Dye sensitized photovoltaic cells: Attaching conjugated polymers to zwitterionic ruthenium dyes

The synthesis of a zwitterionic ruthenium dye that binds to anatase surfaces and has a built-in functionality that allows for the attachment of a conjugated polymer chain is presented. The system was found to adsorb on the surface of anatase anchored by the ruthenium dye. Two types of devices were prepared: standard photoelectrochemical (PEC) solar cells and polymer solar cells. The PEC solar cells employed a sandwich geometry between TiO₂ nanoporous photoanodes and Pt counter electrodes using LiI/I₂ in CH₃CN as an electrolyte. The polymer solar cells employed planar anatase electrodes and the complex was adsorbed onto the surface before evaporation of gold electrodes. Alternative devices were obtained by spincoating of the polymer solution onto PEDOT:PSS covered indium-doped tin oxide substrates. PEC solar cells gave the best results and the main finding was that the polymer chain served as a light harvesting antenna for the ruthenium dye.     

On the photovoltaic response of the J-domain and the JA-assembly

Photovoltaic devices based on poly-2′,5′-dioctyl-4,4′′-terphenylenecyanovinylene (J-domain) and 4-aza-4-(4′-(poly-2′,5′-dioctyl-4,4′′-terphenylene-1-cyanovinylene-2-yl)biphen-4-yl)-8,12-dioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenium tetrafluoroborate (JA-assembly) were prepared using indiumtinoxide (ITO) as the transparent electrode and aluminium as the second electrode. While the photovoltaic response of the J-domain exhibited low short circuit currents of −0.1 nA cm⁻², the corresponding short circuit current of the JA-assembly was observed to be +10 nA cm⁻². The 100-fold increase in magnitude was related to the known energy transfer from the J-domain to the A-domain in the JA-assembly, and the inversion of the sign of the photovoltaic response that implies that the electrodes have a reversed polarity was explained on the basis of the positions of the energy levels and involves the action of the A-domain as a blocking layer and a light operated charge pump that efficiently transfers electrons to the ITO electrode.     

Characterisation and application of new carboxylic acid-functionalised ruthenium complexes as dye-sensitisers for solar cells

A series of ruthenium complexes with and without TiO₂ anchoring carboxylic acid groups have been synthesised and characterised using nuclear magnetic resonance (NMR), UV–vis and luminescence. These complexes were adsorbed on thin films of the wide band-gap semiconductor anatase and were tested as photosensitisers under standard conditions. I/V characteristics of such devices revealed superior performance of the non-symmetric complexes [4′-(4-bromophenyl)-[2,2′; 6′,2″] terpyridine]Ru(II) [4′-(4-bromophenyl)-[2,2′; 6′,2″] terpyridine-4,4″-dicarboxylic acid] and [2,2′; 6′,2″] terpyridine Ru(II) [2,2′; 6′,2″] terpyridine-4′-carboxylic acid with a maximum output power 0.016 mW cm⁻² under illumination at 100 mW cm⁻² AM1.5 and efficiencies 3 times higher than the symmetric complexes.     

Single and bi-metallic silver modified ZSM-5 for waste gases neutralization

Single and bi-metallic silver modified ZSM-5 catalysts were synthesized using three methods of preparation, characterized by different techniques: X-ray powder diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption, X-ray fluorescence (XRF), inductively coupled plasma atomic emission spectrometry (ICP-AES) and tested in heterogeneous catalytic decomposition of ozone at ambient temperature. The highest degree of ozone decomposition was observed over 5Ag(Imp)-H(IE)-ZSM-5 catalyst, which exhibit 97% conversion and does not show any deactivation with the time. The method of preparation, amount of supported silver and the presence of modifiers as Cu, Ce, and Zr were found to be important for the ozone decomposition reaction.     

Fast Switching ITO Free Electrochromic Devices

Indium‐doped tin oxide free electrochromic devices are prepared by coating electrochromic polymers onto polyethylene terephthalate substrates encompassing two different silver grids as electrodes. One design comprises a flexoprinted highly conductive silver grid electrode, yielding electrochromic devices with a response time of 2 s for an optical contrast of 27%. The other design utilizes an embedded silver grid electrode whereupon response times of 0.5 s for a 30% optical contrast are realized when oxidizing the device. A commercially available conductive poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate acid) formulation (PEDOT:PSS) is coated onto the silver grids as a charge balancing polymer, and is in this setting found to be superior to a polypyrrole previously employed in electrochromic devices. In addition, the PEDOT:PSS layer increases the conductivity in the hexagonal grid structure.     

