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Mid-infrared sensing properties of a plasmonic metal-insulator-metal waveguide with a single stub including the defects
摘要： A highly sensitive surface plasmon polariton (SPP) based sensor with a simple structure that composes of a metal-insulator-metal waveguide with a single stub including several silver nanorod defects, is designed and numerically investigated using finite element method for the applications of refractive index sensors and temperature sensors. The simulation results show that the existence of silver nanorod defects in the single stub have a great influence on the sensitivity performance, which provides an additional degree to manipulate the system response in the nanometer scale. The refractive index sensitivity can be reached as high as 5140 nm/RIU (RIU is refractive index unit) and the temperature sensitivity is about 2.05 nm/0C, which can be further improved by varying the length of stub (h), radius of defect rod (r) and the number of defects (N) in the stub. The sensing characteristics of the proposed simple structure would pay the way for highly integrated optical circuits for designing nanoscale refractive index sensors and temperature sensors with the single stub including the defects.
关键词： integrated optical circuits,refractive index sensors,silver nanorod defects,metal-insulator-metal waveguide,temperature sensors,surface plasmon polariton,finite element method
更新于2025-09-12 10:27:22
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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) - Effective Coupling of a Plasmonic Nanorod to a Microsphere Resonator
摘要： Coupled photonic-plasmonic systems have already proven successful as ultra-sensitive sensors with the potential of single virus detection. Such systems are e.g. composed of a plasmonic nanoparticle in vicinity of an optical resonator usually in the form of a microsphere, a mirroring or a microdisk. These systems are proven highly sensitive due to their large quality factor and are thus utilized as bio, pressure, gas or temperature sensors. When a plasmonic nanoparticle is positioned near such resonator, coupling of the plasmonic and photonic modes can result in an ultra-sensitive biosensor, since nanoparticle presence enhance ambient refractive index (RI) variation sensitivity. In this paper, photonic-plasmonic coupling of a gold nanorod in close vicinity of a silica microsphere is simulated in order to investigate various types of coupling settings in such systems. The presence of the nanorod results in a frequency shift as well as in a reduction of the quality factor, which are both highly dependent on nanorod properties such as size, distance between the particle and the sphere as well as the nanorod orientation relative to the sphere surface. A single gold nanorod is positioned in 50nm distance to a 15.5μm silica microsphere which supports a whispering gallery mode at 1550nm and both resonance frequency and quality factor are computed using the simulation platform COMSOL Multiphysics. The nanorod orientation is altered starting from the tangential direction with respect to the sphere surface (0o) to the perpendicular direction (90o). In the Fig 1a) the quality factor together with the damping constant is shown as a function of the nanorod orientation for at an operating wavelength of 1550nm. The 90o direction results in higher quality factor as well as a better mode stability although the frequency shift associated to a 90o turn is only about 10GHz. In Fig 1b) the frequency shift and quality factor for the perpendicular nanorod versus ambient medium RI is plotted, which confirms the ultra-sensitivity of the designed optical resonator up to a 10-3 RI shift. The electric field distribution outside and inside of the nanorod is illustrated in Fig. 1c) for the three directions 90o, 45o and 0o where the perpendicular nanorod shows the weakest interaction with the excited whispering gallery mode and thus yields the largest quality factor.
关键词： silica microsphere,photonic-plasmonic coupling,gold nanorod,COMSOL Multiphysics,whispering gallery mode
更新于2025-09-12 10:27:22
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Effect of Ag/rGO on the Optical Properties of Plasmon-Modified SnO2 Composite and Its Application in Self-Powered UV Photodetector
摘要： A facile hydrothermal method was employed to synthesize silver–reduced graphene oxide (Ag/rGO) plasmon-modi?ed SnO2 composite, by incorporating Ag–reduced graphene oxide (Ag/rGO) into SnO2 nanorods as a photoanode for assembling a self-powered ultraviolet photodetector (UVPD). The as-synthesized samples were investigated in detail by X-ray di?raction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and UV visible spectrophotometer. The as-prepared Ag/rGO ?lms show enhanced light absorption attributed to the localized surface plasmon resonance (LSPR). The optimized 1.0 wt.% Ag/rGO incorporated into SnO2-based UVPD exhibits a signi?cant photocurrent response due to the enhanced absorption light and e?ective suppression of charge recombination. This UVPD demonstrates a high performance, with photocurrent density reaching 0.29 mAcm?2. This device also exhibits a high on:o? ratio of 195 and fast response time, which are superior to that of the free-modi?ed one. In addition, the UVPD based on plasmon-modi?ed SnO2 photoanode treated with TiCl4-aqueous solution has attained a higher photocurrent with a maximum value reaching 5.4 mAcm?2, making this device favorable in ultraviolet detection.
