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671.
Electron tunneling through double-electric barriers on HgTe/CdTe heterostructure interface
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Liang-Zhong Lin 《中国物理 B》2022,31(11):117201-117201
We investigate theoretically the carrier transport in a two-dimensional topological insulator of (001) HgTe/CdTe quantum-well heterostructure with inverted band, and find distinct switchable features of the transmission spectra in the topological edge states by designing the double-electric modulation potentials. The transmission spectra exhibit the significant Fabry-Pérot resonances for the double-electric transport system. Furthermore, the transmission properties show rich behaviors when the Fermi energy lies in the different locations in the energy spectrum and the double-electric barrier regions. The opacity and transparency of the double-modulated barrier regions can be controlled by tuning the modulated potentials, Fermi energy and the length of modulated regions. This electrical switching behavior can be realized by tuning the voltages applied on the metal gates. The Fabry-Pérot resonances leads to oscillations in the transmission which can be observed in experimentally. This electric modulated-mechanism provides us a realistic way to switch the transmission in edge states which can be constructed in low-power information processing devices. 相似文献
672.
673.
Chen Hong-Ya Wang Jia-Fu Ma Hua Qu Shao-Bo Zhang Jie-Qiu Xu Zhuo Zhang An-Xue 《中国物理 B》2015,24(1):14201-014201
We propose a broadband perfect polarization conversion metasurface composed of copper sheet-backed asymmetric double spilt ring resonator(DSRR).The broadband perfect polarization convertibility results from metallic ground and multiple plasmon resonances of the DSRR.Physics of plasmon resonances are governed by the electric and magnetic resonances.Both the simulation and measured results show that the polarization conversion ratio(PCR)is higher than 99%for both x-and y-polarized normally incident EM waves and the fractional bandwidth is about 34.5%.The metasurface possesses the merits of high PCR and broad bandwidth,and thus has great application values in novel polarization-control devices. 相似文献
674.
Probing Distance‐Dependent Plasmon‐Enhanced Near‐Infrared Fluorescence Using Polyelectrolyte Multilayers as Dielectric Spacers
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Dr. Naveen Gandra Christopher Portz Limei Tian Dr. Rui Tang Dr. Baogang Xu Prof. Samuel Achilefu Prof. Srikanth Singamaneni 《Angewandte Chemie (International ed. in English)》2014,53(3):866-870
Owing to their applications in biodetection and molecular bioimaging, near‐infrared (NIR) fluorescent dyes are being extensively investigated. Most of the existing NIR dyes exhibit poor quantum yield, which hinders their translation to preclinical and clinical settings. Plasmonic nanostructures are known to act as tiny antennae for efficiently focusing the electromagnetic field into nanoscale volumes. The fluorescence emission from NIR dyes can be enhanced by more than thousand times by precisely placing them in proximity to gold nanorods. We have employed polyelectrolyte multilayers fabricated using layer‐by‐layer assembly as dielectric spacers for precisely tuning the distance between gold nanorods and NIR dyes. The aspect ratio of the gold nanorods was tuned to match the longitudinal localized surface plasmon resonance wavelength with the absorption maximum of the NIR dye to maximize the plasmonically enhanced fluorescence. The design criteria derived from this study lays the groundwork for ultrabright fluorescence bullets for in vitro and in vivo molecular bioimaging. 相似文献
675.
Activation of Oxygen on Gold and Silver Nanoparticles Assisted by Surface Plasmon Resonances
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Dr. Yi‐Fan Huang Meng Zhang Liu‐Bin Zhao Dr. Jia‐Min Feng Prof. Dr. De‐Yin Wu Prof. Dr. Bin Ren Prof. Dr. Zhong‐Qun Tian 《Angewandte Chemie (International ed. in English)》2014,53(9):2353-2357
Surface plasmon resonances (SPRs) have been found to promote chemical reactions. In most oxidative chemical reactions oxygen molecules participate and understanding of the activation mechanism of oxygen molecules is highly important. For this purpose, we applied surface‐enhanced Raman spectroscopy (SERS) to find out the mechanism of SPR‐assisted activation of oxygen, by using p‐aminothiophenol (PATP), which undergoes a SPR‐assisted selective oxidation, as a probe molecule. In this way, SPR has the dual function of activating the chemical reaction and enhancing the Raman signal of surface species. Both experiments and DFT calculations reveal that oxygen molecules were activated by accepting an electron from a metal nanoparticle under the excitation of SPR to form a strongly adsorbed oxygen molecule anion. The anion was then transformed to Au or Ag oxides or hydroxides on the surface to oxidize the surface species, which was also supported by the heating effect of the SPR. This work points to a promising new era of SPR‐assisted catalytic reactions. 相似文献
676.
