Pores Of Polycarbonate Track-etched Membranes Research Articles

Microstructural, optical and electrical investigations of large scale selenium nanowires prepared by template electrodeposition

Large scale selenium nanowires have been prepared into the pores of polycarbonate track-etched membrane by template electrodeposition. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–Visible spectroscopy have been used to characterize as-prepared crop of selenium nanowires. XRD and FESEM studies confirmed the formation of dense crop of selenium nanowires with trigonal phase. The spectra exhibited a highly crystalline peak corresponding to (100) plane suggesting a preferential growth along [001] direction. Williamson–Hall analysis has been used to determine the crystallite size and micro strain induced due to lattice deformation. The band gap of as-prepared selenium nanowires has been found to be 1.76 eV and of the direct type of transition. The blue shift observed in the optical band gap of selenium nanowires has been attributed to quantum size effect in semiconductor nanowires. Electrical properties of selenium nanowires have been examined using two probe method and showed double diode like current–voltage characteristics. The possible reaction mechanism of the formation of selenium nanowires has also been discussed.

Ultrasensitive detection of ovarian cancer marker using immunoliposomes and gold nanoelectrodes

Mucin-16 (MUC16) is the established ovarian cancer marker used to follow the disease during or after treatment for epithelial ovarian cancer. The emerging science of cancer markers also demands for the new sensitive detection methods. In this work, we have developed an electrochemical immunosensor for antigen MUC16 using gold nanoelectrode ensemble (GNEE) and ferrocene carboxylic acid encapsulated liposomes tethered with monoclonal anti-Mucin-16 antibodies (αMUC16). GNEEs were fabricated by electroless deposition of the gold within the pores of polycarbonate track-etched membranes. Afterwards, αMUC16 were immobilized on preformed self-assembled monolayer of cysteamine on the GNEE via cross-linking with EDC-Sulfo-NHS. A sandwich immunoassay was performed on αMUC16 functionalized GNEE with MUC16 and immunoliposomes. The differential pulse voltammetry was employed to quantify the faradic redox response of ferrocene carboxylic acid released from immunoliposomes. The dose–response curve for MUC16 concentration was found between the range of 0.001–300UmL−1. The lowest detection limit was found to be 5×10−4UmL−1 (S/N=3). We evaluated the performance of this developed immunosensor with commercial ELISA assay by comparing results obtained from spiked serum samples and real blood serum samples from volunteers.

Electroanalysis of urinary l-dopa using tyrosinase immobilized on gold nanoelectrode ensembles

The performance of an amperometric biosensor constructed by associating tyrosinase (Tyr) enzyme with the advantages of a 3D gold nanoelectrode ensemble (GNEE) is evaluated in a flow-injection analysis (FIA) system for the analysis of l-dopa. GNEEs were fabricated by electroless deposition of the metal within the pores of polycarbonate track-etched membranes. A simple solvent etching procedure based on the solubility of polycarbonate membranes is adopted for the fabrication of the 3D GNEE. Afterward, enzyme was immobilized onto preformed self-assembled monolayers of cysteamine on the 3D GNEEs (GNEE-Tyr) via cross-linking with glutaraldehyde. The experimental conditions of the FIA system, such as the detection potential (−0.200 V vs. Ag/AgCl) and flow rates (1.0 mL min−1) were optimized. Analytical responses for l-dopa were obtained in a wide concentration range between 1 × 10−8 mol L−1 and 1 × 10−2 mol L−1. The limit of quantification was found to be 1 × 10−8 mol L−1 with a resultant % RSD of 7.23% (n = 5). The limit of detection was found to be 1 × 10−9 mol L−1 (S/N = 3). The common interfering compounds, namely glucose (10 mmol L−1), ascorbic acid (10 mmol L−1), and urea (10 mmol L−1), were studied. The recovery of l-dopa (1 × 10−7 mol L−1) from spiked urine samples was found to be 96%. Therefore, the developed method is adequate to be applied in the clinical analysis.

