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1. Ultra‐Flyweight Cryogels of MXene/Graphene Oxide for Electromagnetic Interference Shielding

   https://doi.org/10.1002/adfm.202304748  

   Ghaffarkhah, Ahmadreza ; Hashemi, Seyyed Alireza ; Rostami, Sara ; Amini, Majed ; Ahmadijokani, Farhad ; Pournaghshband Isfahani, Ali ; Mhatre, Sameer E. ; Rojas, Orlando J. ; Kamkar, Milad ; Wuttke, Stefan ; et al ( August 2023 , Advanced Functional Materials)

   MXene and graphene cryogels have demonstrated excellent electromagnetic interference (EMI) shielding effectiveness due to their exceptional electrical conductivity, low density, and ability to dissipate electromagnetic waves through numerous internal interfaces. However, their synthesis demands costly reduction techniques and/or pre‐processing methods such as freeze‐casting to achieve high EMI shielding and mechanical performance. Furthermore, limited research has been conducted on optimizing the cryogel microstructures and porosity to enhance EMI shielding effectiveness while reducing materials consumption. Herein, a novel approach to produce ultra‐lightweight cryogels composed of Ti₃C₂T_x/graphene oxide (GO) displaying multiscale porosity is presented to enable high‐performance EMI shielding. This method uses controllable templating through the interfacial assembly of filamentous‐structured liquids that are readily converted into EMI cryogels. The obtained ultra‐flyweight cryogels (3–7 mg cm⁻³) exhibit outstanding specific EMI shielding effectiveness (33 000–50 000 dB cm² g⁻¹) while eliminating the need for chemical or thermal reduction. Furthermore, exceptional shielding is achieved when the Ti₃C₂T_x/GO cryogels are used as the backbone of conductive epoxy nanocomposites, yielding EMI shielding effectiveness of 31.7–51.4 dB at a low filler loading (0.3–0.7 wt%). Overall, a one‐of‐a‐kind EMI shielding system is introduced that is readily processed while affording scalability and performance.

    

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2. Bayesian optimization of nanophotonic electromagnetic shielding with very high visible transparency

   https://doi.org/10.1364/OE.468843  

   Li, Mingxuan ; McCourt, Michael_J ; Galante, Anthony_J ; Leu, Paul_W ( August 2022 , Optics Express)

   Transparent electromagnetic interference (EMI) shielding is needed in many optoelectronic applications to protect electronic devices from surrounding radiation while allowing for high visible light transmission. However, very high transmission (over 92.5%), high EMI shielding efficiency (over 30 dB) structures have yet to be achieved in the literature. Bayesian optimization is used to optimize different nanophotonic structures for high EMI shielding efficiency (SE) and high visible light transmission (${\stackrel{¯<\#comment/>}{T}}_{vis}$). Below 90% average visible light transmission, sandwich structures consisting of high index dielectric/silver/high index dielectric films are determined to be optimal, where they are able to achieve 43.1 dB SE and 90.0%${\stackrel{¯<\#comment/>}{T}}_{vis}$. The high index of refraction dielectric layers reduce absorption losses in the silver and can be engineered to provide for antireflection through destructive interference. However, for optimal EMI shielding with${\stackrel{¯<\#comment/>}{T}}_{vis}$above 90%, the reflection losses at the air/dielectric interfaces need to be further reduced. Optimized double sided nanocone sandwich structures are determined to be best where they can achieve 41.2 dB SE and 90.8%${\stackrel{¯<\#comment/>}{T}}_{vis}$as well as 35.6 dB SE and 95.1%${\stackrel{¯<\#comment/>}{T}}_{vis}$. K-means clustering is utilized to show the performance of characteristic near-Pareto optimal structures. Double sided nanocone structures are shown to exhibit omnidirectional visible transmission withSE = 35.6 dB and over 85%${\stackrel{¯<\#comment/>}{T}}_{vis}$at incidence angles of 70${}^{\circ <\#comment/>}$.

