Harmonizing Material Quantity and Terahertz Wave Interference Shielding Efficiency with Metallic Borophene Nanosheets

Harmonizing Material Quantity and Terahertz Wave Interference Shielding Efficiency with Metallic Borophene Nanosheets | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Harmonizing Material Quantity and Terahertz Wave Interference Shielding Efficiency with Metallic Borophene Nanosheets Huanjun Chen, Haojian Lin, Ximiao Wang, Zhaolong Cao, Hongjia Zhu, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4763119/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Jul, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Materials with electromagnetic interference (EMI) shielding in the terahertz (THz) regime, while minimizing the quantity used, are highly demanded for future information communication, healthcare and mineral resource exploration applications. Currently, there is often a trade-off between the amount of material used and the absolute EMI shielding effectiveness (EESt) for the EMI shielding materials. Here, we address this trade-off by harnessing the unique properties of two-dimensional (2D) β12-borophene (β12-Br) nanosheets. Leveraging β12-Br’s light weight and exceptional electron mobility characteristics, which represent among the highest reported values to date, we simultaneously achieve a THz EMI shield effectiveness (SE) of 70 dB and an EESt of 4.8 × 105 dB·cm2/g (@0.87 THz) using a β12-Br polymer composite. This surpasses the values of previously reported THz shielding materials with an EESt less than 3 × 105 dB·cm2/g and a SE smaller than 60 dB, while only needs 0.1 wt.% of these materials to realize the same SE value. Furthermore, by capitalizing on the composite’s superior mechanical properties, with 158% tensile strain at a Young’s modulus of 33 MPa, we demonstrate the high-efficiency shielding performances of conformably coated surfaces based on β12-Br nanosheets, suggesting their great potential in EMI shielding area. Physical sciences/Nanoscience and technology/Nanoscale materials/Two-dimensional materials Physical sciences/Materials science/Materials for optics/Nanophotonics and plasmonics Figures Figure 1 Figure 2 Figure 3 Introduction THz radiation, spanning from 0.1 to 10 THz in frequency, represents a frontier in technology with vast potential across multiple applications including information communications, radar imaging, noninvasive inspection, and biomedical sensing 1 . Its appeal lies in distinctive characteristics, such as low photon energy, robust penetration capabilities and the ability to discern characteristic molecular signatures within this spectral range. However, despite its promise, THz electronic and optoelectronic devices are not immune to electromagnetic interference (EMI) pollution, a challenge well-known in the radio-frequency realm 2 – 4 . Such interference can markedly degrade device performance and do harm to the surrounding environment, underscoring the need for effective EMI shielding materials. An ideal EMI shielding material should effectively block electromagnetic waves (EMW) while simultaneously ensure that the isolated electromagnetic field does not emit into the surrounding environment. Meanwhile, such a material is also anticipated to be low-cost and easily producible, lightweight and possess good stretchability, enabling it to conform to arbitrary surfaces. This flexibility is particularly crucial for effective EMI shielding in wearable devices and portable equipment for consumer electronics. Currently, research on THz EMW shielding materials follows two main approaches. On one hand, traditional materials originally designed for the microwave frequency range are still utilized, such as metal thin films 5 – 7 and carbon-based composite films, including conductive carbon inks 8 , 9 , carbon fibers 9 , 10 , carbon nanotubes 9 , 11 , and graphene 9 , 12 . These materials are highly conductive and inhibit EMW through reflection, resulting in a significant portion of the waves being radiated into the surrounding environment, thus producing secondary pollution 5 , 13 . This inherent characteristic renders them less suitable for serving as EMI shielding materials in miniaturized devices with a demand of high integration. Alternatively, EMW can be shielded through absorption by the charged carriers within the EMI shielding materials. This has led to a recent shift in research focus towards exploring new-type materials with high electromagnetic absorption properties. These materials include polymer composite films 14 , 15 , nanocomposite films 16 , 17 , multilayer assemblies 5 , 15 , porous foams/aerogel composites 17 , 18 , and so on. Typically, these materials consist of segregated conductive fillers with a high density of free electrons with large mobility, facilitating the absorption of EMW through scattering at defects and interfaces presenting on each filler surface, followed by re-absorption by the free electrons. In particular two–dimensional (2D) conductive materials, such as MXene and graphene, have recently been employed as the fillers due to their outstanding electrically conductive characteristics. For example, a very recent study demonstrates that MXene assemblies can approach the intrinsic absorption limit in the 0.5–10 THz frequency range, with a small thickness of 10.2 nm 19 . A thin graphene/PMMA nanolaminate composite is displayed with a high conductivity to exhibit a shielding effectiveness (SE) reaching 60 dB for a small thickness of 33 µm 15 . Our recent study indicates that a transparent MXene film can have an SE of 21 dB over a wide frequency range of 0.1–10 THz 20 . While these exciting results provide a pathway for developing high-performance THz EMI shielding materials, there usually needs a trade-off between the mass amount of material used and the shielding effectiveness. This typically leads to an absolute EMI shielding effectiveness (EES t ) of less than 3 × 10 4 dB·cm 2 /g and an SE smaller than 60 dB (Table S1 , Supporting Information) 15 . To further enhance the shielding performance of these materials, an increased filler content or increment of the material’s thickness is usually necessary. However, this inevitably increases the overall mass and thickness of EMI shielding material, which could compromise their mechanical stability and limit their developments in portable and miniaturized devices requiring lightweight, flexible, and conformable coatings. All these requirements highlight the necessity for a flexible shielding material with both high EES t and shielding SE values. Moreover, for practical applications, an environmentally favorable and scalable manufacturing process for the EMI shielding materials is urgently demanded, yet very challenging 2 , 21 . Borophene, often termed the boron analogue of graphene, represents a unique class of 2D material characterized by its presence in multiple phases, stemming from the arrangement and deficiency of boron atoms 22 , 23 . These phases encompass triangular, honeycomb, stripe and rectangular configurations, among others 24 . The diverse structural landscape of borophene, composed of the lightest solid element, underpins its ultralow density and distinguished flexibility, characterized by a high Young’s modulus 22 . Furthermore, borophene is predicted to have outstanding electronic mobility alongside a large carrier density, suggesting it is one of the very few metallic or semi–metallic 2D materials with high conductivity 25 , 26 . These properties render borophene an attractive candidate for embedding into polymer matrices to develop advanced flexible EMI shielding materials. However, the absence of a synthesis method for growing freestanding metallic borophene with high yield has hindered their developments on THz EMI shielding area, causing the low EES t smaller than 0.125 dB·cm 2 /g and SE lower than 42 dB 27 , 28 , far from fully utilizing its advantages. Here, we establish a scalable synthesis method for creating a wafer-scale composite of polydimethylsiloxane (PDMS) embedded with few-layer β 12 -Br single crystalline nanosheets 29 as conductive fillers. The resulting composite film can reach a maximum size of up to 5 inches and has a thickness ranging from 0.2 to 4 mm. The single-crystalline β 12 -Br fillers display superhigh-density free electrons (~ 3.4×10 19 m − 2 ) and large conductivity. These free electrons are excited by THz illumination, dissipating through scattering at the boundaries of the β 12 -Br nanosheets. This phenomenon significantly contributes to the exceptional performance of the composite film in THz EMI shielding. The film achieves a mean SE as high as over 70 dB and an ultrahigh EES t of 4.8 × 10 5 dB·cm 3 /g, the highest value to date as we know, across the 0.5 to 2 THz frequency range, with potential extension up to 10 THz. These results overwhelm those of previously reported EMI shielding materials designed for the THz spectral regime, which require at least 10 4 times more mass than the 2D borophene utilized in our current study to realize the comparable SE value. Additionally, the flexible composite film exhibits an ultrahigh tensile strain of over 158% at a Young’s modulus of 33 MPa, enabling effective shielding of conformably coated surfaces. The results undoubtedly underscore the potential of few-layer metallic β 12 -Br nanosheets as extremely efficient, low-density, and highly elastic materials for advanced THz shielding applications. Results and discussion Fabrication and characterization of β 12 -Br/PDMS composites The β 12 -Br comprises five atoms per unit cell, characterized by alternating rows of empty and filled hexagons along the x -direction. This arrangement usually produces stripes of vacancies along this axis. Along the y -direction, the structure consists of columns featuring a continuous line of atoms interspersed with incomplete hexagons, as shown in Fig. 1 a. The unique crystalline structure of β 12 -Br results in a high electron density (3.4 × 10 9 /m 2 ), accompanied by a large electron mobility (2.84 × 10 6 cm 2 /(V·s)) and a high Young’s modulus (382 GPa) 24 , 25 . Furthermore, it is the most stable among the various allotropes of borophene in its freestanding state 23 , 29 – 32 . In this study, the borophene nanosheets were synthesized by our developed low-temperature liquid phase exfoliation (LTLE) technique (see Methods for details) 33 , as depicted in Fig. 1 b. The crystalline structure and stoichiometric ratio of the products are respectively confirmed by X-ray diffraction (XRD) and confocal Raman spectroscopy, revealing the nanosheets are the β 12 phase with high crystallinity (Supplementary Figs. 1 and 2). The β 12 -Br nanosheets are a few atomic layers in thickness and well-dispersed into an aqueous solution, with an average thickness about 4 nm (Fig. 1 c, Supplementary Fig. 3) and a six-fold symmetry (Fig. 1 d, Supplementary Fig. 4). Additionally, over 94 at.% of the boron atoms remain unoxidized (Supplementary Figs. 5 and 6). It should be noted that fabricating robust, stretchable, and continuous thin film based on pure borophene nanosheets alone has significant challenges, especially when attempting to scale up to larger area 27 . Instead, we employ the β 12 -Br nanosheets as the fillers embedded into PDMS film to form a flexible composite. Specifically, the composite film was produced using a simple sol-gel method (Fig. 1 b), where the β 12 -Br nanosheets were intricately linked together via robust intermolecular bonding interactions involving hydrogen atoms from PDMS molecules and boron atoms located on the surface of the β 12 -Br (Fig. 1 a). This approach has been previously employed, where α -Br flakes were used as fillers 27 . However, due to the inefficient EMI shielding of α -Br reported in those studies, elevated concentration of borophene, up to 100 wt.