677.
Mohammad Kamal Hossain Yasutaka Kitahama Genin Gary Huang Xiaoxia Han Yukihiro Ozaki 《Analytical and bioanalytical chemistry》2009,394(7):1747-1760
Surface-enhanced Raman scattering (SERS) enhancement and the reproducibility of the SERS signal strongly reflect the quality
and nature of the SERS substrates because of diverse localized surface plasmon resonance (LSPR) excitations excited at interstitials
or sharp edges. LSPR excitations are the most important ingredients for achieving huge enhancements in the SERS process. In
this report, we introduce several gold and silver nanoparticle-based SERS-active substrates developed solely by us and use
these substrates to investigate the influence of LSPR excitations on SERS. SERS-active gold substrates were fabricated by
immobilizing colloidal gold nanoparticles on glass slides without using any surfactants or electrolytes, whereas most of the
SERS-active substrates that use colloidal gold/silver nanoparticles are not free of surfactant. Isolated aggregates, chain-like
elongated aggregates and two-dimensional (2D) nanostructures were found to consist mostly of monolayers rather than agglomerations.
With reference to correlated LSPR and SERS, combined experiments were carried out on a single platform at the same spatial
position. The isolated aggregates mostly show a broadened and shifted SPR peak, whereas a weak blue-shifted peak is observed
near 430 nm in addition to broadened peaks centered at 635 and 720 nm in the red spectral region in the chain-like elongated
aggregates. In the case of 2D nanostructures, several SPR peaks are observed in diverse frequency regions. The characteristics
of LSPR and SERS for the same gold nanoaggregates lead to a good correlation between SPR and SERS images. The elongated gold
nanostructures show a higher enhancement of the Raman signal than the the isolated and 2D samples. In the case of SERS-active
silver substrates for protein detection, a new approach has been adopted, in contrast to the conventional fabrication method.
Colloidal silver nanoparticles are immobilized on the protein functionalized glass slides, and further SERS measurements are
carried out based on LSPR excitations. A new strategy for the detection of biomolecules, particularly glutathione, under aqueous
conditions is proposed. Finally, supramolecular J-aggregates of ionic dyes incorporated with silver colloidal aggregates are
characterized by SERS measurements and correlated to finite-difference time-domain analysis with reference to LSPR excitations.
Figure SPR and SERS images for isolated, elongated and two-dimensional gold nanostructures 相似文献
678.
In this paper the inverse resonance problem for the Hermite operator is investigated. The Hermite operator
with the creation operator
, the annihilation operator
, and a finitely supported multiplication operator b, is an unbounded operator on ℓ
2(ℕ0) having finitely many eigenvalues and infinitely many resonances (except for b=0, when there are no eigenvalues or resonances). It is shown that knowing the location of eigenvalues and resonances determines
the potential b uniquely.
相似文献
679.
In this article, we study the (1/2) ± and (3/2)± triply heavy baryon states in a systematic way by subtracting the contributions from the corresponding (1/2)■ and (3/2)■ triply heavy baryon states with the QCD sum rules, and make reasonable predictions for their masses. 相似文献
680.
The properties of scattering phases and density of states in a quantum wire with an attractive scatterer are analyzed. We consider two bound states which couple to a scattering channel and give rise to two Fano resonances. It is shown that varying the parameters of the scatterer (such as its strength and position) produces significantly different effects on the phase behavior and density of states, depending on the subband they occur. These effects stem mainly from the difference between the coupling matrix elements of the two resonant levels with the propagating channel mode. 相似文献