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3D Multi-Branched SnO2 Semiconductor Nanostructures as Optical Waveguides
摘要： Nanostructures with complex geometry have gathered interest recently due to some unusual and exotic properties associated with both their shape and material. 3D multi-branched SnO2 one-dimensional nanostructrures, characterized by a “node”—i.e., the location where two or more branches originate, are the ideal platform to distribute signals of di?erent natures. In this work, we study how this particular geometrical con?guration a?ects light propagation when a light source (i.e., laser) is focused onto it. Combining scanning electron microscopy (SEM) and optical analysis along with Raman and Rayleigh scattering upon illumination, we were able to understand, in more detail, the mechanism behind the light-coupling occurring at the node. Our experimental ?ndings show that multi-branched semiconductor 1D structures have great potential as optically active nanostructures with waveguiding properties, thus paving the way for their application as novel building blocks for optical communication networks.
关键词： SnO2,waveguiding e?ect in nanostructures,3D multi-branched nanostructures,nanowires,light scattering,tin oxide nanostructure,nano-optics
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Complex-Birefringent and Chiral Waveplates with Metasurfaces
摘要： Metasurfaces composed of arrays of nano-resonators are a powerful tool for manipulation of polarization of light. All-dielectric metasurfaces do not suffer absorption losses and are highly transparent in contrast to metallic structures, and combined with recent advances in their design and fabrication, have enabled efficient polarization manipulation and arbitrary phase shaping. A new regime of complex-valued birefringence has been recently suggested, extending the notion of real-valued birefringence through the specially introduced polarization-sensitive loss or gain. This can enable fundamentally new possibilities for polarization control, such as amplifying the angle between polarization vectors to improve detection sensitivity. However, a practical realization of complex-valued birefringence concept was missing. In particular, the theoretical approach in Ref. [4] was based on a complicated metamaterial with loss and gain, which is challenging to fabricate and not suitable for quantum applications. Here, we report on a new conceptual approach for implementing arbitrary complex-valued birefringence with pairwise birefringent elements using high-index dielectric nanostructures. We formulate a practical design principle, which is optimal for achieving any desirable polarization transformation. While loss is inherently necessary for implementing complex birefringence, our all-dielectric metasurface design achieves the mathematically minimum required amount of loss through tailored diffraction without any material absorption.
关键词： metasurfaces,birefringence,polarization control,dielectric nanostructures
更新于2025-09-11 14:15:04
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Green synthesized plasmonic nanostructure decorated TiO2 nanofibers for photoelectrochemical hydrogen production
摘要： We herein present the Au and Ag NPs synthesized via chemical reduction with green synthesized carbon nanolights (CNL) as a visible light photosensitizer for TiO2 nanofibers (TNFs) towards photoelectrochemical water splitting. The synthesized photoanodes (PA1: TNFs, PA2: Ag@CNLs/TNFs and PA3: Au@CNLs/TNFs) were probed ex-situ for morphological, structural, optical and electronic properties before being used for the PEC experiments. We first show the efficient photocatalytic activity of these photoanodes for the degradation of methylene blue under visible light irradiation. Followed by the photoelectrochemical (PEC) water splitting investigation, which reveals the substantially improved photocurrent density to 13 mA/cm2 and 18 mA/cm2, for PA2 and PA3, respectively under simulated AM 1.5 solar illumination at 1.36 V vs RHE, ~15 fold enhancement compared to that obtained for a PA1. This improvement we attributed to the synergic consequence, improved absorption and effective charge carrier separation & transport due to surface plasmonic effect, which is well evident in the decrease of measured charge transfer resistance (Rct), for PA2 (15.1 Ω) and PA3 (6.71 Ω), as compared to PA1 (139 Ω).
