Tai-Long Gui

Dual-Band Terahertz Metamaterial Absorber with Polarization Insensitivity and Wide Incident Angle

This paper presents the design, simulation and mea- surement of a dual-band terahertz metamaterial absorber with polarization-insensitivity and wide incident angle. The unit cell of the metamaterial consists of top resonator structures and low metal- lic ground plane, separated by an isolation material spacer to realize both electric and magnetic resonances. The physical mechanism of dual-band absorption and the sensitivity to the polarization direction and incident direction of the EM wave are theoretically investigated by simulating the x-component and normal component electric fleld distribution, current distribution on ERRs and metallic ground plane, and distribution of power ∞ow and loss at the resonance frequencies as well as difierent modes EM waves, based the FDTD calculated method, respectively. The results show that the absorber is not only correctly coupling to the incident electric fleld and magnetic fleld, but also can trap the input power into speciflc positions of the devices and ab- sorb it, besides insensitivity to the polarized angle and incident angle. Moreover, the experiment demonstrates that the absorber achieves two strong absorptions of 82.8% and 86.8% near 1.724 and 3.557THz.

Synthesis and properties of poly(2-ethynylpyridinium bromide) having side-chain liquid crystalline moieties

Abstract Novel conjugated polymer having side chain liquid crystalline moieties was easily synthesized by the direct polymerization of 2-ethynylpyridine with the corresponding alkyl bromide having a liquid crystalline moiety, 4-{4′-{10′′-bromodecyl}oxyphenyl}azobenzoic acid. The polymerization proceeded well to give the resulting polymer in moderate yields. The polymer structure was characterized by various instrumental methods to have conjugated polymer system with liquid crystalline moieties. The photoluminescence spectrum of the polymer film shows that the photoluminescence peak is located at 430 and 454 nm corresponding to the photon energy of 2.80 and 2.66 eV. A needle shape of texture, which is a typical optical texture of smectic phase, was observed.

Polymerization of 4-dimethylamino-N-propargylpyridinium bromide by transition metal catalysts

The polymerization of an ionic propargyl derivative, 4-dimethylamino-N-propargylpyridinium bromide (DMAPPB), was carried out by palladium, platinum, and ruthenium chlorides. The polymerization of DMAPPB by these transition metal catalysts proceeded well to give a relatively high polymer yield. The chemical structure of the resulting polymer was characterized by such instrumental methods as elemental analysis, infrared, NMR, UV–visible spectroscopies to have conjugated polymer backbone system bearing 4-dimethylamino-N-methylenepyridinium bromide. The polymer was soluble in DMF, DMSO, and formic acid, and found to be less hygroscopic than those of similar homologues having more smaller substituents. The resulting polymers were mostly black powders and showed the amorphous morphology.

Electrochemical properties of poly(2-ethynylpyridinium bromide) having propargyl side chains

An ionic conjugated polymer, poly(2-ethynylpyridinium bromide)having propargyl side chain(PEPB-P), was prepared by the activated polymerization of 2-ethynylpyridine with propargyl bromide in high yield. The electrochemical properties of PEPB-P were studied by using cyclic voltammograms. PEPB-P showed the well-defined and stable redox process at − 0.1 to + 1.6 V. The oxidation and reduction occurred at 0.84 and 0.69 V, respectively. The redox current value increased as the increased scan rate and the exponent of scan rate, x value was found to be 0.75, which means that the redox kinetics is mainly controlled by both electron transfer and diffusion process.

Synthesis and Electro-Optical Properties of Poly(4-ethynylaniline)

A new conjugated polymer with amine groups was synthesized in high yields by the polymerization of 4-ethynylaniline with various transition metal catalysts. The polymer structure was identified by various instrumental methods to have a conjugated polymer backbone system with p-aminophenyl substituents. The photoluminescence peak of poly(4-ethynylaniline) is located at 478 nm corresponding to the photon energy of 2.60 eV. From the CV measurements, the HOMO energy level of the polymer was calculated to be 5.03 eV.

