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Lattice Zenneck Modes on Subwavelength Antennas
摘要： Optical resonances in isolated nanoparticles made out of commonly occurring materials with high optical losses, such as transition metal dichalcogenides, germanium, carbide, and others, are weak and not sufficient for field enhancement and competing with plasmonic resonances in noble metal nanoparticles. This work presents a novel approach to achieve strong resonances in the arrays of such nanoparticles with large optical losses and points to their potential for efficient light control in ultra-thin optical elements, sensing, and photovoltaic applications. Materials with large imaginary part of permittivity (LIPP) are studied and nanostructures of these materials are shown to support not only surfaces modes, known as Zenneck waves, but also modes localized on the subwavelength particle. This approach opens up the possibility of exciting strong localized nanoparticle resonances without involving plasmonic or high-refractive-index materials. Arranging LIPP particles in a periodic array plays a crucial role allowing for collective array resonances, which are shown to be much stronger in particle array than in single particle. The collective lattice resonances can be excited at the wavelength defined mainly by the array period and thus easily tuned in a broad spectral range not being limited by particle permittivity, size, or shape.
关键词： transition metal dichalcogenides,lattice resonance,Kerker effect,molybdenum diselenide,directional scattering,nanoparticle arrays
更新于2025-09-23 15:23:52
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A New Family of Two-Dimensional Topological Materials: CdX (X?=?F, Cl, Br, and I)
摘要： Two-dimensional (2D) transition-metal halides have attracted great interest owing to their versatile applications in electronics, optoelectronics, and renewable energy storage/conversions. Using first-principles calculations, it is proposed that a new series of 2D transition-metal halide CdX (X ? F, Cl, Br, and I) monolayers with honeycomb lattice structure show topological properties. When omitting the spin–orbital coupling (SOC) effect, all of them behave as Dirac semimetal whose Fermi surface is composed of two Dirac points at high symmetry K and K’ points in Brillouin zone. When considering the SOC effect, CdCl, CdBr, and CdI monolayers behave as topological insulators with global band gap, whereas CdF is converted from Dirac semimetal into topological metal with local band gap. The nontrivial topological properties are further proved by their nontrivial edge states. The fascinating properties of the CdX (X ? F, Cl, Br, and I) monolayers show their potential for future quantum computing and next generation of high-speed electronic devices.
关键词： topological insulators,topological metals,two-dimensional transition-metal halides
更新于2025-09-23 15:23:52
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Growth Order-Dependent Strain Variations of Lateral Transition Metal Dichalcogenide Heterostructures
摘要： Understanding the heterojunction of a lateral heterostructured transition metal dichalcogenide (hTMD) is important to take advantage of the combined optoelectronic properties of individual TMDs for various applications but, however, is hampered by mingled effects from lattice mismatch and substrate interaction. Here, we systematically investigated the strain occurring at lateral hTMDs consisting of molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2) prepared by chemical vapor deposition. Comparison of homologous TMDs and hTMDs from controlled growth order revealed systematic change in photoluminescence behavior depending on substrate interaction and relative lattice mismatch. Near the heterojunction, a TMD with a larger lattice constant (a) exhibits photoluminescence (PL) red-shift, whereas a TMD with smaller a shows an opposite trend owing to lattice-induced strain. These effects are augmented in a subtractive or additive manner by tensile strain from the substrate interaction. Moreover, comparison of PLs revealed that the shell region grown from the core edges exhibits weak substrate interaction contrasted by that of a shell region independently grown on a shell. This study provides detailed understandings of the heterojunction at a lateral hTMD for various applications.
关键词： photoluminescence,lateral heterostructure,strain,transition metal dichalcogenides,chemical vapor deposition
更新于2025-09-23 15:23:52
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Fe doping effect of vanadium oxide films for enhanced switching electrochromic performances
摘要： In the present study, Fe-doped V2O5 films showing impressive electrochromic (EC) performance were developed using the sol-gel spin-coating method. To confirm the optimized Fe-doping effect on the V2O5 films for the EC performance, we adjusted the Fe atomic percentages to 0.0, 0.5, 1.0, and 1.5 at%, respectively. With the effect of Fe doping on the V2O5 films, the obtained films resulted in the formation of the oxygen vacancies. As the result, when the optimum Fe atomic percentage was 1.0 at%, the enhanced switching speeds (3.7 s for the bleaching speed and 2.0 s for the coloration speed) and enhanced coloration efficiency value (47.3 cm2/C) compared to the other films were implemented. This can be attributed to the improved electrical conductivity and Li+ diffusion coefficient that led to efficient generation of the EC reaction activity and narrowing the optical bandgap at the coloration state to increase transmittance modulation. Therefore, this unique film can be a promising EC material to improve the performance for the EC devices.
