Biocompatible and Biodegradable Materials for Organic Field‐Effect Transistors

Biocompatible‐ingestible electronic circuits and capsules for medical diagnosis and monitoring are currently based on traditional silicon technology. Organic electronics has huge potential for developing biodegradable, biocompatible, bioresorbable, or even metabolizable products. An ideal pathway for such electronic devices involves fabrication with materials from nature, or materials found in common commodity products. Transistors with an operational voltage as low as 4–5 V, a source drain current of up to 0.5 μA and an on‐off ratio of 3–5 orders of magnitude have been fabricated with such materials. This work comprises steps towards environmentally safe devices in low‐cost, large volume, disposable or throwaway electronic applications, such as in food packaging, plastic bags, and disposable dishware. In addition, there is significant potential to use such electronic items in biomedical implants.     

Gold Nanoparticle‐Based Sensors Activated by External Radio Frequency Fields

A novel molecular beacon (a nanomachine) is constructed that can be actuated by a radio frequency (RF) field. The nanomachine consists of the following elements arranged in molecular beacon configuration: a gold nanoparticle that acts both as quencher for fluorescence and a localized heat source; one reporter fluorochrome, and; a piece of DNA as a hinge and recognition sequence. When the nanomachines are irradiated with a 3 GHz RF field the fluorescence signal increases due to melting of the stem of the molecular beacon. A control experiment, performed using molecular beacons synthesized by substituting the gold nanoparticle by an organic quencher, shows no increase in fluorescence signal when exposed to the RF field. It may therefore be concluded that the increased fluorescence for the gold nanoparticle‐conjugated nanomachines is not due to bulk heating of the solution, but is caused by the presence of the gold nanoparticles and their interaction with the RF field; however, existing models for heating of gold nanoparticles in a RF field are unable to explain the experimental results. Due to the biocompatibility of the construct and RF treatment, the nanomachines may possibly be used inside living cells. In a separate experiment a substantial increase in the dielectric losses can be detected in a RF waveguide setup coupled to a microfluidic channel when gold nanoparticles are added to a low RF loss liquid. This work sheds some light on RF heating of gold nanoparticles, which is a subject of significant controversy in the literature.     

Bio-electro-remediation: electrokinetic transport of nitrate in a flow-through system for enhanced toluene biodegradation

The availability of electron acceptors and nutrients is often limiting the microbiological clean-up of polluted groundwater at contaminated sites. In this study, the feasibility of electrokinetic processes to improve mass transfer was demonstrated in a model system simulating laminar groundwater flow conditions. Electrokinetic nitrate transport and enhanced biodegradation of toluene under denitrifying conditions was studied as function of voltage gradient in a new flow-through system. The study was done in a three-dimensional anaerobic model aquifer system filled with coarse sand. The influent area was divided into seven chambers thus enabling a separate addition of toluene and nitrate. Mesh electrodes were inserted laterally in order to form an electric field perpendicular to the flow direction with voltage gradients of 0, 0.125 and 0.25 V cm⁻¹, respectively. Biodegradation was studied after inoculation with a denitrifying microbial mixed culture. Application of the electric field resulted in nitrate migration into areas containing toluene. In the presence of denitrifying bacteria, the availability of nitrate in toluene polluted areas resulted in toluene biodegradation, demonstrated by nitrite formation and decreased toluene concentration.     

Structure-activity relationship in water-gas shift reaction over gold catalysts supported on Y-doped ceria

The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas shift reaction at low temperature. The aim of the present study was to investigate the effect of:(i) different preparation methods(impregnation and coprecipitation) to obtain a modified ceria support,and(ii) the amount of Y_2 O_3(1.0 wt%, 2.5 wt%, 5.0 wt% and 7.5 wt%) as dopant on the water-gas shift activity of Au/CeO_2 catalysts. An extended characterization by means of S_(BET), XRD, HRTEM/HAADF, FTIR,H_2-TPR and CO-TPR measurements in combination with careful evaluation of the catalyst behavior allowed to shed light on the parameters governing the water-gas shift activity. The catalysts show very high activity(90% CO conversion) in the temperature range 180-220 ℃,with a slightly better performance of the gold catalysts on supports prepared by impregnation. The decreased activity with increasing Y_2 O_3 concentration is related to the hindering of oxygen mobility due to ordering of surface oxygen vacancies in vicinity of segregated Y~(3+). The effect of catalyst pre-treatments and the stability of the best performing samples were examined as well.     