The rotating disc as a device to study the adhesive properties of endothelial cells under differential shear stresses

Hemocompatibility can be conferred on a biomaterial by covering this material with a monolayer of endothelial cells. The endothelial cell is an epithelial cell of mesenchymal origin, that features a specific phenotype with homotypic intercellular interactions and with specialized cell-matrix interactions. These interactions are mandatory to the normal barrier function and the non-thrombogenicity of the endothelial monolayer and are maintained in vivo at shear stresses ranging from 10^-5 to 10^-3 N cm^-2. The endothelial monolayer grafted on a biomaterial should meet similar requirements. We have constructed a rotating disc device to investigate the effects of differential shear stresses on cell-cell and cell-matrix interactions in a monolayer of endothelial cells grafted on a disc-shaped biomaterial. The range of shear stresses that are being applied by the device vary from 0–10^-4 N cm^-2 to 0–2×10^-3 N cm^-2. In a series of experiments with discs of plasma discharge treated polycarbonate (PC) that are coated with fibronectin, it has been shown that a monolayer of endothelial cells grafted on these discs starts to lose intercellular contacts and cell-fibronectin interactions at shear stresses of 10^-4 N cm^-2. Coating of the PC discs with a complex extracellular matrix, synthesized by arterial smooth muscle cells in culture, prior to endothelial cell seeding results in the formation of a monolayer, which retains its integrity at shear stresses up to 2×10^-3 N cm^-2.     

A Thermodynamic Model of the EAF Process for Stainless Steel

A time‐dependent thermochemical model has been developed for the electric arc furnace (EAF) process for stainless steel production. Time dependency is implemented by a stepwise input of energy and matter into an equilibrium reactor. The equilibrium calculations are performed using data from FACT‐databases and implemented using the programming library ChemApp. The material input for the model was generated by reconciliation of industrial data and the energy input is approximated from the industrial data and scaled through an efficiency factor. The model is used to calculate the evolution of temperature and composition of gas, slag and metal phases with time. Agreement of the end composition in the metal phase with industrial data is good. In the slag phase, however, Cr, Fe, Mn and Si are oxidized significantly less than expected due to excess formation of CO‐gas. The dynamics of the slag composition are examined in more detail. Here a fair agreement is reached for the main slag components. However, for Cr, Fe and Mn the model cannot predict the dynamics, which seem to be strongly kinetically controlled. The results of the equilibrium model can thus provide some insight into the kinetics of the process.     

An augmented reality system for patient-specific guidance of cardiac catheter ablation procedures

We present a system to assist in the treatment of cardiac arrhythmias by catheter ablation. A patient-specific three-dimensional (3-D) anatomical model, constructed from magnetic resonance images, is merged with fluoroscopic images in an augmented reality environment that enables the transfer of electrocardiography (ECG) measurements and cardiac activation times onto the model. Accurate mapping is realized through the combination of: a new calibration technique, adapted to catheter guided treatments; a visual matching registration technique, allowing the electrophysiologist to align the model with contrast-enhanced images; and the use of virtual catheters, which enable the annotation of multiple ECG measurements on the model. These annotations can be visualized by color coding on the patient model. We provide an accuracy analysis of each of these components independently. Based on simulation and experiments, we determined a segmentation error of 0.6 mm, a calibration error in the order of 1 mm and a target registration error of 1.04 +/- 0.45 mm. The system provides a 3-D visualization of the cardiac activation pattern which may facilitate and improve diagnosis and treatment of the arrhytmia. Because of its low cost and similar advantages we believe our approach can compete with existing commercial solutions, which rely on dedicated hardware and costly catheters. We provide qualitative results of the first clinical use of the system in 11 ablation procedures.     

Impact of Different Hop Compounds on the Overfoaming Volume of Beer Caused by Primary Gushing

When weather conditions favour the growth of moulds on barley, beers brewed from the resulting malts often tend to gush. Certain Fusarium species (e.g., F. graminearum and F. culmorum) may cause this problem. Supersaturated with CO₂, a primary gushing beer contains an overcritical concentration of microbubbles; these are reputed to be stabilised by Fusarium‐derived hydrophobins. Research with varying brewhouse parameters has been performed to investigate the factors of primary gushing. As hops are known to contribute to a wide range of both gushing positive and negative substances in beer, the hopping regime has emerged as an important aspect. This paper examines the impact of different hop varieties on gushing. Hop oils and unsaturated fatty acids are reputed to be gushing‐suppressors. Compounds such as dehydrated humulinic acid can intensify the effect. Hop pellets, with a prevalent range of conductometric values (5–10% α‐acid), commonly employed in breweries to adjust bitterness and aroma were selected. By working with the same “gushing malt”, the spectrum of compounds in the finished beer only differed through the hop product used. The overfoaming volumes of different samples were determined according to MEBAK guidelines. Respective hop oil and fatty acid concentrations (by GC) and iso‐α‐acid contents (by HPLC) were compared and a chronological sequence of the changing percentages of beer loss is shown.