In this paper a novel enzymatic glucose biosensor has been reported in which platinum coated alumina membranes (Anodisc™s) have been employed as templates for the growth of polypyrrole (PPy) nanotube arrays using electrochemical polymerization. The PPy nanotube arrays were grown on Anodisc™s of pore diameter 100 nm using potentiostatic electropolymerization. In order to optimize the polymerization time, immobilization of glucose oxidase (GOx) was first performed using physical adsorption followed by measuring its biosensing response which was examined amperometrically for increasing concentrations of glucose. In order to further improve the sensing performance of the biosensor fabricated for optimum polymerization duration, enzyme immobilization was carried out using cross-linking with glutaraldehyde and bovine serum albumin (BSA). Approximately six fold enhancement in the sensitivity was observed in the fabricated electrodes. The biosensors also showed a wide range of linear operation (0.2–13 mM), limit of detection of 50 μM glucose concentration, excellent selectivity for glucose, notable reliability for real sample detection and substantially improved shelf life.

In this paper, we report fabrication of enzymatic glucose biosensor based on growth of high density polypyrrole (PPy) nanofiber network using one step template free electropolymerization method. PPy was grown potentiostatically on gold coated glass substrates. Significant changes in the sensing response were observed for biosensors fabricated with different concentrations of pyrrole (Py) monomer and polymerization potentials. Among the fabricated biosensors, the highest sensitivity of 1.9 mA cm(-2) M-1, with a wide range of linear operation (125 mu M-11.25 mM) was observed for 0.15 M Py concentration and 0.8 V polymerization potential. The observed results indicate that low monomer concentration and moderately low polymerization potential is highly suitable for growth of PPy nanofiber network with controllable fiber diameters having high aspect ratio, resulting in high sensitivity for biosensor application. (C) 2014 Elsevier B.V. All rights reserved.

In this paper, we report the growth of polypyrrole (PPy) nanotube arrays using template-assisted electrochemical polymerization to fabricate enzymatic glucose biosensors. The PPy nanotubes were grown on platinum-coated alumina membranes (Anodisc™s). By varying the polymerization time during the potentiostatic electropolymerization, the size/diameter of the PPy nanotubes were controlled, leading to changes in the subsequent enzyme immobilization (via physical adsorption). Enzyme electrode thus fabricated resulted in to the optimum sensitivity of 18.6 mA cm−2 M−1, a wide range of linear operation (0.25–20 mM) and the lowest detection limit of 0.25 mM glucose concentration for the biosensor with the polymerization time of 40 s. The effect of polymerization duration on the sensitivity has been explained on the basis of porosity and enzyme-loading capacity of polymerized electrodes.

In this study, the sensing behaviour of palladium nanoparticle layers and thin film samples has been investigated for hydrogen and deuterium at room temperature and pressures between 4 and 5Torr. Deuterium has been synthesised using electrolysis of heavy water. Nanoparticle as well as thin film samples show higher sensitivity for deuterium gas, in comparison to hydrogen gas, at all the gas pressures investigated. Nanoparticle sample shows faster sensing response for deuterium in comparison to hydrogen. It is interesting to note that palladium thin films show different sensitivity towards deuterium and hydrogen in comparison to palladium nanoparticles. This may be attributed to the difference in diffusivities of the two gases (deuterium and hydrogen) in palladium thin films. The results of this study indicate that by using a hybrid gas sensor, employing comparison of electrical resistance change in palladium nanoparticles and thin film, it may be feasible to differentiate between hydrogen and deuterium. The proposed sensor is based on the higher palladium diffusivity of deuterium in comparison to hydrogen, when the two gases are below the respective solubility limits.

A detailed structural study involving in situ glancing angle x-ray diffraction (GAXRD) analysis carried out on Pd nanoparticle and thin film samples at hydrogen concentrations of 2%, 5%, and 10% over temperature ranging from −100 to 55 °C and hydrogen pressures ranging from 250 to 1000 mbars is reported. Variation in the lattice constant has been interpreted in terms of hydrogen content in α and β PdHx phases, and decrease in XRD peak intensity has been interpreted in terms of hydrogen induced degradation in crystalline quality and temperature induced lattice disorder. It is observed that Pd–H interaction is strongly influenced by the temperature and pressure dependences of physisorption, chemisorption, and diffusion. These results show that the increased surface area, interparticle gaps, and electronic enhancement result in enhanced Pd–H interaction in case of nanoparticles. In addition, the presence of single β phase and lower crystallinity degradation is observed in the case of Pd nanoparticles in comparison to thin films. The above mentioned differences between nanoparticles and thin films are more pronounced at lower temperatures due to the increased presence of subsurface sites.