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Excitonic Aharonov-Bohm Oscillations in Core-Shell Nanowires
摘要： Phase coherence in nanostructures is at the heart of a wide range of quantum effects such as Josephson oscillations between exciton–polariton condensates in microcavities, conductance quantization in 1D ballistic transport, or the optical (excitonic) Aharonov–Bohm effect in semiconductor quantum rings. These effects only occur in structures of the highest perfection. The 2D semiconductor heterostructures required for the observation of Aharonov–Bohm oscillations have proved to be particularly demanding, since interface roughness or alloy fluctuations cause a loss of the spatial phase coherence of excitons, and ultimately induce exciton localization. Experimental work in this field has so far relied on either self-assembled ring structures with very limited control of shape and dimension or on lithographically defined nanorings that suffer from the detrimental effects of free surfaces. Here, it is demonstrated that nanowires are an ideal platform for studies of the Aharonov–Bohm effect of neutral and charged excitons, as they facilitate the controlled fabrication of nearly ideal quantum rings by combining all-binary radial heterostructures with axial crystal-phase quantum structures. Thanks to the atomically flat interfaces and the absence of alloy disorder, excitonic phase coherence is preserved even in rings with circumferences as large as 200 nm.
关键词： excitonic Aharonov–Bohm effect,phase coherence,core–shell nanowires,3D nanostructures
更新于2025-09-23 15:21:01
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Enhancing interfacial charge transfer on novel 3D/1D multidimensional MoS2/TiO2 heterojunction toward efficient photoelectrocatalytic removal of levofloxacin
摘要： Structure-controlled visible light driven photo-anode with high catalytic performance, plays important roles in environmental pollutants treatment. In this work, a mild hydrothermal assisted anodization approach has been reported to design an integrated self-assembled 3D flower-like MoS2/1D TiO2 nanotube arrays (NTAs) hierarchical electrode. The constructed multidimensional electrode not only broadened the absorption spectrum response range but also promoted rapidly electron-hole pairs separation, exhibiting the excellent photoelectron catalytic (PEC) performance and stability in the degradation of target pollutants, which the photocurrent conversion efficiency was 6.5 times higher than that of pure TiO2. Furtherly, a comprehensive mechanism was proposed to explain the charge transfer on the interface of intimate integration of 3D/1D hybrid nanostructure towards PEC properties in terms of the energy band structures and DFT. Furthermore, the photo-generated active species (?OH and ?O2-) have been proved by electron paramagnetic resonance spectroscopy and fluorescence probe over the composites. Thus, this work could provide an effective strategy to design multidimensional coupled heterojunction materials toward solar energy conversion for environmental purification.
关键词： Interfacial charge transfer,Photoelectrocatalytic,Active radicals,DFT,3D/1D hybrid nanostructures
更新于2025-09-23 15:21:01
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Epitaxial lateral overgrowth of GaN on nano-cavity patterned sapphire substrates
摘要： The epitaxial lateral overgrowth of GaN by metal-organic chemical vapor deposition using a nano-cavity patterned sapphire substrate (NCPSS) was investigated. The NCPSS, with a hexagonal non-close-packed nano-cavity pattern on the sapphire substrate, was fabricated by polystyrene sphere coating and size reduction by reactive ion etching, followed by deposition of alumina and thermal oxidation. The coalescence of GaN on the NCPSS was achieved by the formation of relatively large GaN islands and enhanced lateral overgrowth of the GaN islands over several nano-cavity pattern areas. The threading dislocation density (TDD) measured by cathodoluminescence measurement was significantly reduced from 2.4 108 cm-2 to 6.9 107 cm-2 by using the NCPSS. Dislocation behaviors that contribute to the reduction of TDD of the GaN layer were observed by transmission electron microscopy. Raman spectroscopy revealed that the compressive stress in the GaN layer was reduced by 21% due to the embedded nano-cavities. In addition, the diffuse reflectance of GaN on the NCPSS was enhanced by 54% ~ 62%, which is attributed to the increased probability of light extraction through effective light scattering by nano-cavities.
