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

A very sensitive photodector based on molybdenum disulphide with potential for integrated optoelectronic circuits, light sensing, biomedical imaging, video recording or spectroscopy is now demonstrated.

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Ultrasensitive photodetectors based on monolayer MoS2.

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Since the discovery of highly conducting polyacetylene by Shirakawa, MacDiarmid, and Heeger in 1977, π-conjugated systems have attracted much attention as futuristic materials for the development and production of the next generation of electronics, that is, organic electronics. Conceptually, organic electronics are quite different from conventional inorganic solid state electronics because the structural versatility of organic semiconductors allows for the incorporation of functionality by molecular design. This versatility leads to a new era in the design of electronic devices. To date, the great number of π-conjugated semiconducting materials that have either been discovered or synthesized generate an exciting library of π-conjugated systems for use in organic electronics. 11 However, some key challenges for further advancement remain: the low mobility and stability of organic semiconductors, the lack of knowledge regarding structure property relationships for understanding the fundamental chemical aspects behind the structural design, and realization of desired properties. Organic field-effect transistors (OFETs) are a kind of device consisting of an organic semiconducting layer, a gate insulator layer, and three terminals (drain, source, and gate electrodes). OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but they also provide an important insight into the charge transport of πconjugated systems. Therefore, they act as strong tools for the exploration of the structure property relationships of πconjugated systems, such as parameters of field-effect mobility (μ, the drift velocity of carriers under unit electric field), current on/off ratio (the ratio of the maximum on-state current to the minimum off-state current), and threshold voltage (the minimum gate voltage that is required to turn on the transistor). 17 Since the discovery of OFETs in the 1980s, they have attracted much attention. Research onOFETs includes the discovery, design, and synthesis of π-conjugated systems for OFETs, device optimization, development of applications in radio frequency identification (RFID) tags, flexible displays, electronic papers, sensors, and so forth. It is beyond the scope of this review to cover all aspects of π-conjugated systems; hence, our focus will be on the performance analysis of π-conjugated systems in OFETs. This should make it possible to extract information regarding the fundamental merit of semiconducting π-conjugated materials and capture what is needed for newmaterials and what is the synthesis orientation of newπ-conjugated systems. In fact, for a new science with many practical applications, the field of organic electronics is progressing extremely rapidly. For example, using “organic field effect transistor” or “organic field effect transistors” as the query keywords to search the Web of Science citation database, it is possible to show the distribution of papers over recent years as shown in Figure 1A. It is very clear

Semiconducting π-conjugated systems in field-effect transistors: a material odyssey of organic electronics.

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

This work presents a systematic study toward the design and first demonstration of high-performance n-type monolayer tungsten diselenide (WSe2) field effect transistors (FET) by selecting the contact metal based on understanding the physics of contact between metal and monolayer WSe2. Device measurements supported by ab initio density functional theory (DFT) calculations indicate that the d-orbitals of the contact metal play a key role in forming low resistance ohmic contacts with monolayer WSe2. On the basis of this understanding, indium (In) leads to small ohmic contact resistance with WSe2 and consequently, back-gated In–WSe2 FETs attained a record ON-current of 210 μA/μm, which is the highest value achieved in any monolayer transition-metal dichalcogenide- (TMD) based FET to date. An electron mobility of 142 cm2/V·s (with an ON/OFF current ratio exceeding 106) is also achieved with In–WSe2 FETs at room temperature. This is the highest electron mobility reported for any back gated monolayer TMD materia...

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Role of metal contacts in designing high-performance monolayer n-type WSe2 field effect transistors.

Biosensors based on field-effect transistors (FETs) have attracted much attention, as they offer rapid, inexpensive, and label-free detection. While the low sensitivity of FET biosensors based on bulk 3D structures has been overcome by using 1D structures (nanotubes/nanowires), the latter face severe fabrication challenges, impairing their practical applications. In this paper, we introduce and demonstrate FET biosensors based on molybdenum disulfide (MoS2), which provides extremely high sensitivity and at the same time offers easy patternability and device fabrication, due to its 2D atomically layered structure. A MoS2-based pH sensor achieving sensitivity as high as 713 for a pH change by 1 unit along with efficient operation over a wide pH range (3–9) is demonstrated. Ultrasensitive and specific protein sensing is also achieved with a sensitivity of 196 even at 100 femtomolar concentration. While graphene is also a 2D material, we show here that it cannot compete with a MoS2-based FET biosensor, which ...

