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

Graphene and other two-dimensional materials, such as transition metal dichalcogenides, have rapidly established themselves as intriguing building blocks for optoelectronic applications, with a strong focus on various photodetection platforms The versatility of these material systems enables their application in areas including ultrafast and ultrasensitive detection of light in the ultraviolet, visible, infrared and terahertz frequency ranges These detectors can be integrated with other photonic components based on the same material, as well as with silicon photonic and electronic technologies Here, we provide an overview and evaluation of state-of-the-art photodetectors based on graphene, other two-dimensional materials, and hybrid systems based on the combination of different two-dimensional crystals or of two-dimensional crystals and other (nano)materials, such as plasmonic nanoparticles, semiconductors, quantum dots, or their integration with (silicon) waveguides

http://www-g.eng.cam.ac.uk/nms/publications/pdf/nnano.2014.215.pdf

Photodetectors based on graphene, other two-dimensional materials and hybrid systems

We report a comprehensive study of transparent and conductive silver nanowire (Ag NW) electrodes, including a scalable fabrication process, morphologies, and optical, mechanical adhesion, and flexibility properties, and various routes to improve the performance. We utilized a synthesis specifically designed for long and thin wires for improved performance in terms of sheet resistance and optical transmittance. Twenty Ω/sq and ∼80% specular transmittance, and 8 ohms/sq and 80% diffusive transmittance in the visible range are achieved, which fall in the same range as the best indium tin oxide (ITO) samples on plastic substrates for flexible electronics and solar cells. The Ag NW electrodes show optical transparencies superior to ITO for near-infrared wavelengths (2-fold higher transmission). Owing to light scattering effects, the Ag NW network has the largest difference between diffusive transmittance and specular transmittance when compared with ITO and carbon nanotube electrodes, a property which could gr...

/pdf/scalable-coating-and-properties-of-transparent-flexible-83mkmpnvqi.pdf

Scalable Coating and Properties of Transparent, Flexible, Silver Nanowire Electrodes

Two-dimensional layered materials (2DLMs) have been a central focus of materials research since the discovery of graphene just over a decade ago. Each layer in 2DLMs consists of a covalently bonded, dangling-bond-free lattice and is weakly bound to neighbouring layers by van der Waals interactions. This makes it feasible to isolate, mix and match highly disparate atomic layers to create a wide range of van der Waals heterostructures (vdWHs) without the constraints of lattice matching and processing compatibility. Exploiting the novel properties in these vdWHs with diverse layering of metals, semiconductors or insulators, new designs of electronic devices emerge, including tunnelling transistors, barristors and flexible electronics, as well as optoelectronic devices, including photodetectors, photovoltaics and light-emitting devices with unprecedented characteristics or unique functionalities. We review the recent progress and challenges, and offer our perspective on the exploration of 2DLM-based vdWHs for future application in electronics and optoelectronics. With a dangling-bond-free surface, two dimensional layered materials (2DLMs) can enable the creation of diverse van der Waals heterostructures (vdWHs) without the conventional constraint of lattice matching or process compatibility. This Review discusses the recent advances in exploring 2DLM vdWHs for future electronics and optoelectronics.

Van der Waals heterostructures and devices

We report a comprehensive study of transparent and conductive silver nanowire (Ag NW) electrodes,includingascalablefabricationprocess,morphologies,andoptical,mechanicaladhesion,andflexibility properties, and various routes to improve the performance. We utilized a synthesis specifically designed for long andthinwiresforimprovedperformanceintermsofsheetresistanceandopticaltransmittance.Twenty/sqand 80% specular transmittance, and 8 ohms/sq and 80% diffusive transmittance in the visible range are achieved, whichfallinthesamerangeasthebestindiumtinoxide(ITO)samplesonplasticsubstratesforflexibleelectronics andsolarcells.TheAgNWelectrodesshowopticaltransparenciessuperiortoITOfornear-infraredwavelengths(2- foldhighertransmission).Owingtolightscatteringeffects,theAgNWnetworkhasthelargestdifferencebetween diffusive transmittance and specular transmittance when compared with ITO and carbon nanotube electrodes, a propertywhichcouldgreatlyenhancesolarcellperformance.AmechanicalstudyshowsthatAgNWelectrodeson flexiblesubstratesshowexcellentrobustnesswhensubjectedtobending.Wealsostudytheelectricalconductance ofAgnanowiresandtheirjunctionsandreportafacileelectrochemicalmethodforaAucoatingtoreducethewire- to-wire junction resistance for better overallfilm conductance. Simple mechanical pressing was also found to increasetheNWfilmconductanceduetothereductionofjunctionresistance.Theoverallpropertiesoftransparent Ag NW electrodes meet the requirements of transparent electrodes for many applications and could be an immediate ITO replacement forflexible electronics and solar cells.

