Track-etch

Track-etched membranes are made by exposing thin films (mica, polycarbonate, etc) to fission fragments from a radiation source. The high energy particles chemically alter material in their path. The material is then dissolved by suitable reagents, leaving nearly cylindrical holes (19). 

FIG. 22-70 Track-etched 0,4 j.im polvcaibonate memlu ane, (Coniiasy MiUi-jiore CorpornlUm.)... 

Many molecular dynamics simulations have focused on the electrolyte solution factors and ignored the atomic features of the pore wall. The assumptions of these simulations may match more closely the experiments of inorganic channels, such as track-etched nu-... 

Within the scope of thermoelectric nanostructures, Sima et al. [161] prepared nanorod (fibril) and microtube (tubule) arrays of PbSei. , Tej by potentiostatic electrodeposition from nitric acid solutions of Pb(N03)2, H2Se03, and Te02, using a 30 fim thick polycarbonate track-etch membrane, with pores 100-2,000 nm in diameter, as template (Cu supported). After electrodeposition the polymer membrane was dissolved in CH2CI2. Solid rods were obtained in membranes with small pores, and hollow tubes in those with large pores. The formation of microtubes rather than nanorods in the larger pores was attributed to the higher deposition current. 

Sima M, Enculescu I, Visan T, Spohr R, Trautmann C (2004) Electrochemical deposition of PbSei j Tej nanorod arrays using ion track etched membranes as template. Mol Cryst Liq Cryst 418 749-755... 

Track-Etched Track-etched membranes (Fig. 20-66) are now made by exposing a thin polymer film to a collimated beam of radiation strong enough to break chemical bonds in the polymer chains. The film is then etched in a bath which selectively attacks the damaged polymer. The technique produces a film with photogenic pores. 

FIG. 20-66 Track-etched 0.4-)lm polycarbonate membrane. Courtesy Milli-pore Corporation.)... 

Several papers present reviews of measurement methods or improvements in existing methods. Yamashita et al. (1987) present the description of a portable liquid scintillation system that can be used for thoron (Rn-220) as well as radon (Rn-222) in water samples. Thoron measurements have not been made for houses where radon in water may be a significant source. Such an instrument could be useful in making such determinations as well as in studying geochemical problems as described in this report. A review of measurement methods by Shimo et al. (1987) and of development and calibration of track-etch detectors (Yonehara et al., 1987) are also included. Samuelsson... 

In 47 houses, Rn-222 measurements were performed by Track Etch detectors from Terradex Inc. during two periods, November-May and June-October. From these measurements, the normal seasonal variations were assessed. In Fig. 2 a plot of the cumulative distribution of mean Rn-222 concentrations during summer and winter are shewn. From this figure, the mean concentration during sunnier is about 50 % of the mean concentration during the winter months. 

M kel inen, I., Experiences with track etch detectors. Proc. of the 13th International Conference on Solid State Nuclear Track Detectors, Rome (September 1985) (to be published). 

Urban, M. and Piesch, E., Low Level Environmental Radon Dosimetry with a Passive Track Etch Detector Device, Rad. Prot. Dos. 1 97-109 (1981). 

Measurements were made using two types of passive track-etch alpha dosimeters. One of them was the bare detector of CR-39. After exposure these dosimeters were etched by 30 % NaOH at 70°C for 5 hours. The number of pits was scored under a microscope with a television camera in Shiga University of Medical Science. Methods of calibration and adjustment for deposition of radon daughters introduced by Yonehara (Yonehara et al., 1986) were adopted. The second detectors were Terradex type SF (Alter and Price, 1972). These detectors consist of a plastic cup, covered by a filter to allow entry only of gases, with a track-etch detector inside. The reading of results was carried out by Terradex Corp. in Walnut Creek, California, U.S.A.. The measurements of radon concentration were carried out by both methods in each location, except for Hokkaido where the measurements were done only by Terradex. However, the data obtained by CR-39 detectors will be mainly presented in this paper, because the two methods did not give identical results as separately reported in this proceedings by Yonehara et al. (Yonehara et al., 1986). 

