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This article describes the ability of the Chlorella vulgaris BEIJ strain G-120 to produce hydrogen (H2) via both direct and indirect pathways without the use of nutrient starvation. Photobiological H2 production reached a maximum rate of 12 mL H2 L1 h1 , corresponding to a light conversion efficiency (light to H2) of 7.7% (average 3.2%, over the 8-day period) of PAR, (photosynthetically active irradiance). Cells presented a maximum in vivo hydrogenase activity of 25.5 ± 0.2 nmoles H2 mgChl1 h1 and the calculated in vitro hydrogenase activity was 830 ± 61 nmoles H2 mgChl1 h1 . The strain is able to grow either heterotrophically or photo autotrophically. The total output of 896 mL of H2 was attained for illuminated culture and 405 mL for dark cultures. The average H2 production rate was 4.98 mL L1 h1 for the illuminated culture and 2.08 mL L1 h1 for the one maintained in the dark. Universidad de Costa Rica/[808-C0-107]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)

Photo-fermentation seems to be an attractive hydrogen production pathway. However, the light conversion efficiency and photo-hydrogen production of purple non-sulphur bacteria (PNSB) are very low, and hence, various biotechnological approaches are investigated to improve biohydrogen production. This article presents an overview of the advanced biotechnological approaches to enhance the photo-fermentative biohydrogen production. The advancements reviewed include optimisation of the medium, abiotic factors, the lighting regime, immobilisation techniques, application of photoluminating nanomaterials, genetic engineering, and other strategies. These approaches show positive results in the enhancement of photo-hydrogen production by PNSB. Some recommendations are suggested for further studies in the enhancement of photo-hydrogen production, such as green nanomaterials application, integrated dark- and photo-fermentation, genetic manipulation, and the application of the non-technological analysis approaches.

The synergistic effects and optimization of pH, carbon-to-nitrogen ratio (C/N), and light intensity (I) on the photo-fermentative hydrogen production of Rhodobacter sphaeroides 158 DSM and light conversion efficiency have been investigated under different conditions of pH (6.5–8); C/N (15–35); and light intensity (35–185 W m−2). Response surface methodology (RSM) and Box-Behnken experimental design (BBD) were used to identify the optimum values of the three key parameters of pH, C/N, and I, based on the impact on hydrogen production potential (HPP), hydrogen production rate (HPR), and light conversion efficiency η . With desirability value of 0.91, the optimum values of 7.4, 27.5, and 126 W m−2 were identified for pH, C/N, and I respectively, with HPP, HPR and η reaching 960 mL L−1, 41.74 mL L−1 h−1, and 0.31 respectively. Regression analysis indicated a good fit between experimental and model data. The study showed that both C/N ratio and I have crucial and significant effect on the HPP, HPR and η , followed by pH, the synergistic effect of pH–I and C/N I on the light conversion efficiency ( η ) was significant while pH C/N was insignificant. The results and analysis obtained could be very useful for better optimizing the photo-fermentative hydrogen production.

In the present work, a Chlorella vulgaris mutant, named as SDEC-3M, was screened out through the combination of the isolation using 96-well microplates and traditional UV mutagenesis. Compared with its parent (wild type), the growth of SDEC-3M preferred higher CO2 (15% v/v) environment to ambient air (0.038% CO2 (v/v)), indicating that the mutant qualified with good tolerance and growth potential under high level CO2 (high CO2 tolerance) but was defective in directly utilizing the low level CO2 (high CO2 requiring). The genetic stability under ambient air and high level CO2 was confirmed by a continuous cultivation for five generations. Higher light conversion efficiency (14.52%) and richer total carbohydrate content (42.48%) demonstrated that both solar energy and CO2 were more effectively productively fixed into carbohydrates for bioethanol production than the parent strain. The mutant would benefit CO2 biofixation from industrial exhaust gas to mitigate of global warming and promote biofuel production to relieve energy shortage.

H 2 is a clean, renewable and energy-efficient fuel. However, in order for it to be a fuel effectively utilizable at an industrial level, key issues about its economically and environmentally sustainable production have still to be solved. Microbial hydrogen production is a process with a low environmental impact and, among microbial processes, photofermentation is considered a promising and sustainable solution. However, the energy input for the biological processes is still higher than the energy output in the form of H 2 gas. One possibility for improving this ratio is to increase the efficiency of the process while at the same time reducing electricity consumption, both of which relate to the issue of an optimal photobioreactor design. This review focuses on recent advances made in photobioreactor design towards higher light conversion efficiency, a greater hydrogen production rate and substrate conversion in hydrogen production processes carried out with purple non sulfur bacteria, giving particular attention to the light source and to illumination protocols. Recent achievements in outdoor hydrogen production in large scale photobioreactors are also reviewed.

