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

The need to develop inexpensive renewable energy sources stimulates scientific research for efficient, low-cost photovoltaic devices.1 The organic, polymer-based photovoltaic elements have introduced at least the potential of obtaining cheap and easy methods to produce energy from light.2 The possibility of chemically manipulating the material properties of polymers (plastics) combined with a variety of easy and cheap processing techniques has made polymer-based materials present in almost every aspect of modern society.3 Organic semiconductors have several advantages: (a) lowcost synthesis, and (b) easy manufacture of thin film devices by vacuum evaporation/sublimation or solution cast or printing technologies. Furthermore, organic semiconductor thin films may show high absorption coefficients4 exceeding 105 cm-1, which makes them good chromophores for optoelectronic applications. The electronic band gap of organic semiconductors can be engineered by chemical synthesis for simple color changing of light emitting diodes (LEDs).5 Charge carrier mobilities as high as 10 cm2/V‚s6 made them competitive with amorphous silicon.7 This review is organized as follows. In the first part, we will give a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells. In the second part, we will focus on conjugated polymer/fullerene bulk heterojunction solar cells, mainly on polyphenylenevinylene (PPV) derivatives/(1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61) (PCBM) fullerene derivatives and poly(3-hexylthiophene) (P3HT)/PCBM systems. In the third part, we will discuss the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells. In the fourth part, we will suggest possible routes for further improvements and finish with some conclusions. The different papers mentioned in the text have been chosen for didactical purposes and cannot reflect the chronology of the research field nor have a claim of completeness. The further interested reader is referred to the vast amount of quality papers published in this field during the past decade.

Conjugated polymer-based organic solar cells

A polymer solar-cell based on a bulk hetereojunction design with an internal quantum efficiency of over 90% across the visible spectrum (425 nm to 575 nm) is reported. The device exhibits a power-conversion efficiency of 6% under standard air-mass 1.5 global illumination tests.

Bulk heterojunction solar cells with internal quantum efficiency approaching 100

Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Polymer-based organic photovoltaic systems hold the promise for a cost-effective, lightweight solar energy conversion platform, which could benefit from simple solution processing of the active layer. The function of such excitonic solar cells is based on photoinduced electron transfer from a donor to an acceptor. Fullerenes have become the ubiquitous acceptors because of their high electron affinity and ability to transport charge effectively. The most effective solar cells have been made from bicontinuous polymer–fullerene composites, or so-called bulk heterojunctions. The best solar cells currently achieve an efficiency of about 5 %, thus significant advances in the fundamental understanding of the complex interplay between the active layer morphology and electronic properties are required if this technology is to find viable application.

Polymer–Fullerene Composite Solar Cells

Toward high performance inverted polymer solar cells

This paper reports the synthesis and physical properties of a series of novel bipyridine-containing poly(benzobisoxazole)s and poly(benzobisthiazole)s. The polymers were synthesized by polycondensation of 2,2‘-bipyridine-5,5‘-dicarboxylic acid with diaminobenzenediols in poly(phosphoric acid). Some model compounds were also synthesized by a similar approach for comparison. The polymers exhibited extremely high thermal stabilities in air or nitrogen atmosphere. From the polarized microscopic studies, lyotropic mesophases were observed in some polymer solutions in methanesulfonic acid. The 2,2‘-bipyridyl moieties on the polymer main chain were able to form metal complexes with bis(2,2‘-bipyridyl)ruthenium(II) compounds, which was proved by different characterization methods such as electronic and luminescence spectroscopy, cyclic voltammetry, and thermal analysis. The charge carriers mobilities of the polymer metal complexes are of the order of 10-5 cm2 V-1 s-1, which are 2 orders of magnitude higher than t...

Synthesis and Characterization of Poly(benzobisoxazole)s and Poly(benzobisthiazole)s with 2,2`-Bipyridyl Units in the Backbone

High-detectivity near-infrared (NIR) polymer photodetectors (PDs) fabricated by a novel low-bandgap semiconducting polymer blended with fullerene derivatives are reported. Operating at room temperature, the polymer PDs have a spectral response from 400 to 1100 nm. By incorporation of an alcohol/water-soluble polymer as a cathode interlayer in bulk heterojunction polymer PDs, the polymer PDs exhibit a high detectivity of 1.75 × 1013 cm•Hz1/2/W at 800 nm. These results demonstrated that the NIR polymer PDs are comparable to Si-based PDs.

Solution-Processed High-Detectivity Near-Infrared Polymer Photodetectors Fabricated by a Novel Low-Bandgap Semiconducting Polymer

Novel conjugated alternating copolymer based on 2, 7-carbazole and 2, 1, 3-benzoselenadiazole

Development and understanding of antifreezing materials are fundamentally and practically important for materials design and delivery. However, almost all of antifreezing materials are either organic/icephobic materials containing no water or hydrophilic hydrogels containing antifreezing additives. Here, a general crosslinking strategy to fabricate a family of EGINA-crosslinked double-network hydrogels with intrinsic, built-in antifreezing and mechanical properties, but without any antifreezing additives is proposed and demonstrated. The resultant hydrogels, despite large structural and compositional variations of hydrophilies, electrolytes, zwitterions, and macromolecules of polymer chains, achieved strong antifreezing and mechanical properties in different environments including solution state, gel state, and hydrogel/solid interfaces. Such general antifreezing property of EGINA-crosslinked hydrogels, regardless network compositions, is likely stemmed from their highly hydrophilic and tightly crosslinked DN structures for inducing strong water-network bindings to prevent ice crystal formation from free waters in hydrogel networks. EGINA-crosslinked hydrogels can also serve as a key component to be fabricated into smart windows with high optical transmittance and supercapacitors with excellent electrochemical stability at subzero temperatures. This work provides a simple, blueprint antifreezing design concept and a family of antifreezing hydrogels for the better understanding of the composite-structure-property relationship of antifreezing materials and the fundamentals of confined water in wet soft materials.

Xiong Gong

Papers

Toward high performance inverted polymer solar cells

Synthesis and Characterization of Poly(benzobisoxazole)s and Poly(benzobisthiazole)s with 2,2`-Bipyridyl Units in the Backbone

Solution-Processed High-Detectivity Near-Infrared Polymer Photodetectors Fabricated by a Novel Low-Bandgap Semiconducting Polymer

Novel conjugated alternating copolymer based on 2, 7-carbazole and 2, 1, 3-benzoselenadiazole

A General Crosslinker Strategy to Realize Intrinsic Frozen Resistance of Hydrogels.