Pulsed voltage driven organic field-effect transistors for high stability transient current measurements

In this article, we propose the usage of gate voltage pulses of alternating polarity, to effectively suppress the hysteresis in organic field effect transistors (OFETs). The hysteretic behaviour of poly(3-hexylthiophene-2,5-diyl) (P3HT) based OFETs is systematically investigated by using continuous and pulsed sweep voltage mode. On the basis of the experimental results, both time settings and mode of gate bias voltage influence the carrier transport in the semiconductor channel. Hysteresis-free transfer characteristic curves are obtained by applying diametrically opposed gate pulses of a few milliseconds in duration. Stable on-current transient measurements are also achieved by implementing the pulse mode, thus allowing on-line gas sensing measurements to be successfully performed. Finally, the response of the sensor upon exposure to different concentrations of analyte vapours is found to be in good agreement with the Langmuir adsorption isotherm model.     

Synthesis and characterization of 2-D and 3-D covalent networks derived from triazine central cores and bridging aromatic diamines

Nucleophilic substitutions of the reactive chlorine atoms in either cyanuric or phosphonitrilic chloride by the bridging 1,4-phenylenediamine and benzidine units lead to the formation of two- (2-D) or three-dimensional (3-D) covalent networks, according to the spatial arrangement of the chlorine atoms in each particular triazine core. The materials are electrochemically active and stable, and exhibit interesting optical properties. The UV-visible spectral absorptions are significantly red-shifted and can been altered upon chemical oxidation. Furthermore, a three-band absorption spectrum typical of polaronic nature is observed in the case of the layered benzidine/cyanuric chloride network. Either spherical (2-D) or cubic (3-D) morphologies were revealed by SEM analysis, while the XRD patterns indicated partial crystallinity. Due to the inherited ion-exchange properties of the 2-D and 3-D ionic networks, the materials can be regarded as the organic analogues of conventional inorganic layered or zeolitic ion-exchangers.     

Hydrophilic modification of silicone elastomer films: Thermal,mechanical and theophylline permeability properties

The improvement of the hydrophilicity of silicone rubber (SR) is sought in many biomedical applications. In the present work, we have prepared neat films coming from condensation-type SR, modified either through blending or end-linking reaction with low molecular weight poly(ethylene glycol) (PEG). The films were studied with respect to their water uptake capacity, stability of embedment of ethylenoxy moieties, and mechanical and thermal properties. Subsequently, we prepared drug-loaded films with theophylline, a relatively hydrophilic model drug, and studied the release performance of these systems. Results on neat films showed that blending increases significantly the overall water uptake of the films and, at the same time, has a limited detrimental effect on their mechanical properties. On the other hand, end-linked films loaded with theophylline exhibited better rate-controlling properties in vitro, due to better dispersion of the sorbed water.     

Oligonucleotide-functionalized gold nanoparticles as probes in a dry-reagent strip biosensor for DNA analysis by hybridization

The highly specific molecular recognition properties of oligonucleotides are combined with the unique optical properties of gold nanoparticles for the development of a dry-reagent strip-type biosensor that enables visual detection of double stranded DNA within minutes. The assay does not require instrumentation and avoids the multiple incubation and washing steps performed in most current assays. Gold nanoparticle reporters with oligo(dT) attached to their surface form an integral part of the strip. Biotinylated PCR products (233 bp or 495 bp) are hybridized (5 min) with a poly(dA)-tailed oligo and applied on the strip, which is then immersed in the appropriate buffer. As the buffer migrates upward, it rehydrates the nanoparticles that are linked to the target DNA through poly(dA)/(dT) hybridization. Capture of the hybrids by immobilized streptavidin in the test zone of the strip generates a characteristic red band. A second red band is formed, by hybridization, in the control zone of the strip to indicate proper test performance. The sensor offers at least 8 times higher detectability than ethidium bromide staining of agarose gels and provides confirmation of the amplified fragments. Quantitative data are obtained by densitometric analysis of the bands. As low as 2 fmol of amplified DNA were detectable by the strip sensor. Also, 500 copies of prostate-specific antigen cDNA were detected by combining PCR and the strip sensor. The sensor was used successfully for detection of hepatitis C virus in plasma samples from 20 patients. The strip detected 16 out of 16 positive samples and gave no signal for 4 samples that were negative for the virus. To our knowledge, this is the first dry-reagent system that makes use of oligonucleotide-conjugated gold nanoparticles as probes.     

Flow and Telepresence contributing to Internet Abuse: Differences according to Gender and Age

Flow describes immersive tendencies to Internet activities, and Telepresence defines the level one is absorbed in his virtual environment. The aim of this study was twofold: (a) to test whether and how Flow and Telepresence may contribute to Internet Abuse and (b) to examine group differences in Internet Abuse, Flow and Telepresence according to gender and age among adolescents. The sample consisted of 1609 adolescents, with a mean age of 16 years old. Internet Abuse was assessed with the Internet Addiction Test (Young, 1998), Flow with the Flow Questionnaire (Chen, Wigand, & Nilan, 1999) and Telepresence with the Presence II questionnaire (Witmer & Singer, 1998). Findings revealed that Flow and Telepresence were related with Internet Abuse with Telepresence positively moderating the effect of Flow. Considering group differences, males were at higher risk of Internet Abuse and were more likely to experience Flow and Telepresence, while older adolescents scored higher only in Telepresence.     

