Monitoring of electro-active biofilm in soil

The present paper describes a new tool for on-line monitoring of biofilm growth in the soil. The work deals with the application in soil of the same electrochemical techniques already successfully used in water systems to monitor biofilm growth and mainly based on the cathodic polarisation of stainless steel electrodes. Experiments at laboratory level with sterilised and unsterilised soils, different soil humidities, different levels of nutrients have been performed by using a set of soil microcosms containing electrochemical probes. Weekly humidity tests and adjustments, chemical and microbiological analyses of the soils have been regularly carried out. Microbiological analyses and microscopy observation performed on the surface of the stainless steel electrochemical probes at the end of the tests confirmed a direct correlation between the increase of cathodic characteristic and the biofilm development on the working electrodes. The results suggest that simple electrochemical techniques are applicable in soil to monitor the early stage of biofilm growth on stainless steel. It was confirmed, in particular, a key role of soil humidity in the development of a stable and easily detectable biofilm. Soil humidity level resulted as the most critical and limiting factor for biofilm growth, more than the environment temperature, nutrient and carbon content. The best conditions to achieve a quick and full electro-active biofilm on electrodes in a soil microcosms suitable for experiments and studies at laboratory level have been detailed.     

Simulation support for performance assessment of building components

The determination of performance metrics for novel building components requires that the tests are conducted in the outdoor environment. It is usually difficult to do this when the components are located in a full-scale building because of the difficulty in controlling the experiments. Test cells allow the components to be tested in realistic, but controlled, conditions. High-quality outdoor experiments and identification analysis methods can be used to determine key parameters that quantify performance. This is important for achieving standardised metrics that characterise the building component of interest, whether it is a passive solar component such as a ventilated window, or an active component such as a hybrid photovoltaic module.     

A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts

An effective anode electrocatalyst in direct methanol fuel cell (DMFC) should have high activity for the oxidation of methanol and the decomposition of water, while remaining stable under the relatively harsh anode environment. Although the Pt/Ru bimetallic alloy is currently the most effective anode electrocatalyst, both Pt and Ru are expensive due to limited supplies and both are susceptible to CO poisoning. Consequently, the discovery of less expensive and more CO tolerant alternatives to the Pt/Ru catalysts would help facilitate the commercialization of DMFC. In this paper we will discuss the possibility of using tungsten carbides (WC) and Pt-modified WC as potential anode electrocatalysts in DMFC. We will provide an overview of our recent work, using a combined approach of fundamental surface science studies and in-situ electrochemical evaluation of the activity and stability of tungsten carbides. We will demonstrate the feasibility to bridge fundamental surface science studies on single crystals with the electrochemical evaluation on polycrystalline WC films. We will also discuss the synergistic effect by supporting low coverages of Pt on the WC substrate to further enhance the electrochemical performance of WC.     

Surface nanocrystalline Si structure and its surface passivation for highly efficient black Si solar cells

19.5% conversion efficiency crystalline silicon (Si) solar cells having simple structure without antireflection coating have been fabricated using the surface structure chemical transfer method which produces a nanocrystalline Si layer simply by contacting catalytic platinum with Si wafers in hydrogen peroxide plus hydrofluoric acid solutions. The reflectivity becomes less than 3% after the surface structure chemical transfer method due to formation of black Si. Deposition of phosphosilicate glass and heat treatment at 925 °C performed for formation of pn‐junction effectively passivate the nanocrystalline Si surface. With this phosphosilicate glass passivation plus the hydrogen treatment at 400 °C, the internal quantum efficiency is greatly improved and reaches 81% at a wavelength of 400 nm. Analysis of ellipsometry data shows that incident light with wavelength shorter than 400 nm is almost completely absorbed by the nanocrystalline Si layer. The high internal quantum efficiency for short wavelength light is attributed to effective surface passivation and the nanocrystalline Si layer band‐gap energy which decreases with the distance from the top of the network structure of the nanocrystalline Si layer. Copyright © 2017 John Wiley & Sons, Ltd.     

The Role of Bloom Index of Gelatin on the Interaction with Retinal Pigment Epithelial Cells

Biocompatible materials are of considerable interest in the development of cell/drug delivery carriers for therapeutic applications. This paper investigates the effects of the Bloom index of gelatin on its interaction with retinal pigment epithelial (RPE) cells. Following two days of culture of ARPE-19 cells with gelatin samples G75-100, G175, and G300, the in vitro biocompatibility was determined by cell proliferation and viability assays, and glutamate uptake measurements, as well as cytokine expression analyses. The mitochondrial dehydrogenase activity in the G300 groups was significantly lower than that of G75-100 and G175 groups. The Live/Dead assays also showed that the gelatin samples G300 induced mild cytotoxicity. In comparison with the treatment of gelatins with low Bloom index, the exposure to high Bloom strength gelatins markedly reduced the glutamate uptake capacity of ARPE-19 cells. One possible explanation for these observations is that the presence of gelatin samples G300 with high viscosity in the medium may affect the nutrient availability to cultured cells. The analyses of pro-inflammatory cytokine IL-6 expression at both mRNA and protein levels showed that the gelatins with low Bloom index caused less cellular inflammatory reaction and had more acceptable biocompatibility than their high Bloom strength counterparts. These findings suggest that the Bloom index gives influence on cellular responses to gelatin materials.     