关键词： TiO2 nanofibers,Green synthesis,Hydrogen,Photo-electrochemical,Carbon quantum dots,Plasmonic nanostructures
更新于2025-09-11 14:15:04
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Coupled Halide-deficient and Halide-rich Reaction System for Doping in Perovskite Armed Nanostructures
摘要： Insights of Mn(II) doping in CsPbCl3-armed hexapod nanostructures is reported. These complex structures were typically formed in halide concentration tuned modulated reactions. Cores were first formed under halide deficient condition and with enriching halides; these were transformed to armed structures. Doping of Mn(II) was observed facilitated during the arm growth in the second stage of the reaction. These observations were supported with decoupled reactions with minimized and maximized halide concentrations carried out in separate reactions. However, less interference for the exciton to dopant energy transfer was noticed for the defect states created in halide-deficient medium, and the intensity of the dopant emission remained proportional to the amount of dopant inserted in the nanocrystals. Being this is an in situ observation in the coupled reactions of both poor and rich halide reaction systems, the finding would strengthen the understanding of doping in perovskite host nanocrystals.
关键词： CsPbCl3,hexapod nanostructures,Mn(II) doping,halide concentration,dopant emission
更新于2025-09-11 14:15:04
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An Unexpected Transformation of Organic Solvents into 2D Fluorescent Quantum Dots During Ultrasonication Assisted Liquid Phase Exfoliation
摘要： Ultrasonication within organic solvents is widely used to exfoliate layered materials and produce two-dimensional (2D) nanostructures. Several 2D materials synthesized by such liquid phase exfoliation (LPE) approaches are reported to exhibit photoluminescence. In these approaches, it is presumed that while the 2D nanostructures are derived from the layered parent material undergoing delamination, the organic solvent serves as a dispersing medium. However, in this study, we show that the organic solvent also contributes towards formation of 2D nanostructures that are optically active. We show that that bare organic solvent, when exposed to ultrasonication, transforms into 2D photoluminescent carbon quantum dots (CQDs) that display blue, cyan, green, and yellow emissions depending upon the excitation wavelength. Although this finding is intuitive, it has remained unacknowledged in the design of experiments which require ultrasonication of layered materials in organic solvents. Our results suggest that optical properties of dispersions obtained by LPE embody a contribution not only from the 2D nanostructures derived from the layered material but also from the 2D CQDs that are formed as a natural result of the liquid medium being exposed to ultrasonication. We anticipate that this new physical insight would form an important addition to the guidelines for exfoliation and help in rightly inferring the optical properties of the 2D material dispersions produced by these methods.
关键词： 2D nanostructures,Carbon quantum dots,Organic solvents,Liquid phase exfoliation,Ultrasonication,Photoluminescence
更新于2025-09-11 14:15:04
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Effects of energy and hydrogen peroxide concentration on structural and optical properties of CuO nanosheets prepared by pulsed laser ablation
摘要： Laser ablation of copper targets using Ce:Nd:YAG laser with pulses of 1064 nm wavelengths at 10 ns pulse width and with different laser pulse energies and in different concentrations of H2O2 solution is investigated experimentally. Cu/CuO flake-like nanostructures with visible band gap and the extension of its light absorption by changing the synthesis parameters such as laser pulse energy and concentration of H2O2 solution were observed. Characterization and comparison of the obtained suspensions are exploited by X-ray diffraction (XRD), UV–vis spectroscopy and field emission scanning electron microscopy (FE-SEM). The XRD analysis data show that in 10 vol% H2O2 solution CuO phase has been synthesized, while with decreasing the H2O2 concentration, Cu phase is also observed. The mean crystallite sizes of CuO were estimated using XRD patterns and were between 2.1 and 3.3 nm. The comparison of the UV–visible absorption spectra indicates that with decreasing pulse energy and decreasing H2O2 concentration up to 5 vol% the band gap of nanoparticles increased from 2.19 eV to 2.34 eV, which is accordant with the quantum confinement effect. FESEM image of all the synthesized samples illustrate the formation of flake-like nanostructure with the thickness of about 12–15 nm.
