There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

/pdf/electronics-and-optoelectronics-of-two-dimensional-2jbqr1unvw.pdf

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.

http://science.sciencemag.org/content/sci/297/5582/787.full.pdf

Carbon Nanotubes--the Route Toward Applications

Fabrication techniques developed for graphene research allow the disassembly of many layered crystals (so-called van der Waals materials) into individual atomic planes and their reassembly into designer heterostructures, which reveal new properties and phenomena. Andre Geim and Irina Grigorieva offer a forward-looking review of the potential of layering two-dimensional materials into novel heterostructures held together by weak van der Waals interactions. Dozens of these one-atom- or one-molecule-thick crystals are known. Graphene has already been well studied but others, such as monolayers of hexagonal boron nitride, MoS2, WSe2, graphane, fluorographene, mica and silicene are attracting increasing interest. There are many other monolayers yet to be examined of course, and the possibility of combining graphene with other crystals adds even further options, offering exciting new opportunities for scientific exploration and technological innovation. Research on graphene and other two-dimensional atomic crystals is intense and is likely to remain one of the leading topics in condensed matter physics and materials science for many years. Looking beyond this field, isolated atomic planes can also be reassembled into designer heterostructures made layer by layer in a precisely chosen sequence. The first, already remarkably complex, such heterostructures (often referred to as ‘van der Waals’) have recently been fabricated and investigated, revealing unusual properties and new phenomena. Here we review this emerging research area and identify possible future directions. With steady improvement in fabrication techniques and using graphene’s springboard, van der Waals heterostructures should develop into a large field of their own.

/pdf/van-der-waals-heterostructures-3nf3oeh0jk.pdf

Van der Waals heterostructures

Flexible optoelectronics is a rapidly growing field, with a wide range of potential applications. From wearable sensors to bendable solar cells, curved displays, and curved focal plane arrays, the possibilities are endless. The criticality of flexible photodetectors for many of these applications is acknowledged, however, devices that are demonstrated thus far are limited in their spectral range. In this study, flexible photodetectors are demonstrated using a VOx nanoparticle ink, with an extremely broad operating wavelength range of 0.4 to 20 µm. This ink is synthesized using a simple and scalable wet-chemical process. These photodetectors operate at room temperature and exhibit minimal variance in performance even when bent at angles of up to 100 ° at a bend radius of 6.4 mm. In addition, rigorous strain testing of 100 bend and release cycles revealed a photoresponse with a standard deviation of only 0.55%. This combination of mechanical flexibility, wide spectral response, and ease of fabrication makes these devices highly desirable for a wide range of applications, including low-cost wearable sensors and hyperspectral imaging systems. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adfm.202301790

Flexible Vanadium Dioxide Photodetectors for Visible to Longwave Infrared Detection at Room Temperature

We demonstrate bright electroluminescence in WSe 2 monolayers using pulsed injection, without the use of split gates, chemical doping, or heterostructures. Electroluminescence quantum efficiency approaches that of photoluminescence, indicating efficient exciton formation with injected carriers.

Bright Electroluminescence from Back-Gated WSe 2 P-N Junctions Using Pulsed Injection

We demonstrate long wave infrared photodetectors based on the transition metal dichalcogenide platinum diselenide (PtSe 2 ) in its bulk form for the first time to our knowledge. Fabricated devices show sub-millisecond response times. © 2019 The Author(s)

Long-Wave Infrared Photodetectors Based on Platinum Diselenide

Over the past several years, the inherent scaling limitations of electron devices have fueled the exploration of high carrier mobility semiconductors as a Si replacement to further enhance the device performance. To ensure effective gate control, semiconductors with ultrathin body thickness are needed. At such regime, strong quantum confinement usually comes into play; therefore, we call these ultrathin compound semiconductor membranes as quantum membranes (QMs). Compound quantum membranes heterogeneously integrated on Si substrates have been studied by us, combining the high mobility of compound semiconductors and the well-established Si technology.

Quantum membranes: A new materials platform for future electronics

Contacting metallic single-walled carbon nanotubes by palladium (Pd) affords highly reproducible ohmic contacts and allows for detailed elucidation of ballistic transport in metallic nanotubes. The Pd ohmic contacts are more reliable than titanium (Ti) previously used for ballistic nanotube devices. In contrast, Pt contacts appear to give non-ohmic contacts to metallic nanotubes. For both ohmic and non-ohmic contacts, the length of the nanotube under the metal contact area is electrically turned off. Transport occurs from metal to nanotube at the edges of the contacts. Measurements with large numbers of Pd contacted nanotube samples reveal that the mean free path for defect scattering in SWNTs grown by chemical vapor deposition can be up to 4 microns. The mean free paths for acoustic phonon scattering are on the order of 500 nm at room temperature and >> 4 microns at low temperatures.

Ali Javey

Papers

Flexible Vanadium Dioxide Photodetectors for Visible to Longwave Infrared Detection at Room Temperature

Bright Electroluminescence from Back-Gated WSe 2 P-N Junctions Using Pulsed Injection

Long-Wave Infrared Photodetectors Based on Platinum Diselenide

Quantum membranes: A new materials platform for future electronics

Ballistic Transport in Metallic Nanotubes With Reliable Pd Ohmic Contacts