Metal-insulator-metal (MIM) waveguide has deep sub-wavelength field confinements, which makes it an important component in many aspects. In MIM structure, both of the symmetric and anti-symmetric ...modes could be supported. However, the anti-symmetric mode was hardly used in the SPP-based devices due to the critical excitation condition. Here, we demonstrate anti-symmetric mode excitation and Fano resonance in a compact MIM-based plasmonic structure. By changing the position of the output channel, the symmetric mode is suppressed and only anti-symmetric mode is excited. Then, we tune the position of the output channel; anti-symmetric and symmetric mode are both achieved. Furthermore, Fano resonance is realized due to the coupling between anti-symmetric mode and symmetric mode. In addition, we analyze the effects of the parameters of the structure on the transmission spectra, and a plasmonic refractive index sensor with sensitivity about 800 nm/RIU and 1100 nm/RIU based on different waveguide modes is also realized. The proposed structure provides a novel method to achieve anti-symmetric mode excitation, and it has important applications in nanophotonic devices such as filter, sensor, and photoswitch, and has important significance in achieving all-optical on-chip integration.
Electrochemical study of the decorated Pt@Au catalyst synthesized by Cu underpotential deposition (UPD)-Pt redox replacement technique has been conducted in this work. The parameters affecting the Cu ...UPD on Au/C nanoparticles in sulfuric acid electrolyte, including the UPD potential, deposition time and potential sweep rate, were investigated in detail. Anode stripping method was used to calculate the charge of the deposited Cu adlayers. Results showed that Pt@Au catalyst prepared by this UPD-redox replacement approach is not a core-shell structure but a decorated structure. A series of decorated Pt@Au/C catalysts with various Pt coverages were synthesized and examined for formic acid oxidation (FAO). It is found that the specific activity of Pt atoms increases with the decrease of Pt surface coverage on Au. Life test showed that better stability was pertained for this decorated Pt@Au/C catalyst compared to Pt/C towards FAO.
Highly active Pt-decorated Au nanoparticles on carbon support with Pt:Au mole ratio ranging from 1:10 to 1:2 was successfully synthesized based on successive reduction strategy. The successful ...formation of this structure was suggested by transmission electron microscopy, UV–vis and voltammetry analyses. The electrocatalytic activity of this decorated structure toward formic acid oxidation surprisingly increases despite the low amount of Pt being used. At 0.1
V, the specific activity of PtAu/C with Pt/Au mole ratio 1:8 was more than one order of magnitude higher than the conventional Pt/C. The enhancement was attributed to the less Pt ensemble sites that the decorated structure possesses (ensemble effect) and the increase in the Pt atom reactivity on Au nanocrystal. The formic acid oxidation mechanism on this decorated structure was also elucidated using electrochemical impedance spectroscopy technique. It is proposed that besides the dehydrogenation reaction pathway happening on clean Pt sites, the reactive intermediate i.e. formate species could also be oxidized by the adsorbed water species on Pt at higher potential.
This paper presents a near-infrared (near-IR) photodetector based on a gold nanoparticles-doped (AuNPs-doped), single-walled carbon nanotube–germanium (SWCNT/Ge) heterojunction. The responsivity, ...detectivity, and response time of the AuNPs-doped, SWCNT/Ge heterojunction photodetector measured 476 mA W−1 (a 291% improvement), 1.0 × 1012 cm Hz1/2 W−1 (a 208% improvement), and 8 μs, respectively. The mechanism of the enhanced performance originated from the surface modification by gold doping, which effectively improved the work function of the carbon nanotube films and thus increased the barrier height between the heterojunctions, as measured by the contact potential distribution (CPD) and open circuit voltage (Voc) of the SWCNT/Ge interface. In addition, we investigated the effect of various particle sizes on the performance and stability of the photodetector. The results demonstrate the promising prospects of the presented heterojunction photodetector for infrared detection applications.
