Ion-track Membranes Research Articles

Controlled fabrication of poly- and single-crystalline bismuth nanowires

Poly- and single-crystalline Bi nanowires are fabricated by electrochemical deposition inetched ion-track membranes. Two deposition parameters, voltage and temperature,strongly influence the nanowires’ morphology and texture. X-ray diffraction (XRD) andtransmission electron microscopy (TEM) reveal that potentiostatically deposited nanowiresare textured, the texture increasing for wires deposited at higher temperatures and smaller overpotentials.At T = 60 °C and low overpotentials, single-crystalline wires are produced. Wires deposited with reversepulses exhibit a texture, which is more pronounced for shorter cathodic cycles and higher anodic voltages.They consist of several crystals of size at least .

Non-galvanic synthesis of nanowalled polypyrrole microtubules in ion track membranes

Polypyrrole nanowalled microtubules were fabricated by chemically synthesizing polypyrrole within the pores of porous polycarbonate particle track etch membranes. The morphology of the microtubules was characterized by scanning electron microscopy. The electrical conductivity of the microcylinders was measured by leaving the microcylinders embedded in the insulating template membrane and measuring the trans membrane resistance.

Non-galvanic synthesis of nanowalled polypyrrole microtubules in ion track membranes

Polypyrrole nanowalled microtubules were fabricated by chemically synthesizing polypyrrole within the pores of porous polycarbonate particle track etch membranes. The morphology of the microtubules was characterized by scanning electron microscopy. The electrical conductivity of the microcylinders was measured by leaving the microcylinders embedded in the insulating template membrane and measuring the trans membrane resistance.

Anisotropically conducting films consisting of sub-micron copper wires in the ion track membranes of poly(ethylene terephthalate)

Ion track membranes of poly(ethylene terephthalate) (PET) are applied to the production of anisotropically conducting films possessing copper wires of less than sub-micron in diameter. The membranes possessing cylindrical pores of 1.9 μm and 200 nm in diameter were prepared by irradiation of 129 Xe 23+ ion beams followed by etching in an aqueous NaOH. Copper wires were deposited into the pores by electrochemical plating in aqueous copper sulfate solution to prepare the PET/Cu hybrid membranes. The copper wires with 1.9 μm in diameter showed wavelike surface roughness, resulting from the roughness of the pore side wall, whereas the copper wires with 200 nm in diameter showed smooth surfaces. The resistances of the membranes measured by a four terminal resistance method are in good agreement with the calculated values, indicating that the hybrid membranes possess conductivity perpendicular to the membrane surfaces but not parallel to the surfaces.

Anisotropically conducting films consisting of sub-micron copper wires in the ion track membranes of poly(ethylene terephthalate)

Ion track membranes of poly(ethylene terephthalate) (PET) are applied to the production of anisotropically conducting films possessing copper wires of less than sub-micron in diameter. The membranes possessing cylindrical pores of 1.9 μm and 200 nm in diameter were prepared by irradiation of 129Xe 23+ ion beams followed by etching in an aqueous NaOH. Copper wires were deposited into the pores by electrochemical plating in aqueous copper sulfate solution to prepare the PET/Cu hybrid membranes. The copper wires with 1.9 μm in diameter showed wavelike surface roughness, resulting from the roughness of the pore side wall, whereas the copper wires with 200 nm in diameter showed smooth surfaces. The resistances of the membranes measured by a four terminal resistance method are in good agreement with the calculated values, indicating that the hybrid membranes possess conductivity perpendicular to the membrane surfaces but not parallel to the surfaces.

Role of UV light illumination and DMF soaking in production of PET ion track membranes

The pretreatment effects using UV light illumination and DMF soaking on bulk and track etching rates of PET films were investigated. The wavelength of illuminated UV light plays an important role in sensitizing track etching. Illumination with the light at wavelengths longer than 320 nm showed strong enhancement in the track etching rates without influence on the bulk etching rates, whereas light with the wavelengths lower than 320 nm causes large enhancement in both track and bulk etching rates even in the interior of the material. The track etching rate is found to be not constant along ion tracks, which is attributed to the inhomogeneous distribution of reactive chemical species induced during post-UV light illumination. Furthermore, the DMF soaking of PET after UV light illumination can enhance the etching sensitivity of the track by more than 100 times. The phenomenon is attributed to the high diffusion of organic solution along tracks after UV light illumination.

Ion track membranes providing heat pipe surfaces with capillary structures

The microgalvanic method for metal filling of etched ion tracks in organic foils is of particular interest for the fabrication of microsized structures. Microstructures like copper whiskers with a high aspect ratio produced in ion track membranes are suitable for the generation of high-performance heat transfer surfaces. A surface with good heat transfer characteristics is defined as a surface on which a small temperature difference causes a large heat transfer from the surface material to the liquid. It is well-known that a porous surface layer transfers to an evaporating liquid a given quantity of heat at a smaller temperature difference than does a usual smooth surface. Copper whiskers with high aspect ratio and a density 10 5 per cm 2 form such a porous structure, which produces strong capillary forces and therefore a maximum of heat transfer coefficients.

