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Towards silicon-based metamaterials
摘要： We study periodic lattices of silicon nanorods and introduce the concept of a phase diagram that characterizes a transition between the regimes of photonic crystals and dielectric metamaterials when the lattice spacing and operational wavelength vary. We find the conditions when a hexagonal periodic lattice of silicon nanorods can operate as a metamaterial described by averaged parameters. In general, we reveal that the metamaterial regime can be achieved for dielectric permittivity exceeding the value ε = 14, being commonly available for semiconductors in both visible and near-infrared frequency ranges. Thus, advanced semiconductor technologies can offer a versatile platform for novel designs of all-dielectric Mie-resonant metadevices.
关键词： phase diagram,photonic crystals,dielectric metamaterials,Mie resonances,silicon nanorods
更新于2025-09-23 15:21:21
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Time Dependent Facile Hydrothermal Synthesis of TiO2 Nanorods and their Photoelectrochemical Applications
摘要： In the present investigation, we report facile hydrothermal synthesis of TiO2 nanorods with high density rutile phase on Transparent Conducting Oxide (TCO) for enhanced solar cell application. The structural, optical, morphological, compositional and electrochemical properties are investigated by detailed XRD, UV-Vis-NIR spectrophotometer, FESEM, TEM, EDAX, XPS and photoelectrochemical studies. It is demonstrated that, the deposited TiO2 thin film shows pure rutile phase with tetragonal crystal structure. Optical spectra showed strong light absorption in UV region and FESEM images confirm the time dependent growth of TiO2 nanorods. EDAX and XPS Spectra confirm the formation of pure TiO2 nanorods. Photoelectrochemical performance with respect to time dependent growth of TiO2 nanorods showed highest photoconversion efficiency = 5.1%.
关键词： Hydrothermal synthesis,Photoelectrochemical cell property,Single crystalline,Photoconversion efficiency,TiO2 nanorods,Transparent conducting oxide (TCO)
更新于2025-09-23 15:21:21
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Constructing 1D CdS nanorod composites with high photocatalytic hydrogen production by introducing the Ni-based cocatalysts
摘要： Various 1D CdS nanorod composites (e.g. NiO/CdS, NiS/CdS and Ni(OH)2/CdS) were constructed by anchoring Ni-based cocatalysts on the surface of CdS nanorods. Photocatalytic reforming of lactic acid in aqueous medium for hydrogen generation using CdS composites was investigated, and Ni(OH)2/CdS sample displayed the best activity. Evidently, Ni(OH)2 cocatalyst can offer a suitable potential position to boost the transfer of photo-generated electrons and much more active sites. Furthermore, the result of LSV curves discloses that the higher photocatalytic activity is due to the smaller onset overpotential, which can accelerate the reduction of protons into H2. This work provides a full comprehension of the mechanism that Ni species cocatalysts improve photocatalytic activity.
关键词： cocatalyst,hydrogen production,CdS nanorods,visible light,Ni-based
更新于2025-09-23 15:21:21
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Electron–hole correlations govern Auger recombination in nanostructures
摘要： The fast nonradiative decay of multiexcitonic states via Auger recombination is a fundamental process affecting a variety of applications based on semiconductor nanostructures. From a theoretical perspective, the description of Auger recombination in confined semiconductor nanostructures is a challenging task due to the large number of valance electrons and exponentially growing number of excited excitonic and biexcitonic states that are coupled by the Coulomb interaction. These challenges have restricted the treatment of Auger recombination to simple, noninteracting electron–hole models. Herein we present a novel approach for calculating Auger recombination lifetimes in confined nanostructures having thousands to tens of thousands of electrons, explicitly including electron–hole interactions. We demonstrate that the inclusion of electron–hole correlations are imperative to capture the correct scaling of the Auger recombination lifetime with the size and shape of the nanostructure. In addition, correlation effects are required to obtain quantitatively accurate lifetimes even for systems smaller than the exciton Bohr radius. Neglecting such correlations can result in lifetimes that are 2 orders of magnitude too long. We establish the utility of the new approach for CdSe quantum dots of varying sizes and for CdSe nanorods of varying diameters and lengths. Our new approach is the first theoretical method to postdict the experimentally known “universal volume scaling law” for quantum dots and makes novel predictions for the scaling of the Auger recombination lifetimes in nanorods.
