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

The oxidant-activated reactivity of Si toward nucleophiles was evaluated for Si nanocrystals (Si-NCs) of differing diameters, d. In the presence of ferrocenium as a one-electron, outer-sphere oxidant, d ≥ 8 nm Si-NCs readily reacted with nucleophiles, including methanol, butanol, butylamine, butanoic acid, butylthiol, and diethylphosphine. However, d < 8 nm Si-NCs did not undergo such reactions, and stronger oxidants such as acetylferrocenium or 1,1′-diacetylferrocenium were required. Butylamine-, butylthiol-, and butanol-functionalized d ≥ 8 nm Si-NCs were partially oxidized and exhibited photoluminescence originating from defect states. In contrast, butanoic acid-functionalized Si-NCs were minimally oxidized and displayed core emission resulting from the excitation and relaxation of electrons across the Si-NC bandgap. Diethylphosphine-functionalized Si-NCs were stable only under inert conditions and showed core emission, with the Si–P bonds being highly susceptible to oxidation and rapidly decomposing u...

Oxidant-Activated Reactions of Nucleophiles with Silicon Nanocrystals

Semiconductor/liquid junction photoelectrochemical solar cells

Chemical functionalization of semiconductor surfaces can provide high-efficiency photoelectrochemical devices through molecular-level control of the energetics, surface dipole, surface electronic d

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Surface Passivation and Positive Band-Edge Shift of p-Si(111) Surfaces Functionalized with Mixed Methyl/Trifluoromethylphenylacetylene Overlayers

Thin films of carbon black-organic polymer composites have been deposited across two metallic leads, with sorption of vapors producing swelling-induced resistance changes of the detector films. To identify and classify vapors, arrays of such vapor sensing elements have been constructed in which each element of the array contains a different polymer as the insulating phase and a common conductor, carbon black, as the conducting phase. The differing gas-solid partition coefficients for the various polymers of the detector array produce a pattern of differential resistance changes that is used to classify vapors and vapor mixtures. The performance of this detector array system towards 2,4-dinitrotoluene, the predominant signature in the vapor phase above land mines, in the presence high concentrations of water or of acetone has been evaluated.

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Array-based carbon black-polymer composite vapor detectors for detection of DNT in environments containing complex analyte mixtures

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.

Nathan S. Lewis

Papers

Oxidant-Activated Reactions of Nucleophiles with Silicon Nanocrystals

Semiconductor/liquid junction photoelectrochemical solar cells

Surface Passivation and Positive Band-Edge Shift of p-Si(111) Surfaces Functionalized with Mixed Methyl/Trifluoromethylphenylacetylene Overlayers

Array-based carbon black-polymer composite vapor detectors for detection of DNT in environments containing complex analyte mixtures

Longitudinal alignment of microwires