关键词： Films,Optical properties,Transition metal oxides,Electrical properties,Electrochromic performances
更新于2025-09-23 15:23:52
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Valley and spin splitting in monolayer TX2/antiferromagnetic MnO (T=Mo, W; X=S, Se) van der Waals heterostructures
摘要： The electronic structure of monolayer MoS2, WS2, MoSe2 and WSe2 on top of antiferromagnetic MnO(111) is investigated systematically by first-principles calculations. It is found that the time-reversal symmetry is broken by the stacking on MnO that leads to the valley polarization. The valley splitting of MoS2/MnO, WS2/MnO, MoSe2/MnO and WSe2/MnO is 161, 193, 171 and 125 meV for K point, and 18 to 253 meV for K' point. The pattern of stacking also induces p- or n-type doping of MoS2, revealing that the conductivity of the heterostructues could be tuned by stacking on MnO. Besides, we also calculate electronic structures of WS2/MnO, MoSe2/MnO and WSe2/MnO heterostructures in the configuration of Mn-terminated (III), and find the spin splitting at K point is 553, 324 and 481 meV, and 215, 9 and 284 meV for K' point, respectively. Furthermore, the termination of MnO substrate can switch the spin splitting of monolayer MoS2, WS2, MoSe2 and WSe2. The spin splitting of MoS2/MnO for six possible interface configurations is varied from 24 to 291 meV for K point, and 18 to 253 meV for K' point. The results present a new type of novel heterostructure that has potential applications in the spintronic and valleytronic devices.
关键词： Two dimensional materials,Heterostructure,Transition metal dichalcogenides,First-principles calculations
更新于2025-09-23 15:23:52
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Antimicrobial-Peptide-Conjugated MoS2 Based Nanoplatform for Multimodal Synergistic Inactivation of Superbugs
摘要： Development of new antibacterial therapeutics material is becoming increasingly urgent due to the huge threat of superbugs, which are responsible for more than half million death each year in this world. Here, we report the development of novel nano-biomaterial based on melittin antimicrobial peptide (AMP) attached transition metal dichalcogenide MoS2 based theranostic nanoplatform. Reported nanoplatform has capability for targeted identification and synergistic inactivation of 100% multidrug-resistant superbugs by combined photo thermal therapy (PTT), photodynamic therapy (PDT) and AMP process. A novel approach for the design of melittin antimicrobial peptide attached MoS2 based nanoplatform is reported, which emits very bright and photo stable fluorescence. It also generates heat as well as reactive oxygen species (ROS) in the presence of 670 nm near infrared light, which allow it to be used as PTT & PDT agent. Due to the presence of AMP, multifunctional AMP exhibits significantly improved antibacterial activity for superbugs via multimodal synergistic killing mechanism. Reported data demonstrate that nanoplatforms are capable of identification of multidrug-resistant superbugs via luminescence imaging. Experimental results show that it is possible to kill only ~45% of superbugs via MoS2 nanopaltform based on PTT & PDT processes together. On the other hand, killing of less than 10% of superbugs is possible using melittin antimicrobial peptide alone. Whereas, 100% Methicillin-resistant Staphylococcus aureus (MRSA), drug resistance Escherichia coli (E. coli) and drug resistance Klebsiella pneumoniae (KPN) superbugs can be killed using antimicrobial peptide attached MoS2 QDs, via synergistic killing mechanism. Mechanisms for possible synergistic killing of multidrug-resistant superbugs have been discussed.
关键词： theranostic transition metal dichalcogenide,photodynamic therapy,multimodal therapy for multidrug-resistant superbugs,Melittin antimicrobial peptide attached MoS2 based nanoplatform,photo thermal therapy
更新于2025-09-23 15:23:52
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Functionalization of the transition metal oxides FeO, CoO, and NiO with alkali metal atoms decreases their ionization potentials by 3–5 eV
摘要： The existence and stabilities of various neutral metal oxides of formula MON and MON2 (M = Fe, Co, Ni; N = Li, Na) and their corresponding cations MON+ and MON2+ are predicted using density functional theory (B3LYP) with the 6-311 + G(d) basis set. Ab initio calculations carried out at the CCSD(T)/6-311 + G(3df) level of theory reveal that the ionization potentials (IPs) of the oxides MO decrease by ca. 3–5 eV upon functionalization with N to give either MON or MON2. The influences of the chemical constitution and local spin magnetic moment (on the transition metal atom) of the oxide or cation on its IP are presented and discussed.
