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

THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films

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

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)

Heterogeneous photocatalyst materials for water splitting

Semiconductor/liquid contacts provide very efficient systems for converting sunlight into electrical and/or chemical energy. Until recently, relatively little was understood about the factors that control the rates of interfacial charge transfer in such systems. This Forum Article summarizes recent results that have elucidated the key factors that control such charge-transfer rates, including verification of the Marcus inverted region, identification of the maximum charge-transfer rate constant for outer-sphere, nonadsorbing redox couples at optimal exoergicity, the role of nuclear reorganization on the value of the interfacial charge-transfer rate constant at semiconductor electrodes, and the effects of pH-induced changes in the driving force on the rates of such systems. In addition, we discuss methods for using main group inorganic chemistry to control the electrical properties of surfaces of important semiconductors for solar energy conversion, with specific emphasis on alkylation of the (111)-oriented surface of Si. Control of the rates at which carriers cross such interfaces, along with control of the rates at which carriers recombine at such interfaces, forms the basis for exerting chemical control over the key solar energy conversion properties of semiconductor photoelectrode-based devices.

Chemical Control of Charge Transfer and Recombination at Semiconductor Photoelectrode Surfaces

A method of aligning microwires includes modifying the microwires so they are more responsive to a magnetic field. The method also includes using a magnetic field so as to magnetically align the microwires. The method can further include capturing the microwires in a solid support structure that retains the longitudinal alignment of the microwires when the magnetic field is not applied to the microwires.

Method for alignment of microwires

A quantitative study has been performed on the stability of GaAs surfaces to photoanodic corrosion in contact with the 1.0 M KOH(aq)-0.10 M K[sub 2]Se(aq)-0.01 M K[sub 2]Se[sub 2](aq) electrolyte. In this electrolyte, chemically etched n-type GaAs electrodes displayed significant photocorrosion in competition with faradaic charge transfer to Se[sup 2[minus]](aq). Chemisorption of group VIIIB metal ions, including complexes of Co(III), Os(III), and Ru(III), onto the etched GaAs surface yielded improved current-voltage (I-V) behavior of the GaAs photoanode and also resulted in a significant reduction in photocorrosion. This behavior implies that the chemisorbed metal ions act to increase the rate of hole transfer to the Se[sup 2[minus]] donor species, as opposed to the passivation of nonradiative surface recombination. Related experiments on n-GaAs photoanodes in contact with the 1.0 M KOH(aq)-0.3 M Te[sup 2[minus]](aq)-0.01 M Te[sub 2][sup 2[minus]](aq) electrolyte have also been performed. The I-V properties of n-GaAs, p-GaAs, and Sn-doped In[sub 2]O[sub 3] electrodes have been investigated in this electrolyte, and these measurements have been used to elucidate common mechanistic features of charge-transfer reactions for the Se[sup 2[minus]](aq) and Te[sup 2[minus]](aq) redox systems.

Chemical Modification of n-GaAs Photoanodes with Group VIIIB Metal Ions: Stability in Contact with 1.0 M KOH(aq)-0.10 M K2Se(aq) Solutions and I-V Properties in Contact with 1.0 M KOH(aq)-0.3 M K2Te( aq) Electrolytes.

Nathan S. Lewis

Papers

Chemical Control of Charge Transfer and Recombination at Semiconductor Photoelectrode Surfaces

Method for alignment of microwires

Chemical Modification of n-GaAs Photoanodes with Group VIIIB Metal Ions: Stability in Contact with 1.0 M KOH(aq)-0.10 M K2Se(aq) Solutions and I-V Properties in Contact with 1.0 M KOH(aq)-0.3 M K2Te( aq) Electrolytes.

Characterization of Y-Ba-Cu-O films grown on silicon substrates by sequential evaporation

Microstructural characterization of YBaCuO Films on LaAlO3 substrates