关键词： Oxides,Nanostructures,Semiconductors,Optical properties,Laser ablation
更新于2025-09-11 14:15:04
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Nanocrystal Aerogels with Coupled or Decoupled Building Blocks
摘要： The influence of inter-particle contact in nanoparticle-based aerogel network structures is investigated by selectively connecting or isolating the building blocks inside the network thereby coupling and decoupling them in regard to their optical and electronic properties. This is achieved by tuning the synthesis sequence and exchanging the point of shell growth and the point of particle assembly leading to two distinctly different structures as examined by electron microscopy. By thorough examination of the resulting optical properties of the generated structures the clear correlation between nanoscopic/microscopic structure and macroscopic optical properties is demonstrated. Temperature dependent measurements and effective mass approximation calculations support our findings.
关键词： Spectroscopy,Nanoparticles,Fluorescence,Aerogels,Nanostructures
更新于2025-09-11 14:15:04
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Femtosecond laser fabrication of silver nanostructures on glass for surface enhanced Raman spectroscopy
摘要： We report on an optimized fabrication protocol for obtaining silver nanoparticles on fused silica substrates via laser photoreduction of a silver salt solution. We find that multiple scans of the laser over the surface leads to a more uniform coverage of densely packed silver nanoparticles of approximately 50 nm diameter on the fused silica surface. Our substrates yield Raman enhancement factors of the order of 1011 of the signal detected from crystal violet. We use a theoretical model based on scanning electron microscope (SEM) images of our substrates to explain our experimental results. We also demonstrate how our technique can be extended to embedding silver nanoparticles in buried microfluidic channels in glass. The in situ laser inscription of silver nanoparticles on a laser machined, sub-surface, microfluidic channel wall within bulk glass paves the way for developing 3D, monolithic, fused silica surface enhance Raman spectroscopy (SERS) microfluidic sensing devices.
关键词： SERS,surface enhanced Raman spectroscopy,microfluidic sensing devices,femtosecond laser fabrication,silver nanostructures
更新于2025-09-11 14:15:04
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Nanostructure fabrication on the top of laser-made micropillars for enhancement of water repellence of aluminium alloy
摘要： Fabrication of superhydrophobic surfaces is a popular topic in research and industry due to many potential applications including self-cleaning, anti-icing or drag reduction. Laser micro and nanostructuring is an efficient method to replicate lotus leaves double-scale structures to achieve superhydrophobicity without chemical treatment. Immediately after laser processing, samples are hydrophilic and become hydrophobic in a few days, exposed to atmospheric conditions. This time was significantly reduced by vacuum processing to only 4 h. Two-step fabrication method of superhydrophobic surfaces have been developed using nanosecond laser system. In the first step, large scale micropillars are fabricated and covered by nano-scale protrusions in the following step using defocused laser beam. The nanostructure formation increased the apparent contact angle from 149° to 175°.
关键词： Nanostructures,Aluminium,Superhydrophobic,Fiber laser
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing APPLICATION OF MATHEMATICS IN TECHNICAL AND NATURAL SCIENCES: 11th International Conference for Promoting the Application of Mathematics in Technical and Natural Sciences - AMiTaNS’19 - Albena, Bulgaria (20–25 June 2019)] APPLICATION OF MATHEMATICS IN TECHNICAL AND NATURAL SCIENCES: 11th International Conference for Promoting the Application of Mathematics in Technical and Natural Sciences - AMiTaNS’19 - The possibility of self-assembly of complex nanostructures with pre-defined geometry under the action of laser field
摘要： Self-assembly remains one of the simplest and cheapest methods of nanostructuring. And the dependence of the properties of the objects obtained, not only on their composition, but also on the form, brings to the fore the question of developing methods for forming structures of a predetermined form and searching for system parameters in which the formation of a structure becomes possible. This paper is devoted to modeling the process of self-assembly of a multiparticle nanostructure of a predetermined shape in the field of laser radiation.
关键词： nanostructures,laser field,self-assembly,pre-defined geometry
更新于2025-09-11 14:15:04