Uncatalyzed Synthesis and Properties of Polyacetylene with N-Pentylpyridinium Iodide

Uncatalyzed synthesis of a new ionic conjugated polymer, poly(3-ethynyl-N-pentylpyridinium iodide) [P3EPPI] was performed by the activated polymerization of 3-ethynylpyridine using 1-iodopentane. The polymerization proceeded in homogeneous manner to provide a moderate yield of polymer. The polymer structure was characterized by such instrumental methods as NMR (1H- and 13C-), IR, and UV-visible spectroscopies to have a conjugated polymer backbone system having N-pentyl-3-pyridinium iodide as substituents. The photoluminescence maximum peak of P3EPPI was located at 534 nm, which corresponds to the photon energy of 2.32 eV. The cyclovoltamograms of polymer exhibited the electrochemically stable window at the −1.53∼1.50 V region. The kinetics of the redox process of P3EPPI was found to be mainly controlled by the reactant diffusion process from the experiment of the oxidation current density of polymer versus the scan rate.

Surface Plasmon Resonant THz Wave Transmission on Carbon Nanotube Film

The properties of the terahertz resonant surface plasmons wave on the carbon nanotube film and dielectric interface have been investigated. As a first step towards engineering terahertz SPPs-like surface modes, we present a computer experiment to demonstrate that the carbon nanotube film surface can also be employed to concentrate and guide the terahertz SPPs wave. The carbon nanotube film is modeled in an experimentally realizable geometry. It is shown that a unique electromagnetic surface mode in terahertz region can be supported along the carbon nanotube film/dielectric interface when the free-space broadband terahertz pulse is incident on the carbon nanotube film with subwavelength gratings. Comparing with noble metals, plasmonic nano-structure materials based on carbon nanotube film offer a potentially more versatile approach to engineering tightly confined surface modes in the THz regime.

Properties of carbon nanotubes loop antenna at Terahertz range

It is the first time this paper investigates the fundamental characteristics of the loop antenna formed single-walled carbon nanotubes from 1.0∼10 terahertz frequency region using finite integral methods. The armchair single-walled carbon nanotubes can be considered due to their metallic conducting. The surface current dense, electric field and magnetic field distribution, scattering coefficient, input admittance, radiation patterns and gain are presented and compared to carbon nanotubes dipole antenna with the same size of the perimeter of the loop antenna. The results demonstrate that carbon nanotubes loop antenna with a radius of 15 µm takes on the resonant frequency properties from 7.35 terahertz to 7.46 terahertz in the center frequency of 7.4 terahertz, corresponding scattering coefficient less than −10dB. The maximum gain of carbon nanotubes loop antenna is 5.7 dB. All results is can be used for the design of carbon nanotubes antenna in the terahertz region.

Electrochemical Properties of Poly(α-methylbenzyl dipropargylamine) Prepared by the Cyclopolymerization of α-Methylbenzyl dipropargylamine

The electrochemical properties of poly(α-methylbenzyl dipropargylamine) was studied by cyclic voltametry. Poly(α-methylbenzyl dipropargylamine) was prepared by the cyclopolymerization of α-methylbenzyl dipropargylamine in high yield. The photoluminescence peaks of the present polymer was observed at 443 nm corresponding to the photon energy of 2.80 eV. The cyclovoltamograms of the polymer exhibited the irreversible electrochemical behaviors between the doping and undoping peaks. It was found that the kinetics of the redox process of poly(MBDPA) might be mainly controlled by the electron transfer process from the experiment of the oxidation current density of poly(MBDPA) versus the scan rate.

Electro-Optical and Electrochemical Properties of Poly(2-ethynyl-N-glycidylpyridinium bromide)

An ionic polyacetylene with the pendent N-glycidylpyridinium bromide, poly(2-ethynyl-N-glycidylpyridinium bromide), was synthesized in 91% yield by the activated polymerization of 2-ethynylpyridine with epibromohydrin without any additional catalyst or catalyst. This polymer exhibited characteristic UV-visible absorption band at 515 nm and yellow PL spectrum at 598 nm corresponding to the photon energy of 2.07 eV. The cyclovoltamograms of polymer exhibited the electrochemically stable window in the region of −1.4 ∼ 1.8 V and the redox current value gradually increased as the scan rate increased. The kinetics of the redox process of polymer was found to be well-controlled by the reactant diffusion process from the experiment of the oxidation current density of PEGPB versus the scan rate.