This paper is expected at the study of Ga 1-x In x P/GaAs based solar cell. The effects of indium concentration, lattice parameter mismatch and thickness of the SiO 2 insulating layer on the characteristics and efficiency of the Ga 1-x In x P/GaAs structure were investigated. We noticed that for higher indium concentration, the band gap energy decreases considerably. We found that the efficiency reaches 18% in a lattice-matched δ=50A. For a concentration x > 0.48, we have a compressive strain Δa/a > 0 which leads to a higher efficiency. For x=90%, δ=5 nm and a strain equal Δa/a= 3%, we achieved an efficiency of 27%. The results show that light conversion efficiency has considerably boosted by varying insulating strain values.

Activated carbon fibers (ACFs) were firstly applied as fluidized solid carrier to immobilize photo-fermentative bacteria (PFB) for H 2 production in batch culture. The observations by scanning electronic microscopy (SEM) demonstrated the close interaction between ACFs and PFB. The amount of immobilized bacteria and the performance of H 2 production were strongly affected by specific surface area, length and amount of ACFs, respectively. Large specific surface area provided more surface attachment sites and more PFB were immobilized. ACFs with proper length avoided intertwining with each other and better fluidized during reactor operation. Excessive amount of ACFs not only limited the light conversion efficiency, but also increased biofilm detachment, resulting in low H 2 yield. The maximum yield (3.08 mol H 2 mol −1 acetate) and rate (32.85 ml l −1 h −1 ) of H 2 production were obtained, using specific surface area (1500 m 2 g −1 ), length (1 mm) and amount (0.8 g l −1 ) of ACFs. Compared with the conventional solid carriers, ACFs were effective solid carriers to immobilize PFB for improving H 2 production, due to bacteria immobilized on the external surface of fluidized ACFs and formed a layer of dense biofilm.

This paper studies the effect of the annealing process on the performance of P3HT/PCBM photovoltaic devices, in terms of their efficiencies. The basic photovoltaic devices are annealed on a hot-plate, at a temperature of 150 °C for 10 min in air. For comparison, the thermal annealing of photovoltaic devices is carried out using rapid thermal annealing (RTA) equipment, at a temperature of 150 °C for 10 min in different environments such as in vacuum, in nitrogen and in argon, individually. The light conversion efficiency (Eff) of the resulting photovoltaic devices increases from 2.29% (hot-plate annealing) to 2.77% after annealing in a vacuum environment. As a result, the organic photovoltaic devices, annealed in a vacuum show enhanced efficiencies compared with those annealed in different gas environments.

Efficient silicon light emitting diodes (LEDs) could allow “super-integration” of optical and electronic functions in high density silicon microelectronic circuits [1] and are consequently of considerable interest. However , performance with standard p-n junction emitters has been modest , with devices with electrical to light conversion efficiency in the 0.01–0 .1% range recentl y described as “high performance” [2]. Slightly better results have been obtained using approaches based on porous silicon [3], although this material is fragile and not fully compatible with standard microelectronics processing.

An X-ray imaging detector based on the graded-gap Al x Ga 1− x As structures with the CCD camera as an image read-out tool is investigated. High X-ray – light conversion efficiency and X-ray image spatial resolution better than 20 line/mm are obtained.

A new type of Hybrid PhotoDetectors (HPDs) with an 18-mm-diameter GaAsP photocathode was developed in order to lower the energy threshold of the MAGIC-II Project. The Quantum Efficiency (QE) reaches more than 50% at around 500 nm and is enhanced in the UV region by the wavelength shifting technique. The total light conversion efficiency could be practically improved by about a factor 2 compared to the conventional PhotoMultiplier Tubes (PMT). Photocathode ageing measurements indicate that GaAsP photocathode have a sufficiently long lifetime for being used in the MAGIC telescope imaging camera.

The present paper reviews the development of X-ray phosphors from the first introduction of CaWO 4 in 1896 to the currently used new phosphors Gd 2 O 2 S:Tb, LaOBr:Tm and YTaO 4 Nb. In each case, the important parameters of X-ray absorption, X-ray to light conversion efficiency, emission characteristics, density, morphology, and stability will be stressed. Finally, an assessment of how other modalities, such as magnetic resonance imaging, ultrasound and digital radiography will influence film/screen systems in the future will be made.