抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Since its discovery, the asymmetric Fano resonance has been a characteristic feature of interacting quantum systems. The shape of this resonance is distinctively different from that of conventional symmetric resonance curves. Recently, the Fano resonance has been found in plasmonic nanoparticles, photonic crystals, and electromagnetic metamaterials. The steep dispersion of the Fano resonance profile promises applications in sensors, lasing, switching, and nonlinear and slow-light devices.

The Fano resonance in plasmonic nanostructures and metamaterials

Plasmons in strongly coupled metallic nanostructures.

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

/pdf/present-and-future-of-surface-enhanced-raman-scattering-34aqgcm385.pdf

Present and Future of Surface-Enhanced Raman Scattering

The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the electric and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielectric nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), respectively, but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there has been a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all four quadrants of possible permittivities and permeabilities have been achieved using completely transparent and high-refractive-index dielectric building blocks. Moreover, an emerging class of all-dielectric metamaterials consisting of anisotropic crystals has been shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. In this Review, we present a broad outline of the whole range of electromagnetic effects observed using all-dielectric metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Finally, we discuss current challenges and future goals for the field at the intersection with quantum, thermal and silicon photonics, as well as biomimetic metasurfaces.

All-dielectric metamaterials

Hyperbolic materials exhibit unique properties that enable intriguing applications in nanophotonics The topological insulator Bi2Se3 represents a natural hyperbolic optical medium, both in the THz and visible range Here, using cathodoluminescence spectroscopy and electron energy-loss spectroscopy, we demonstrate that Bi2Se3 supports room-temperature exciton polaritons and explore the behavior of hyperbolic edge exciton polaritons, which are hybrid modes resulting from the coupling of the polaritons bound to the upper and lower edges of Bi2Se3 nanoplatelets We compare Fabry-Perot-like resonances emerging in edge polariton propagation along pristine and artificially structured edges and experimentally demonstrate the possibility to steer edge polaritons by means of grooves and nanocavities The observed scattering of edge polaritons by defect structures is found to be in good agreement with finite-difference time-domain simulations Our findings reveal the extraordinary capability of hyperbolic polariton propagation to cope with the presence of defects, providing an excellent basis for applications such as nanooptical circuitry, nanoscale cloaking and nanoscopic quantum technology Hyperbolic materials have unique optical properties such as negative refraction and highly directional polaritons, relevant in super-resolution imaging Here, the topological insulator Bi2Se3 is shown to host hyperbolic edge-confined exciton polaritons that can be steered via engineered edge defects

/pdf/interaction-of-edge-exciton-polaritons-with-engineered-4ia68b6fen.pdf

Interaction of edge exciton polaritons with engineered defects in the hyperbolic material Bi2Se3

Yttrium is a metal whose optical properties are tunable by hydrogen incorporation. Commonly, this happens via exposure to hydrogen gas. Here, we demonstrate that the hydrogenation of yttrium is also possible via the deprotonation of alcoholic liquids. Palladium-covered yttrium is placed in an ethanol bath that causes the deprotonation of ethanol and the hydrogenation of yttrium to yttrium dihydride. Proof-of-concept is presented with a study on thin films, which is followed by tuning the optical properties of plasmonic nanoantennas. The liquid hydrogenation causes the plasmonic resonance to shift by more than 300 nm in the near-infrared spectral range. Consequently, we show that our plasmonic nanoantennas serve as a local nanooptical indicator for the deprotonation process. Our findings pave to road toward a (nano)optical investigation and detection of catalytic processes in liquids without the need of electrical, chemical, or electrochemical read-out.

Liquid Hydrogenation of Plasmonic Nanoantennas via Alcohol Deprotonation

We demonstrate a chiral optical response in stacked arrangements of plasmonic nanostructures. They exhibit resonant plasmonic coupling between particles of similar size and dipolemoment. Moreover, we demonstrate that such particle groupings possess the capability to encode their three-dimensional arrangement in unique and well modulated spectra making then ideal candidates for a three-dimensional chiral plasmonic ruler. Our results are crucial for the future design and improvement of plasmonic chiral optical systems, e.g., for ultrasensitive enatiomer sensing on the single molecule level.

Three-dimensional chiral plasmonic oligomers

We report resonantly enhanced and switchable third order nonlinearity in magnesium thin films. Utilizing an optical parametric oscillator as a tunable broadband light source, we find a highly wavel...

Switchable Optical Nonlinearity at the Metal to Insulator Transition in Magnesium Thin Films

We study nonlinear optics in plasmonic nanosystems, discuss the role of structural symmetries and the influence of linear optical properties. In particular, we investigate third harmonic generation from dimer nanoantennas and show that the nonlinear optical response, in contrast to common belief, is not governed by gap nonlinearities but fully described by the linear optical properties of the antenna. A simple nonlinear harmonic oscillator model is shown to reproduce all experimental features.

Nonlinear Plasmon Optics

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