关键词： plasmon-modi?ed-SnO2 composite,Ag/rGO,UV photodetector,SnO2 nanorod,surface plasmon
更新于2025-09-12 10:27:22
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Sol–gel approach for the growth of vertically aligned 3D-TiO2 nanorod arrays as an efficient photoanode for high-performance dye-sensitized solar cells
摘要： In this study, a facile, low cost, and scalable sol–gel method has been proposed for the coating of ultra-thin layer of TiO2 on FTO substrate as a seed layer for the growth of 3D-TiO2 nanorod (3D-TiO2-NR) arrays on FTO. Then, the two-step hydrothermal process including nanorod growth and the chemical etching treatment was proceeded for the fabrication of FTO/3D-TiO2-NR photoanodes. The thickness of the deposited TiO2 in FTO/TiO2-sg samples was measured with small-angle X-ray scattering technique, and it was obtained to be 21.3 nm. FE-SEM and TEM techniques were used for the morphological characterization of 3D-TiO2-NR, and it was obtained that the tightly adhered film of vertically aligned 3D-TiO2-NR with two-layer nanostructuring is formed with a cubic base and a nanorods head. Finally, DSSCs with iodine-based and cobalt(II/III) tris(2,2′-bipyridine) complex-based electrolytes with two different photoanodes including 3D-TiO2-NR and TiO2-NP were assembled and their photovoltaic characteristics were investigated. For [Co(bpy)3]2+/3+ shuttle-based DSSC, the obtained power conversion efficiency (η) was about 3.5% with Jsc of 9.36 mA cm?2 in 3D-TiO2-NR-based DSSC, while η of TiO2-NP-based DSSC was about 1.4%. The results showed that employing 3D-TiO2-NR-based photoanode in DSSCs with bulky electron shuttles remarkably improves the photovoltaic characteristics of DSSCs. Electrochemical impedance spectroscopic studies also showed the lower charge transfer resistances for DSSCs with nanorod-based photoanode building blocks.
关键词： Adhesion,Electron shuttle,TiO2 nanorod arrays,DSSC,Cobalt(II/III) tris(2,2′-bipyridine) complexes,Sol–gel
更新于2025-09-12 10:27:22
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Photovoltaic performance improvement via designing nanorod parameter in composite-structure solar cells
摘要： In this work, the optical characteristics of electrodeposited Cu2O films was studied, and the depth of photogenerated carriers in Cu2O films was obtained. In order to improve the collection depth of the photogenerated carrier in ZnO/Cu2O solar cells, ZnO nanorod array were employed to construct composite-structure solar cells. The influence of the ZnO nanorod arrays on short-circuit current and open circuit voltage was systematically analyzed in the nanorod cells. For optimizing device performance, ordered ZnO nanorod arrays that incorporated design spacing that matched the carrier diffusion length of the absorption layer were used. Analyses of the photovoltaic properties revealed that ordered nanorod arrays with a proper spacing could improve carrier generation efficiency in high-efficient collection regions of the carriers. These observations indicate that nanorod spacing is an important variable in the construction of high-efficient nanorod-based solar cells.
关键词： Radial heterojunction,Carrier collection length,Optical absorption depth,Ordered ZnO nanorod array
更新于2025-09-12 10:27:22
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Growth mechanism of gold nanorods: the effect of tip-surface curvature as revealed by molecular dynamics simulations
摘要： To understand the anisotropic growth mechanism of gold nanorods (AuNRs) during colloidal synthesis is critical for controlling the nanocrystal size and shape and thus has implications in tuning the properties for applications in a wide range of research and technology fields. In order to investigate the role of the cetyltrimethylammonium bromide (CTAB) coating in the anisotropic growth mechanism of AuNRs, we used molecular dynamics (MD) simulations and built a computational model that considered explicitly the effect of the curvature of the gold surface on CTAB adsorption and therefore differentiated the CTAB arrangements on flat and curved surfaces, representing the lateral and tip facets of growing AuNRs, respectively. We verified that on a curved surface, a lower CTAB coverage density and larger intermicellar channels are generated compared to those on a flat surface. Using umbrella sampling simulations, we measured the free energy profile and verified that the environment around a curved surface corresponds to an easier migration from the solution to the gold surface for the [AuBr2]? species than does a flat surface. Long unbiased molecular dynamics simulations also corroborated the umbrella sampling results. Therefore, the [AuBr2]? diffusion through the environment of the tips is much more favorable than in the case of lateral facets. This shows that the surface curvature is an essential component of the anisotropic growth mechanism.