Electrical characterization of electrochemically grown single copper nanowires

Single- and poly-crystalline copper wires with diameters down to 30 nm are grown in etched ion-track membranes. Individual nanowires are isolated and contacted by means of optical lithography. Electronic transport properties and oxidation processes are investigated. Depending on the oxidation state, the wire resistance varies between a few hundred ohms and several megaohms, enabling its usage as metallic or semiconducting structural elements for devices on the nanometer scale.

Formation of metal membranes by direct duplication of etched ion-track templates

A method for direct electrochemical metal duplication of pores in ion-track polymer membranes is described. It allows fabrication of metallic membranes using any metal, which is readily deposited by electroplating from aqueous solutions. The metal is deposited on one side of the template membrane, facing the anode, which is made conductive by a thin metal cladding layer. During electroplating, the lateral tapping of the pores is prevented by applying a counter-solution from the opposite non-metallized side of the plastic membrane, which increases dramatically the deposition overvoltage in the vicinity of the pore orifices. Such metallic membranes can be generated with pore diameters in the nano- and micrometer range and with densities from single pores up to 106–107 pores/cm2. They can replace plastic filters in cases when an application of polymer material is not desirable. They could be advantageous particularly in catalysis as well as in biological science and technology. Further, they may be useful as apertures and collimators for different kinds of radiation.

Electrochemical Copper Deposition in Etched Ion Track Membranes : Experimental Results and a Qualitative Kinetic Model

Etched ion track polycarbonate membranes served as templates for the potentiostatic deposition of copper nanowires. For different overvoltages, current vs. time curves were recorded and analyzed. A qualitative model describing the deposition process has been developed. Up to six different time periods can be distinguished in each curve corresponding to different steps that dominate the overall deposition process. For short times, copper deposition is controlled by charge transfer. Then a transition region follows where the charge transfer and the diffusion overvoltage are comparable. The following three regions are assigned to diffusion control. Initially, while the thickness of the diffusion layers is smaller than the remaining empty pore length, the diffusion occurs linearly inside the pores. When the diffusion layers increase in size, the overall process becomes determined by radial diffusion of ions toward the pore openings. After some time the radial diffusion fields start to overlap for neighboring pores, and the deposition is characterized by linear diffusion toward the whole surface. Finally, when the pores are filled up with copper, metal caps start to grow on top of the membrane. For each time regime, existing theories were used to analyze the process quantitatively. Agreement with experimental data was found for two regimes. © 2003 The Electrochemical Society. All rights reserved.

Ion beam-induced positive imaging of polyimide via two step imidization

The preparation of ion track membranes of thermally stable polyimide films has been performed by ion beam irradiation of partially imidized polyamic acid (PAA) films followed by alkaline etching and final imidization. No discernible positive hole patterns were observed on the irradiated films of partially imidized PAA containing sulfonyl linkages, although sulfonyl group is known to be highly sensitive to ion beams. In contrast, positive hole patterns appeared on the irradiated films of the partially imidized PAA with 68–89% imidization degrees that contains sulfonyl linkages along with a methylene group in the main chain. The most contrasty hole patterns with 0.3 μm diameter were observed on the irradiated PAA films of 89% imidization degree. The irradiated PAA film with the hole patterns was then transformed to the corresponding polyimide film with curing at 350 °C for 1 h. From the structural comparison of the polyimides, the possible mechanism for the hole pattern formation is suggested.

Suitable test structures for submicron ion beam analysis

For the precise determination of the sizes of submicron beam spots test structures with an excellent edge definition are required. For this purpose a semiconductor heterostructure consisting of an 1.62 μm GaInP epi-layer grown on (0 0 1) GaAs has been made, which provides atomically sharp edges for beam spot size measurements. Since the sample has been thinned down by standard transmission electron microscope (TEM) preparation techniques, it can be used for both PIXE and STIM. The sample has been investigated with a TEM and the ion nanoprobe LIPSION. A one-dimensional beam profile in the low current mode was determined by a STIM measurement using 2 MeV protons and yielded a FWHM of (41±4) nm, which is the smallest value reported so far for high energy nuclear micro- and nanoprobes. Furthermore we present nickel nanowhiskers produced at the GSI Darmstadt by electrochemical preparation of etched ion track membranes that have been used to obtain two-dimensional images of the shapes of submicron beam spots. For these measurements a scan over a single nickel nanowhisker having a diameter of 220 nm and a height of about 6 μm was performed.

High-energy radiation and polymers: A review of commercial processes and emerging applications

Ionizing radiation has been found to be widely applicable in modifying the structure and properties of polymers, and can be used to tailor the performance of either bulk materials or surfaces. Fifty years of research in polymer radiation chemistry has led to numerous applications of commercial and economic importance, and work remains active in the application of radiation to practical uses involving polymeric materials. This paper provides a survey of radiation-processing methods of industrial interest, ranging from technologies already commercially well established, through innovations in the active R&D stage which show exceptional promise for future commercial use. Radiation-processing technologies are discussed under the following categories: cross-linking of plastics and rubbers, curing of coatings and inks, heat-shrink products, fiber–matrix composites, chain-scission for processing control, surface modification, grafting, hydrogels, sterilization, natural product enhancement, plastics recycling, ceramic precursors, electronic property materials, ion-track membranes and lithography for microdevice production. In addition to new technological innovations utilizing conventional gamma and e-beam sources, a number of promising new applications make use of novel radiation types which include ion beams (heavy ions, light ions, highly focused microscopic beams and high-intensity pulses), soft X-rays which are focused, coherent X-rays (from a synchrotron) and e-beams which undergo scattering to generate patterns.