Chemical Blowing Approach for Ultramicroporous Carbon Nitride Frameworks and Their Applications in Gas and Energy Storage

A scalable, template‐free synthetic strategy is presented for the preparation of ultramicroporous carbon nitride frameworks (CNFs) through a chemical blowing approach by using ammonium chloride as blowing agent and hexamethylene tetraamine as the C and N precursor and a subsequent potassium hydroxide chemical activation is employed to obtain CNFs with surface areas up to 1730 m² g^?1 along with a high nitrogen content of 13.3 wt%. CNFs showed CO₂ uptake capacities up to 5.74 mmol g^?1 at 1 bar and 1.67 mmol g^?1 at 0.15 bar, 273 K along with a very high CO₂/N₂ selectivity. In addition, H₂ uptake capacity of 1.9 wt% and the isosteric heats of adsorption (Q _st) value of 9.0 kJ mol^?1 at zero coverage have been also observed. Moreover, the presence of nitrogen‐doped graphene walls in CNFs also facilitated their application as supercapacitors, with capacitance values up to ≈114 F g^?1 at 0.5 A g^?1, along with a good cyclability and capacitance retention. This approach effectively extends unique surface properties of carbon nitrides into the micropore regime for effective capture of small gases and energy storage applications. Importantly, textural properties of CNFs can be simply tuned by judicious choice of organic precursors and the blowing agent.     

Thermal and mechanical properties of 3D printed boron nitride – ABS composites

The current work investigates the thermal conductivity and mechanical properties of Boron Nitride (BN)-Acrylonitrile Butadiene Styrene (ABS) composites prepared using both 3D printing and injection molding. The thermally conductive, yet electrically insulating composite material provides a unique combination of properties that make it desirable for heat dissipation and packaging applications in electronics. Materials were fabricated via melt mixing on a twin-screw compounder, then injection molded or extruded into filament for fused deposition modeling (FDM) 3D printing. Compositions of up to 35 wt.% BN in ABS were prepared, and the infill orientation of the 3D printed composites was varied to investigate the effect on properties. Injection molding produced a maximum in-plane conductivity of 1.45 W/m-K at 35 wt.% BN, whereas 3D printed samples of 35 wt.% BN showed a value of 0.93 W/m-K, over 5 times the conductivity of pure ABS. The resulting thermal conductivity is anisotropic; with the through-plane thermal conductivity lower by a factor of ~3 for injection molding and ~4 for 3D printing. Adding BN flakes caused a modest increase in the flexural modulus, but resulted in a large decrease in the flexural strength and impact toughness. It is shown that although injection molding produces parts with superior thermal and mechanical properties, BN shows much potential as a filler material for rapid prototyping of thermally conductive composites.     

Effect of retained austenite stability on cyclic deformation behavior of low‐alloy transformation‐induced plasticity steels

The retained austenite (RA) characteristics of Al‐containing TRIP700 steels have been manipulated using varying bainitic isothermal transformation (BIT) processing. The microstructural evolution was investigated using optical microscopy and quantitative image analysis, while the amount of transformed RA was evaluated with the saturation magnetization (SM) technique. Cyclic behavior is found to depend on the applied strain amplitude and stability of RA. At strain amplitudes with comparable elastic and plastic strain components, cyclic softening prevails, facilitated by more stable RA microstructures and Low Cycle Fatigue (LCF) performance benefits from a lower RA stability, which controls the amount of cyclic softening rate. With increasing plastic strain component, a transition to cyclic hardening is observed, and the transition strain increases with increasing RA stability. LCF performance deteriorates because of excessive cyclic strain hardening promoting martensitic transformation. The effect is accompanied by a transition from mixed dimple/cleavage to cleavage‐type fracture characteristics.     

The Effects of Intravitreal Administration of Antifungal Drugs on the Structure and Mechanical Properties Peripheral Blood Erythrocyte Surface in Rabbits

Background: Fungal infections can pose great threat to sight. Immediate treatment is usually required; antifungal agents are widely accepted and are effective in most cases. The present experimental study aims to investigate the probable effects of intravitreal injection of antifungal agents on the structure and mechanical properties of the surface of peripheral blood erythrocytes. Methods: Nine albino New Zealand white rabbits, aged five months old, were chosen for the experiment. Solutions of micafungin, voriconazole, or balanced salt solution (BSS) were injected into the midvitreous. Animals were divided into two experimental groups and one control group. Blood sampling from an intravenous (IV) line was performed after 10 days from the last IV injection. An atomic force microscope (AFM) was used to study the structural and mechanical properties of cell surfaces. Results: The analysis results showed that the parameters of the cytoskeleton’s spatial organization changed insignificantly with the antifungal drug treatment. Conclusions: Our findings suggest that locally administered antifungal drugs can cause significant changes to the structure and frictional properties of the erythrocyte surface. These effects occur in the long-term period after administration of the drugs and represent a potential possibility for violation of blood supply to tissues, and the further development of negative side effects.