%, was necessary. This undoubtedly causes the difficulties in achieving uniform and continuous thin films owe to potential cracking of the PDMS matrix. For the β 12 -Br, as discussed below, leveraging the ultrahigh EES t of the β 12 -Br allows for exceptionally low borophene content of less than 0.5 wt.% in the matrix and minimizing the breakage probability of PDMS intermolecular bond. This obvious decrease of the β 12 -Br content facilitates their homogeneous dispersion within the PDMS matrix (Fig. 1 f, inset), enabling the formation of flexible large-area thin films up to 5 inches (Fig. 1 e, f). In-situ electrical measurements are conducted on individual β 12 -Br nanosheet to explore its native electrical transport behaviors, as shown in Fig. 2 a. Based on the I-V characteristics exhibit a clear linear relationship (inset), the average electrical conductivity ( \(\:\stackrel{-}{{\sigma\:}_{B}}\) ) of individual nanosheets can be calculated to be about 3.0 × 10 4 S/m, suggesting their metallic conduction behaviors. It is noted that the electrical conductivity of a single β 12 -Br nanosheet with a 4-nm thickness is two orders of magnitude higher than that of individual MoS 2 (303.03 S/m) and WS 2 (416.67 S/m) 34 and close to that of graphene (~ 10 6 S/m) 35 . Figure 2 c gives the morphology and measurement circuit of bare β 12 -Br nanosheet film with a 400-nm thickness. As presented in Fig. 2 d, the mean sheet resistance ( \(\:\stackrel{-}{{R}_{S}}\) ) of the β 12 -Br nanosheet film is determined to be 1.7 × 10 4 Ω/sq according to the I-V curves (inset), which is approximately five orders of magnitude lower than that (6.0 × 10 9 Ω/sq) of the nanostructure film consisted of the mixed β 12 -Br and χ 3 -Br phases 36 , 37 . The above transport results prove the superior crystallinity and purity of β 12 -Br sheets synthesized by our method, suggesting the β 12 -Br nanosheets with ultrahigh electrical conductivity should have promising future in THz-wave EMI shielding. THz shielding performance and mechanism of β 12 -Br/PDMS composite film The THz-wave shielding performance of the β 12 -Br/PDMS composite film was evaluated using a THz time-domain spectroscope (THz-TDS) system, as given in the inset of Fig. 3 a. From Fig. 3 a, the excellent EMW shielding performances of 1-mm-thickness composite film can extend across a very wide frequency range from 0.1 to 7 THz, highlighting that the β 12 -Br/PDMS composite film serves as an ultra-broadband EMW shielding material. To better comprehend the contribution of different components to the THz shielding performance of the composite film, both the reflectance and transmittance spectra of the composite film are measured together to obtain the EMI absorption effectiveness (SE A ) and reflection effectiveness (SE R ), respectively. It is obviously seen that the average SE A reaches up to 60 dB while the SE R is only ~ 5 dB when the illumination frequency is larger than 0.2 THz, revealing that the absorption loss should dominate over the THz-wave shielding behaviors of β 12 -Br/PDMS composite film rather than the reflection or transmission loss. With a thickness of 2 mm and containing 0.13 wt.% of β 12 -Br, the EMI SE of the composite film can reach as high as 70 dB (Fig. 3 c). Furthermore, the EMI EES t , which offers a more comprehensive assessment of the shielding performance of the material under idealized conditions by considering the mass of the shielding material and the spot size of incident EMW (see Methods), is obtained to be in the range of 2.5 × 10 5 – 4.8 × 10 5 dB·cm 2 /g across the frequency range of 0.8 THz to 2 THz. Notably, several films, comprising of graphene or MXene composites among others, demonstrate the EMI SSE t maxima capped at 3 × 10 5 dB·cm 2 /g. However, these composite materials, even at concentrations of at least 5 wt.%, fell short of achieving the benchmark of 80 dB in terms of EMI SE (Fig. 3 d, Table S1 , Supporting Information). In stark contrast, the β 12 -Br/PDMS film, comprising a mere 0.13 wt.% weight fraction and measuring 2 mm in thickness, showcased an impressive average EMI SSE t of 4.8 × 10 5 dB·cm 2 /g. Furthermore, with an increase in the weight fraction to 0.5 wt.% and the thickness to 4 mm, the film attained an average EMI SE as high as 85 dB. Such comparison evidently underscores that despite of the evidently improved performance of the β 12 -Br/PDMS film, the mass of the shielding materials is four orders of magnitude smaller than that of other excellent shielding materials previously reported. A series of β 12 -Br/PDMS composite films were prepared to investigate the influence of the weight ratio (wt.%) of β 12 -Br nanosheets and the film thickness on the THz EMI shielding performance (Supplementary Fig. 7). The power of THz EMW is effectively dissipated by the composite film, specifically by the β 12 -Br nanosheets, which is elucidated by monitoring the SE spectra measured from composite films with varying concentrations of β 12 -Br nanosheet but identical thickness (2 mm). By progressively increasing the borophene content from 0.13 to 2.1 wt.%, the EMI SE initially experiences rapid augmentation, eventually reaching a plateau for mass ratios over 0.5 wt.%. Notably, the highest SE achieved can arrive at 76 dB at 0.87 THz for a mass ratio of 2.1 wt.%, unveiling that the EMW shielding of the composite film is primarily attributed to the addition of β 12 -Br nanosheets. The aforementioned results clearly show that even a small (2.1 wt.%) addition of β 12 -Br nanosheet into the polymer matrix can yield a superhigh EMI SE of 76 dB. This obviously surpasses previous findings, where an SE of only 42 dB was achieved with 100 wt.% of α -Br filled into the same matrix 27 . Most of all, for a weight ratio of 0.13 wt.%, the EMI SSE t can reach up to 4.8 × 10 5 dB·cm 3 /g, superior to all reported composite films with conductive fillers such as graphene and MXene (Fig. 3 d). Simultaneously, the EMI SE value of β 12 -Br/PDMS composite film can still maintain as high as 68 dB, which achieves the best value reported up to date. The addition of β 12 -Br nanosheet fillers is found to be very essential for evidently improving the THz shielding performance of composite film. If the filler is changed from bulk boron powers to the β 12 -Br nanosheets, the THz shielding performances of the composite film were significantly improved (Fig. 4 a). For instance, in a composite film with 0.13 wt.%, the SE already reaches as high as 68 dB at 0.87 THz. To probe the decisive factors of the EMW shielding performance of the β 12 -Br/PDMS composite film, the dependence of EMI SSE t on the mass ratio of borophene nanosheets is characterized, revealing a nonlinear increase with the reduction of the weight ratio (Fig. 4 b). The THz-wave shielding performance of the composite film is strongly dependent on the film thickness, as manifested from the EMI SE spectra against the film thickness (Fig. 4 c). If the weight ratio of borophene nanosheets was kept at 0.5 wt.%, both of the EMI SE and SSE t values monotonically increase with the film thickness (Fig. 4 d). Particularly, for a film thickness of 4 mm, the maximum EMI SE and SSE t can reach as high as 85 dB and 2.5 × 10 5 dB·cm 2 ·g − 1 at 0.87 THz, respectively. These results evidently demonstrate the exceptional EMW shielding performance of the β 12 -Br/PDMS composite film. Afterwards, the mechanism governing the strong THz EMW absorption of the β 12 -Br/PDMS composite film are further explored. The preceding discussion unambiguously suggests that the incident EMW are efficiently absorbed and dissipated by various β 12 -Br nanosheets within the composite film. Each single crystalline β 12 -Br nanosheet supports a high concentration of free electrons with large mobilities. Upon excitation by the THz wave, these free electrons become excited and accelerated by the electric field of the EMW, leading to collective oscillations. However, due to the small planar size of the borophene nanosheets (approximately 3 µm, Fig. 1 c), the electrons encounter boundaries and suffer from multiple reflections, ultimately losing their kinetic energies into the lattice of the β 12 -Br nanosheets, as seen in Fig. 4 e. In this manner, nearly all of the absorbed EMW are dissipated as heat, resulting in the ultrahigh EMI absorption effectiveness observed. This mechanism can be further supported by simulating the dynamics of electrons and the corresponding absorption of EMW energy within a β 12 -Br nanosheet (Methods and Supplementary Section 5). The behavior of free electrons in β 12 -Br nanosheet in response to the EMW is governed by the alternating-current conductivity, which can be characterized using the Drude model (Supplementary Figs. 8 and 9). For a disk-shaped sheet with a monolayer thickness, multiple electromagnetic resonances, characterized by strong absorption peaks, can be excited upon irradiation by the THz wave (Supplementary Fig. 10). As shown in Fig. 4 f, these resonances induce strong EMW localizations in β 12 -Br nanosheets, where the associated free electrons become localized and subsequently reflected by the disk boundary (Fig. 4 g). Accordingly, lots of Joule loss will occur within the borophene nanosheets (Fig. 4 h), which can be further confirmed by THz near-field optical measurements (Method) conducted on an individual β 12 -Br nanosheet (Fig. 4 i). As a result, the Joule loss leads to a very strong absorption efficiency of up to 50% at the resonance, even for a nanosheet with a monolayer thickness (Supplementary Fig. 10). It is noteworthy that, according to the simulation results, the resonance frequency of the β 12 -Br nanosheet is strongly dependent on its size and shape, covering a broad spectral range, for example, from 0.2 to 2 THz (Supplementary Fig. 10). However, the maximum absorption efficiency nearly remains unvaried at 50%, irrespective of the geometrical parameters of the borophene nanosheets (Supplementary Fig. 10). Consequently, the broadband yet relatively steady THz EMI absorption shielding performance of the β 12 -Br/PDMS composite film observed in our study should originate from the containing β 12 -Br nanosheet with varied thickness and shapes in the composite film. Interestingly, even after being exposed to air over 15 days, the EMI shielding performances of the β 12 -Br/PDMS composite film showed no obvious degradation and retained 92.94% of the original performance (Fig. 4 j), revealing the high stability of the β 12 -Br/PDMS film under ambient conditions. Mechanical properties of the β 12 -Br/PDMS composite film Good mechanical property is another critical requirement for THz EMW shielding materials in portable and wearable electronic devices 5 , 38 . By taking advantage of the exceptional Young’s modulus of β 12 -Br (theoretical value of 163 to 382 GPa) 39 , the composite film can be easily bent up to a high angle of 180° without any breakage or cracks observed through 500 bending experiments, revealing its excellent flexibility. Further uniaxial tensile experiments were conducted to quantitatively assess the elastic behavior of the composite film with various weight fractions of borophene nanosheets. It is noted that the 0.13 wt.% β 12 -Br/PDMS composite film exhibits a tensile strain, σ s , of 50% at a tensile stress, ε s , of 13 MPa, while that with 2.10 wt.% achieves a σ s of 158% at ε s = 33 MPa (Fig. 5 a). The corresponding Young’s moduli, E c = σ s / ε s × 100, 40 were approximately 26 MPa and 21 MPa, respectively. One can obviously see that the mechanical properties of the composite film are gradually enhanced with increasing the weight fraction of borophene, overwhelming those of many other high-modulus 2D materials (Table S2, Supporting Information). Also, this observed trend corroborates that the ultrahigh theoretical Young’s modulus of borophene nanosheets should be responsible for the excellent mechanical properties of the composite film. THz shielding measurements were then performed on the 2-mm-thickness composite film with 0.5 wt.