We report herein the template-directed synthesis, characterization, and electric properties of single-walled carbon nanotube- (SWNT-) based coaxial nanowires, that is, core (SWNT)-shell (conducting polypyrrole and polyaniline) nanowires. The SWNTs were first dispersed in aqueous solutions containing cationic surfactant cetyltrimethylammonium bromide (CTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonyl phenyl ether (O pi-10). Each individual nanotube (or small bundle) was then encased in its own micellelike envelope with hydrophobic surfactant groups orientated toward the nanotube and hydrophilic groups orientated toward the solution. And thus a hydrophobic region within the micelle/SWNT (called a micelle/SWNT hybrid template) was formed. Insertion and growth of pyrrole or aniline monomers in this hybrid template, upon removal of the surfactant, produce coaxial structures with a SWNT center and conducting polypyrrole or polyaniline coating. Raman and Fourier transform infrared (FTIR) spectroscopy and scanning (SEM) and transmission (TEM) electron microscopy were used to characterize the composition and the structures of these coaxial nanowires. The results revealed that the micellar molecules used could affect the surface morphologies of the resulting coaxial nanowires but not the molecular structures of the corresponding conducting polymers. Electric properties testing indicated that the SWNTs played the key roles in the conducting polymer/SWNT composites during electron transfer in the temperature range 77 K to room temperature. Compared with the SWNT network embedded in the conducting polymers, the composites within which SWNTs were coated perfectly by the identical conducting polymers exhibited higher barrier heights during electron transfer.
Abstract. In order to characterize the features of particulate pollution in the Pearl River Delta (PRD) in the summer, continuous measurements of particle number size distributions and chemical compositions were simultaneously performed at Guangzhou urban site (GZ) and Backgarden downwind regional site (BG) in July 2006. Particle number concentration from 20 nm to 10 µm at BG was (1.7 ± 0.8)×10 4 cm −3 , about 40% lower than that at GZ, (2.9 ± 1.1)×10 4 cm −3 . The total particle volume concentration at BG was 94 ± 34 µm 3 cm −3 , similar to that at GZ, 96 ± 43 µm 3 cm −3 . More 20-100 nm particles, significantly affected by the traffic emissions, were observed at GZ, while 100-660 nm particle number concentrations were similar at both sites as they are more regional. PM 2.5 values were similar at GZ (69 ± 43 µg m −3 ) and BG (69 ± 58 µg m −3 ) with R 2 of 0.71 for the daily average PM 2.5 at these two sites, indicating the fine particulate pollution in the PRD region to be regional. Two kinds of pollution episodes, the accumulation pollution episode and the regional transport pollution episode, were observed. Fine particles over 100 nm dominated both number and volume concentrations of total particles during the late periods of these pollution episodes. Accumulation and secondary transformation are the main reasons for the nighttime accumulation pollution episode. Correspondence to: M. Hu (minhu@pku.edu.cn) 660 nm particle mass and PM 2.5 increase. When south or southeast wind prevailed in the PRD region, regional transport of pollutants took place. Regional transport contributed about 30% to fine particulate pollution at BG during a regional transport case. Secondary transformation played an important role during regional transport, causing higher increase rates of secondary ions in PM 1.0 than other species and shifting the peaks of sulfate and ammonium mass size distributions to larger sizes. SO 2− 4 , NO − 3 , and NH + 4 accounted for about 70% and 40% of PM 1.0 and PM 2.5 , respectively.
We demonstrate plasmon-induced absorption (PIA) in an ultra-compact graphene waveguide system which is composed of a single graphene sheet with two air cavities side-coupled to a graphene nanoribbon. By designing two coherent optical pathways, the pronounced PIA can be achieved due to the extreme destructive interference between the radiant and subradiant modes supported by the two graphene nanoribbons. The resonant strength shows strong dependence on the coupling distance between the two graphene nanoribbons and the resonance wavelength can be dynamically tuned by varying their Fermi energy. Furthermore, the group delay time up to −0.14 ps can be reached at the PIA window, suggesting unique fast-light feature. In addition, the double PIA phenomenon is also analyzed by introducing another graphene nanoribbon. Our results may pave the way for controlling the transmission of a light signal in the design of ultracompact plasmonic devices.
