistor circuits. The Ti3C2Tx films are prepared on glass substrates by a spray coatin...

MXene-based hydrogels have received significant attention due to several promising properties that distinguish them from conventional hydrogels. In this study, it is shown that both strain and pH level can be exploited to tune the electronic and ionic transport in MXene-based hydrogel (M-hydrogel), which consists of MXene (Ti3C2Tx)-polyacrylic acid...

Efficient thermoelectric generators require further progress in developing n-type semiconductors that combine low thermal conductivity with high electrical conductivity. By embedding colloidal quantum dots (CQDs) in a metal halide matrix (QDMH), the metal halide matrix can enhance phonon scattering, thus suppressing thermal transport; however, simu...

Fully solution-processed, large-area, electrical double-layer transistors (EDLTs) are presented by employing lead sulfide (PbS) colloidal quantum dots (CQDs) as active channels and Ti3C2T x MXene as electrical contacts (including gate, source, and drain). The MXene contacts are successfully patterned by standard photolithography and plasma-etch tec...

Electronic applications of porous metal-organic frameworks (MOFs) have recently emerged as an important research area. However, there is still no report on using MOF solid electrolytes in iontronics, which could take advantage of the porous feature of MOFs in the ionic transport. In this article, MXene-derived two-dimensional porphyrinic MOF (MX-MO...

With recent growing interest in biomimetic smart nanochannels, a biological sensory transduction in response to external stimuli has been of particular interest in the development of biomimetic nanofluidic systems. Here we demonstrate the MXene-based subnanometer ion channels that convert external temperature changes to electric signals via prefere...

As a thriving member of the 2D nanomaterials family, MXenes, i.e., transition metal carbides, nitrides, and carbonitrides, exhibit outstanding electrochemical, electronic, optical, and mechanical properties. They have been exploited in many applications including energy storage, electronics, optoelectronics, biomedicine, sensors, and catalysis. Com...

Ultrasound is a source of ambient energy that is rarely exploited. In this work, a tissue-mimicking MXene-hydrogel (M-gel) implantable generator has been designed to convert ultrasound power into electric energy. Unlike the present harvesting methods for implantable ultrasound energy harvesters, our M-gel generator is based on an electroacoustic ph...

Growing III-nitride nanowires on 2D materials is advantageous as it effectively decouples the underlying growth substrate from the properties of the nanowires. As a relatively new family of 2D materials, MXenes are promising candidates as III-nitride nanowire nucleation layers capable of providing simultaneous transparency and conductivity. In this...

A titanium carbide (Ti3C2Tx) MXene is employed as an efficient solid support to host a nitrogen (N) and sulfur (S) coordinated ruthenium single atom (RuSA) catalyst, which displays superior activity toward the hydrogen evolution reaction (HER). X‐ray absorption fine structure spectroscopy and aberration corrected scanning transmission electron micr...

MXenes, a rapidly growing family of 2D materials based on transition metal carbides and nitrides, have shown great potentials as multi-functional nanomaterials. Their unique combination of metallic conductivity, hydrophilicity, and highly charged surfaces endow them with excellent electrochemical performance. Yet, these same characteristics are equ...

Colloidal quantum dots (CQDs) are attractive materials for thermoelectric applications due to their simple and low‐cost processing; advantageously, they also offer low thermal conductivity and high Seebeck coefficient. To date, the majority of CQD thermoelectric films reported upon have been p‐type, while only a few reports are available on n‐type...

In article number 1900180, Xiaosheng Fang, Husam N. Alshareef, Jr‐Hau He and co‐workers demonstrate a delaminated multi‐layer Ti3C2Tx MXene contacted Si solar cell with a maximum power conversion efficiency (PCE) of ≈11.5%. The formation of an Ohmic junction of the metallic MXene to the n+‐Si surface efficiently extracts the photogenerated electron...

Thermoelectric (TE) generators that are capable of providing sustainable energy conversion under dynamic mechanical stresses have been explored for realizing autonomous wearable electronics. However, finding extremely deformable, efficient as well as air-stable TE materials is still a major challenge. Here, we report highly stretchable and efficien...

MXenes, a large family of two-dimensional transition metal carbides and nitrides, have been attracting great interest since the discovery of Ti 3 C 2 T x in 2011. The unique combination of metallic conductivity and hydrophilicity in Ti 3 C 2 T x resulted in outstanding performances in electrochemical applications. The surface of MXene is highly che...

The development of wearable electronics, point-of-care testing, and soft robotics requires strain sensors that are highly sensitive, stretchable, capable of adhering conformably to arbitrary and complex surfaces, and preferably self-healable. Conductive hydrogels hold great promise as sensing materials for these applications. However, their sensiti...

Two‐dimensional metal carbides (MXenes) are successfully integrated into oxide semiconductor electrical switching devices for the first time by Husam N. Alshareef and co‐workers in article number 1706656. Both p‐ and n‐type oxide thin‐film transistors are fabricated entirely using MXene electrical contacts. The inside front cover shows complementar...

2D MXenes have shown great promise in electrochemical and electromagnetic shielding applications. However, their potential use in electronic devices is significantly less explored. The unique combination of metallic conductivity and hydrophilic surface suggests that MXenes can also be promising in electronics and sensing applications. Here, it is s...

MXenes are an interesting class of 2D materials consisting of transition metal carbides and nitrides, which are currently a subject of extensive studies. Although there have been theoretical calculations estimating the thermoelectric properties of MXenes, no experimental measurements have been reported so far. In this report, three compositions of...

Extraordinary oxidant-dependent changes in the thermoelectric properties of undoped ZnO thin films deposited by atomic layer deposition (ALD) have been observed. Specifically, deionized water and ozone oxidants are used in the growth of ZnO by ALD using diethylzinc as zinc precursor. No substitutional atoms have been added to the ZnO films. By usin...