Accurate characterization of single track-etched, conical nanopores

Single track-etched conical nanopores in polymer foils have attracted considerable attention in recent years due to their potential applications in biosensing, nanofluidics, information processing, and other fields. The performance of a nanopore critically depends on the size and shape of its narrowest, nanometer-sized region. In this paper, we reconstructed the profiles of both doubly-conical and conical pores, using an algorithm based on conductometric measurements performed in the course of etching, coupled with SEM data. We showed that pore constriction deviates from the conical shape, and the deviation depends on the energy loss of the particle that produced the track. Funnel-like profiles of tracks of four ions with different atomic numbers were derived from experimental data. The simulations, using a Poisson–Nernst–Planck model, demonstrated that the ion current rectification properties of the funnel-shaped asymmetrical pores significantly differ from those of conical ones if the tip radius of the pore is smaller than 10 nm. Upon subjecting to further etching, the pores gradually approach the ‘‘ideal’’ conical geometry, and the ion transport properties of these two pore configurations become almost indistinguishable.The authors are grateful to the Material Research group (GSI Darmstadt) for providing irradiated samples. The authors thank O. M. Ivanov for the irradiation of the polymer foils with accelerated ions. The help with SEM imaging provided by N. E. Lizunov is also appreciated. P. R. acknowledges financial support from the Generalitat Valenciana (project PROMETEO/GV/0069), Ministry of Science and Innovation of Spain, Materials Program (project MAT2012-32084), and FEDER. 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Nanopores with controlled profiles in track - etched membranes

Track-etched membranes are porous systems consisting of a polymer foil with thin channels-pores - from surface to surface. The increasing interest in this kind of material is connected with the development of nanoporous materials with unique properties such as diode-like effects in membranes with highly asymmetrical nanopores. The materials can be used for molecular sensors and atom beam optics, development of nanocapillary bodies for modelling the transport of molecules and ions in constrained volumes. Control over pore geometry opens the way to a number of new applications of track-etch membranes (TMs). The nanopores were obtained by the ion-track etching method using surfactant-doped alkaline solutions. Control over the pore profile and dimensions was achieved by varying the alkali concentration in the etchant and the etching time. The pore geometry was characterized in detail using field-emission scanning electron microscopy (SEM). SEM images of the surfaces and cleavages of TMs with different pore morphology are shown

Silica materials with biocidal activity

Pathogenic microorganisms like fungi, bacteria and algae are harmful to human beings and animals. Moreover, they contribute to the destruction of building materials by their biodegradation. Therefore, they create serious hazard for the natural environment. To prevent these phenomena, different materials with biocidal activity are being developed. In elaboration of such materials, one of the most difficult problems to be solved is the achievement of their high effectiveness in controlling harmful microorganism population with the guarantee of safety of their application to the natural environment and humans. As a result of investigation carried out in the INCT on new biocides based on quaternary N-alkylammonium salts (QAC), mainly benzalkonium chloride, and water glass (WG) large group of new silica materials with biocidal activity were synthesised. Possibilities of technology modification in order to obtain different profitable properties of materials are presented in the paper. Preliminary investigations concerning biocidal activity against selected mould fungi, bacteria and algae were performed. Results of microbiological investigations proved stable effectiveness of biocides for protection from harmful microorganisms growth, which does not decrease even after washing of biocidal material with water. Silica materials with biocidal activity due to structural binding of biocidal agent (QAC) can be applied in building industry as materials of high ecological safety

Montmorillonite modified by unsaturated compatibilizing agents and by ionizing radiation as a potential filler in polymeric composites

For last several years we have studied modifications of montmorillonite (MMT) with different agents and the structural changes resulting from the processes. The aim of present work was focused on the preparation of polymer composites from epoxy resin and dispersed phase modified chemically and subsequently activated by irradiation. The paper presents investigations concerning intercalation of MMT by the synthesized unsaturated organophilic agents (on the basis of quaternary ammonium salts). The process was studied by: wide-angle X-ray scattering (WAXS), Fourier- -transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA); additionally mechanical properties of the polymer composite as well as its microscopic structure were tested. It was found that unsaturated quaternary ammonium salts can intercalate between MMT layers. The possibility of radiation-induced compatibilization between modified MMT particles and polymeric matrix was also studied. It was confirmed by electron paramagnetic resonance (EPR) spectroscopy that in the synthesized salts stable radicals are formed during irradiation, however their influence on mechanical properties of the final composite is insignificant

Investigations of protons passing through the CR-39/PM-355 type of solid state nuclear track detectors

Solid State Nuclear Track Detectors of the CR-39/PM-355 type were irradiated with protons with energies in the range from 0.2 to 8.5 MeV. Their intensities and energies were controlled by a Si surface barrier detector located in an accelerator scattering chamber. The ranges of protons with energies of 6–7 MeV were comparable to the thickness of the PM-355 track detectors. Latent tracks in the polymeric detectors were chemically etched under standard conditions to develop the tracks. Standard optical microscope and scanning electron microscopy techniques were used for surface morphology characterization