% β 12 -Br nanosheets. After 500 bending cycles, the mean EMI SE value of the film slightly decreased from 81 dB to 75 dB, with an average fading rate as low as 0.015% per bending cycle (Fig. 5 b). Similarly, the mean THz EMI SE value of the composite film mildly reduced from 78 dB to 71 dB after 500 stretching cycles, with an average fading rate of less than 0.018% per stretching cycle (Fig. 5 c). Despite of these tiny attenuation, the sample can recover over 80% of its initial EMI SE efficiency for THz waves after both bending and stretching tests. These findings validate the great potential of β 12 -Br/PDMS composite film to combine high flexibility with superior mechanical strength, making them promising candidates for advanced flexible electronic applications. Application demonstration of the β 12 - Br/PDMS composite film The discussion above clearly exhibits the excellent THz shielding performance and flexibility of the β 12 -Br/PDMS composite film, which ensure them highly suitable for applications in EMW shielding of objects with irregular surfaces. To this end, the β 12 -Br/PDMS composite film was employed to conformably coated onto practical objects to show its excellent EMI SE upon THz EMW illumination. A 1-mm-thickness β 12 -Br/PDMS composite film was placed on the surface of a dry leaf for THz shielding imaging (Fig. 5 d). As observed in Fig. 5 e, the THz signal is almost completely absorbed where the composite film covers the leaf, causing the emergence of the shadow for imaging leaf. Additionally, the same composite film was wrapped around a human finger, effectively blocking off the THz signal at the wrapped region. Moreover, the composite film can also be fabricated into different patterns to match the outlines of target objects for demonstrating different characters, as presented in Fig. 5 f. It is obviously seen that the contour profile of “Sun Yat-sen University” is very clear and sharp, further showcasing the versatility of the composite film in being processed into EMW shielding materials with arbitrary shapes to meet diverse application requirements. Discussion Borophene, an important member of 2D material family, has attracted much attention since the birth due to its unique electrical and mechanical properties, as well as low mass density. While their applications in energy conversion and storage have been widely studied, their photonic and optoelectronic applications remain unexplored. The main obstacle lies in that it is still a challenging issue to produce freestanding borophene with high yield and high purity out of a variety of different phases. In this study, we demonstrate the successful applications of borophene in THz EMW shielding by developing a facile approach for creating composite film consisted of PDMS filled with single-phase and high-crystallinity few-layer β 12 -Br nanosheets of high conductivity. Such composite film, which can be scaled up to 5 inches and with tailorable thickness, exhibits an ultrahigh SE and EESt over 70 dB and 4.8 × 10 5 dB·cm 3 /g, respectively, with only 0.13 wt.% filling ratio of the β 12 -Br nanosheets. This successfully circumvents the trade-off between the amount of filling material used and the shielding effectiveness, which usually present in the previous reported EMI shielding materials designed for the THz spectral regime. Moreover, the remarkable mechanical property of single crystalline β 12 -Br nanosheets guarantees the composite film not only handily conforms to different object surfaces with various three-dimensional curvatures, but also produces efficient shielding on these objects. One possible application for our flexible composite film is to prevent the EMW pollution in electrical and optoelectrical circuits from the surrounding environment or adjacent neighborhoods in future 6G communication networks or large-scale integrated circuits. Besides, with its low-weight, high-efficiency, good-flexibility, and high-stability, and broadband shielding performances, the composite film based on β 12 -Br nanosheets could be successfully utilized in a wearable device for daily consumer electronics in the future. Methods Materials. Boron powders (99.8%, 325 mesh) were purchased from ZhongNuo (China) Co. Ltd. Polydimethylsiloxane (PDMS, SYLGARD 184) and N-methyl pyrrolidone (NMP, 99.8%) was bought from Dow–Corning (USA) Co. Ltd. and Innochem (China) Co. Ltd, respectively. Sample Fabrication. β 12 -Br nanosheets can be synthesized using our previously developed LTEP method 33 . And PDMS gel was prepared by mixing the base component with the hardener in a weight ratio of 10:1. The procedures to fabricate β 12 -Br/PDMS composite film are as follows. Firstly, the as-grown β 12 -Br nanosheet powders were dissolved into 1 mL deionized water via 30 min of bath ultrasonic dispersion, and subsequently added into the PDMS solvent to form the uniform sol by a 1 hour of continuous stirring. Secondly, the sol was coated on the surface of laboratory dish and sat for 2 days in air to realize the solidification of the gel. Finally, they were handed into the vacuum chamber and treated at 60 o C for about 12 hours to remove the residual moisture. Through the above procedures, the fabrication of large-area β 12 -Br/PDMS composite film was accomplished, as shown in Fig. 1 b. Characterization. The thickness of β 12 -Br nanosheets was measured by an atom force microscope (AFM, Bruker Dimension Icon). The morphology and crystalline structure of the nanosheets were investigated by a scanning electron microscope (SEM, Zeis Supra 60) and transmission electron microscope (TEM, FEI Titan 80–300). The scanning transmission electron microscope (STEM), energy disperse X-ray (EDX) mapping and electron energy loss spectroscopy (EELS) techniques were carried out in a JEM ARM200F thermal-field emission microscope with a Cs corrector probe working at 300 kV. For the high-angle annular dark field (HAADF) measurement, a convergence angle of about 21 mrad and collection angle range of 65–172 mrad were adopted for the incoherent atomic number imaging. The chemical compositions were analyzed by XRD patterns recorded on a D-MAX 2200 VPC system. The Raman spectrum of the β 12 -Br nanosheets was obtained by inVia Reflex (532 nm laser) made by Renishaw. And the current-voltage characteristics of the borophene nanosheet were tested in an ultra-high vacuum (UHV) probe made by Wavetest. Computational model of β 12 -Br nanosheet. The theoretically model of few-layer β 12 -Br nanosheet was obtained by the density functional theory (DFT), and more details can be found in our previous report 33 . THz Shielding Measurements. The THz shielding effectiveness of the samples was studied using a THz-TDS (Toptica) system at room temperature under N 2 . The samples were attached onto a hollow iron plate for test, and THz wave focused on the sample with a spot radius of 2.5 mm. The EMI SE of the material can be described by decibels (dB) and derived using the following equation: 5 EMI SE (dB) = \(\:\text{-}\text{20}{\text{log}}_{\text{10}}\left(\frac{{\text{E}}_{\text{in}}}{{\text{E}}_{\text{out}}}\right)\) (1) , where \(\:{\text{E}}_{\text{in}}\) and \(\:{\text{E}}_{\text{out}}\) denote the incident field strength and transmitted field intensity of THz waves, respectively. The EMI SSE t of the material can be calculated based on the following equation: 15 EMI SSE t (dB·cm 2 ·g − 1 ) = \(\:\frac{\text{EMI SE · }{\text{S}}^{\text{2}}}{\text{m}}\) (2) , where S and m respectively represent the area of the focal spot of THz wave and the mass of β 12 -Br nanosheets. THz Optical Nanoimaging. Optical nanoimaging was conducted on the samples using a scattering-type THz optical microscope (THz-NeaSNOM, Neaspec GmbH). To image the β 12 -Br nanosheet in real space, a THz laser with tunable frequency from 0.1 to 3 THz was focused onto both the sample and a metal-coated AFM tip (25PtIr200B-H, Rocky Mountain Nanotechnology) with a radius below 20 nm. The back-scattered light from the tip was demodulated and detected at a harmonic higher than that of the tip. Numerical Simulation. Because β 12 -Br nanosheet belongs to a metallic 2D material, its conductivity ( \(\:{\sigma\:}_{jj}\) ) can be obtained by the Drude model and written as: 41 , 42 $$\:{\sigma\:}_{jj}=\frac{i{D}_{j}}{\pi\:\left(\omega\:+\frac{i}{\tau\:}\right)}\:,\:{D}_{j}=\frac{\pi\:{e}^{2}n}{{m}_{j}}$$ 3 , where j represents the x or y direction of the optical axis of β 12 -Br nanosheet in our paper. In Eq. ( 3 ), \(\:e,\:n,\:\omega\:,\:\tau\:,\:{D}_{j}\) and \(\:{m}_{j}\) stand for electron charge, density of electrons, frequency of excitation, carrier lifetime, Drude weight along x or y direction, and effective electron mass in x and y directions, respectively. Therefore, the real ( \(\:{\epsilon\:}_{r,jj}\) ) and imaginary ( \(\:{\epsilon\:}_{i,jj}\) ) parts of the complex permittivity along each direction can be derived based on the following equation: $$\:{\epsilon\:}_{r,jj}={\epsilon\:}_{r}-\frac{{e}^{2}n}{{m}_{j}{\epsilon\:}_{0}h\left({\omega\:}^{2}+\frac{1}{{\tau\:}^{2}}\right)}\:,\:{\epsilon\:}_{i,jj}=\frac{\raisebox{1ex}{${e}^{2}n$}\!\left/\:\!\raisebox{-1ex}{$\tau\:$}\right.}{{m}_{j}{\epsilon\:}_{0}h\omega\:\left({\omega\:}^{2}+\frac{1}{\tau\:}\right)}$$ 4 , where \(\:{\epsilon\:}_{r}=\text{11}\) is the relative permittivity, \(\:{\epsilon\:}_{0}=\text{8.854}\times\:{\text{10}}^{\text{\--}\text{12}}\) F/m is the vacuum permittivity, and h represents the thickness of β 12 -Br nanosheet. The effective electron mass (m x /m y ) of β 12 -borophene nanosheet along x or y directions are respectively 3.5 m 0 and 3.7 m 0 , where \(\:{m}_{0}=\text{9.11}\times\:{\text{10}}^{\text{\--}\text{31}}\) kg is the mass of electron 25 . Using Matlab R2021b software, the permittivity spectra in the frequency range of 0.1 ̶ 2 THz of β 12 -Br nanosheets can be calculated according to Eqs. ( 3 ) and ( 4 ), where the carrier density ranges from 1.0 \(\:\times\:\) 10 19 to 5.0 \(\:\times\:\) 10 19 m − 2 and the mean free time of electrons varies from 3 \(\:\times\:\) 10 –14 to 12 \(\:\times\:\) 10 –14 s. And then, the permittivity spectra were imported into CST software to construct a β 12 -Br nanosheet. Finally, we carried out the finite-difference time-domain simulations (FDTD, Lumerical Inc.) to simulate the THz absorbance of β 12 -Br nanosheets. Declarations Data availability The authors declare that the main data supporting the findings of this study are available within the paper. Extra data are available from the corresponding authors upon reasonable request. Source data are provided with this paper. Online content Any methods, additional references, Nature Research reporting summaries, source data, extended data, supplementary information, acknowledgements, details of author contributions and competing interests; and statements of data and code availability are available at https://doi.org/xxxx . Competing interests The authors declare no competing interests. Author contributions S. D., H. C. and F. L. proposed and supervised the projects. H.L. synthesized the materials, characterized their surface morphology and chemical compositions, and carried out the THz shielding performances measurements. Z.C. and H.Z. simulated the absorption spectra of borophene in THz band by FTDT software. X.W. was responsible for the terahertz imaging of the β 12 -Br/PDMS composite film. J.W. created a flowchart illustrating the experimental process. All the authors involved in the analysis and discussion of the experimental results. And all authors approve to submit the final version of the manuscript. Acknowledgements The authors are very thankful for the support of the National Key Research and Development Program of China (2022YFA1203503), the National Science Foundation of China (Grant No. 51872337), Guangdong Basic and Applied Basic Research Foundation (Grant Nos. 2021A1515012592, 2020B1515020009), the Science and Technology Department of Guangdong Province (Grant No. 2020B1212060030), and Guangzhou Science and Technology Program (Grant 2024A04J6359). References Wu Z et al (2022) Dimensional design and core–shell engineering of nanomaterials for electromagnetic wave absorption. Adv Mater 34:2107538 Iqbal A, Hassan T, Naqvi SM, Gogotsi Y, Koo C (2024) M. MXenes for multispectral electromagnetic shielding. Nat Rev Electr Eng 1:180–198 Lv H et al (2023) Staggered circular nanoporous graphene converts electromagnetic waves into electricity. 