关键词： semiconductor nanocrystals,quantum dots,excitons,auger recombination,biexcitons,nanorods
更新于2025-09-23 15:21:21
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Reduced graphene oxide supported MnO2 nanorods as recyclable and efficient adsorptive photocatalysts for pollutants removal
摘要： The emerging concept of two dimensional (2D) hybrid materials with large surface area and good interfacial contacts is highly desirable for diverse catalytic applications. Herein, we have designed and developed novel 1D-2D nanocomposite by loading manganese dioxide (MnO2) nanorods over reduced graphene oxide (RGO) nanosheets by facile hydrothermal synthesis method to exploit the large surface area, close contact of 1D-2D components with abundant reaction sites. The as prepared MnO2-RGO nanocomposite has been characterized in detail using state-of-art techniques and has been successfully utilized efficient adsorptive photocatalysts for the removal of a colored dye (neutral red) and a colorless pollutant (ciprofloxacin) from water. In addition, the stability and recyclability of this catalyst has also been demonstrated. This work is expected to pave way for the development of many new 1D-2D binary nanocomposite catalysts for environmental remediation applications.
关键词： Reduced graphene oxide,MnO2 nanorods,Photocatalysis,Pollutants removal,Ciprofloxacin,Neutral red
更新于2025-09-23 15:21:21
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Schottky Contacts on Polarity-Controlled Vertical ZnO Nanorods
摘要： Polarity-controlled growth of ZnO by chemical bath deposition provides a method for controlling the crystal orientation of vertical arrays of nanorods. The ability to define the morphology and structure of the nanorods is essential to maximising the performance of optical and electrical devices such as piezoelectric nanogenerators; however, well-defined Schottky contacts to the polar facets of the structures have yet to be explored. In this work, we demonstrate a process to fabricate metal-semiconductor-metal device structures from vertical arrays with Au contacts on the uppermost polar facets of the nanorods and show the O-polar nanorods (~0.44 eV) have a greater effective barrier height than the Zn-polar nanorods (~0.37 eV). Oxygen plasma treatment is shown by Cathodoluminescence (CL) spectroscopy to reduce mid-gap defects associated with radiative emissions that improves the Schottky contacts from weakly-rectifying to strongly-rectifying. Interestingly, the plasma treatment was shown to have a much greater effect in reducing the number of carriers in O-polar nanorods through quenching of the donor-type substitutional hydrogen on oxygen sites (HO) when compared to the zinc vacancy related hydrogen defect complexes (VZn, Hn) in Zn-polar nanorods that evolve to lower coordinated complexes. The effect on HO in the O-polar nanorods coincided with a large reduction in the visible range defects producing a lower conductivity and creating the larger effective barrier heights. This combination can allow radiative losses and charge leakage to be controlled enhancing devices such as dynamic photodetectors, strain sensors, and LEDs while showing the O-polar nanorods can outperform Zn-polar nanorods in such applications.
关键词： ZnO,Cathodoluminescence,Electrical Transport,Polarity,Schottky Contacts,Nanorods,Defects
更新于2025-09-23 15:21:01
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Nonlinear Plasmonic Sensing for Label-Free and Selective Detection of Mercury at Picomolar Level
摘要： We present the concept of a nonlinear plasmonic sensing approach for rapid, sensitive, and label-free detection of mercury. Nonlinear plasmonic sensing of mercury relies on a systematic combination of nonlinear optics (NLO) with well-known concepts of amalgamation chemistry and plasmonic properties of gold nanorods. Exploiting the extreme sensitivity of the NLO process toward Hg-induced change in the local electric field of plasmonic nanorods, we succeed in improving the limit of detection (LOD) of mercury by 2?3 orders of magnitude as compared to the commonly used linear localized surface plasmon resonance (LSPR) based sensing. Using our method, an LOD of as low as 58 pM (11 ppt) has been achieved with high selectivity. Nonlinear plasmonic sensing approach is found to work excellently for detecting mercury in real samples like blood plasma.