MoS2 Field-Effect Transistor for Next-Generation Label-Free Biosensors

A new type of device, the band-to-band tunnel transistor, which has atomically thin molybdenum disulfide as the active channel, operates in a fundamentally different way from a conventional silicon (MOSFET) transistor; it has turn-on characteristics and low-power operation that are better than those of state-of-the-art MOSFETs or any tunnelling transistor reported so far. Traditional transistor technology is fast approaching its fundamental limits, and two-dimensional semiconducting materials such as molybdenum disulfide (MoS2) are seen as possible replacements for silicon in a next generation of high-density, lower-power chip electronics. A particularly promising prospect is their potential in band-to-band tunnel transistors, which operate in a fundamentally different way from conventional silicon (MOSFET) transistors. So far, few such devices with overall characteristics better than silicon transistors have been demonstrated. Now Kaustav Banerjee et al. have built a tunnel transistor by making a vertical structure with atomically thin MoS2 as the active channel and germanium as the source electrode. It has turn-on characteristics and low-power operation that are better than those of existing silicon transistors, and the results will be of interest in a range of electronic applications including low-power integrated circuits, as well as ultra-sensitive bio sensors or gas sensors. The fast growth of information technology has been sustained by continuous scaling down of the silicon-based metal–oxide field-effect transistor. However, such technology faces two major challenges to further scaling. First, the device electrostatics (the ability of the transistor’s gate electrode to control its channel potential) are degraded when the channel length is decreased, using conventional bulk materials such as silicon as the channel. Recently, two-dimensional semiconducting materials1,2,3,4,5,6,7 have emerged as promising candidates to replace silicon, as they can maintain excellent device electrostatics even at much reduced channel lengths. The second, more severe, challenge is that the supply voltage can no longer be scaled down by the same factor as the transistor dimensions because of the fundamental thermionic limitation of the steepness of turn-on characteristics, or subthreshold swing8,9. To enable scaling to continue without a power penalty, a different transistor mechanism is required to obtain subthermionic subthreshold swing, such as band-to-band tunnelling10,11,12,13,14,15,16. Here we demonstrate band-to-band tunnel field-effect transistors (tunnel-FETs), based on a two-dimensional semiconductor, that exhibit steep turn-on; subthreshold swing is a minimum of 3.9 millivolts per decade and an average of 31.1 millivolts per decade for four decades of drain current at room temperature. By using highly doped germanium as the source and atomically thin molybdenum disulfide as the channel, a vertical heterostructure is built with excellent electrostatics, a strain-free heterointerface, a low tunnelling barrier, and a large tunnelling area. Our atomically thin and layered semiconducting-channel tunnel-FET (ATLAS-TFET) is the only planar architecture tunnel-FET to achieve subthermionic subthreshold swing over four decades of drain current, as recommended in ref. 17, and is also the only tunnel-FET (in any architecture) to achieve this at a low power-supply voltage of 0.1 volts. Our device is at present the thinnest-channel subthermionic transistor, and has the potential to open up new avenues for ultra-dense and low-power integrated circuits, as well as for ultra-sensitive biosensors and gas sensors18,19,20,21.

A subthermionic tunnel field-effect transistor with an atomically thin channel.

Modern electronics rely on semiconductors such as silicon. Researchers show how a new class of semiconductors---monolayer transition-metal dichalcogenides---can be optimized to improve device performance.

Computational Study of Metal Contacts to Monolayer Transition-Metal Dichalcogenide Semiconductors

In this Letter, molybdenum (Mo) is introduced and evaluated as an alternative contact metal to atomically-thin molybdenum disulphide (MoS2), and high-performance field-effect transistors are experimentally demonstrated. In order to understand the physical nature of the interface and highlight the role of the various factors contributing to the Mo-MoS2 contacts, density functional theory (DFT) simulations are employed, which reveal that Mo can form high quality contact interface with monolayer MoS2 with zero tunnel barrier and zero Schottky barrier under source/drain contact, as well as an ultra-low Schottky barrier (0.1 eV) at source/drain-channel junction due to strong Fermi level pinning. In agreement with the DFT simulations, high mobility, high ON-current, and low contact resistance are experimentally demonstrated on both monolayer and multilayer MoS2 transistors using Mo contacts. The results obtained not only reveal the advantages of using Mo as a contact metal for MoS2 but also highlight the fact that the properties of contacts with 2-dimensional materials cannot be intuitively predicted by solely considering work function values and Schottky theory.

Wei Liu

Papers

Role of metal contacts in designing high-performance monolayer n-type WSe2 field effect transistors.

MoS2 Field-Effect Transistor for Next-Generation Label-Free Biosensors

A subthermionic tunnel field-effect transistor with an atomically thin channel.

Computational Study of Metal Contacts to Monolayer Transition-Metal Dichalcogenide Semiconductors

High-performance MoS2 transistors with low-resistance molybdenum contacts