关键词： molecular dynamics,growth mechanism,CTAB,umbrella sampling,surface curvature,gold nanorod synthesis
更新于2025-09-12 10:27:22
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Effect of Surface Modification on SILAR Deposited CdS Quantum Dot Sensitized Hydrothermally Synthesised Titania Nanostructure
摘要： In the present work titaniana noflakes-nanorods were prepared on a flexible titanium metal foil by modified hydrothermal method. The titania nanoflakes-nanorods were further sensitized with CdS quantum dots through SILAR deposition. The surface charge of the titania surfaces were tuned using triethanolamine (TEA) to obtain maximum loading of CdS particles on the surface. The samples were characterized by XRD, FE-SEM and EDX analysis, which confirms the enhanced deposition of CdS quantum dots on the titania surface by TEA modification. The visible light photocatalytic studies were done by methylene blue degradation study. The modification in the SILAR cycle using TEA improves the photocatlytic performance around 4 times than those without TEA. The OH.radical formed in the photocatalytic reaction followed by photoluminescence study.
关键词： SILAR,Photocatalysis,Triethanolamine,CdS quantum dot,Titania nanorod
更新于2025-09-12 10:27:22
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Optical properties and electromagnetically induced grating in a hybrid semiconductor quantum dot-metallic nanorod system
摘要： An arti?cial molecule consisting of an SQD and an MNR embedded in 3D photonic crystal is proposed to realize EIG. Using the quantum mechanical density matrix approach, we have derived an expression of the absorption coe?cient in the SQD in presence of MNR. Nanoparticle geometry can modify the local ?elds that determine SQD-MNP coupling and to engineer the hybrid optical response. The probe absorption is reduced via a strong coupling ?eld, demonstrating spectral transparency window. It is worth noting that the background affects the relaxations of SQD. So, by making use of 3D photonic crystal as the background medium, reduced decay rate and consequently substantial local-?eld enhancement rate are provided. Based on EIT effect and a strong standing-wave ?eld, diffraction grating is achievable. The ?rst-order diffraction intensity can reach its maximum by tuning the system parameters. This model may be useful in designing new devices in all-optical communication.
关键词： Metallic nanorod (MNR),Semiconductor quantum dot (SQD),Electromagnetically induced grating (EIG),Photonic crystal (PC)
更新于2025-09-12 10:27:22
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Oxygen non-stoichiometry in TiO2 and ZnO nano rods: Effect on the photovoltaic properties of dye and Sb2S3 sensitized solar cells
摘要： Rutile TiO2 (TiO2-NR) and ZnO (ZnO-NR) in nanorod microstructural forms are synthesized by hydrothermal route. The oxides are grown directly on fluorine doped SnO2 coated glass, and annealed in air (AA) and hydrogen (HA) atmosphere for 3 h at 450 °C. A detailed structural, optical, and microstructural study confirms the phase formation in the AA and stability in HA samples. EPR signal with g-values of ~1.99 and ~1.95 from TiO2-NR and ZnO-NR photoanodes respectively confirms the presence of oxygen vacancy (OV) related defects. The EPR signals are stronger in TiO2-NR-HA compared to TiO2-NR-AA and is absent in ZnO-NR-AA suggesting increased defect concentration on hydrogenation. Further this leads to two order increase in photoconductivity for hydrogenated TiO2-NR-HA and ZnO-NR-HA photoanodes when measured under 1 Sun illumination compared to AA photoanodes. Photovoltaic power conversion efficiency for both dye and Sb2S3 sensitized solar cells are found to increase by 2 to 3 times in hydrogenated ZnO-NR. In contrast, TiO2-NR show two-fold decrease in efficiency on hydrogenation. The efficiency change is consistent with the change in interface impedance, which increases for dye or Sb2S3 sensitized TiO2-NR-HA photoanode, whereas, decreases for sensitized ZnO-NR-HA photoanode. These studies show that despite of one to two to three order increase in photoconductivity, the sensitizer/photoanode interface impedance play a significant role in deciding the efficiency.
关键词： Oxygen vacancy,Nanorod,Photoanode,Efficiency,ZnO,Solar cell,TiO2
更新于2025-09-12 10:27:22
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Enhanced PEC performance of hematite photoanode coupled with bimetallic oxyhydroxide NiFeOOH through a simple electroless method
摘要： The oxygen evolution reaction (OER) is one important bottleneck in the development of economical photoelectrodes. Herein, we firstly prepared bimetallic oxyhydroxide NiFeOOH layer on Fe2O3 photoanode through a simple electroless ligand-regulated oxidation method in order to build highly-matched semiconductor/cocatalyst interface. Benefited from the accelerated OER kinetics and low overpotential of bimetallic oxyhydroxide NiFeOOH, the resultant Fe2O3/NiFeOOH core-shell with strongly-bound heterojunction interface possesses better visible light absorption, enhanced photocurrent density (1.83 mA/cm2 at 1.23 VRHE) and good stability than bare Fe2O3 and semi-FeOOH and NiOOH decorated Fe2O3 photoanodes. We believe this work provides a new pathway for designing high-quality contact interface of various photoelectrode/catalyst.
关键词： electroless ligand-regulated oxidation,photoelectrochemical water splitting,Fe2O3,core-shell nanorod arrays,NiFeOOH
更新于2025-09-12 10:27:22