    

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3. Layer‐by‐Layer Assembly of Cross‐Functional Semi‐transparent MXene‐Carbon Nanotubes Composite Films for Next‐Generation Electromagnetic Interference Shielding

   https://doi.org/10.1002/adfm.201803360  

   Weng, Guo‐Ming ; Li, Jinyang ; Alhabeb, Mohamed ; Karpovich, Christopher ; Wang, Hang ; Lipton, Jason ; Maleski, Kathleen ; Kong, Jaemin ; Shaulsky, Evyatar ; Elimelech, Menachem ; et al ( September 2018 , Advanced Functional Materials)

   Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness are highly desirable for next‐generation portable and wearable electronic devices. Here, spin spray layer‐by‐layer (SSLbL) to rapidly assemble Ti₃C₂T_xMXene‐carbon nanotube (CNT) composite films is shown and their potential for EMI shielding is demonstrated. The SSLbL technique allows strategic combinations of nanostructured materials and polymers providing a rich platform for developing hierarchical architectures with desirable cross‐functionalities including controllable transparency, thickness, and conductivity, as well as high stability and flexibility. These semi‐transparent LbL MXene‐CNT composite films show high conductivities up to 130 S cm⁻¹and high specific shielding effectiveness up to 58 187 dB cm²g⁻¹, which is attributed to both the excellent electrical conductivity of the conductive fillers (i.e., MXene and CNT) and the enhanced absorption with the LbL architecture of the films. Remarkably, these values are among the highest reported values for flexible and semi‐transparent composite thin films. This work could offer new solutions for next‐generation EMI shielding challenges.

    

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4. Single‐ and Double‐Layer Embedded Metal Meshes for Flexible, Highly Transparent Electromagnetic Interference Shielding

   https://doi.org/10.1002/admt.202302057  

   Zarei, Mehdi ; Li, Mingxuan ; Papazekos, Ekaterini ; Su, Yang‐Duan ; Sinha, Sneh ; Walker, S Brett ; LeMieux, Melbs ; Ohodnicki, Paul R ; Leu, Paul W ( May 2024 , Advanced Materials Technologies)

   Simulation and experimental studies are carried out on single‐layer and double‐layer embedded metal meshes (SLEMM and DLEMM) to assess their performance as transparent electromagnetic interference (EMI) shielding. The structures consist of silver meshes embedded in polyethylene terephthalate (PET). As a transparent electrode, SLEMMs exhibit a transparency of 82.7% and a sheet resistance of 0.61 Ωsq⁻¹as well as 91.0% and 1.49 Ωsq⁻¹. This performance corresponds to figures of merit of 3101 and 2620, respectively. The SLEMMs achieve 48.0 dB EMI shielding efficiency (SE) in the frequency range of 8–18 GHz (X‐ and Ku‐bands) with 91% visible transmission and 56.2 dB EMI SE with 82.7% visible transmission. Samples exhibit stable performance after 1000 bending cycles with a radius of curvature of 4 mm and 60 tape test cycles. DLEMMs consist of fabricating SLEMM on opposite sides of the substrate where the distance can be varied using a spacer. Simulations are performed to investigate how varying spacer distance between two layers of metal meshes influences the EMI SE. DLEMMs are fabricated and achieved an EMI SE of 77.7 dB with 81.7% visible transmission. SLEMMs and DLEMMs may have a wide variety of applications in aerospace, medical, and military applications.

    

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5. The Defects Genome of Janus Transition Metal Dichalcogenides

   https://doi.org/10.1002/adma.202403583  

   Sayyad, Mohammed ; Kopaczek, Jan ; Gilardoni, Carmem_M ; Chen, Weiru ; Xiong, Yihuang ; Yang, Shize ; Watanabe, Kenji ; Taniguchi, Takashi ; Kudrawiec, Robert ; Hautier, Geoffroy ; et al ( May 2024 , Advanced Materials)

   2D Janus Transition Metal Dichalcogenides (TMDs) have attracted much interest due to their exciting quantum properties arising from their unique two‐faced structure, broken‐mirror symmetry, and consequent colossal polarization field within the monolayer. While efforts are made to achieve high‐quality Janus monolayers, the existing methods rely on highly energetic processes that introduce unwanted grain‐boundary and point defects with still unexplored effects on the material's structural and excitonic properties Through high‐resolution scanning transmission electron microscopy (HRSTEM), density functional theory (DFT), and optical spectroscopy measurements; this work introduces the most encountered and energetically stable point defects. It establishes their impact on the material's optical properties. HRSTEM studies show that the most energetically stable point defects are single (V_S andV_Se) and double chalcogen vacancy (V_S−V_Se), interstitial defects (M_i), and metal impurities (M_W) and establish their structural characteristics. DFT further establishes their formation energies and related localized bands within the forbidden band. Cryogenic excitonic studies on h‐BN‐encapsulated Janus monolayers offer a clear correlation between these structural defects and observed emission features, which closely align with the results of the theory. The overall results introduce the defect genome of Janus TMDs as an essential guideline for assessing their structural quality and device properties.

    

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