Genesis and Propagation of Fractal Structures During Photoelectrochemical Etching of n-Silicon.

The genesis, propagation, and dimensions of fractal-etch patterns that form anodically on front- or back-illuminated n-Si(100) photoelectrodes in contact with 11.9 M NHF (aqueous) have been investigated during either a linear potential sweep or a constant potential hold ( = +6.0 V versus Ag/AgCl).

Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment.

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the Earth's atmosphere. So-called 'solar fuel' devices, currently developed for terrestrial applications in the quest for realizing a sustainable energy economy on Earth, provide promising alternative systems to existing air-revitalization units employed on the International Space Station (ISS) through photoelectrochemical water-splitting and hydrogen production. One obstacle for water (photo-) electrolysis in reduced gravity environments is the absence of buoyancy and the consequential, hindered gas bubble release from the electrode surface.

Efficient solar hydrogen generation in microgravity environment.

Long-term space missions require extra-terrestrial production of storable, renewable energy. Hydrogen is ascribed a crucial role for transportation, electrical power and oxygen generation. We demonstrate in a series of drop tower experiments that efficient direct hydrogen production can be realized photoelectrochemically in microgravity environment, providing an alternative route to existing life support technologies for space travel.

Advancing semiconductor-electrocatalyst systems: application of surface transformation films and nanosphere lithography.

Photoelectrochemical (PEC) cells offer the possibility of carbon-neutral solar fuel production through artificial photosynthesis. The pursued design involves technologically advanced III-V semiconductor absorbers coupled via an interfacial film to an electrocatalyst layer. These systems have been prepared by in situ surface transformations in electrochemical environments.

Nanoelectrical and Nanoelectrochemical Imaging of Pt/p-Si and Pt/p -Si Electrodes.

The interfacial properties of electrolessly deposited Pt nanoparticles (Pt-NPs) on p-Si and p -Si electrodes were investigated on the nanometer scale using a combination of scanning probe methods. Atomic force microscopy (AFM) showed highly dispersed Pt-NPs with diameters of 20-150 nm on the Si surface. Conductive AFM measurements showed that only approximately half of the particles exhibited measurable contact currents, with a factor of 10 difference in current observed between particles at a given bias.

Efficiency limits for photoelectrochemical water-splitting.

Theoretical limiting efficiencies have a critical role in determining technological viability and expectations for device prototypes, as evidenced by the photovoltaics community's focus on detailed balance. However, due to their multicomponent nature, photoelectrochemical devices do not have an equivalent analogue to detailed balance, and reported theoretical efficiency limits vary depending on the assumptions made. Here we introduce a unified framework for photoelectrochemical device performance through which all previous limiting efficiencies can be understood and contextualized.

Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure.

Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis.

Epitaxial III-V films and surfaces for photoelectrocatalysis.

Efficient photoelectrochemical devices for water splitting benefit from the highest material quality and dedicated surface preparation achieved by epitaxial growth. InP(100)-based half-cells show significant solar-to-hydrogen efficiencies, but require a bias due to insufficient voltage. Tandem absorber structures may provide both adequate potential and efficient utilization of the solar spectrum.

Fundamental aspects of electrodeposition for the realization of plasmonic nanostructures.

Electrodeposition is used for the preparation of nanoparticles and nanostructures that allow, in principle, surface plasmon excitation. The (photo)electrodeposition process of Rh and Au nanoparticles as well as of heterodimeric enzymes onto silicon surfaces is investigated and the resulting structures are discussed with regard to applications in photoelectroctalysis and biosensing. Electrodeposition of Rh onto H-terminated p-Si surfaces generates nanostructures of the metal nanoparticles with simultaneous oxidation of the substrate thus forming nano-dimensioned metal-oxide-semiconductor (MOS)-type contacts.

Advances in photoelectrocatalysis with nanotopographical photoelectrodes.

The design of photoelectrodes for high efficiency solar fuel energy conversion devices is based on the search for adequate surface conditioning to achieve efficient light harvesting, stability, minimized surface recombination losses and high electron-transfer rates at the electrolyte interface. An overview on established and novel approaches is given. A recent viable solution is provided by electroplating of nanoscale catalytic metals on passivated semiconductor surfaces, thereby forming reactive centers and avoiding contact between the semiconductor surface and the electrolyte.

Use of molybdenum telluride as a substrate for the imaging of biological molecules during scanning tunnelling microscopy.

