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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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Direct Z-scheme MoSe2 decorating TiO2 nanotube arrays photocatalyst for water decontamination
摘要： Exploring a Z-scheme heterojunction photocatalyst with efficient charge separation and outstanding redox ability is necessary but very challenging. Herein, a novel direct Z-scheme MoSe2 decorating TiO2 nanotube arrays photocatalyst (denoted as MoSe2@TNTs) was prepared by a facile in situ hydrothermal method. Few-layer MoSe2 nanosheets distribute on the surface of the TNTs without shielding the tubular structure. Compared with individual TNTs and MoSe2, the as-prepared MoSe2@TNTs composite displays much better photocatalytic activity for eliminating pollutants (such as 4-nitrophenol and hexavalent chromium). Investigation results reveal that TNTs combined with appropriate amount of MoSe2 as co-catalyst has direct Z-scheme construction instead of traditional type-II heterojunction, which can offer abundant photo-generated active species with high redox capacity.
关键词： Photocatalysis,TiO2 nanotube arrays,Z-scheme,Molybdenum diselenide
更新于2025-09-23 15:23:52
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Ultralow Thermal Conductivity of Turbostratically Disordered MoSe2 Ultra-Thin Films and Implications for Heterostructures
摘要： Films containing 8, 16, 24, 32 and 64 MoSe2 layers were synthesized using the modulated elemental reactants (MER) method. X-ray reflectivity patterns showed that the annealed films were the targeted number of MoSe2 layers thick with atomically smooth interfaces. In-plane x-ray diffraction scans contained only hk0 reflections for crystalline MoSe2 monolayers. Specular x-ray diffraction patterns contained only 00l reflections, also indicating that the hk0 plane of the MoSe2 layers are parallel to the substrate. Both x-ray diffraction and electron microscopy techniques indicated that the hk0 planes are rotationally disordered with respect to one another, with all orientations equally probable for large areas. The rotational disorder between MoSe2 layers is present even when analyzed spots are within 10 nm of one another. Cross-plane thermal conductivities of 0.07 – 0.09 W m-1 K-1 were measured by time domain thermoreflectance, with the thinnest films exhibiting the lowest conductivity. The structural analysis suggests that the ultralow thermal conductivity is a consequence of rotational disorder, which increases the separation between MoSe2 layers. The bonding environment of the Se atoms also becomes significantly distorted from C3v symmetry due to the rotational disorder between layers. This structural disorder efficiently reduces the group velocity of the transverse phonon modes but not that of longitudinal modes. Since rotational disorder between adjacent layers in heterostructures is expected if the constituents have incommensurate lattices, this study indicates that these heterostructures will have very low cross-plane thermal conductivity.
关键词： rotational disorder,heterostructure,TMDs,turbostratic disorder,thermal conductivity,molybdenum diselenide
更新于2025-09-23 15:22:29
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Plasmonic Hot Hole Transfer in Gold Nanoparticle-decorated Transition Metal Dichalcogenide Nanosheets
摘要： This work studies photogenerated carrier dynamics in gold nanoparticle (AuNP)-decorated mono- to few-layer transition metal dichalcogenide (TMD) nanosheets using transient absorption spectroscopy (TA). TA unveiled the presence of a long-lived photo-induced absorption (PIA) feature in both MoSe2 and WSe2 decorated with covalently bound AuNPs. This long-lived PIA feature emerges only from direct Au interband excitation in AuNP-decorated MoSe2 and WSe2; it does not manifest from intraband excitation nor in AuNP-decorated MoS2 or WS2. Based on x-ray/ultraviolet photoelectron spectroscopy and previous theoretical studies, it is proposed that this PIA signature arises from hot hole transfer from the AuNP to the adjacent TMD, producing a charge-separated state. This suggests charge separation at the metal-semiconductor interface may be used to extend the lifetime of interband excitation generated hot holes. This development could represent an important advance in harnessing plasmonic dissipation pathways to generate long-lived carriers suited for solar-driven light harvesting and catalysis.
关键词： molybdenum diselenide,hot carriers,transient absorption,carrier dynamics,intraband,interband transitions,ultrafast spectroscopy
更新于2025-09-12 10:27:22