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

We report the first measurements of photocurrent quantum yields for semiconductor/liquid junctions in the short-wavelength region of the spectrum (200-600 nm). The key feature of this wavelength region is the short penetration depth for the absorbed photon (less than 100 A), which allows measurement of the majority carrier collection velocity. Spectra have been obtained for semiconductor/liquid, semiconductor/metal, and semiconductor/insulator/metal junctions. For all semiconductors studied (n-Si, p-Si, n-GaAs, n-InP, a-Si:H), the spectral responses of the liquid junctions showed higher quantum yields than the metal junctions, indicating greater majority carrier losses at the metal junctions. This general trend was independent of redox species, solvent, supporting electrolyte, and metal overlayer. The spectral response data can also be used to distinguish Schottky barrier behavior from electrocatalytic behavior of metal overlayers, and this approach has been used to study several semiconductor/metal film junctions in contact with electrolytes.

Short-Wavelength Spectral Response Properties of Semiconductor/Liquid Junctions.

Studies of the n-GaAs/KOH-Se2- 2-Se2- Semiconductor/Liquid Junction.

Spurendetektion von analyten mit hilfe artifizieller olfaktometrie

for integrated photoelectrochemical water-splitting systems Shu Hu, e Chengxiang Xiang, e Sophia Haussener, d Alan D. Berger c d and Nathan S. Lewis* e a Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, California Institute of Technology, Pasadena, CA, 91125, USA. E-mail: nslewis@caltech.edu b Institute of Mechanical Engineering, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne, Switzerland c Department of Chemical and Biomolecular Engineering, University of California, 201Gilman Hall, Berkeley, CA 94720, USA d Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA e Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA, 91125, USA

/pdf/optimal-band-gap-combinations-of-light-absorbers-for-292ia8z81l.pdf

Optimal Band Gap Combinations of Light Absorbers for Integrated Photoelectrochemical Water-Splitting Systems

The theoretical maximum photovoltaic efficiency is bounded by the Shockley-Queisser model which assumes that the photovoltaic material has step-function like absorptance, with zero absorption below its bandgap and perfect absorption above. However, typical photovoltaic materials exhibit absorption with an exponential dependence below its bandgap, known as the“Urbach tail” whose steepness is dependent on the Urbach parameter. Using a modified detailed balance model that accounts for sub-gap absorption we show that photovoltaic performance is strongly affected by the magnitude of the Urbach parameter.

Nathan S. Lewis

Papers

Short-Wavelength Spectral Response Properties of Semiconductor/Liquid Junctions.

Studies of the n-GaAs/KOH-Se2- 2-Se2- Semiconductor/Liquid Junction.

Spurendetektion von analyten mit hilfe artifizieller olfaktometrie

Optimal Band Gap Combinations of Light Absorbers for Integrated Photoelectrochemical Water-Splitting Systems

Effects of Sub-gap Absorption on Photovoltaic Performance