Sensing with MXenes: Progress and Prospects Ho, Dong Hae; Choi, Yoon Young; Jo, Sae Byeok ...
Advanced materials (Weinheim),
11/2021, Letnik:
33, Številka:
47
Journal Article
Recenzirano
Various fields of study consider MXene a revolutionary 2D material. Particularly in the field of sensors, the metal‐like high electrical conductivity and large surface area of MXenes are desirable ...characteristics as an alternative sensor material that can transcend the boundaries of existing sensor technology. This critical review provides a comprehensive overview of recent advances in MXene‐based sensor technology and a roadmap for commercializing MXene‐based sensors. The existing sensors are systematically categorized as chemical, biological, and physical sensors. Each category is then classified into various subcategories depending on the electrical, electrochemical, structural, or optical sensing mechanism, which are the four fundamental working mechanisms of sensors. Representative structural and electrical approaches for boosting the performance of each category are presented. Finally, factors that hinder commercializing MXene‐based sensors are discussed, and several breakthroughs in realizing commercially available MXene‐based sensors are suggested. This review provides broad insights pertaining to previous and existing MXene‐based sensor technology and perspectives on the future generation of low‐cost, high‐performance, and multimodal sensors for soft‐electronics applications.
Metal‐like electrical conductivity and a large MXene surface area are desirable characteristics for alternative sensor material. An overview of recent advances in MXene‐based sensor technology that utilize the beneficial properties of MXenes is offered. Insights into low‐cost, high‐performance MXene‐based sensors for next generation soft‐electronics applications are also provided.
Electrochromic materials reversibly change colors by redox reactions depending on the oxidation states. To utilize electrochromic materials for active‐matrix display applications, an electrochromic ...display (ECD) requires simultaneous implementation of various colors and a fine‐pixelation process. Herein, flexible and transparent ECDs with simultaneously implementable subpixelated EC gels by sequential multiple patterning are successfully demonstrated. Ionic liquid‐based EC gels of monoheptyl‐viologen, diheptyl‐viologen (DHV), and diphenyl‐viologen (DPV) are used to create the colors of ECDs: magenta, blue, and green, respectively. Especially, to realize an improved green color, DHV–DPV composite gels are synthesized. Three EC gels exhibit stable properties without degradation during repetitive operation. Moreover, a transmittance greater than 90% is maintained in a bleached state, which is sufficient for application as a transparent display. The subpixelation process for multicolored‐flexible ECDs is designed to facilitate both easy fabrication and rapid operation with various patterns at low cost. The subpixelated EC gels using a film mask can be implemented to a minimum size of 200 µm. Furthermore, the subpixelated flexible ECDs exhibit high durability even after 1000 cycles of mechanical bending tests at a bending radius of 10 mm. Therefore, these EC materials can be used directly for flexible and transparent active‐matrix displays.
Flexible and transparent electrochromic displays (ECDs) with simultaneously implementable subpixelated EC gels by sequential multiple patterning are demonstrated. A transmittance greater than 90% is maintained in a bleached state, which is sufficient for transparent display. Moreover, the ECDs exhibit high durability after 1000 cycles of bending tests. These EC materials can be used directly for flexible and transparent active‐matrix displays.
Perovskite light‐emitting diodes (PeLEDs) have garnered considerable interest in recent years owing to their unique optoelectronic properties. However, the performance of PeLEDs is limited by their ...low quantum efficiency and unbalanced charge injection. In this study, to address these issues, a novel co‐hole transport layer (HTL) of 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP) and poly(9‐vinylcarbazole) (PVK) is introduced into PeLEDs. By optimizing the composition ratio of CBP and PVK, the performance of CsPbBr3‐based PeLEDs is significantly improved via efficient Förster resonant energy transfer and an enhanced charge transfer owing to the well‐aligned energy levels of the HTLs with the emission layers. The PeLED with an optimized composition ratio of the PVK0.5–CBP0.5 HTL exhibits the best device performance with a luminance of 31641 cd∙m−2, current efficiency of 39.2 cd∙A−1, and external quantum efficiency of 15.4%. Thus, the proposed strategy engineering dual transfer of energy and charge is expected to be revolutionary in the field of PeLED research.