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Nanomaterials 12:2702 Cuxart MG et al Borophenes made easy. Sci Adv 7, eabk1490 Kiraly B et al (2019) Borophene synthesis on Au(111). ACS Nano 13:3816–3822 Omambac KM et al (2021) Segregation-enhanced epitaxy of borophene on Ir(111) by thermal decomposition of borazine. ACS Nano 15:7421–7429 Liu X et al (2022) Borophene synthesis beyond the single-atomic-layer limit. Nat Mater 21:35–40 Lin H et al (2021) Scalable production of freestanding few-layer β 12 -borophene single crystalline sheets as efficient electrocatalysts for lithium-sulfur batteries. ACS Nano 15:17327–17336 Wang Y et al (2019) Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors. Nature 568:70–74 Novoselov KS et al (2004) Electric field effect in atomically thin carbon films. Science 306:666–669 Chahal S et al (2021) Borophene via micromechanical exfoliation. Adv Mater 33:2102039 Ranjan P et al (2019) Freestanding borophene and its hybrids. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4763119","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":336374786,"identity":"7fccc151-6215-4f15-9480-ad83e920162c","order_by":0,"name":"Huanjun 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China","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hongjia","middleName":"","lastName":"Zhu","suffix":""},{"id":336374791,"identity":"29234d46-5f98-4a2c-be5c-cc60cd603b2c","order_by":5,"name":"Jiahao Wu","email":"","orcid":"","institution":"Sun Yat-sen University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jiahao","middleName":"","lastName":"Wu","suffix":""},{"id":336374792,"identity":"5887ffa9-cad9-4747-a26e-f30b3b7f4761","order_by":6,"name":"Runze Zhan","email":"","orcid":"","institution":"Sun Yat-sen University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Runze","middleName":"","lastName":"Zhan","suffix":""},{"id":336374793,"identity":"67af82f0-578b-4d09-bde3-7df917d7364a","order_by":7,"name":"Ningsheng Xu","email":"","orcid":"","institution":"Guangdong Province Key Laboratory of Display Material and Technology, School of Electronics and Information Technology, Sun Yat-sen 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14:00:56","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4763119/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4763119/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-025-60892-1","type":"published","date":"2025-07-01T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":64878944,"identity":"d12c7db5-51a0-4d00-bf02-9d54e957cf3d","added_by":"auto","created_at":"2024-09-20 02:41:10","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":66920736,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacterization and THz shielding measurements of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eβ\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cstrong\u003e12\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e-Br/PDMS composite film. a,\u003c/strong\u003e A schematic diagram illustrating the preparation process of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets and \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film. \u003cstrong\u003eb,\u003c/strong\u003e The production route for \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film. \u003cstrong\u003ec,\u003c/strong\u003e An AFM image displaying the topography of few-layer \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets synthesized by LTLE way, where the monolayer thickness is indicated by the inserted height profile. \u003cstrong\u003ed,\u003c/strong\u003e A typical HRTEM image of a \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet, with the inset presenting the theoretical surface configuration of borophene (001) face using density functional theory (DFT). \u003cstrong\u003ee,\u003c/strong\u003e Representative photograph showcasing the as-synthesized centimeter-scale \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film. \u003cstrong\u003ef,\u003c/strong\u003e A photograph demonstrating the excellent flexibility of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film, with an inset showing the corresponding cross-section image. \u003cstrong\u003eg,\u003c/strong\u003e The frequency-dependence analysis of EMI SE curves of the 4-mm-thickness composite film with a 0.5 wt.% \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets before and after undergoing 500 bending cycles. \u003cstrong\u003eh,\u003c/strong\u003e Comparison between EMI SE, and EMI SSE\u003csub\u003et\u003c/sub\u003e values obtained from \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS film and other excellent shielding materials.\u003c/p\u003e","description":"","filename":"image1.tiff.png","url":"https://assets-eu.researchsquare.com/files/rs-4763119/v1/8800841749e321e0381c4dee.png"},{"id":64878536,"identity":"5d89c6f8-03e4-4473-8ae7-20253bc6b7ac","added_by":"auto","created_at":"2024-09-20 02:33:10","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":79451791,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEMI shielding properties of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eβ\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cstrong\u003e12\u003c/strong\u003e\u003c/sub\u003e-\u003cstrong\u003eBr/PDMS composite film.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, The EMI SE curves of the composite film with various weight fractions of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets. \u003cstrong\u003eb\u003c/strong\u003e, The curves of EMI SE/EMI SSE\u003csub\u003et\u003c/sub\u003e to the weight fraction of borophene nanosheets at 0.87 THz. \u003cstrong\u003ec\u003c/strong\u003e, The frequency-dependent EMI SE curves of the composite film with different thickness. \u003cstrong\u003ed\u003c/strong\u003e, The relationship between EMI SE/EMI SSE\u003csub\u003et\u003c/sub\u003e and film thickness at 0.87 THz. \u003cstrong\u003ee\u003c/strong\u003e, Schematic showing the excitation of electron oscillations in \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets under THz radiation. \u003cstrong\u003ef–h\u003c/strong\u003e, Characterization of the simulated charge density, joule loss and energy density of individual \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet in the frequency range of 0.1 – 2 THz. \u003cstrong\u003ei\u003c/strong\u003e, The THz near-field image of a single \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet on a SiO\u003csub\u003e2\u003c/sub\u003e wafer. \u003cstrong\u003ej\u003c/strong\u003e, The EMI SE stability of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film after 15 days’ air storage.\u003c/p\u003e","description":"","filename":"image2.tiff.png","url":"https://assets-eu.researchsquare.com/files/rs-4763119/v1/a0a22af579962d190f793d04.png"},{"id":64878534,"identity":"3cbb04a6-8c62-4300-a6bf-71c788012d76","added_by":"auto","created_at":"2024-09-20 02:33:10","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":47792898,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMechanical properties of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eβ\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cstrong\u003e12\u003c/strong\u003e\u003c/sub\u003e-\u003cstrong\u003eBr/PDMS composite films and their THz shielding applications. a\u003c/strong\u003e, Representative stress-strain curves of the 2-mm-thickness composite film with different borophene contents in uniaxial tensile test. The inset at the top left corner shows a photograph of the composite film undergoing tensile testing. \u003cstrong\u003eb\u003c/strong\u003e, EMI SE values of the composite film after 500 times’ bending or stretching measurements. The photograph of the composite film undergoing bending is displayed in the inset. \u003cstrong\u003ec\u003c/strong\u003e, The EMI SE value and EMI SE decay ratio of the composite film at 0.87 THz during 500 bending or stretching cycles, respectively. \u003cstrong\u003ed\u003c/strong\u003e, \u003cstrong\u003ee\u003c/strong\u003e, Digital images of the leaf coating and the human finger coated by the planar and curved composite film, respectively, in which the THz wave is effectively shielded and the inner information can’t be differentiated.\u0026nbsp; \u003cstrong\u003ef\u003c/strong\u003e, THz imaging of the Sun Yat-sen University masked by shaped \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film.\u003c/p\u003e","description":"","filename":"image3.tiff.png","url":"https://assets-eu.researchsquare.com/files/rs-4763119/v1/647a3fc0fdb1b883bb9192b8.png"},{"id":64878533,"identity":"cdd8ce6b-6f2b-41f7-ae6e-4b4a2a79ee54","added_by":"auto","created_at":"2024-09-20 02:33:10","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":39076374,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformationBoropheneforTHzEMshieldingNM20240718.docx","url":"https://assets-eu.researchsquare.com/files/rs-4763119/v1/6543c2a015d1ae06f42dbd87.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Harmonizing Material Quantity and Terahertz Wave Interference Shielding Efficiency with Metallic Borophene Nanosheets","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTHz radiation, spanning from 0.1 to 10 THz in frequency, represents a frontier in technology with vast potential across multiple applications including information communications, radar imaging, noninvasive inspection, and biomedical sensing\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Its appeal lies in distinctive characteristics, such as low photon energy, robust penetration capabilities and the ability to discern characteristic molecular signatures within this spectral range. However, despite its promise, THz electronic and optoelectronic devices are not immune to electromagnetic interference (EMI) pollution, a challenge well-known in the radio-frequency realm\u003csup\u003e\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Such interference can markedly degrade device performance and do harm to the surrounding environment, underscoring the need for effective EMI shielding materials.\u003c/p\u003e \u003cp\u003eAn ideal EMI shielding material should effectively block electromagnetic waves (EMW) while simultaneously ensure that the isolated electromagnetic field does not emit into the surrounding environment. Meanwhile, such a material is also anticipated to be low-cost and easily producible, lightweight and possess good stretchability, enabling it to conform to arbitrary surfaces. This flexibility is particularly crucial for effective EMI shielding in wearable devices and portable equipment for consumer electronics.