关键词： TPRS,Nonlinear plasmonic sensing,SHG,mercury sensing,nanorods,nonlinear spectroscopy
更新于2025-09-23 15:21:01
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Subwavelength-scale nanorods implemented hexagonal pyramids structure as efficient light-extraction in Light-emitting diodes
摘要： Subwavelength-scale nanorods were implemented on the hexagonal pyramid of photochemically etched light-emitting diodes (LEDs) to improve light extraction efficiency (LEE). Sequential processes of Ag deposition and inductively coupled plasma etching successfully produce nanorods on both locally unetched flat surface and sidewall of hexagonal pyramids. The subwavelength-scale structures on flat surface offer gradually changed refractive index, and the structures on side wall of hexagonal pyramid reduce backward reflection, thereby enhancing further enhancement of the light extraction efficiency. Consequently, the nanorods implemented LED shows a remarkable enhancement in the light output power by 14% compared with that of the photochemically etched LEDs which is known to exhibit the highest light output power. Theoretical calculations using a rigorous coupled wave analysis method reveal that the subwavelength-scale nanorods are very effective in the elimination of TIR as well as backward reflections, thereby further enhancing LEE of the LEDs.
关键词： subwavelength-scale nanorods,light-emitting diodes,light extraction efficiency,hexagonal pyramids,photochemical etching
更新于2025-09-23 15:21:01
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Graphene oxide coated flower-shaped ZnO nanorods: Optoelectronic properties
摘要： In this paper, the influence of graphene oxide coating on optical and photoluminescence properties of zinc oxide nanorods (ZnO NRs) has been investigated. ZnO NRs were prepared using a hydrothermal route (from zinc nitrate hexahydrate and hexamethylenetetramine), graphene oxide (GO) was fabricated by Hummer's method, while for synthesis of ZnO nanorods:graphene oxide nanocomposite (ZnO NRs:GO) on Si (100) substrate, a facile technique (drop coating) was proposed. The structural, morphological, optical and luminescence properties of the films were investigated using X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), together with Fourier transform infrared (FT-IR), Raman, ultraviolet- visible- near-infrared (UV/VIS/NIR) and photoluminescence (PL) spectroscopies. As revealed by XRD analysis, composites display a hexagonal wurtzite type structure with a (101) preferred grain orientation. The average crystallite sizes decrease from 45 to 40 nm after GO coating. The SEM study confirms successful coating of GO layers on flower-like ZnO nanostructures. The FTIR and Raman analyses validated the hybridization of nanocomposite and the strong interaction between ZnO NRs and GO. The band gap of the ZnO NRs:GO nanocomposite is lower (2.95eV) compared to that of ZnO NRs (3.11 eV), as determined from the analysis of UV absorbance spectra. The ZnO NRs:GO nanocomposite exhibits a broad PL band, from ~450 nm to ~750 nm, with a nearly white-light integrated emission and a chromaticity coordinate of (0.25, 0.34). Gaussian deconvoluted broad PL band exhibits three distinct sub-bands, associated with radiative recombinations in ZnO and GO.
关键词： graphene oxide,optical properties,nanocomposite,ZnO nanorods
更新于2025-09-23 15:21:01
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Self-assembled CdS@BN core-shell photocatalysts for efficient visible-light-driven photocatalytic hydrogen evolution
摘要： CdS@BN NRs core-shell photocatalysts for hydrogen evolution were synthesized by a solvothermal and chemical adsorption method. CdS NRs coated by 5 wt% boron nitride (BN) shell exhibited remarkably visible-light photocatalytic hydrogen evolution activity of up to 30.68 mmol g?1 h?1, nearly 6.79 times higher than that of pure CdS NRs, and the apparent quantum efficiency at 420 nm was 7.5%. Transmission electron microscopy showed the CdS NRs were coated with a thin (~5 nm) BN layer, which together with the hydrogen evolution results proved the photocatalytic ability of CdS NRs was significantly improved. The hydrogen evolution rate of CdS NRs coated by 5 wt% BN remained at 91.4% after four cycles, indicating the photocorrosion of CdS NRs was effectively alleviated. Moreover, the large and close coaxial interfacial contact between the CdS core and the BN shell was beneficial to the separation and transfer of photogenerated electron-hole pairs.
关键词： Core-shell structure,Photocatalytic hydrogen evolution,CdS Nanorods,Boron nitride
更新于2025-09-23 15:21:01