The perovskite light‐emitting diodes with a novel co‐hole transport layer of 4,4‐bis(N‐carbazolyl)‐1,1′‐biphenyl and poly(9‐vinylcarbazole) exhibited excellent device performance due to efficient Förster resonant energy transfer and enhanced charge transfer.
Metal halide perovskites have attracted considerable attention for light‐emitting diode (LED) applications due to their desirable optoelectronic properties including high brightness and color purity. ...However, the performance of blue perovskite LEDs (PeLEDs) remains inferior to their red and green counterparts. Herein, an ionic liquid (IL), specifically 1‐butyl‐3‐methylimidazolium tetrafluoroborate is introduced as the interlayer on the hole transport layer (HTL). This IL demonstrates a strong interaction with the perovskite emissive layer, resulting in effective defect passivation and a shallower valence band maximum. Consequently, nonradiative recombination is reduced, and hole injection is enhanced. Additionally, a soft lithography method employing a transfer process is successfully developed that enables precise micropatterning of the perovskite light‐emitting layer. Through these advancements, the IL‐modified PeLED exhibits pure blue emission at 470 nm with a maximum luminance of 891 cd m−2 and an impressive maximum EQE of 8.3%. Furthermore, the micro PeLED with an IL interlayer achieves a maximum luminance of 400 cd m−2 and a maximum EQE of 3.9%.
The introduction of an ionic liquid interfacial modification layer effectively passivates defects and improves the exciton energy transfer by regulating the crystallization growth kinetics of perovskite. This significantly improves the performance and spectral stability of the blue perovskite light‐emitting diodes. Additionally, this strategy is also effective for micro perovskite light‐emitting diodes fabricated through the transfer of the micro‐patterned blocking layer.
Blue emissive perovskites can be prepared by incorporating chlorine into bromine‐based perovskites to tune their bandgap. However, mixed‐halide perovskites exhibit intrinsic phase instability, ...particularly under electrical potential, owing to halide migration. To achieve high‐performance blue perovskite‐based light‐emitting diodes (PeLEDs) with operational stability, organic ammonium cations are used for passivating the anionic defects of the CsPbBr2Cl film. Diphenylpropylammonium chloride (DPPACl), used as a passivating agent, successfully prevents the spectral instability of blue PeLEDs by passivating the Cl− vacancies. Consequently, the blue PeLED prepared with this passivating agent delivers excellent device performance with a maximum external quantum efficiency of 3.03%. Moreover, upon tuning the DPPACl concentration, the PeLED emits stably in the deep‐blue spectral region (464 nm) with a half‐life time of 420 s. Thus, the use of organic ammonium cation as a passivating agent is an effective strategy for developing high‐performance blue PeLEDs with operational stability.
The introduction of an appropriate passivating agent into the perovskite film is an effective technique for preventing the halide migration of mixed‐halide perovskites to develop high‐performance blue perovskite light emitting diodes (PeLEDs) with spectral stability. The PeLED with 60% diphenylpropylammonium chloride shows stable emission in the deep‐blue spectral region (464 nm) with a maximum external quantum efficiency of 1.92%.
Due to the increasing interest in wearable devices, flexible and stretchable film heaters have been widely studied, as alternatives to heaters with conventional rigid shapes. Herein, a highly ...stretchable film heater (SFH) based on the silver nanowire (Ag NW)–single‐walled carbon nanotube composite with a thermochromic display on a polydimethylsiloxane (PDMS) substrate is successfully fabricated. The SFH shows excellent electrical conductivity, high mechanical stretchability, and outstanding reliability, with no significant degradation after 10 000 stretching cycles under tensile strain. The SFH can be heated to the target temperature (≈60 °C) within 30 s at a low applied voltage. In addition, a thermochromic display is fabricated to help prevent the risk of low‐temperature burns. Red (R), green (G), and blue (B) thermochromic microparticles (TMPs) are synthesized using drop‐based microfluidic technology. The TMPs show RGB colors at room temperature but change to a white color above a certain temperature. The TMPs are arrayed into a PDMS stencil on the basis of their particle sizes using the rubbing technique. The micropatterned thermochromic display, which functions as a visual alarm, combined with the SFH can pave the way for the development of thermotherapy pads for next‐generation wearable devices in the medical field.