Study of transportation of atrazine and paraquat through nanochannels

The transportation of paraquat and atrazine through the modified gold nanochannels polycarbonate track etched (PCTE) membrane was described. The gold nanochannels can be electrolessly plated within the pores of PCTE membranes. The gold nanochannels were hydrophobic because of modification of thiol (HSC18H37). They can forbid paraquat and allow atrazine to transport through the membranes. However, these hydrophobic membranes can be switched from an “off” state (no or lower ion-current through the membrane) to an “on” state (higher ion-current) due to the presence of some surfactants. The effects of different surfactants, including cationic surfactant such as C16H29 (CH3)3NH4Br, nonionic surfactant like emulsifier OP, on the transport properties of paraquat through the membrane were investigated. It is found that for some alkyl surfactants with a 12-carbon chain length can switch the membrane to the on state even if their concentrations were lower than critical micelle concentrations. Specially, for a 10-carbon chain alkyl surfactant, 1-decanesulfonic acid sodium has the same function of switching the membrane to the on state as long as its concentration is high enough. But other chemical substances, regardless of cation, anion or molecule, cannot switch the membrane.

Gold nanotube membranes functionalised with fluorinated thiols for selective molecular transport

Gold nanotube membranes were prepared by electroless deposition of gold within the pores of polycarbonate track-etched membranes. This approach provides control over the pore size of the membrane, with pore sizes being reduced to molecular dimensions. The effect of the surface chemistry on the transport properties of these gold nanotube membranes has been explored through functionalisation with self-assembled monolayers. The transport properties and the selectivity of fluoro-derivatised membranes (1H,1H,2H,2H-perfluorodecanethiol) towards hydrophobic and hydrophilic molecules was compared with a membrane modified with an analogous alkanethiol; 1-decanethiol.

An In Situ EIS Study during the Electrochemical Growth of Copper Nanowires into Porous Polycarbonate Membranes

Detailed information about the electrochemical and physicochemical phenomena associated with copper nanowire growth within the nanosized pores of polycarbonate track-etched membranes (PCM) was in situ obtained by electrochemical impedance spectroscopy. From an equivalent circuit that reproduces the ac-impedance results, it was found that the charge-transfer resistances associated with the Cu 2+ → Cu + and Cu + → Cu° electrochemical processes presented low and high values, respectively. It was also possible to observe the change from a diffusional growth process inside the pores (first stages) to a growth process in solution (film formation onto PCM).

Bienzyme HRP–GOx-modified gold nanoelectrodes for the sensitive amperometric detection of glucose at low overpotentials

Gold nanotubular electrode ensembles were prepared by using electroless deposition of the metal within the pores of polycarbonate track-etched membranes. Mono-enzyme (GOx) and monolayer/bilayer bienzyme (GOx/HRP) bioelectrodes were prepared by immobilizing the enzymes onto gold nanotubes surfaces modified with mercaptoethylamine. Batch amperometric responses to glucose for the different bioelectrodes were determined and compared. The response of the two geometries (monolayer and bilayer) of the bienzyme electrodes was shown to vary with regard to sensitivity at detection potentials above 0 V. On the contrary, at detection potentials below 0 V, no noticeable influence of the configuration of the bienzyme on the response intensity was observed. The mono-enzyme (650 μA mM −1 in benzoquinone (BQ) at −0.8 V versus Ag/AgCl) and the two bienzyme bioelectrodes (±400 μA mM −1 in hydroquinone (H 2Q) at −0.2 V versus Ag/AgCl) display remarkable sensitivities compared to a classical GOx-modified gold macroelectrode (13 μA mM −1 in BQ at −0.8 V versus Ag/AgCl). A remarkable feature of the bienzyme electrodes is the possibility to detect glucose at very low applied potentials where the noise level and interferences from other electro-oxidizable compounds are minimal. Another important characteristic of the monolayer bienzyme electrode is the possible existence of a direct electronic communication between HRP and the transducer surface.

Pore size distributions of nanoporous track-etched membranes

Replicas of the pores of polycarbonate track-etched membranes were produced by electrodeposition of nickel and cobalt. These nanowires were studied by transmission electron microscopy. Pore size distributions in the range 10 to 200 nm were determined. The waterflow data given by the manufacturers is shown to be consistent with our estimation of the average pore size. The saturation magnetization values of filled membranes also confirm our results.