In order to characterize the features of particulate pollution in the Pearl River Delta (PRD) in the summer, continuous measurements of particle number size distributions and chemical compositions were simultaneously performed at Guangzhou urban site (GZ) and Back-garden downwind regional site (BG) in July 2006. Particle number concentration from 20 nm to 10 μm at BG was (1.7±0.8)×10<sup>4</sup> cm<sup>−3</sup>, about 40% lower than that at GZ, (2.9±1.1)×10<sup>4</sup> cm<sup>−3</sup> with intensive traffic emissions. The total particle volume concentration at BG was 94±34 μm<sup>3</sup> cm<sup>−3</sup>, similar to that at GZ, 96±43 μm<sup>3</sup> cm<sup>−3</sup>. More 20–100 nm particles, significantly affected by the traffic emissions, were observed at GZ, while 100–660 nm particle number concentrations were similar at both sites as they are more regional. PM<sub>2.5</sub> values were also similar at GZ (69±43 μg m<sup>−3</sup>) and BG (69±58 μg m<sup>−3</sup>), indicating the fine particulate pollution in the PRD region to be regional. Two kinds of pollution episodes, the accumulation pollution episode and the regional transport pollution episode, were observed. Fine particles over 100 nm dominated both number and volume concentrations of total particles during the late periods of these pollution episodes. Accumulation and secondary transformations are two main reasons for the nighttime accumulation pollution episode. SO<sub>4</sub><sup>−2</sup>, NO<sub>3</sub><sup>−</sup>, and NH<sub>4</sub><sup>+</sup> accounted for about 60% in 100–660 nm particle mass and PM<sub>2.5</sub>. When south or south-southeast wind prevailed in the PRD region, regional transport of pollutants takes place. Regional transport contributed about 30% to fine particulate pollution at BG during a regional transport case. Secondary transformation played an important role during regional transport, causing higher increase rates of secondary ions in PM<sub>1.0</sub> than other species and shifting the peaks of sulfate and ammonium mass size distributions to larger sizes. SO<sub>4</sub><sup>−2</sup>, NO<sub>3</sub><sup>−</sup>, and NH<sub>4</sub><sup>+</sup> accounted for about 70% and 40% of PM<sub>1.0</sub> and PM<sub>2.5</sub>, respectively
[[abstract]]Measurements of aerosol physical, chemical and optical parameters were carried out in Guangzhou, China from 1 July to 31 July 2006 during the Pearl River Delta Campaign. The dry aerosol scattering coefficient was measured using an integrating nephelometer and the aerosol scattering coefficient for wet conditions was determined by subtracting the sum of the aerosol absorption coefficient, gas scattering coefficient and gas absorption coefficient from the atmospheric extinction coefficient. Following this, the aerosol hygroscopic growth factor, f(RH), was calculated as the ratio of wet and dry aerosol scattering coefficients. Measurements of size-resolved chemical composition, relative humidity (RH), and published functional relationships between particle chemical composition and water uptake were likewise used to find the aerosol scattering coefficients in wet and dry conditions using Mie theory for internally- or externally-mixed particle species [(NH4)2SO4, NH4NO3, NaCl, POM, EC and residue]. Closure was obtained by comparing the measured f(RH) values from the nephelometer and other in situ optical instruments with those computed from chemical composition and thermodynamics. Results show that the model can represent the observed f(RH) and is appropriate for use as a component in other higher-order models
R. (2010). A basic introduction to fixed-effect and randomeffects models for meta-analysis. Research Synthesis Methods, 1(2), 97-111. Bruininks, R. H., & Bruininks, B. D. (2005). Bruininks-Oseretsky test of motor proficiency (2th ed.), Minneapolis, MN: NCS Pearson.
The constructive interference of bright and dark plasmonic modes results in plasmon-induced absorption (PIA) effect. Here, we theoretically investigate PIA effect, which is realized by the constructive interference between a Fabry-Perot (F-P) resonance mode and a graphene quasi-guided mode. Numerical simulation reveals at least three advantages of our structure over previous ones. First, the extinction ratio can reach ~ 99.999%, resulting in the ultra-high figure of merit* (FOM*) as high as 10 6 . Second, the intensity of this pronounced PIA effect can be optimized by adjusting the coupling distance. Third, the resonance frequency can be easily tunable by tuning the graphene Fermi level. This system may have potential applications in dynamically optical switching and biochemical sensing. Electronic supplementary material The online version of this article (10.1186/s11671-019-3121-9) contains supplementary material, which is available to authorized users.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.