Transport properties of thermo-responsive ion track membranes

The permeation of orange G (MW 452), methylene blue (MW 319), and bovine albumin (MW 68000), through thermo-responsive ion track membranes was studied. For this purpose, poly- N-isopropylacrylamide (poly-NIPAAm) hydro-gel was chemically grafted onto single/multi-pore ion track membranes of poly(ethylene terephthalate) (PET). The local transport properties were studied by measuring the electrical current through single pore membranes. It was found that the incorporation of the hydro-gel into the pores does not influence the phase transition temperature. The switching of the responsive membrane was reversible over 200 switching cycles applied during 30–50 days. The closed pores represent a physical barrier excluding organic molecules larger than 2±0.2 nm. This fact is based on the size exclusion method using mixtures of polyethylene glycol (PEG) of various molecular weights and 0.1 N potassium chloride. The global transport properties were studied using multi-pore membranes with 5×10 5 to 5×10 7 pores per cm 2 and pore diameters between 0.6 and 4.5 μm. For bovin insulin permeation in the open state was 35 times above the level of the closed state corresponding to the detection limit of the used permeation cell. In the open state the transport rates of the solvent and the solute were identical implying that the free space in the open pores was larger than the size of the permeating bovine albumin molecules (about 7.3 nm). The linear relation between pressure and mass current enabled to determine an effective open-pore diameter between 0.2 and 1 μm. In the open state, the membrane this is not molecular selective.

ChemInform Abstract: Single‐Crystalline Copper Nanowires Produced by Electrochemical Deposition in Polymeric Ion Track Membranes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Single-Crystalline Copper Nanowires Produced by Electrochemical Deposition in Polymeric Ion Track Membranes

The fabrication of copper nanowires by electrodeposition in ion track membranes is reported. The large-grain copper needle deposited at 40 °C shown in the Figure is a transition between the polycrystalline needles formed at room temperature and the single-crystalline morphology at 60 °C. A systematic study of the DC deposition parameters required for single-crystalline growth is presented.

Single-Crystalline Copper Nanowires Produced by Electrochemical Deposition in Polymeric Ion Track Membranes

Single-Crystalline Copper Nanowires Produced by Electrochemical Deposition in Polymeric Ion Track Membranes

Uniform magnetization rotation in single ferromagnetic nanowires

Using electrochemical deposition, $6\ensuremath{\mu}\mathrm{m}$ long Ni nanowires, with typical diameters of the order of 80 nm, are grown in ion-track etched membranes. Electrical contacts are established during the growth, allowing measurements of single wires. The full magnetoresistive hysteresis loop is studied as a function of the angle between the applied field and the wire direction. For each field sweep, a discontinuity is observed. It corresponds to the irreversible switching of the magnetization. A model of uniform reversal of the magnetization accounts for the reversible part of these magnetoresistive loops using the conventional ${\mathrm{cos}}^{2}\ensuremath{\omega}$ dependence of the resistance with the angle $\ensuremath{\omega}$ defined between magnetization and electric current. The angular dependence of the switching field is discussed.

Periodic reverse current electrodeposition of gold in an ultrasonic field using ion-track membranes as templates: growth of gold single-crystals

Reversal of current electrodeposition has been applied to grow gold single-crystals in organic ion-track membranes used as templates. The influence of an ultrasonic agitation of the electrolyte has been also investigated. Two electrolytes were used for gold deposition: (1) potassium dicyanoaurate(I) and (2) sodium disulfitoaurate(I) solutions. Gold single-crystals have been successfully grown only from the cyanidic solutions. The perfection of the crystals was defined by the deposition conditions, namely by the parameters of the reverse current pulses. The ultrasonic field led to a depolarization effect that favoured the growth of single-crystals when a direct current was used. Its influence on the crystal growth during pulse electrolysis was not so pronounced. However, the macrothrowing power of the bath was increased. Gold deposition from a sodium disulfite bath resulted in polycrystalline claddings independent of the variation of deposition conditions.

Electrochemical growth of copper single crystals in pores of polymer ion-track membranes

Copper single-crystals are grown by a galvanic method, using etched ion tracks in a polymer foil as templates. The copper deposition is carried out by reversible pulse electrolysis in an ultrasonic field. The method applied for this purpose permits fabrication of stable standing cylindrical single crystals with diameters in the nanometer and micrometer range with high aspect ratio and density of 105–107 per cm2 on a large area. The experimental results obtained in this way are compared with the results obtained by direct current plating under ultrasonic treatment and sole reversible electrolysis. The effects of all these deposition processes on the structure of copper claddings are shown.