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

Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

http://pubs.acs.org/doi/pdf/10.1021/cr1002326

Solar Water Splitting Cells

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

Recent years have seen a renewed interest in the harvesting and conversion of solar energy. Among various technologies, the direct conversion of solar to chemical energy using photocatalysts has received significant attention. Although heterogeneous photocatalysts are almost exclusively semiconductors, it has been demonstrated recently that plasmonic nanostructures of noble metals (mainly silver and gold) also show significant promise. Here we review recent progress in using plasmonic metallic nanostructures in the field of photocatalysis. We focus on plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks, and recently reported plasmon-mediated photocatalytic reactions on plasmonic nanostructures of noble metals. We also discuss the areas where major advancements are needed to move the field of plasmon-mediated photocatalysis forward.

Plasmonic-metal nanostructures for efficient conversion of solar to chemical energy

Solar cells are attractive candidates for clean and renewable power; with miniaturization, they might also serve as integrated power sources for nanoelectronic systems. The use of nanostructures or nanostructured materials represents a general approach to reduce both cost and size and to improve efficiency in photovoltaics. Nanoparticles, nanorods and nanowires have been used to improve charge collection efficiency in polymer-blend and dye-sensitized solar cells, to demonstrate carrier multiplication, and to enable low-temperature processing of photovoltaic devices. Moreover, recent theoretical studies have indicated that coaxial nanowire structures could improve carrier collection and overall efficiency with respect to single-crystal bulk semiconductors of the same materials. However, solar cells based on hybrid nanoarchitectures suffer from relatively low efficiencies and poor stabilities. In addition, previous studies have not yet addressed their use as photovoltaic power elements in nanoelectronics. Here we report the realization of p-type/intrinsic/n-type (p-i-n) coaxial silicon nanowire solar cells. Under one solar equivalent (1-sun) illumination, the p-i-n silicon nanowire elements yield a maximum power output of up to 200 pW per nanowire device and an apparent energy conversion efficiency of up to 3.4 per cent, with stable and improved efficiencies achievable at high-flux illuminations. Furthermore, we show that individual and interconnected silicon nanowire photovoltaic elements can serve as robust power sources to drive functional nanoelectronic sensors and logic gates. These coaxial silicon nanowire photovoltaic elements provide a new nanoscale test bed for studies of photoinduced energy/charge transport and artificial photosynthesis, and might find general usage as elements for powering ultralow-power electronics and diverse nanosystems.

http://www.eecs.umich.edu/zhonglab/pub/NW_Solar_Lieber.pdf

Coaxial silicon nanowires as solar cells and nanoelectronic power sources

A structure consisting of vertically aligned wire arrays on a Si substrate and a method for producing such wire arrays. The wire arrays are fabricated and positioned on a substrate with an orientation and density particularly adapted for conversion of received light to energy. A patterned oxide layer is used to provide for wire arrays that exhibit narrow diameter and length distribution and provide for controlled wire position.

STRUCTURES OF AND METHODS FOR FORMING VERTICALLY ALIGNED Si WIRE ARRAYS

Silicon nanorods have been grown by chemical vapor deposition of silane, using both gold and indium as catalysts for the vapor liquid solid (VLS) process. Conditions for optimal rod morphology for each catalyst were identified by varying silane partial pressure and temperature in the range P = 0.05-1 Torr and T = 300-600 C, respectively. In most cases, catalyst particles were formed by partial de-wetting of evaporated films of the catalytic material to form droplets with diameters of tens to hundreds of nanometers. Also, periodic arrays of catalyst particles with controlled size and spacing were achieved both by the use of porous alumina membranes and also by electron-beam lithography. Using these techniques, silicon nanorods were grown with diameters of 100 nm to microns and lengths of microns to tens of microns. Four-point and gate-bias-dependent resistance measurements were made on single wires, and these indicate that rods we have grown with gold catalysts and phosphine doping have metal-like conductivity.

/pdf/synthesis-and-characterization-of-silicon-nanorod-arrays-for-3lotcrfn5n.pdf

Synthesis and Characterization of Silicon Nanorod Arrays for Solar Cell Applications

Embodiments of the invention generally relate to photovoltaic devices. In one embodiment, a method for forming a gallium arsenide based photovoltaic device includes providing a semiconductor structure, the structure including an absorber layer comprising gallium arsenide. A bypass function is provided in a p-n junction of the semiconductor structure, where under reverse-bias conditions the p-n junction breaks down in a controlled manner by a Zener breakdown effect.

Self-bypass diode function for gallium arsenide photovoltaic devices

Embodiments of the invention generally relate to optoelectronic semiconductor devices such as photovoltaic devices including solar cells. In one aspect, an optoelectronic semiconductor device includes an absorber layer made of gallium arsenide (GaAs) and having only one type of doping. An emitter layer is located closer than the absorber layer to a back side of the device, the emitter layer made of a different material than the absorber layer and having a higher bandgap than the absorber layer. A heterojunction formed between the emitter layer and the absorber layer, and a p-n junction is formed between the emitter layer and the absorber layer and at least partially within the different material at a location offset from the heterojunction. The p-n junction causes a voltage to be generated in the device in response to the device being exposed to light at a front side of the device.

Optoelectronic devices including heterojunction

We present results from a p-n junction device physics model for GaInP/GaAs/GaInAsP/GaInAs four junction solar cells. The model employs subcells whose thicknesses have an upper bound of 5μm and lower bound of 200nm, which is just above the fully depleted case for the assumed doping of NA = 1 x 1018 cm-3 and ND = 1 x 1017 cm-3. The physical characteristics of the cell model include: free carrier absorption, temperature and doping effects on carrier mobility, as well as recombination via Shockley-Read-Hall recombination from a single midgap trap level and surface recombination. Upper bounds on cell efficiency set by detailed balance calculations can be approached by letting the parameters approach ideal conditions. However whereas detailed balance calculations always benefit from added subcells, the current matching requirements for series connected p-n multi-junctions indicate a minimum necessary performance from an added subcell to yield a net increase in overall device efficiency. For the four junction cell considered here, optimizing the subcell thickness is an important part of optimizing the efficiency. Series resistance limitations for concentrator applications can be systematically explored for a given set of subcells. The current matching limitation imposed by series connection reduces efficiency relative to independently-connected cells. The overall trend indicates an approximately 5% drop in efficiency for series connected cells relative to identical independently connected cells. The series-connected devices exhibit a high sensitivity to spectral changes and individual subcell performance. If any single subcell within the series-connected device is degraded relative to its optimal design, the entire device is severely hindered. This model allows complex heterostructure solar cell structures to be evaluated by providing device physics-based predictions of performance limitations.

/pdf/p-n-junction-heterostructure-device-physics-model-of-a-four-4xb0bkmlr2.pdf

Brendan M. Kayes

Papers

STRUCTURES OF AND METHODS FOR FORMING VERTICALLY ALIGNED Si WIRE ARRAYS

Synthesis and Characterization of Silicon Nanorod Arrays for Solar Cell Applications

Self-bypass diode function for gallium arsenide photovoltaic devices

Optoelectronic devices including heterojunction

p-n junction heterostructure device physics model of a four junction solar cell