\u003c/p\u003e \u003cp\u003eCurrently, research on THz EMW shielding materials follows two main approaches. On one hand, traditional materials originally designed for the microwave frequency range are still utilized, such as metal thin films\u003csup\u003e\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e and carbon-based composite films, including conductive carbon inks\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e, carbon fibers\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, carbon nanotubes\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e, and graphene\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. These materials are highly conductive and inhibit EMW through reflection, resulting in a significant portion of the waves being radiated into the surrounding environment, thus producing secondary pollution\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. This inherent characteristic renders them less suitable for serving as EMI shielding materials in miniaturized devices with a demand of high integration. Alternatively, EMW can be shielded through absorption by the charged carriers within the EMI shielding materials. This has led to a recent shift in research focus towards exploring new-type materials with high electromagnetic absorption properties. These materials include polymer composite films\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e, nanocomposite films\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, multilayer assemblies\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e, porous foams/aerogel composites\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, and so on. Typically, these materials consist of segregated conductive fillers with a high density of free electrons with large mobility, facilitating the absorption of EMW through scattering at defects and interfaces presenting on each filler surface, followed by re-absorption by the free electrons. In particular two\u0026ndash;dimensional (2D) conductive materials, such as MXene and graphene, have recently been employed as the fillers due to their outstanding electrically conductive characteristics. For example, a very recent study demonstrates that MXene assemblies can approach the intrinsic absorption limit in the 0.5\u0026ndash;10 THz frequency range, with a small thickness of 10.2 nm\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. A thin graphene/PMMA nanolaminate composite is displayed with a high conductivity to exhibit a shielding effectiveness (SE) reaching 60 dB for a small thickness of 33 \u0026micro;m\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Our recent study indicates that a transparent MXene film can have an SE of 21 dB over a wide frequency range of 0.1\u0026ndash;10 THz\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eWhile these exciting results provide a pathway for developing high-performance THz EMI shielding materials, there usually needs a trade-off between the mass amount of material used and the shielding effectiveness. This typically leads to an absolute EMI shielding effectiveness (EES\u003csub\u003et\u003c/sub\u003e) of less than 3 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e/g and an SE smaller than 60 dB (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, Supporting Information)\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. To further enhance the shielding performance of these materials, an increased filler content or increment of the material\u0026rsquo;s thickness is usually necessary. However, this inevitably increases the overall mass and thickness of EMI shielding material, which could compromise their mechanical stability and limit their developments in portable and miniaturized devices requiring lightweight, flexible, and conformable coatings. All these requirements highlight the necessity for a flexible shielding material with both high EES\u003csub\u003et\u003c/sub\u003e and shielding SE values. Moreover, for practical applications, an environmentally favorable and scalable manufacturing process for the EMI shielding materials is urgently demanded, yet very challenging\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBorophene, often termed the boron analogue of graphene, represents a unique class of 2D material characterized by its presence in multiple phases, stemming from the arrangement and deficiency of boron atoms\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. These phases encompass triangular, honeycomb, stripe and rectangular configurations, among others\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. The diverse structural landscape of borophene, composed of the lightest solid element, underpins its ultralow density and distinguished flexibility, characterized by a high Young\u0026rsquo;s modulus\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Furthermore, borophene is predicted to have outstanding electronic mobility alongside a large carrier density, suggesting it is one of the very few metallic or semi\u0026ndash;metallic 2D materials with high conductivity\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. These properties render borophene an attractive candidate for embedding into polymer matrices to develop advanced flexible EMI shielding materials. However, the absence of a synthesis method for growing freestanding metallic borophene with high yield has hindered their developments on THz EMI shielding area, causing the low EES\u003csub\u003et\u003c/sub\u003e smaller than 0.125 dB\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e/g and SE lower than 42 dB\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, far from fully utilizing its advantages.\u003c/p\u003e \u003cp\u003eHere, we establish a scalable synthesis method for creating a wafer-scale composite of polydimethylsiloxane (PDMS) embedded with few-layer \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br single crystalline nanosheets\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e as conductive fillers. The resulting composite film can reach a maximum size of up to 5 inches and has a thickness ranging from 0.2 to 4 mm. The single-crystalline \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br fillers display superhigh-density free electrons (~\u0026thinsp;3.4\u0026times;10\u003csup\u003e19\u003c/sup\u003e m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) and large conductivity. These free electrons are excited by THz illumination, dissipating through scattering at the boundaries of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets. This phenomenon significantly contributes to the exceptional performance of the composite film in THz EMI shielding. The film achieves a mean SE as high as over 70 dB and an ultrahigh EES\u003csub\u003et\u003c/sub\u003e of 4.8 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e3\u003c/sup\u003e/g, the highest value to date as we know, across the 0.5 to 2 THz frequency range, with potential extension up to 10 THz. These results overwhelm those of previously reported EMI shielding materials designed for the THz spectral regime, which require at least 10\u003csup\u003e4\u003c/sup\u003e times more mass than the 2D borophene utilized in our current study to realize the comparable SE value. Additionally, the flexible composite film exhibits an ultrahigh tensile strain of over 158% at a Young\u0026rsquo;s modulus of 33 MPa, enabling effective shielding of conformably coated surfaces. The results undoubtedly underscore the potential of few-layer metallic \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets as extremely efficient, low-density, and highly elastic materials for advanced THz shielding applications.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e \u003cb\u003eFabrication and characterization of\u003c/b\u003e \u003cb\u003eβ\u003c/b\u003e\u003csub\u003e\u003cb\u003e12\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e-Br/PDMS composites\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br comprises five atoms per unit cell, characterized by alternating rows of empty and filled hexagons along the \u003cem\u003ex\u003c/em\u003e-direction. This arrangement usually produces stripes of vacancies along this axis. Along the \u003cem\u003ey\u003c/em\u003e-direction, the structure consists of columns featuring a continuous line of atoms interspersed with incomplete hexagons, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea. The unique crystalline structure of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br results in a high electron density (3.4 \u0026times; 10\u003csup\u003e9\u003c/sup\u003e/m\u003csup\u003e2\u003c/sup\u003e), accompanied by a large electron mobility (2.84 \u0026times; 10\u003csup\u003e6\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e/(V\u0026middot;s)) and a high Young\u0026rsquo;s modulus (382 GPa) \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Furthermore, it is the most stable among the various allotropes of borophene in its freestanding state\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan additionalcitationids=\"CR30 CR31\" citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. In this study, the borophene nanosheets were synthesized by our developed low-temperature liquid phase exfoliation (LTLE) technique (see Methods for details)\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb. The crystalline structure and stoichiometric ratio of the products are respectively confirmed by X-ray diffraction (XRD) and confocal Raman spectroscopy, revealing the nanosheets are the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e phase with high crystallinity (Supplementary Figs.\u0026nbsp;1 and 2). The \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets are a few atomic layers in thickness and well-dispersed into an aqueous solution, with an average thickness about 4 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec, Supplementary Fig.\u0026nbsp;3) and a six-fold symmetry (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed, Supplementary Fig.\u0026nbsp;4). Additionally, over 94 at.% of the boron atoms remain unoxidized (Supplementary Figs.\u0026nbsp;5 and 6).\u003c/p\u003e \u003cp\u003eIt should be noted that fabricating robust, stretchable, and continuous thin film based on pure borophene nanosheets alone has significant challenges, especially when attempting to scale up to larger area\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Instead, we employ the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets as the fillers embedded into PDMS film to form a flexible composite. Specifically, the composite film was produced using a simple sol-gel method (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), where the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets were intricately linked together \u003cem\u003evia\u003c/em\u003e robust intermolecular bonding interactions involving hydrogen atoms from PDMS molecules and boron atoms located on the surface of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). This approach has been previously employed, where \u003cem\u003eα\u003c/em\u003e-Br flakes were used as fillers\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. However, due to the inefficient EMI shielding of \u003cem\u003eα\u003c/em\u003e-Br reported in those studies, elevated concentration of borophene, up to 100 wt.%, was necessary. This undoubtedly causes the difficulties in achieving uniform and continuous thin films owe to potential cracking of the PDMS matrix. For the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br, as discussed below, leveraging the ultrahigh EES\u003csub\u003et\u003c/sub\u003e of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br allows for exceptionally low borophene content of less than 0.5 wt.% in the matrix and minimizing the breakage probability of PDMS intermolecular bond. This obvious decrease of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br content facilitates their homogeneous dispersion within the PDMS matrix (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef, inset), enabling the formation of flexible large-area thin films up to 5 inches (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee, f).