Plasmon-induced transparency (PIT), usually observed in plasmonic metamaterial structure, remains an attractive topic for research due to its unique optical properties. However, there is almost no ...research on using the interaction of plasmonic metamaterial and high refractive index dielectric to realize PIT. Here, we report a novel nanophotonics system that makes it possible to realize PIT based on guided-mode resonance and numerically demonstrate its transmission and reflection characteristics by finite element method simulations. The system is composed of a high refractive-index dielectric material and a two-dimensional metallic photonic crystal with 4-fold asymmetric holes. The interaction mechanism of the proposed structure is analyzed by the coupled-mode theory, and the effects of the parameters on PIT are investigated in detail. In addition, we first consider this PIT phenomenon of such fields on atom trapping (
Rb), and the results show that a stable 3D atom trapping with a tunable range of position of about ~17 nm is achieved. Our work provides a novel, efficient way to realize PIT, and it further broadens the application of plasmonic metamaterial systems.
In this work we have systematically characterized the adsorption of formic acid, its decomposed intermediates and products on the (100) surfaces of Pt, Au, monolayer and decorated Pt@Au surfaces. The ...calculated thermodynamic results validate our previous experimental results that the decorated Pt@Au surface may facilitate formic acid oxidation compared with the benchmark Pt catalyst; while the monolayer Pt@Au surface is not suitable for formic acid oxidation.
Graphical Abstract
We have systematically characterized the adsorption of formic acid, its decomposed intermediates and products on the (100) surfaces of Pt, Au, monolayer and decorated Pt@Au surfaces. The calculated thermodynamic results validate our previous experimental results that the decorated Pt@Au surface may facilitate formic acid oxidation compared with the benchmark Pt catalyst; while the monolayer Pt@Au surface is not suitable for formic acid oxidation
In this research, we report on a high-performance near-infrared (near-IR) photodetector based on single-walled carbon nanotube-germanium (SWCNT-Ge) heterojunction by assembling SWCNT films onto ...n-type Ge substrate with ozone treatment. The ozone doping enhances the conductivity of carbon nanotube films and the formed interfacial oxide layer (GeO
) suppresses the leakage current and carriers' recombination. The responsivity and detectivity in the near-IR region are estimated to be 362 mA W
and 7.22 × 10
cm Hz
W
, respectively, which are three times the value of the untreated device. Moreover, a rapid response time of ~11 μs is obtained simultaneously. These results suggest that the simple SWCNT-Ge structure and ozone treatment method might be utilized to fabricate high-performance and low-cost near-IR photodetectors.
CO stripping experiments were carried out on a series of submonolayer decorated Pt@Au/C electrocatalysts with different Pt surface coverages which were synthesized by the Cu underpotential deposition ...(UPD)-Pt redox replacement technique. Combined with density functional theory calculations, the correlation between the CO adsorption strength and surface morphology of the catalyst is well illustrated. Results showed that whether the surface Pt atom could form a PtPt surface ensemble with another neighboring Pt atom is critical, which determines CO adsorption and oxidation behaviors on the electrocatalyst.
All-carbon nanotube (CNT) hybrid films are fabricated through a facile vacuum filtration method by using hydrophilic single-walled carbon nanotube (SWCNT) films as filters and multi-walled carbon ...nanotube (MWCNT) powder dispersed in ethanol as liquor. The hydrophilic SWCNT film provides penetration channels for water, while the superhydrophobic MWCNTs have self-cleaning, self-spreading, and broadband absorption ability. The hybrid film exhibits ultra-high solar absorbance (∼99%), low thermal conductivity, and excellent light-to-heat conversion capacity. The temperature of the hybrid film increases from 24 to 60 °C in 1 s under one-sun illumination in air. The individual hybrid film exhibits a high water evaporation rate of 1.37 kg m−2 h−1 and a solar thermal efficiency of 87.4% under one-sun after 1 h illumination. The solar thermal efficiency maintains at ∼80% when many pieces of hybrid films self-assemble into a large film (∼40 cm2). The hybrid films have great potential in the desalination of seawater and sewage treatment. Ion concentrations in seawater decrease significantly to drinkable water standards by only one distillation treatment. Organic pollutants, such as rhodamine B and methylene blue, are removed effectively from sewage water by using the hybrid films in a solar steam generator.
All-carbon nanotube hybrid films with broadband optical absorption and self-cleaning ability are prepared. The films are efficient and effective in solar steam generation with a high solar evaporation efficiency of 87.4%, showing great potentials in seawater desalination and sewage purification. Display omitted
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