https://web.stanford.edu/group/cui_group/papers/Transprent%20Ag.pdf

Scalable Coating and Properties of Transparent, Flexible, Silver Nanowire

Using current-voltage (I-V) and capacitance-voltage (C-V) measurements, we report on the unusual physics and promising technical applications associated with the formation of Schottky barriers at the interface of a one-atom-thick zero-gap semiconductor (graphene) and conventional semiconductors. When chemical vapor deposited graphene is transferred onto n-type Si, GaAs, 4H-SiC and GaN semiconductor substrates, there is a strong van der Waals attraction that is accompanied by charge transfer across the interface and the formation of a rectifying (Schottky) barrier. Thermionic emission theory in conjunction with the Schottky-Mott model within the context of bond-polarization theory provides a surprisingly good description of the electrical properties. Applications, such as to sensors where in forward bias there is exponential sensitivity to changes in the Schottky barrier height due to the presence of absorbates on the graphene or to analogue devices for which Schottky barriers are integral components are promising because of graphene's mechanical stability, its resistance to diffusion, its robustness at high temperatures and its demonstrated capability to embrace multiple functionalities.

Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor Based Diodes

Diodes based on metal-semiconductor interfaces are common place in semiconductor electronics. What happens when the normal metal is replaced by monolayer graphene? A group of physicists at University of Florida experimentally demonstrate that graphene-semiconductor interfaces make interesting diodes for a surprisingly wide variety of semiconductors.

https://link.aps.org/pdf/10.1103/PhysRevX.2.011002

Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor-Based Diodes

Electrodes based on printed networks of single-walled carbon nanotubes (SWNTs) are integrated with ultrathin layers of the organic semiconductor pentacene to produce bendable, transparent thin-film transistors on plastic substrates The physical and structural properties of the SWNTs lead to the remarkably good electrical contacts with the pentacene Optical transmittances of ∼70%, device mobilities >05cm2V−1s−1, ON/OFF ratios >105 and tensile strains as large as 18% are achieved in devices of this type These characteristics indicate promise for applications in power conserving flexible display systems and other devices

Transparent flexible organic thin-film transistors that use printed single-walled carbon nanotube electrodes

We report on the p doping of graphene with the polymer TFSA ((CF3SO2)2NH). Modification of graphene with TFSA decreases the graphene sheet resistance by 70%. Through such modification, we report sheet resistance values as low as 129 � , thus attaining values comparable to those of indium‐tin oxide (ITO), while displaying superior environmental stability and preserving electrical properties over extended time scales. Electrical transport measurements reveal that, after doping, the carrier density of holes increases, consistent with the acceptor nature of TFSA, and the mobility decreases due to enhanced short-range scattering. The Drude formula predicts that competition between these two effects yields an overall increase in conductivity. We confirm changes in the carrier density and Fermi level of graphene through changes in the Raman G and 2D peak positions. Doped graphene samples display high transmittance in the visible and near-infrared spectrum, preserving graphene’s optical properties without any significant reduction in transparency, and are therefore superior to ITO films in the near infrared. The presented results allow integration of doped graphene sheets into optoelectronics, solar cells, and thermoelectric solar cells as well as engineering of the electrical characteristics of various devices by tuning the Fermi level of graphene.

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Stable hole doping of graphene for low electrical resistance and high optical transparency

Rectification and thermal stability of diodes formed at graphene/GaN interfaces have been investigated using Raman Spectroscopy and temperature-dependent current-voltage measurements. The Schottky barriers formed between GaN and mechanically transferred graphene display rectification that is preserved up to 550 K with the diodes eventually becoming non-rectifying above 650 K. Upon cooling, the diodes show excellent recovery with improved rectification. We attribute these effects to the thermal stability of graphene, which acts like an impenetrable barrier to the diffusion of contaminants across the interface, and to changes in the interface band alignment associated with thermally induced dedoping of graphene.

/pdf/graphene-gan-schottky-diodes-stability-at-elevated-b16lqtzci4.pdf

Maxime G. Lemaitre

Papers

Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor Based Diodes

Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor-Based Diodes

Transparent flexible organic thin-film transistors that use printed single-walled carbon nanotube electrodes

Stable hole doping of graphene for low electrical resistance and high optical transparency

Graphene/GaN Schottky diodes: Stability at elevated temperatures