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn-situ electrical measurements are conducted on individual \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet to explore its native electrical transport behaviors, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. Based on the I-V characteristics exhibit a clear linear relationship (inset), the average electrical conductivity (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{{\\sigma\\:}_{B}}\\)\u003c/span\u003e\u003c/span\u003e) of individual nanosheets can be calculated to be about 3.0 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e S/m, suggesting their metallic conduction behaviors. It is noted that the electrical conductivity of a single \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet with a 4-nm thickness is two orders of magnitude higher than that of individual MoS\u003csub\u003e2\u003c/sub\u003e (303.03 S/m) and WS\u003csub\u003e2\u003c/sub\u003e (416.67 S/m)\u003csup\u003e34\u003c/sup\u003e and close to that of graphene (~\u0026thinsp;10\u003csup\u003e6\u003c/sup\u003e S/m)\u003csup\u003e35\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec gives the morphology and measurement circuit of bare \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet film with a 400-nm thickness. As presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed, the mean sheet resistance (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{{R}_{S}}\\)\u003c/span\u003e\u003c/span\u003e) of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet film is determined to be 1.7 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e Ω/sq according to the I-V curves (inset), which is approximately five orders of magnitude lower than that (6.0 \u0026times; 10\u003csup\u003e9\u003c/sup\u003e Ω/sq) of the nanostructure film consisted of the mixed \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br and \u003cem\u003eχ\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e-Br phases\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. The above transport results prove the superior crystallinity and purity of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br sheets synthesized by our method, suggesting the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets with ultrahigh electrical conductivity should have promising future in THz-wave EMI shielding.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eTHz shielding performance and mechanism of\u003c/b\u003e \u003cb\u003eβ\u003c/b\u003e\u003csub\u003e\u003cb\u003e12\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e-Br/PDMS composite film\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe THz-wave shielding performance of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film was evaluated using a THz time-domain spectroscope (THz-TDS) system, as given in the inset of Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea. From Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, the excellent EMW shielding performances of 1-mm-thickness composite film can extend across a very wide frequency range from 0.1 to 7 THz, highlighting that the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film serves as an ultra-broadband EMW shielding material. To better comprehend the contribution of different components to the THz shielding performance of the composite film, both the reflectance and transmittance spectra of the composite film are measured together to obtain the EMI absorption effectiveness (SE\u003csub\u003eA\u003c/sub\u003e) and reflection effectiveness (SE\u003csub\u003eR\u003c/sub\u003e), respectively. It is obviously seen that the average SE\u003csub\u003eA\u003c/sub\u003e reaches up to 60 dB while the SE\u003csub\u003eR\u003c/sub\u003e is only\u0026thinsp;~\u0026thinsp;5 dB when the illumination frequency is larger than 0.2 THz, revealing that the absorption loss should dominate over the THz-wave shielding behaviors of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film rather than the reflection or transmission loss. With a thickness of 2 mm and containing 0.13 wt.% of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br, the EMI SE of the composite film can reach as high as 70 dB (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). Furthermore, the EMI EES\u003csub\u003et\u003c/sub\u003e, which offers a more comprehensive assessment of the shielding performance of the material under idealized conditions by considering the mass of the shielding material and the spot size of incident EMW (see Methods), is obtained to be in the range of 2.5 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e \u0026ndash; 4.8 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e/g across the frequency range of 0.8 THz to 2 THz. Notably, several films, comprising of graphene or MXene composites among others, demonstrate the EMI SSE\u003csub\u003et\u003c/sub\u003e maxima capped at 3 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e/g. However, these composite materials, even at concentrations of at least 5 wt.%, fell short of achieving the benchmark of 80 dB in terms of EMI SE (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, Supporting Information). In stark contrast, the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS film, comprising a mere 0.13 wt.% weight fraction and measuring 2 mm in thickness, showcased an impressive average EMI SSE\u003csub\u003et\u003c/sub\u003e of 4.8 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e/g. Furthermore, with an increase in the weight fraction to 0.5 wt.% and the thickness to 4 mm, the film attained an average EMI SE as high as 85 dB. Such comparison evidently underscores that despite of the evidently improved performance of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS film, the mass of the shielding materials is four orders of magnitude smaller than that of other excellent shielding materials previously reported.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA series of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite films were prepared to investigate the influence of the weight ratio (wt.%) of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets and the film thickness on the THz EMI shielding performance (Supplementary Fig.\u0026nbsp;7). The power of THz EMW is effectively dissipated by the composite film, specifically by the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e\u003cem\u003e12\u003c/em\u003e\u003c/sub\u003e-Br nanosheets, which is elucidated by monitoring the SE spectra measured from composite films with varying concentrations of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet but identical thickness (2 mm). By progressively increasing the borophene content from 0.13 to 2.1 wt.%, the EMI SE initially experiences rapid augmentation, eventually reaching a plateau for mass ratios over 0.5 wt.%. Notably, the highest SE achieved can arrive at 76 dB at 0.87 THz for a mass ratio of 2.1 wt.%, unveiling that the EMW shielding of the composite film is primarily attributed to the addition of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets.\u003c/p\u003e \u003cp\u003eThe aforementioned results clearly show that even a small (2.1 wt.%) addition of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet into the polymer matrix can yield a superhigh EMI SE of 76 dB. This obviously surpasses previous findings, where an SE of only 42 dB was achieved with 100 wt.% of \u003cem\u003eα\u003c/em\u003e-Br filled into the same matrix\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Most of all, for a weight ratio of 0.13 wt.%, the EMI SSE\u003csub\u003et\u003c/sub\u003e can reach up to 4.8 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e3\u003c/sup\u003e/g, superior to all reported composite films with conductive fillers such as graphene and MXene (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). Simultaneously, the EMI SE value of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film can still maintain as high as 68 dB, which achieves the best value reported up to date.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe addition of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet fillers is found to be very essential for evidently improving the THz shielding performance of composite film. If the filler is changed from bulk boron powers to the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets, the THz shielding performances of the composite film were significantly improved (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). For instance, in a composite film with 0.13 wt.%, the SE already reaches as high as 68 dB at 0.87 THz. To probe the decisive factors of the EMW shielding performance of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film, the dependence of EMI SSE\u003csub\u003et\u003c/sub\u003e on the mass ratio of borophene nanosheets is characterized, revealing a nonlinear increase with the reduction of the weight ratio (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). The THz-wave shielding performance of the composite film is strongly dependent on the film thickness, as manifested from the EMI SE spectra against the film thickness (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). If the weight ratio of borophene nanosheets was kept at 0.5 wt.%, both of the EMI SE and SSE\u003csub\u003et\u003c/sub\u003e values monotonically increase with the film thickness (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). Particularly, for a film thickness of 4 mm, the maximum EMI SE and SSE\u003csub\u003et\u003c/sub\u003e can reach as high as 85 dB and 2.5 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 0.87 THz, respectively. These results evidently demonstrate the exceptional EMW shielding performance of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film.\u003c/p\u003e \u003cp\u003eAfterwards, the mechanism governing the strong THz EMW absorption of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film are further explored. The preceding discussion unambiguously suggests that the incident EMW are efficiently absorbed and dissipated by various \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets within the composite film. Each single crystalline \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet supports a high concentration of free electrons with large mobilities. Upon excitation by the THz wave, these free electrons become excited and accelerated by the electric field of the EMW, leading to collective oscillations. However, due to the small planar size of the borophene nanosheets (approximately 3 \u0026micro;m, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), the electrons encounter boundaries and suffer from multiple reflections, ultimately losing their kinetic energies into the lattice of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee. In this manner, nearly all of the absorbed EMW are dissipated as heat, resulting in the ultrahigh EMI absorption effectiveness observed.\u003c/p\u003e \u003cp\u003eThis mechanism can be further supported by simulating the dynamics of electrons and the corresponding absorption of EMW energy within a \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet (Methods and Supplementary Section 5). The behavior of free electrons in \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet in response to the EMW is governed by the alternating-current conductivity, which can be characterized using the Drude model (Supplementary Figs.\u0026nbsp;8 and 9). For a disk-shaped sheet with a monolayer thickness, multiple electromagnetic resonances, characterized by strong absorption peaks, can be excited upon irradiation by the THz wave (Supplementary Fig.\u0026nbsp;10). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef, these resonances induce strong EMW localizations in \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets, where the associated free electrons become localized and subsequently reflected by the disk boundary (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg). Accordingly, lots of Joule loss will occur within the borophene nanosheets (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh), which can be further confirmed by THz near-field optical measurements (Method) conducted on an individual \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ei). As a result, the Joule loss leads to a very strong absorption efficiency of up to 50% at the resonance, even for a nanosheet with a monolayer thickness (Supplementary Fig.\u0026nbsp;10).\u003c/p\u003e \u003cp\u003eIt is noteworthy that, according to the simulation results, the resonance frequency of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet is strongly dependent on its size and shape, covering a broad spectral range, for example, from 0.2 to 2 THz (Supplementary Fig.