Preparation of lithium titanate by sol-gel method

Medium sized spherical particles of Li2TiO3 (with diameters below 100 mi m) can be prepared from peroxy lithium titanate solution (stabilized with citric acid) by a modified INCT variant of the sol-gel process. The process consists of the following main steps: (I) formation of aqueous phase emulsion in 2-ethylhexanol-1 containing the surfactants 1v/o SPAN-80 and 1v/o Ethomen S-15 (EH); (II) gelation of emulsion drops by extraction of water with partially dehydrated EH; (III) filtration and washing with carbon tetrachloride or acetone; (IV) non-destructive thermal treatment. The tritium release from sol-gel process preparation of Li2TiO3 micro-spheres was found very close to that observed for other traditional material however, the new process is more efficient than other processes because of the morphology of the sintered specimens

Calibration and applications of modern track detectors CR-39/PM-355 in nuclear physics and high temperature plasma experiments

Solid-state nuclear track detectors (SSNTDs) have been used for the registration of charged particles practically since the beginning of the 1960s, when a new class of detectors, called dielectric track detectors, were discovered. The paper describes applications of the SSNTDs type PM-355 for diagnostics of fusion-reaction protons and other ions emitted from plasma focus (PF) devices, tokamaks and laser facilities. Such detectors were also used in biomedical experiments for beam profile measurements. The results of our calibration studies of SSNTDs as well as charged particle- and biomedical measurements, which were carried out within different facilities, are presented

Tribological Properties of AISI 316L Steel Surface Layer Implanted with Rare Earth Element

Stainless steels with their very good corrosion resistance are used in nuclear, petrochemical, chemical, pulp and paper chemical industries as well as in food processing and others. Unfortunately, poor tribological properties of this kind of steel can be the limitation in the situations in which wear can be responsible for material degradation, like corrosion-erosion. Improvement of the wear resistance of austenitic stainless steels can be achieved using different methods of surface modification, for example: enrichment of the surface layer with reactive elements. Rare earth elements were implanted to AISI 316L austenitic stainless steel using the MEVVA type implanter (65 kV). Different rare earth elements implanted doses: 10¹⁵, 5×10¹⁵, and 5×10¹⁶ ion/cm² were applied. Initial and modified surfaces were investigated using scanning electron microscopy, elemental analysis with the energy dispersive spectroscopy method, X-ray diffraction analysis and the Rutherford backscattered spectroscopy. Tribological properties were investigated using the Amsler method. The most important result was that the surface layers of AISI 316L steel implanted with rare earth elements showed improvement of tribological properties as compared with the initial material

Metabolic and immune response of young turkeys originating from parent flocks fed diets with inorganic or organic selenium

The aim of this study was to verify the hypothesis that the health and growth of turkey poults may be improved by supplementing diets fed to parent flocks with available selenium. Experimental poults originated from parent flocks fed with diets containing 0.3 mg/kg inorganic selenium (control group SeM) and organic selenium (experimental group SeO). Egg yolk selenium content was comparable in both flocks (0.72 and 0.70 mg/kg d.m., respectively). Eggs from the SeO flock had a significantly lower content of thiobarbituric acid reactive substances - TBARS (31.13 vs. 53.10 nmol/g, p > 0.001). SeO group poults were characterized by higher activity of glutathione peroxidase (7.54 vs. 5.92 U/mL, P = 0.001) and superoxide dismutase (89.30 vs. 79.23 U/mL, P = 0.026). The thigh muscles of SeO group birds had significantly higher selenium concentrations (0.74 vs. 0.57, p = 0.045) and a significantly lower TBARS content (38.42 vs. 65.01, p = 0.001). No differences were found between the groups with respect to the content of total protein, albumins and uric acid, and the activites of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (DLH) in day-old poults. On day 28, groups SeO and SeM differed in the activity of ALT (20.50 vs. 26.33, p = 0.05) and SOD (87.29 vs. 100.02 U/mL, p = 0.035). There were no differences between the groups regarding the percentages of T lymphocyte subpopulations CD4+, CD8+, CD4+CD8+ and B lymphocyte subpopulations (IgM+) at 1 and 28 days of age. Over the experimental period, mortality rates were similar in both groups (7.32 and 8.87%), and so were the final body weights of birds (1108 vs. 1135 g). The results of the study show that the dietary supplementation of organic selenium in turkey parent flocks reduces the rate of oxidation processes in the egg and in the tissues of newly-hatched poults, yet it has no effect on the analyzed parameters of cell-mediated immunity and the growth performance of birds during the first five weeks of their life

A method for production of nanoMOF and prelimiary characterization by selected analytical techniques

Metal-organic frameworks (MOFs) are a class of porous hybrid materials comprising metal ion-based vertices and multitopic organic ligands (linkers). The possibility of combining a wide range of metals with similarly large number of available ligands opens ways to design the structures meeting specific purposes. At present, many potential applications of MOFs may require them to be constructed at the nanometer length scale (nanoMOFs). The possibility of filling the track-etched membrane pores with MOF HKUST-1 has been demonstrated in this work