关键词： A1. Nanostructures,B1. Nitrides,A2. Single crystal growth,A3. Metalorganic chemical vapor deposition,A3. Nanoscale epitaxial lateral overgrowth
更新于2025-09-23 15:21:01
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Controlled Fabrication of Flower-Shaped Aua??Cu Nanostructures Using a Deep Eutectic Solvent and Their Performance in Surface-Enhanced Raman Scattering-Based Molecular Sensing
摘要： Controlled synthesis of anisotropic bimetallic nanostructures with tunable morphology is of great current interest in surface-enhanced Raman scattering (SERS), plasmonics, and catalysis. Despite huge effort that has been devoted so far, fabrication of bimetallic nanostructures with controlled morphology and size remained to be a great challenge, especially when their shapes are anisotropic. Here, we report a facile, one-step synthetic approach for the fabrication of anisotropic bimetallic gold?copper nanostructures (Au?Cu NSs) of the 200?300 nm size range, using choline chloride/urea (ChCl/urea)-based deep eutectic solvent (DES) as the soft template. A concentration of the CuCl2 precursor in the reaction mixture was found to impact the reduction kinetics of the metal ions, directly affecting the final morphology of the Au?Cu nanostructures and elemental distributions in them. The fabricated anisotropic Au?Cu NSs revealed a high SERS signal for crystal violet (CV) molecules adsorbed at their surfaces, with the signal enhancement factor as high as 0.21 × 106 and capacity of detecting CV molecules of concentrations as low as 10?10 M in their aqueous solutions. The growth mechanism of the anisotropic bimetallic nanostructures in DES and their SERS performance has been discussed. The simple DES-assisted synthesis strategy presented in this work can be adopted for large-scale nonaqueous fabrication of other bimetallic nanostructures in a quite “greener” way.
关键词： deep eutectic solvent,plasmonics,catalysis,anisotropic bimetallic nanostructures,Au?Cu nanostructures,surface-enhanced Raman scattering
更新于2025-09-23 15:19:57
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Prospects of Coupled Organica??Inorganic Nanostructures for Charge and Energy Transfer Applications
摘要： We review the field of organic-inorganic nanocomposites with a focus on materials that exhibit a significant degree of electronic coupling across the hybrid interface. These nanocomposites undergo a variety of charge and energy transfer processes, enabling optoelectronic applications in devices which exploit singlet fission, triplet energy harvesting, photon upconversion or hot charge carrier transfer. We discuss the physical chemistry of the most common organic and inorganic components. Based on those we derive synthesis and assembly strategies and design criteria on material and device level with a focus on photovoltaics, spin memories or optical upconverters. We conclude that future research in the field should be directed towards an improved understanding of the binding motif and molecular orientation at the hybrid interface.
关键词： Inorganic Nanostructures,Self-Assembly,Organic π-Systems,Optoelectronic Devices,Plasmonics
更新于2025-09-23 15:19:57
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Enhanced Ordering and Efficient Photoalignment of Nanostructures in Block Copolymers Enabled by Halogen Bond
摘要： Fabrication and manipulation of macroscopically ordered nanostructures in polymer ?lms via supramolecular self-organization are fascinating from the viewpoints of science and technology. Here, a halogen bond (XB) was introduced into a block copolymer to facilitate its microphase separation process upon XB-driven supramolecular self-assembly. To the best of our knowledge, this is an extremely rare example to elegantly maneuver nanostructures of polymers by the emerging supramolecular interaction, XB. The nonmesogenic block copolymer composed of poly(ethylene oxide) and azopyridine-containing polymethacrylate was transformed into a supramolecular liquid-crystalline polymer through the halogen-bonded interaction between 1,2-diiodo-3,4,5,6-tetra?uorobenzene and the azopyridine group with the optimal molar ratio of 1:1. For comparison, one hydrogen-bonded liquid-crystalline polymer was also fabricated but no such ordering enhancement was acquired, indicating that both the high directionality of XB and the resulting supramolecular mesogenic ordering played key roles in the enhanced ordering of nanostructures in polymer ?lms. In addition, e?cient photoalignment and photoreorientation of nanostructures coinciding with the oriented direction of the supramolecular mesogens were also obtained by manipulating photoirradiation of linearly polarized light for the present XB-involved liquid-crystalline block copolymer, which is promising for the development of a novel generation of advanced composite liquid crystal (LC) materials.
关键词： halogen bond,supramolecular self-assembly,photoalignment,block copolymer,nanostructures
更新于2025-09-23 15:19:57
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Direct and High-Throughput Fabrication of Mie-Resonant Metasurfaces <i>via</i> Single-Pulse Laser Interference
摘要： High-index dielectric metasurfaces featuring Mie-type electric and magnetic resonances have been of a great interest in a variety of applications such as imaging, sensing, photovoltaics and others, which led to the necessity of an efficient large-scale fabrication technique. To address this, here we demonstrate the use of single-pulse laser interference for direct patterning of an amorphous silicon film into an array of Mie resonators with few hundred nanometers in diameter. The proposed technique is based on laser-interference-induced dewetting. A precise control of the laser pulse energy enables the fabrication of ordered dielectric metasurfaces in areas spanning tens of micrometers and consisting of thousands of hemispherical nanoparticles with a single laser shot. The fabricated nanoparticles exhibit a wavelength-dependent optical response with a strong electric dipole signature. Variation of the pre-deposited silicon film thickness allows tailoring of the resonances in the targeted visible and infrared spectral ranges. Such direct and high-throughput fabrication is a step towards a simple realization of spatially invariant metasurface-based devices.