A highly stretchable and wearable thermotherapy pad with a micropatterned thermochromic display based on a Ag nanowire–single‐walled carbon nanotube composite is demonstrated. It has a low resistance, high stretchability, and excellent reliability. Moreover, the thermochromic display has a built‐in visual alarm mechanism to prevent low‐temperature burns. This promising articular thermotherapy pad has potential applications in the medical field.
For resolving toxicity issues of Pb‐based perovskites, Sn‐based perovskites have been widely studied as a promising alternative due to similar valence electron configuration between Sn2+ and Pb2+. ...However, desired Sn2+ in the precursor solution and film is easily oxidized to Sn4+, causing detrimental Sn vacancies and impurities in the films. Unfortunately, dimethyl sulfoxide, a ubiquitously used Lewis base for the fabrication of high‐quality perovskite thin films via the adduct approach, further accelerates the oxidation of Sn2+ in the precursor solution. Herein, N,N′‐dimethylpropyleneurea (DMPU) is proposed as an alternative Lewis base for the fabrication of high‐quality Sn‐based perovskite thin films. The strongly coordinating Lewis base DMPU is shown to suppress the oxidation of Sn2+ in the precursor solution while promoting growth of uniform and highly crystalline thin films. The PEA2SnI4 perovskite light emitting diode (PeLED) based on DMPU demonstrates dramatically improves luminance (L): a more than sixfold enhanced external quantum efficiency (EQE) and better operational stability than those of the device fabricated without DMPU. The optimum PeLED based on DMPU achieves a maximum L and EQE of 68.84 cd m−2 and 0.361%, respectively. This study provides an important methodological base for studying Sn perovskites for development of high‐performance and eco‐friendly PeLEDs.
By adopting Lewis bases with varying coordinating ability, interplays between the coordinating ability of the Lewis base and tin halide perovskite film quality is unraveled. The strongly coordinating N,N′‐dimethylpropyleneurea suppresses oxidation of Sn2+ in the precursor solution while promoting growth of uniform and highly crystalline Sn perovskite thin films for achieving high‐performance lead‐free perovskite light emitting diodes.
•Ethyl trifluoroacetate is hydrolyzed to trifluoroacetic acid during purification.•The trifluoroacetic acid group interacts strongly with uncoordinated Pb ions.•Trifluoroacetylation weakens the ...interaction between oleylamine and bromide ions.•Halogen vacancy is passivated during the purification process.•High-performance pure blue light-emitting diodes are obtained.
In halide perovskite nanocrystals (NCs), insulating long chain ligands such as oleic acid (OA) and oleylamine (OAm) often remove the halide ions during the purification process, leading to surface vacancy defects. This hinders their application in light-emitting devices. Herein, we report an in-situ passivation strategy using ethyl trifluoroacetate, which is hydrolyzed to trifluoroacetic acid, as an antisolvent in the purification process to passivate defects by reacting with uncoordinated Pb2+ and OAm on the surface of NCs, thus anchoring Br− to the surface of NCs. This achieves a mild removal of OAm and OA while passivating both anionic and cationic vacancies. Consequently, we achieved high-performance blue perovskite light-emitting diodes (PeLEDs). The PeLEDs based on these NCs exhibit pure blue electroluminescence at 463 nm with an external quantum efficiency of 4.14 % and a luminance of 1035 cd m−2. This study provides insights and a foundation for the development of high-performance PeLEDs.
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