\u0026nbsp;10). However, the maximum absorption efficiency nearly remains unvaried at 50%, irrespective of the geometrical parameters of the borophene nanosheets (Supplementary Fig.\u0026nbsp;10). Consequently, the broadband yet relatively steady THz EMI absorption shielding performance of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film observed in our study should originate from the containing \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet with varied thickness and shapes in the composite film.\u003c/p\u003e \u003cp\u003eInterestingly, even after being exposed to air over 15 days, the EMI shielding performances of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film showed no obvious degradation and retained 92.94% of the original performance (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ej), revealing the high stability of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS film under ambient conditions.\u003c/p\u003e \u003cp\u003e \u003cb\u003eMechanical properties of the\u003c/b\u003e \u003cb\u003eβ\u003c/b\u003e\u003csub\u003e\u003cb\u003e12\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e-Br/PDMS composite film\u003c/b\u003e\u003c/p\u003e \u003cp\u003eGood mechanical property is another critical requirement for THz EMW shielding materials in portable and wearable electronic devices\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. By taking advantage of the exceptional Young\u0026rsquo;s modulus of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br (theoretical value of 163 to 382 GPa)\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e, the composite film can be easily bent up to a high angle of 180\u0026deg; without any breakage or cracks observed through 500 bending experiments, revealing its excellent flexibility. Further uniaxial tensile experiments were conducted to quantitatively assess the elastic behavior of the composite film with various weight fractions of borophene nanosheets. It is noted that the 0.13 wt.% \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film exhibits a tensile strain, \u003cem\u003eσ\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e, of 50% at a tensile stress, \u003cem\u003eε\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e, of 13 MPa, while that with 2.10 wt.% achieves a \u003cem\u003eσ\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e of 158% at \u003cem\u003eε\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;33 MPa (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). The corresponding Young\u0026rsquo;s moduli, E\u003csub\u003ec\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003eσ\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e/\u003cem\u003eε\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e\u0026thinsp;\u0026times;\u0026thinsp;100,\u003csup\u003e40\u003c/sup\u003e were approximately 26 MPa and 21 MPa, respectively. One can obviously see that the mechanical properties of the composite film are gradually enhanced with increasing the weight fraction of borophene, overwhelming those of many other high-modulus 2D materials (Table S2, Supporting Information). Also, this observed trend corroborates that the ultrahigh theoretical Young\u0026rsquo;s modulus of borophene nanosheets should be responsible for the excellent mechanical properties of the composite film.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTHz shielding measurements were then performed on the 2-mm-thickness composite film with 0.5 wt.% \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets. After 500 bending cycles, the mean EMI SE value of the film slightly decreased from 81 dB to 75 dB, with an average fading rate as low as 0.015% per bending cycle (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). Similarly, the mean THz EMI SE value of the composite film mildly reduced from 78 dB to 71 dB after 500 stretching cycles, with an average fading rate of less than 0.018% per stretching cycle (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec). Despite of these tiny attenuation, the sample can recover over 80% of its initial EMI SE efficiency for THz waves after both bending and stretching tests. These findings validate the great potential of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film to combine high flexibility with superior mechanical strength, making them promising candidates for advanced flexible electronic applications.\u003c/p\u003e \u003cp\u003e \u003cb\u003eApplication demonstration of the\u003c/b\u003e \u003cb\u003eβ\u003c/b\u003e\u003csub\u003e\u003cb\u003e12\u003c/b\u003e\u003c/sub\u003e-\u003cb\u003eBr/PDMS composite film\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe discussion above clearly exhibits the excellent THz shielding performance and flexibility of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film, which ensure them highly suitable for applications in EMW shielding of objects with irregular surfaces. To this end, the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film was employed to conformably coated onto practical objects to show its excellent EMI SE upon THz EMW illumination. A 1-mm-thickness \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film was placed on the surface of a dry leaf for THz shielding imaging (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed). As observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee, the THz signal is almost completely absorbed where the composite film covers the leaf, causing the emergence of the shadow for imaging leaf. Additionally, the same composite film was wrapped around a human finger, effectively blocking off the THz signal at the wrapped region. Moreover, the composite film can also be fabricated into different patterns to match the outlines of target objects for demonstrating different characters, as presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef. It is obviously seen that the contour profile of \u0026ldquo;Sun Yat-sen University\u0026rdquo; is very clear and sharp, further showcasing the versatility of the composite film in being processed into EMW shielding materials with arbitrary shapes to meet diverse application requirements.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eBorophene, an important member of 2D material family, has attracted much attention since the birth due to its unique electrical and mechanical properties, as well as low mass density. While their applications in energy conversion and storage have been widely studied, their photonic and optoelectronic applications remain unexplored. The main obstacle lies in that it is still a challenging issue to produce freestanding borophene with high yield and high purity out of a variety of different phases. In this study, we demonstrate the successful applications of borophene in THz EMW shielding by developing a facile approach for creating composite film consisted of PDMS filled with single-phase and high-crystallinity few-layer \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets of high conductivity. Such composite film, which can be scaled up to 5 inches and with tailorable thickness, exhibits an ultrahigh SE and EESt over 70 dB and 4.8 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e dB\u0026middot;cm\u003csup\u003e3\u003c/sup\u003e/g, respectively, with only 0.13 wt.% filling ratio of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets. This successfully circumvents the trade-off between the amount of filling material used and the shielding effectiveness, which usually present in the previous reported EMI shielding materials designed for the THz spectral regime.\u003c/p\u003e \u003cp\u003eMoreover, the remarkable mechanical property of single crystalline \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets guarantees the composite film not only handily conforms to different object surfaces with various three-dimensional curvatures, but also produces efficient shielding on these objects. One possible application for our flexible composite film is to prevent the EMW pollution in electrical and optoelectrical circuits from the surrounding environment or adjacent neighborhoods in future 6G communication networks or large-scale integrated circuits. Besides, with its low-weight, high-efficiency, good-flexibility, and high-stability, and broadband shielding performances, the composite film based on \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets could be successfully utilized in a wearable device for daily consumer electronics in the future.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e \u003cb\u003eMaterials.\u003c/b\u003e Boron powders (99.8%, 325 mesh) were purchased from ZhongNuo (China) Co. Ltd. Polydimethylsiloxane (PDMS, SYLGARD 184) and N-methyl pyrrolidone (NMP, 99.8%) was bought from Dow\u0026ndash;Corning (USA) Co. Ltd. and Innochem (China) Co. Ltd, respectively.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSample Fabrication.\u003c/b\u003e \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets can be synthesized using our previously developed LTEP method\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. And PDMS gel was prepared by mixing the base component with the hardener in a weight ratio of 10:1.\u003c/p\u003e \u003cp\u003eThe procedures to fabricate \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film are as follows. Firstly, the as-grown \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet powders were dissolved into 1 mL deionized water via 30 min of bath ultrasonic dispersion, and subsequently added into the PDMS solvent to form the uniform sol by a 1 hour of continuous stirring. Secondly, the sol was coated on the surface of laboratory dish and sat for 2 days in air to realize the solidification of the gel. Finally, they were handed into the vacuum chamber and treated at 60 \u003csup\u003eo\u003c/sup\u003eC for about 12 hours to remove the residual moisture. Through the above procedures, the fabrication of large-area \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film was accomplished, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb.\u003c/p\u003e \u003cp\u003e \u003cb\u003eCharacterization.\u003c/b\u003e The thickness of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets was measured by an atom force microscope (AFM, Bruker Dimension Icon). The morphology and crystalline structure of the nanosheets were investigated by a scanning electron microscope (SEM, Zeis Supra 60) and transmission electron microscope (TEM, FEI Titan 80\u0026ndash;300). The scanning transmission electron microscope (STEM), energy disperse X-ray (EDX) mapping and electron energy loss spectroscopy (EELS) techniques were carried out in a JEM ARM200F thermal-field emission microscope with a Cs corrector probe working at 300 kV. For the high-angle annular dark field (HAADF) measurement, a convergence angle of about 21 mrad and collection angle range of 65\u0026ndash;172 mrad were adopted for the incoherent atomic number imaging. The chemical compositions were analyzed by XRD patterns recorded on a D-MAX 2200 VPC system. The Raman spectrum of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets was obtained by inVia Reflex (532 nm laser) made by Renishaw. And the current-voltage characteristics of the borophene nanosheet were tested in an ultra-high vacuum (UHV) probe made by Wavetest.\u003c/p\u003e \u003cp\u003e \u003cb\u003eComputational model of\u003c/b\u003e \u003cb\u003eβ\u003c/b\u003e\u003csub\u003e\u003cb\u003e12\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e-Br nanosheet.\u003c/b\u003e The theoretically model of few-layer \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet was obtained by the density functional theory (DFT), and more details can be found in our previous report\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTHz Shielding Measurements.