In order to assess the accuracy of the present method, we compared it with two other methods. One was the Track Etch detector manufactured by the Terradex Corp. (type SF). Simultaneous measurements with our detectors and the Terradex detectors in 207 locations were made over 10 months. The correlation coefficient between radon concentrations derived from these methods was 0.875, but the mean value by the Terradex method was about twice that by our detectors. The other method used was the passive integrated detector using activated charcoal which is in a canister (Iwata, 1986). After 24 hour exposure, the amount of radon absorbed in the charcoal was measured with Nal (Tl) scintillation counter. The method was calibrated with the grab sampling method using activated charcoal in the coolant and cross-calibrated with other methods. Measurements for comparison with the bare track detector were made in 57 indoor locations. The correlation coefficient between the results by the two methods was 0.323. In the case of comparisons in five locations where frequent measurements with the charcoal method were made or where the radon concentration was approximately constant, the correlation coefficient was 0.996 and mean value by the charcoal method was higher by only 12% than that by the present method. 

Rock, R.L., D.B. Lovett, and S.C. Nelson, Radon-daughter Exposure Measurement with Track Etch Films, Health Physics 16 617-621 (1969). 

Possin, in 1970, was the first to use the pores in track-etched mica membranes as templates to make nanomaterials [23]. This was accom-... 

There has been extensive recent use of track-etched membranes as templates. As will be discussed in detail below, these membranes are ideal for producing parallel arrays of metal nanowires or nanotubules. This is usually done via electroless metal deposition [25], but many metals have also been deposited electrochemically [26]. For example, several groups have used track-etched templates for deposition of nanowires and segmented nanowires, which they then examined for giant magnetoresistance [27-29]. Other materials templated in the pores of track etch membranes include conducting polymers [30] and polymer-metal composites [31]. 

Similar sieving was observed in radiotracer setf-drffusion experiments on lightly etched films prepared via the track-etch process [112]. However, molecular filtration of the type described here was not observed. 

The electroless plating procedure described above was used to plate the Au nanotubules into the pores of commercially available polycarbonate track-etch filters [Osmonics, 6 pm thick, pore dia. = 50 nm (28 nm-dia. Au tubules) or 30 nm (all other Au tubules), 6 X 10 pores cm ]. The... 

In this section a short introduction will be given on the synthesis of porous ceramic membranes by sol-gel techniques and anodization, carbon membranes, glass membranes and track-etch membranes. An extensive discussion will be given in Sections 2.3-2.S. 

Pores with a very regular, linear shape can be produced by the track-etch method (Quinn et al. 1972). Here a thin layer of a material is bombarded with highly energetic particles from a radioactive source. The track left behind in the material is much more sensitive to an etchant in the direction of the track axis than perpendicular to it. So etching the material results in straight pores of uniform shape and size with pore diameters ranging between 6 nm and 1200 nm. To avoid overlap of pores only 2-5% of the surface can be occupied by the pores. This process has been applied on polymers (e.g. Nuclepore membranes) and on some inorganic systems like mica. Membranes so obtained are attractive as model systems for fundamental studies. 

An example of the track-etch membrane was given in Section 2.2 (Quinn et al. 1972). Booman and Delmastro (1974) have also described the layer deposition method to produce a microporous membrane by a track-etch method. 

The track-etch membrane can be used in reverse osmosis and electrodialysis separation processes where it consists of a thin metal layer with a thin layer of insulator material on each side. The membrane pore diameters were in the range 0.5-10 nm. 

The deposition of a conductive polymer (polypyrrole) into either a track-etched polycarbonate or alumina membrane was either achieved by electrochemical reduc-... 

An alternate method to produce templated electrodes is the use of chemical reduction of the monomer in the presence of a track-etched or alumina membrane. Parthasarathy et al. [46] have produced enzyme-loaded nanotubules by a combination of both electrochemical and chemical deposition. Initially, the alumina membrane was sealed at one end with a thick Au film (Figure 1.9a), after which the membrane was placed into a mixture of pyrrole and Et4NBF4. The pyrrole was then electropolymerized to form a small plug of polypyrrole at the closed end of the alumina membrane (Figure 1.9b). Subsequently, the membrane was placed into a... 

The term membrane encompasses a wide range of potential substrates that can be used for the immobihzation of NAs. It includes traditional polymeric cast membranes , such as nitrocellulose, nylon or polypropylene, and also innovations such as ceramic or track-etched materials (alumina membranes). Membranes as substrates in DNA array fabrication can possess advantages over other surfaces their surface area can be much greater (200% more in cast membranes and 500% more in aliuniniiun membranes) than certain other alternatives. This is primarily a consequence of their possession of pores. 

Quinn, J. A., J. L. Anderson, W. S. Ho, and W. J. Petzny, Model pores of molecular dimension - Preparation and characterization of track-etched membranes , Biophysical Journal, 12, 990-1007 (1972). 

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