关键词： Transition metal oxides,Strong reducers,Mixed oxides,Superalkalis
更新于2025-09-23 15:23:52
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2D Schottky Junction between Graphene Oxide and Transition-Metal Dichalcogenides: Photoresponsive Properties and Electrocatalytic Performance
摘要： 2D graphene is conductor and not a semiconductor. 2D transition—metal dichalcogenides (TMD) is a semiconductor and not a conductor. Preparing 2D composite material that simultaneously possesses both advantages of graphene and TMD has proven to be challenging. In this work, both 2D-WS2/2D-GO and 2D-MoS2/2D-GO composites with few layer thickness are synthesized. The electronic structure indicates a high content of Mo4+ 3d5/2 and W4+4f7/2 with lower binding energy in the 2D composite, which is ascribed to partial loss of surface sulfur atoms in 2D composites and the newly formed heteroatomic bond of CWS and CMoS. The Schottky junction between 2D-GO and 2D-TMD (2D G-T junction) is established and exhibits obvious photoelectric responses. Superior electrocatalytic properties of the two 2D-composites are attributable to the 2D Schottky Junction between 2D-TMDs and 2D-GO. Interlayer electronic coupling in 2D Schottky Junction (2D G-T junction) activates inert sites on the 2D surface of 2D-TMDs or GO. The power conversion efficiency of dye-sensitized solar cells (DSCs) based on 2D-WS2/2D-GO is 9.54% under standard solar illumination intensity (AM1.5, 100 mW cm?2). The value is one of the highest reported efficiencies for DSCs based on Pt-free counter electrodes. Finally, 2D-WS2/2D-GO composites exhibit excellent stability as counter electrode of DSCs.
关键词： photoresponse,interlayer electronic coupling,2D,electrocatalyst,graphene,transition-metal dichalcogenides,Schottky junction
更新于2025-09-23 15:23:52
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Exploring the optical beam shifts in monolayers of transition metal dichalcogenides using Gaussian beams
摘要： We have extensively studied Goos-H?nchen (GH) and Imbert-Fedorov (IF) shifts for reflection of a fundamental Gaussian beam using transfer matrix method. By considering a dielectric slab coated with monolayer of transition metal dichalcogenides (TMDC), we theoretically investigate the potential role of four different TMDC monolayers (WS2, WSe2, MoS2, and MoSe2) on the spatial and angular GH and IF shifts for reflection of the light beam that has not been explored previously. We find the nature of GH and IF shifts to be explicitly dependent on the mode of polarization of light beam. In case of partial reflection of light, both GH and IF shifts acquire moderate magnitude. In contrary, giant negative spatial GH shifts are examined for total internal reflection. Our analysis revealed that the typical characteristics of GH and IF shifts are significantly affected by the complex surface conductivity of TMDC monolayers and consequently the shifts are found to differ for different TMDC monolayers. We also present a comparison of the beam shifts for the monolayer TMDC-coated surfaces with the corresponding bulk TMDCs. Finally, we address the most significant question of how the GH and IF shifts depend upon the wavelengths of incident light, in particular, establishing the role of optical conductivity in beam shifts.
关键词： Light matter interaction,Goos-H?nchen shift,Surface Optics,Gaussian beam,Transition metal dichalcogenides,Imbert-Fedorov shift
更新于2025-09-23 15:23:52
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Lateral interfaces of transition metal dichalcogenides: A stable tunable one-dimensional physics platform
摘要： We study in-plane lateral heterostructures of commensurate transition-metal dichalcogenides, such as MoS2-WS2 and MoSe2-WSe2, and find interfacial and edge states that are highly localized to these regions of the heterostructure. These are one-dimensional (1D) in nature, lying within the band gap of the bulk structure and exhibiting complex orbital and spin structure. We describe such heteroribbons with a three-orbital tight-binding model that uses first principles and experimental parameters as input, allowing us to model realistic systems. Analytical modeling for the 1D interfacial bands results in long-range hoppings due to the hybridization along the interface, with strong spin-orbit couplings. We further explore the Ruderman-Kittel-Kasuya-Yosida indirect interaction between magnetic impurities located at the interface. The unusual features of the interface states result in effective long-range exchange noncollinear interactions between impurities. These results suggest that transition-metal dichalcogenide interfaces could serve as stable, tunable 1D platform with unique properties for possible use in exploring Majorana fermions, plasma excitations, and spintronics applications.
关键词： spin-orbit coupling,interface states,transition metal dichalcogenides,RKKY interaction,tight-binding model,lateral heterostructures
更新于2025-09-23 15:23:52