Fabrication,Optical Modeling,and Color Characterization of Semitransparent Bulk‐Heterojunction Organic Solar Cells in an Inverted Structure

Semitransparent inverted organic photodiodes are fabricated with a Baytron PH500 ethylene‐glycol layer/silver grid as the top electrode. Reasonable performances are obtained under both rear‐ and front‐side illumination and efficiencies up to 2% are achieved. Some light is shed on visual prospects through optical simulations for a semitransparent device of poly(3‐hexylthiophene) (P3HT) and the C60 derivative 1‐(3‐methoxycarbonyl)propyl‐1‐phenyl[6,6]C₇₁ (PC70BM) in the inverted structure. These calculations allow the maximum efficiency achievable to be predicted for semitransparent cells based on P3HT:PC70BM versus the transparency perception for a human eye. The simulations suggest that low‐bandgap materials such as poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (PCPDTBT) have a better potential for semitransparent devices. In addition, the color range recognized by the human eye is predicted by the optical simulation for some semitransparent devices including different active layers.     

Micromachining of amplitude and phase modulated reflective computer generated hologram patterns in silicon

Silicon has been machined on lateral resolutions of micrometers and on depth resolutions of nanometers using a recently-developed process based on ion irradiation and electrochemical anodisation. Here we investigate its use as a recording medium for computer generated hologram patterns. We describe the fabrication of both amplitude and phase binary modulated reflective computer generated hologram patterns on a silicon surface with pixel sizes of 5 μm. We further discuss the use of micromachined silicon to variably modulate both amplitude and phase in a continuous, rather than a binary fashion.     

Coprecipitated Ni‐Co Bimetallic Nanocatalysts for Methane Dry Reforming

Methane dry reforming was studied over nanostructure bimetallic Ni‐Co‐MgO catalysts. The catalysts were prepared by coprecipitation with different Ni‐Co contents and characterized by XRD, BET, N₂ adsorption/desorption, temperature‐programmed reduction (TPR), SEM, and temperature‐programmed oxidation (TPO) techniques. XRD results let conclude that all samples contained MgO crystallite phases. With a higher Ni content the intensity of the diffraction peaks became stronger, indicating growth of the crystallite size of the prepared solid solutions. BET analysis demonstrated that a higher Ni‐Co content decreased the surface area. The optimal catalyst could be determined which had the highest activity and a good stability in dry reforming reaction.     

Hydraulic and turbulence structure of triangular labyrinth weir‐pool fishways

Detailed laboratory experiments were conducted to analyze and evaluate a new weir‐pool fishway design. The new design consisted of a series of one‐cycle, triangular labyrinth weirs that formed a weir‐pool fish passage. Hydraulic characteristics of flow over the proposed fishway were examined for three pool lengths and a wide range of discharges. It was found that the new design had superior discharge capacity over classical weir‐pool fishways in plunging flow regime. Spatial and point analyses of measured velocity data were carried out to understand turbulence structure and distribution of turbulent flow. The power dissipation per unit volume was calculated for different tests, and it varied nonlinearly with discharge. Based on the limiting criteria for energy dissipation rates of different fish species, the maximum operating discharge for different slopes was extracted for the proposed design. The model‐to‐prototype scaling analysis was performed based on the recommended scaling factor of three for prototype. It was found that the approach velocity of prototype increased by 12%, whereas the total discharge increased by more than five times. The contour plots of time‐averaged velocity indicated that the proposed fishways offered diversified flow fields without exceeding the maximum velocity above the standards recommended for weir‐pool fishways. To study the size, direction, and periodicity of turbulent eddies, magnitude of the most energetic eddy and dominant frequencies were extracted using power spectrum analysis. Quadrant analysis consistently showed that Reynolds shear stresses in ejection and sweep events became weaker as the pool length increased. The small region of strong ejection and sweep events evidenced a good resting place for fish migration, whereas the generated turbulence was large enough to attract fish species to use the passage.     

Fluid physics around conductive deformable flaps within an induced-charge electrokinetically driven microsystem

The induced-charge electrokinetic motion of a conductive deformable flap (which is installed on the walls of a microchannel) is numerically studied in this article. The relationship between the flap orientation (i.e., vertical, horizontal and oblique positions) and its motion is studied. Stagnation point concept is used to explain the behavior of the flap at different situations. The stagnation point is defined as a point on the flap surface where the induced zeta potential is zero. Thus, the flow velocity at this point becomes zero, and the pressure gradient will be maximum. The direction of the flap motion is determined by the location of the stagnation point. As an example, here, it is shown that the obtuse conductive flap moves in the opposite direction of the flow field because in this case, the stagnation point is located on the back surface of the flap. Interaction of two vertical conductive flaps (located at different distances from each other) is also investigated in this paper. The results indicate that if both of the conductive flaps are fixed on the same microchannel wall, two vortices with opposite spin directions are generated between them. These vortices create a low-pressure zone through which the two flaps attract one another. However, when each flap is fixed on upper and lower microchannel walls, the two vortices with same spin directions are generated between the flaps. These two vortices merge and form a high-pressure zone through which two flaps repel each other.     

Trace metal determination in total atmospheric deposition in rural and urban areas

The wet, dry and total atmospheric depositions of some metals (Al, Cd, Cr, Cu, Fe, Na, Pb and Zn) were sampled at two sites and atmospheric fallout fluxes were determined for these locations. This work, led by two different research groups, allowed to reach two main goals: to define a simple analytical procedure to secure accurate shipboard sampling and analysis of atmospheric deposition, and to assess anthropogenic impacts of heavy metals to the environment. The first step about the validation step showed that the prevalent deposition type was dry deposition which represents 40, 60 and 80% for Cd, Cu and Pb, respectively. This prevalence of dry deposition in total atmospheric fallout supported the necessity of funnel wall rinsing which contains 30, 50 and 40% of collected Cd, Cu and Pb, respectively. Moreover, the reproducibility of atmospheric deposition collection was determined. The second step was performed by comparing two sampling sites. A rural sampling site, situated in Morvan's regional park (250 km south-east of Paris), was chosen for its isolation from any local and regional contamination sources. Fluxes obtained in this area were compared with those obtained at an urban site (Créteil, suburb of Paris) allowing comparison between urban and rural areas and demonstrating the impact of anthropogenic activities on atmospheric deposition of Cr, Cu and Pb.     

A template-free method to synthesize porous G-C3N4 with efficient visible light photodegradation of organic pollutants in water

Porous graphitic carbon nitride with a high surface area was successfully synthesized without using any template or other substances like metals, just by placing melamine powder into a muffle furnace which was heated to 550?°C in advance. To evaluate the structure, morphology, and optical properties, the high performance g-C₃N₄ (HPCN) was analyzed by XRD, SEM-EDX, TEM, N₂ physisorption, FT-IR analysis, UV–Vis DRS, PL, and Zeta potential. HPCN was able to completely degrade rhodamine B under visible light with the rate constant of 0.086?min^?1, which is 3.5 times higher than the traditional g-C₃N₄. The possible mechanism of RhB photodegradation was discussed in detail, which illustrated the reaction is performed in acidic media much better than neutral and basic solutions, and O₂^? and h⁺ are the key reactive species during the reaction. Moreover, the stability of the photocatalyst was investigated and turned out its photocatalytic activity has not considerably changed after 6 cycles, so it was a highly stable photocatalyst.