Analysis of the EWT‐DGB solar cell at low and medium concentration and comparison with a PESC architecture

Silicon represents an interesting material to fabricate low‐cost and relatively simple and high‐efficient solar cells in the low and medium concentration range. In this paper, we discuss a novel cell scheme conceived for concentrating photovoltaic, named emitter wrap through with deep grooved base (EWT‐DGB), and compare it with the simpler passivated emitter solar cell. Both cells have been fabricated by means of a complementary metal–oxide–semiconductor‐compatible process in our laboratory. The experimental characterization of both cells is reported in the range 1–200 suns in terms of conversion efficiency, open circuit voltage, short circuit current density and fill factor. In particular, for the EWT‐DGB solar cells, we obtain an encouraging 21.4% maximum conversion efficiency at 44 suns. By using a calibrated finite‐element numerical electro‐optical simulation tool, validated by a comparison with experimental data, we study the potentials of the two architectures for concentrated light conditions considering possible realistic improvements with respect to the fabricated devices. We compare the solar cell figures of merit with those of the state‐of‐the‐art silicon back‐contact back‐junction solar cell holding the conversion efficiency record for concentrator photovoltaic silicon. Simulation results predict a 24.8% efficiency at 50 suns for the EWT‐DGB cell and up to 23.9% at 100 suns for the passivated emitter solar cell, thus confirming the good potential of the proposed architectures for low to medium light concentration. Finally, simulations are exploited to provide additional analysis of the EWT‐DGB scheme under concentrated light. Copyright © 2017 John Wiley & Sons, Ltd.     

Photovoltaic Processes of Singlet and Triplet Excited States in Organic Solar Cells

This article reports the respective photovoltaic processes of singlet and triplet photoexcited states in dissociation and charge reactions based on the studies of magnetic‐field effects of photocurrents. The magnetic‐field effects of photocurrents reveal that weak donor‐acceptor interactions lead to a two‐step photovoltaic process: dissociation in polaron‐pair states evolved from singlet excitonic states and exciton‐charge reactions occurred in triplet excitonic states in the generation of the photocurrent. However, strong donor‐acceptor interactions yield a one‐step photovoltaic process: direct dissociation of both singlet and triplet excitons in bulk‐heterojunction organic solar cells. In addition, the magnetic‐field effects of photocurrents indicate that the dissociated electrons and holes form charge‐transfer complexes with singlet and triplet spin configurations at donor‐acceptor intermolecular interfaces. As a result, the magnetic‐field effects of photocurrents can deliver a critical understanding of singlet and triplet photovoltaic processes to design advanced solar‐energy materials and devices.     

Cathodic disbonding of a thick polyurethane coating from steel in sodium chloride solution

The cathodic disbonding of a thick, pigmented polyurethane coating from steel in 3.5 wt.% NaCl solution was studied by using an electrochemical AC impedance technique. Double-cylinder electrolyte cells were designed to separate the measurements of cathodic disbonding process from the influence of the impedance of an artificial defect. It was found that for a thick, pigmented polyurethane coating, the more important transport pathway of the reactive species is along the coating/steel interface rather than through the coating. There existed a delay time for the cathodic disbonding process, and cathodic polarization was not a predominant factor in determining the cathodic disbonding behavior in the early stages. The thick polyurethane coating, which was applied on a well sand-blasted steel surface, had excellent resistance to cathodic disbonding.     

Exploration of artificial neural network [ANN] to predict the electrochemical characteristics of lithium-ion cells

CoO anode, as an alternate to the carbonaceous anodes of lithium-ion cells has been prepared and investigated for electrochemical charge-discharge characteristics for about 50 cycles. Artificial neural networks (ANNs), which are useful in estimating battery performance, has been deployed for the first time to forecast and to verify the charge-discharge behavior of lithium-ion cells containing CoO anode for a total of 50 cycles. In this novel approach, ANN that has one input layer with one neuron corresponding to one input variable, viz., cycles [charge-discharge cycles] and a hidden layer consisting of three neurons to produce their outputs to the output layer through a sigmoid function has been selected for the present investigation. The output layer consists of two neurons, representing the charge and discharge capacity, whose activation function is also the sigmoid transfer function. In this ever first attempt to exploit ANN as an effective theoretical tool to understand the charge-discharge characteristics of lithium-ion cells, an excellent agreement between the calculated and observed capacity values was found with CoO anodes with the best fit values corresponding to an error factor of <1%, which is the highlight of the present study.