Scanning tunnelling microscopy was used to image biological molecules including supercoiled deoxyribonacetic acid and specific retrovirus enzymes, the reverse transcriptases of the avian myeloblastosis virus, the moloney murine leukaemia virus and the human immunodeficiency virus. Measurements were carried out on graphite and Group VI transition metal dichalcogenide layered crystals. Images obtained with graphite could not be unequivocally interpreted and attachment appears to occur solely at surface defect sites.

Effects of glucosinolate breakdown products on the hepatic biotransformation system in male rats.

The effects of 5-vinyloxazolidine-2-thione (VOT), 1-cyano-3-butene (CYB) and various isothiocyanates on parameters of hepatic phase I and phase II biotransformation were investigated in male rats after oral treatment for 3 consecutive days. The compounds with the exception of CYB caused increases in liver weight and glutathione S-transferase activity. Cytochrome P-450 level and monooxygenase activities were decreased by the isothiocyanates and CYB.

Direct observation of reverse transcriptases by scanning tunneling microscopy.

First images on a nanometer scale of reverse transcriptases (RT) of the human immunodeficiency virus (HIV-1) and of the Moloney murine leukemia virus (MuLV) obtained by scanning tunneling microscopy (STM) are reported. The common feature of the observed molecules is a ring-type or horseshoe shape with hole diameters of approximately 30 A. The STM images are compared with high resolution transmission electron microscopy (TEM) and existing structure predictions.

Subacute oral toxicity study of benzyl isothiocyanate in rats.

The subacute toxicity of benzyl isothiocyanate (BITC) was investigated in male rats given oral doses of 0, 50, 100 and 200 mg/kg body weight/day for 4 weeks. Body weight gain and food consumption were decreased with increasing doses of BITC. Haematological changes of toxicological relevance were observed in the highest dose group.

Toxicological evaluation of rapeseed products in a subacute feeding study in rats.

Groups of 15 male rats were fed ad libitum for 4 weeks standard diet containing 0, 2.5, 5 or 10% rapeseed protein isolate (RPI), 2.5, 5 or 10% rapeseed extraction residue (RER) or 10% casein.

[The prenatal toxicity of butenylisothiocyanate in rats].

Butenyl isothiocyanate (BylITC), the hydrolysis product of the glucosinolate gluconapin, present in various cruciferous vegetables and in rapeseed, was administered in oral doses of 0, 50, 100 and 150 mg/kg to pregnant rats on day 12 to 19 of gestation. Maternal toxicity was indicated by reduced body weight gain and increases in the weights of liver and kidneys. BylITC doses of 100 and 150 mg/kg caused retardation of fetal growth and ossification.

Scanning tunnelling microscopy observations of biomolecules on layered materials.

Scanning tunnelling microscopy (STM) has been performed on the reverse transcriptases of the human immunodeficiency virus (HIV-1) and the moloney murine leukaemia virus (MuLV). The biological molecules are adsorbed on n-type semiconducting MoTe2. The p66 (66 kD) subunit of the RT of HIV-1 is imaged by STM.

Effects of 5-vinyloxazolidine-2-thione on lactating rats and their sucklings.

5-vinyloxazolidine-2-thione (VOT) administered orally to lactating rats was found to be efficiently transferred to the sucklings via the milk. In mothers the exposure to VOT resulted in an increased percentage of neutrophils, a decreased percentage of lymphocytes and increases in the relative weights of liver and thyroid. Suckling rats showed a decreased number of leucocytes, increases in the relative weights of liver and thyroid and structural changes in the thyroid.

[Toxicological evaluation of saccharose carbonic acid esters in basic subchronic feeding trials with rats. 1. Effect of saccharose fatty acid polyester].

Groups of male and female rats received a sucrose fatty acid polyesters containing product (SPE) in their diet for 13 weeks at levels of 0, 5, 10 or 15%. Additional groups were pair-fed to the high-dose SPE-group (standard diet, 92.5%) or given food containing 7.

[Toxicological effect of a fatty acid mixture in rats].

The effects of a fatty acids mixture containing nearly 50% odd numbered fatty acids (PC-Säure) were studied in a subchronic toxicity test in male and female rats. The animals received PC-Säure in their diet at levels of 0, 1.25, 2.

[Toxicologic evaluation of sucrose carbonic acid esters in basic subchronic feeding studies in rats. 2. Effect of sucroacetoglycerides].

Groups of male and female rats received a sucroacetoglycerides containing product (SAG) for 3 months at dietary levels of 0, 2.5, 5 and 10%. Food consumption was initially increased in females at all SAG-levels.