Stretchable,Transparent,and Ultra-Broadband Terahertz Shielding Thin Films Based on Wrinkled MXene Architectures

With the increasing demand for terahertz(THz)technology in security inspection,medical imaging,and flexible electronics,there is a significant need for stretchable and transparent THz electromagnetic interference(EMI)shielding materials.Existing EMI shielding materials,like opaque metals and carbon-based films,face challenges in achieving both high transparency and high shielding efficiency(SE).Here,a wrinkled structure strategy was proposed to construct ultra-thin,stretchable,and transparent terahertz shielding MXene films,which possesses both isotropous wrinkles(height about 50 nm)and periodic wrinkles(height about 500 nm).Compared to flat film,the wrinkled MXene film(8 nm)demonstrates a remarkable 36.5%increase in SE within the THz band.The wrinkled MXene film exhibits an EMI SE of 21.1 dB at the thickness of 100 nm,and an average EMI SE/t of 700 dBμm^(−1)over the 0.1-10 THz.Theoretical calculations suggest that the wrinkled structure enhances the film’s conductivity and surface plasmon resonances,resulting in an improved THz wave absorption.Additionally,the wrinkled structure enhances the MXene films’stretchability and stability.After bending and stretching(at 30%strain)cycles,the average THz transmittance of the wrinkled film is only 0.5%and 2.4%,respectively.The outstanding performances of the wrinkled MXene film make it a promising THz electromagnetic shielding materials for future smart windows and wearable electronics.

Enhanced Performance of a Monolayer MoS_2/WSe_2 Heterojunction as a Photoelectrochemical Cathode

Transition-metal dichalcogenide(TMD) semiconductors have attracted interest as photoelectrochemical(PEC) electrodes due to their novel band-gap structures,optoelectronic properties, and photocatalytic activities.However, the photo-harvesting efficiency still requires improvement. In this study, A TMD stacked heterojunction structure was adopted to further enhance the performance of the PEC cathode. A P-type WSe_2 and an N-type Mo S_2 monolayer were stacked layer-by-layer to build a ultrathin vertical heterojunction using a micro-fabrication method.In situ measurement was employed to characterize the intrinsic PEC performance on a single-sheet heterostructure.Benefitting from its built-in electric field and type II band alignment, the MoS_2/WSe_2 bilayer heterojunction exhibited exceptional photocatalytic activity and a high incident photo-to-current conversion efficiency(IPCE). Comparing with the monolayer WSe_2 cathode, the PEC current and the IPCE of the bilayer heterojunction increased by a factor of 5.6 and enhanced 50%, respectively. The intriguing performance renders the MoS_2/WSe_2 heterojunction attractive for application in high-performance PEC water splitting.

Molybdenum Nanoscrews:A Novel Non-coinage-Metal Substrate for Surface-Enhanced Raman Scattering

For the first time, Mo nanoscrew was cultivated as a novel non-coinage-metal substrate for surface-enhanced Raman scattering(SERS). It was found that the nanoscrew is composed of many small screw threads stacking along its length direction with small separations. Under external light excitation, strong electromagnetic coupling was initiated within the gaps, and many hot-spots formed on the surface of the nanoscrew, which was confirmed by high-resolution scanning near-field optical microscope measurements and numerical simulations using finite element method. These hotspots are responsible for the observed SERS activity of the nanoscrews. Raman mapping characterizations further revealed the excellent reproducibility of the SERS activity. Our findings may pave the way for design of low-cost and stable SERS substrates.

Room-temperature strong coupling between dipolar plasmon resonance in single gold nanorod and two-dimensional excitons in monolayer WSe_2

All-solid-state strong coupling systems with large vacuum Rabi splitting energy have great potential applications in future quantum information technologies, such as quantum manipulations, quantum information storage and processing,and ultrafast optical switches. Monolayer transition metal dichalcogenides（TMDs） have recently been explored as excellent candidates for the observation of solid-state strong coupling phenomena. In this work, from both experimental and theoretical aspects, we explored the strong coupling effect by integrating an individual plasmonic gold nanorod into the monolayer tungsten diselenide（WSe2）. Evident anti-crossing behavior was observed from the coupled energy diagram at room temperature; a Rabi splitting energy of 98 meV was extracted.

Janus MXene film with gradient structure for highly efficient terahertz and infrared electromagnetic absorption

Electromagnetic interference (EMI) shielding inhigh-frequency range, especially the rapidly growing terahertz(THz) frequency range, attracts increasing attention due tothe potential application of terahertz in 6G wirelesscommunication, and security inspection. However, traditionalconductive EMI films typically achieve high shieldingeffectiveness through strong reflection, which may causesecondary pollution to other devices. Here, a gradientstructure strategy was proposed to constructTi_(3)C_(2)Tx/hydroxypropyl methyl cellulose (HPMC) film, in whichthe content of Ti_(3)C_(2)Tx gradually increases along the thicknessdirection, resulting in different conductivity of the two surfaces(surface-M and surface-H) for the film. The obtained gradientfilmexhibits an EMI shielding efficiency of over 48.5 dB in theTHz range (0.2-1.6 THz) at a thickness of 40 μm. Especially,as the THz waves incident from the surface-H to the film, the absorption effectiveness reaches 48.2 dB (average absorbedpower loss up to 91.4%), and the reflection effectiveness is only 0.3 dB. In additions, the gradient-film also demonstrates ahigh absorption rate of 95.5% in the infrared band (2.5-16.7 μm). Moreover, the gradient-film exhibits an excellent tensilestress and Young’s modulus value of 173.1 MPa and 2.8 GPa, respectively. Therefore, the gradient-film proposed in thiswork, with excellent electromagnetic absorption in both THz and infrared band, provides a promising candidate for the nextgenerationEMI shielding applications.

Sensitive direct-conversion X-ray detectors formed by ZnO nanowire field emitters andβ-Ga_(2)O_(3)photoconductor targets with an electron bombardment induced photoconductivity mechanism

Sensitive X-ray detection is needed in diverse areas motivated by a common desire to reduce radiation dose.Cold cathode X-ray detectors operating with a photoelectron multiplication mechanism called electron bombardment induced photoconductivity(EBIPC)have emerged as promising candidates for low-dose X-ray detection.Herein,the cold cathode detectors formed by ZnO nanowire field emitters andβ-Ga_(2)O_(3)photoconductor targets were proposed for sensitive direct-conversion X-ray detection.The charge carrier transport mechanism of EBIPC effect in X-ray detectors was investigated to achieve a high internal gain(2.9×10^(2))and high detection sensitivity(3.0×10^(3)μCGy^(−1)_(air)cm^(−2))for a 6 keV X-ray at the electric field of 22.5 Vμm−1.Furthermore,the proposed X-ray detectors showed the features of fast response time(40 ms),long-term stability(0.6%for 1 h),and low detection limit(0.28 mGy_(air)s^(−1)),suggesting that the direct-conversion cold cathode X-ray detectors are ideal candidates for low-energy X-ray detecting and imaging applications.

In-plane dipolar nano-antenna steers polariton waves at nanoscale

Hyperbolic polaritons can be launched and guided into mirror-symmetric-broken trajectories using an in-plane dipolar nano-antenna,and this asymmetry can be configured by adjusting the polarization direction of the in-plane dipole moment.