关键词： direct laser interference patterning,metasurfaces,laser-matter interaction,dielectric nanostructures,silicon resonators,multi-beam interference
更新于2025-09-23 15:19:57
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Laser Induced Backward Transfer of ultra-thin metal structures
摘要： Ultra-thin, flexible and stretchable interfaces comprising thin metal films and polymers are attracting increasing interest for applications in sensors and optoelectronics. The transfer of ultra-thin gold films for the digital fabrication of such interfaces was investigated in this study using the Laser-Induced Backward Transfer (LIBT) technique. In particular, the transfer of thin and ultra-thin gold films (60, 10 and 5 nm thick) on Polydimethylosiloxane substrate has been achieved using ps pulses and low laser fluences for controllable material transfer. As the size of the nanograins comprising the Au films decreases, their melting point also decreases, enabling the transfer of intact disk-shaped Au nanostructures at low laser fluence values, with form factors and thickness equal to the pristine films. Moreover, the contribution of the substrate has been clarified: the two substrates (silicon, glass) which were used in this work, have significantly different reflectivity to the selected laser wavelength (532 nm), which can considerably influence the thickness and the quality of the transferred disk. The results presented in this work clearly demonstrate the compatibility of LIBT with ultra-thin metal film/ polymer interfaces and highlight the potential application of this digital process for a variety of optoelectronic applications.
关键词： ultra-thin films,Laser Induced Backward Transfer,metal/ polymer interface,short pulsed heating,nanostructures
更新于2025-09-23 15:19:57
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Laser forming of nanostructures in aqueous suspensions with particular optical and photoelectrical properties
摘要： The self-organizing forming of ordered nanostructures in the aqueous suspensions with inorganic nanoparticles of nickel, copper, silica and bio-organic particles of grinded green leaves were studied by means of the irradiation with red, green and blue lasers. Various forms of self-consistent non-homogeneous distributions of the nanocomponents and the optical ?ows were found. The suspensions with high density of the nickel nanoparticles demonstrated abrupt changes of their transparency and periodicity. These abrupt changes were transformed to more slow oscillations of the particles and light distributions when the nickel particles were mixed with the nanoparticles of copper. The suspensions with the nanoparticles of copper created arc-like agglomerations explained by generation of vortexes. The vortex-like distributions were found in the suspensions with silica as well. The anisotropic agglomerations were observed during the irradiations of the suspensions with the grinded green leaves. These results are promising for the developments of new kinds of optical modulators and switchers, optical memory and green solar batteries.
关键词： laser forming,optical properties,aqueous suspensions,photoelectrical properties,nanostructures
更新于2025-09-23 15:19:57
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Preparation and characterization of organic nanoparticles by laser ablation in liquids technique and their biological activity
摘要： The laser ablation in liquids (LAL) method was used for the synthesis of organic colloidal nanoparticles in deionized water as a liquid medium. The effect of variations of the lens-target distance and laser wavelength on the size, structure, and morphology of the nanoparticles was studied. A target of bulk organic bifenthrin compound (agricultural insecticide) was elaborated for the ablation process. By means of ultraviolet-visible (UV–vis) absorption spectroscopy, the characteristic absorbance spectra were analyzed, con?rming the presence of nanoparticles. Furthermore, the absorbance was related to the nanoparticles concentration. Structural characterization and size determination were carried out by transmission electron microscopy (TEM). The crystalline structure of the nanoparticles was studied by comparing the interplanar distance of the nanoparticles determined by high-resolution transmission electron microscopy (HR-TEM) with the interplanar distances of the bulk material observed by x-ray diffraction (XRD). The study of chemical composition was carried out by gas chromatography coupled to mass spectrometry (GC-MS). The nanoparticles sizes varied between 3 and 20 nm, with a narrow size distribution. According to the results, both the size and structure of the nanoparticles are mainly determined by the incident energy density on the target, whilst wavelength affects morphology. On the other hand, the preliminary biological tests of the nanoparticles carried out with Drosophila melanogaster, showed an enhanced insecticide activity at signi?cant lower concentrations in comparison with doses used with bulk bifenthrin.
关键词： organic nanostructures,nanoparticles,nano-insecticide,laser ablation,bifenthrin
更新于2025-09-23 15:19:57