Hygienic studies of frozen ocean fish

Studied were batches of frozen ocean mackerel (Scomber scombrus L.) and silver hake (Merluccius bilinearis, Mitchill) during storage in a central base and in shops. The evaluation of the fish was made on the basis of organoleptic data, pH values, volatile bases, trimethylamin, volatile fatty acids, the amount of tissue fluids after Kietzmann, luminescence of musculature after Wittfogel, and through microbiologic study of the skin and musculature. It was found that the fish had been frozen in the fishing boats in a very good status. Great variations in the storage temperature are admitted in the central base, no correlation being established between the term of storage and the quantity of the product. The conditions for the preservation of the frozen fish in the shops where fish is especially sold are unappropriate--they contribute to the fast deterioration of the quality and the microbial status of the product.     

Electrochemical formation of bi-metal (copper-palladium) electrocatalyst supported on poly-3,4-ethylenedioxythiophene

Bi-metal modification of poly-3,4-ethylenedioxythiophene (PEDOT) layers by combining palladium and copper deposition is studied. Initial reference measurements are performed on electrodriven deposition and electroless precipitation of palladium, showing the existence of Pd nanocrystals on the PEDOT surface. It is established that by using the electrodeposition sequence - Cu (first step) - Pd (second step) only palladium remains available in the PEDOT layer. By reversing the deposition sequence - Pd (first step) - Cu (second step) a bi-metal modification of PEDOT is achieved. Depending on the parameters potential and time of the copper electroreduction the Pd nanocrystals coexist with either Cu-PEDOT-stabilized species or both Cu crystals and Cu-PEDOT-stabilized species. The voltammetric response of the modified PEDOT electrodes is tested for nitrate electroreduction in neutral solution. It is found that the bi-metal modified PEDOT shows a marked electroactivity for this reaction.     

A comparative study of differently prepared rare earths-modified ceria-supported gold catalysts for preferential oxidation of CO

The preferential oxidation of CO in H₂-rich gas was studied over gold catalysts supported on ceria modified by rare earths (RE = La, Sm, Gd and Y). The ceria supports were prepared by mechanochemical activation or co-precipitation. The amount of RE₂O₃ was 10 wt%. Gold (2 wt%) was added by the deposition-precipitation method. The samples were characterized using XRD, HRTEM, HAADF, TPR, and Raman spectroscopy. It was established that catalysts prepared by co-precipitation were more active than samples made by mechanochemical activation. A gold catalyst on yttrium-modified ceria, prepared by co-precipitation, exhibited the highest catalytic activity and selectivity, and high stability. No substantial differences in the size distribution and average size of the nanogold particles in the studied catalysts were observed. The main reason for the differences in PROX activity of these gold catalysts was searched into the role of the ceria supports, depending on the preparation method, and the nature of the modifier.     

Reduced cognitive ability in alcohol dependence: Examining the role of covarying externalizing psychopathology.

Reduced executive cognitive ability is associated with alcohol dependence (AD) and other comorbid externalizing disorders. Working memory capacity, short-term memory, conditional associative learning, and intelligence were assessed in a sample (N = 477) with variation in lifetime histories of externalizing problems (conduct disorder, adult antisocial behavior, substance problems); this included a subsample (n = 285) with a Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) diagnosis of AD. Individuals with both AD and a history of childhood conduct disorder (CCD) scored lower on cognitive measures compared to those with AD and no history of CCD. Structural equation models showed that reduced ability in all cognitive domains was predicted by a latent externalizing factor reflecting covariation among lifetime problems with alcohol, drugs, childhood conduct, and adult antisocial behavior and was not uniquely related to any one problem. Further, for those with AD, the externalizing factor was associated with reductions in all the domains of cognitive ability. The results suggest that the reduced executive cognitive ability observed in AD individuals is partly accounted for by a general latent externalizing factor rather than alcohol-related problems per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)