\u003c/b\u003e The THz shielding effectiveness of the samples was studied using a THz-TDS (Toptica) system at room temperature under N\u003csub\u003e2\u003c/sub\u003e. The samples were attached onto a hollow iron plate for test, and THz wave focused on the sample with a spot radius of 2.5 mm. The EMI SE of the material can be described by decibels (dB) and derived using the following equation:\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eEMI SE (dB) = \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{-}\\text{20}{\\text{log}}_{\\text{10}}\\left(\\frac{{\\text{E}}_{\\text{in}}}{{\\text{E}}_{\\text{out}}}\\right)\\)\u003c/span\u003e\u003c/span\u003e (1)\u003c/p\u003e \u003cp\u003e, where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{E}}_{\\text{in}}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{E}}_{\\text{out}}\\)\u003c/span\u003e\u003c/span\u003e denote the incident field strength and transmitted field intensity of THz waves, respectively. The EMI SSE\u003csub\u003et\u003c/sub\u003e of the material can be calculated based on the following equation:\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eEMI SSE\u003csub\u003et\u003c/sub\u003e (dB\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) = \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\text{EMI SE \u0026middot; }{\\text{S}}^{\\text{2}}}{\\text{m}}\\)\u003c/span\u003e\u003c/span\u003e (2)\u003c/p\u003e \u003cp\u003e, where \u003cem\u003eS\u003c/em\u003e and \u003cem\u003em\u003c/em\u003e respectively represent the area of the focal spot of THz wave and the mass of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTHz Optical Nanoimaging.\u003c/b\u003e Optical nanoimaging was conducted on the samples using a scattering-type THz optical microscope (THz-NeaSNOM, Neaspec GmbH). To image the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet in real space, a THz laser with tunable frequency from 0.1 to 3 THz was focused onto both the sample and a metal-coated AFM tip (25PtIr200B-H, Rocky Mountain Nanotechnology) with a radius below 20 nm. The back-scattered light from the tip was demodulated and detected at a harmonic higher than that of the tip.\u003c/p\u003e \u003cp\u003e \u003cb\u003eNumerical Simulation.\u003c/b\u003e Because \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet belongs to a metallic 2D material, its conductivity (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{jj}\\)\u003c/span\u003e\u003c/span\u003e) can be obtained by the Drude model and written as: \u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{\\sigma\\:}_{jj}=\\frac{i{D}_{j}}{\\pi\\:\\left(\\omega\\:+\\frac{i}{\\tau\\:}\\right)}\\:,\\:{D}_{j}=\\frac{\\pi\\:{e}^{2}n}{{m}_{j}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e, where \u003cem\u003ej\u003c/em\u003e represents the \u003cem\u003ex\u003c/em\u003e or \u003cem\u003ey\u003c/em\u003e direction of the optical axis of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet in our paper. In Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e3\u003c/span\u003e), \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:e,\\:n,\\:\\omega\\:,\\:\\tau\\:,\\:{D}_{j}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{m}_{j}\\)\u003c/span\u003e\u003c/span\u003e stand for electron charge, density of electrons, frequency of excitation, carrier lifetime, Drude weight along x or y direction, and effective electron mass in \u003cem\u003ex\u003c/em\u003e and \u003cem\u003ey\u003c/em\u003e directions, respectively. Therefore, the real (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\epsilon\\:}_{r,jj}\\)\u003c/span\u003e\u003c/span\u003e) and imaginary (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\epsilon\\:}_{i,jj}\\)\u003c/span\u003e\u003c/span\u003e) parts of the complex permittivity along each direction can be derived based on the following equation:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{\\epsilon\\:}_{r,jj}={\\epsilon\\:}_{r}-\\frac{{e}^{2}n}{{m}_{j}{\\epsilon\\:}_{0}h\\left({\\omega\\:}^{2}+\\frac{1}{{\\tau\\:}^{2}}\\right)}\\:,\\:{\\epsilon\\:}_{i,jj}=\\frac{\\raisebox{1ex}{${e}^{2}n$}\\!\\left/\\:\\!\\raisebox{-1ex}{$\\tau\\:$}\\right.}{{m}_{j}{\\epsilon\\:}_{0}h\\omega\\:\\left({\\omega\\:}^{2}+\\frac{1}{\\tau\\:}\\right)}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e, where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\epsilon\\:}_{r}=\\text{11}\\)\u003c/span\u003e\u003c/span\u003e is the relative permittivity, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\epsilon\\:}_{0}=\\text{8.854}\\times\\:{\\text{10}}^{\\text{\\--}\\text{12}}\\)\u003c/span\u003e\u003c/span\u003e F/m is the vacuum permittivity, and \u003cem\u003eh\u003c/em\u003e represents the thickness of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet. The effective electron mass (m\u003csub\u003ex\u003c/sub\u003e/m\u003csub\u003ey\u003c/sub\u003e) of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-borophene nanosheet along \u003cem\u003ex\u003c/em\u003e or \u003cem\u003ey\u003c/em\u003e directions are respectively 3.5 m\u003csub\u003e0\u003c/sub\u003e and 3.7 m\u003csub\u003e0\u003c/sub\u003e, where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{m}_{0}=\\text{9.11}\\times\\:{\\text{10}}^{\\text{\\--}\\text{31}}\\)\u003c/span\u003e\u003c/span\u003e kg is the mass of electron\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eUsing Matlab R2021b software, the permittivity spectra in the frequency range of 0.1 ̶ 2 THz of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets can be calculated according to Eqs.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and (\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e4\u003c/span\u003e), where the carrier density ranges from 1.0 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\times\\:\\)\u003c/span\u003e\u003c/span\u003e 10\u003csup\u003e19\u003c/sup\u003e to 5.0 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\times\\:\\)\u003c/span\u003e\u003c/span\u003e 10\u003csup\u003e19\u003c/sup\u003e m\u003csup\u003e\u0026minus;\u0026thinsp;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e and the mean free time of electrons varies from 3 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\times\\:\\)\u003c/span\u003e\u003c/span\u003e 10\u003csup\u003e\u0026ndash;14\u003c/sup\u003e to 12 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\times\\:\\)\u003c/span\u003e\u003c/span\u003e 10\u003csup\u003e\u0026ndash;14\u003c/sup\u003e s. And then, the permittivity spectra were imported into CST software to construct a \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheet. Finally, we carried out the finite-difference time-domain simulations (FDTD, Lumerical Inc.) to simulate the THz absorbance of \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br nanosheets.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eThe authors declare that the main data supporting the findings of this study are available within the paper. Extra data are available from the corresponding authors upon reasonable request. Source data are provided with this paper.\u003c/p\u003e \u003c/div\u003e\u003cp\u003e \u003ch2\u003eOnline content\u003c/h2\u003e \u003cp\u003eAny methods, additional references, Nature Research reporting summaries, source data, extended data, supplementary information, acknowledgements, details of author contributions and competing interests; and statements of data and code availability are available at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/xxxx\u003c/span\u003e\u003cspan address=\"https://doi.org/xxxx\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor contributions\u003c/h2\u003e \u003cp\u003eS. D., H. C. and F. L. proposed and supervised the projects. H.L. synthesized the materials, characterized their surface morphology and chemical compositions, and carried out the THz shielding performances measurements. Z.C. and H.Z. simulated the absorption spectra of borophene in THz band by FTDT software. X.W. was responsible for the terahertz imaging of the \u003cem\u003eβ\u003c/em\u003e\u003csub\u003e12\u003c/sub\u003e-Br/PDMS composite film. J.W. created a flowchart illustrating the experimental process. All the authors involved in the analysis and discussion of the experimental results. And all authors approve to submit the final version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe authors are very thankful for the support of the National Key Research and Development Program of China (2022YFA1203503), the National Science Foundation of China (Grant No. 51872337), Guangdong Basic and Applied Basic Research Foundation (Grant Nos. 2021A1515012592, 2020B1515020009), the Science and Technology Department of Guangdong Province (Grant No. 2020B1212060030), and Guangzhou Science and Technology Program (Grant 2024A04J6359).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWu Z et al (2022) Dimensional design and core\u0026ndash;shell engineering of nanomaterials for electromagnetic wave absorption. Adv Mater 34:2107538\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIqbal A, Hassan T, Naqvi SM, Gogotsi Y, Koo C (2024) M. 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Opt Mater Express 11:2627\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":false,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4763119/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4763119/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Materials with electromagnetic interference (EMI) shielding in the terahertz (THz) regime, while minimizing the quantity used, are highly demanded for future information communication, healthcare and mineral resource exploration applications. Currently, there is often a trade-off between the amount of material used and the absolute EMI shielding effectiveness (EESt) for the EMI shielding materials. Here, we address this trade-off by harnessing the unique properties of two-dimensional (2D) β12-borophene (β12-Br) nanosheets. Leveraging β12-Br’s light weight and exceptional electron mobility characteristics, which represent among the highest reported values to date, we simultaneously achieve a THz EMI shield effectiveness (SE) of 70 dB and an EESt of 4.8 × 105 dB·cm2/g (@0.87 THz) using a β12-Br polymer composite. This surpasses the values of previously reported THz shielding materials with an EESt less than 3 × 105 dB·cm2/g and a SE smaller than 60 dB, while only needs 0.1 wt.% of these materials to realize the same SE value. Furthermore, by capitalizing on the composite’s superior mechanical properties, with 158% tensile strain at a Young’s modulus of 33 MPa, we demonstrate the high-efficiency shielding performances of conformably coated surfaces based on β12-Br nanosheets, suggesting their great potential in EMI shielding area.","manuscriptTitle":"Harmonizing Material Quantity and Terahertz Wave Interference Shielding Efficiency with Metallic Borophene Nanosheets","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-09-20 02:33:04","doi":"10.21203/rs.3.rs-4763119/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ed9838be-cdcf-4405-86ee-6c747996c647","owner":[],"postedDate":"September 20th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":35628351,"name":"Physical sciences/Nanoscience and technology/Nanoscale materials/Two-dimensional materials"},{"id":35628352,"name":"Physical sciences/Materials science/Materials for optics/Nanophotonics and plasmonics"}],"tags":[],"updatedAt":"2025-07-02T07:19:40+00:00","versionOfRecord":{"articleIdentity":"rs-4763119","link":"https://doi.org/10.1038/s41467-025-60892-1","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-07-01 04:00:00","publishedOnDateReadable":"July 1st, 2025"},"versionCreatedAt":"2024-09-20 02:33:04","video":"","vorDoi":"10.1038/s41467-025-60892-1","vorDoiUrl":"https://doi.org/10.1038/s41467-025-60892-1","workflowStages":[]},"version":"v1","identity":"rs-4763119","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4763119","identity":"rs-4763119","version":["v1"]},"buildId":"-HB7Z8yhvgn0wM9Nzuekk","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}