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Mira Josowicz

Publications and source records attributed to Mira Josowicz.

7 recordsLinked to original sources
PubMed2006

Enhanced performance of a filter-sensor system.

In this paper are addressed two important, but seemingly unrelated issues: long term performance of a gas sensing array and performance of an air purification unit. It is shown that when considered together, the system can be regarded as a "smart filter". The enhancement is achieved by periodic differential sampling and measurement of the "upstream" and "downstream" gases of a filter. The correctly functioning filter supplies the "zero gas" from the downstream for the continuous sensor baseline correction. A key element in this scheme is the synthetic jet that delivers well-defined pulses of the two gases. The deterioration of the performance of the "smart filter" can be diagnosed from the response pattern of the sensor. The approach has been demonstrated on removal/sensing of ammonia gas from air.

Air Conditioning↗
PubMed2006

Label-free DNA detection based on modified conducting polypyrrole films at microelectrodes.

A label-free electrochemical detection method for DNA hybridization based on electrostatic modulation of the ion-exchange kinetics of a polypyrrole film deposited at microelectrodes is reported. Synthetic single-stranded 27-mer oligonucleotides (probe) have been immobilized at 2,5-bis(2-thienyl)-N-(3-phosphorylpropyl)pyrrole film formed by electropolymerization on the previously formed polypyrrole layer. The 27- or 18-mer target oligonucleotides were monitored via the electrochemically driven anion exchange of the inner polypyrrole film. The performance of the miniaturized DNA biosensor system was studied in respect to selectivity, sensitivity, reproducibility, and regeneration of the sensor. Control experiments were performed with a noncomplementary target of 27-mer DNA and 12 base-pair mismatched 18-mer sequences, respectively, and did not show any unspecific binding. Under optimized experimental conditions, the label-free electrochemical biosensor enabled the detection limits of 0.16 and 3.5 fmol for the 18- and 27-mer DNA strand, respectively. Furthermore, we demonstrate reusability of the electrochemical DNA biosensor after successful recovery of up to 100% of the original signal by regenerating the DNA "label-free" electrode with 50 mM HCl at room temperature.

Base Sequence↗
PubMed2005

Gold-polyaniline composite. Part I. Moving electrochemical interface.

The controlled growth of gold nanoclusters in polyaniline is predicated by the ability of PANI to switch from conducting to insulating form and by the fact that imine nitrogens form a strong complex with chloroaurate anions. The principal technique used in this study has been chronopotentiometric stripping. The chronopotentiograms indicate that the electrochemical interface for the Pt/Au/polyaniline/electrolyte shifts back and forth from the solution/PANI interface to Au/PANI interface. By adjusting experimental conditions the size and the size distribution of Au clusters can be controlled.

Aniline Compounds↗
PubMed2005

Gold-polyaniline composites. Part II. Effects of nanometer sized particles.

The amount of electronic charge transferred between gold particles and polyaniline depends not only on the electron affinity of the two materials but also on the size of the gold particles. As measured by X-ray photoelectron spectroscopy, for particles < approximately 5 nm the binding energy of the electrons is size dependent. This "nano-effect" has its origin in the electrostatics of particles. It is demonstrated as a measurable shift of the binding energy of the Au(4f7/2) photoelectrons emitted from Au particles embedded in a polyaniline matrix. Gold nanoparticle size was evaluated by high resolution transmission electron microscopy.

Aniline Compounds↗
PubMed2003

Label-free DNA hybridization probe based on a conducting polymer.

A new approach to the realization of the electrochemical DNA hybridization probe is described. It is based on the exchange of chloride ion between the polypyrrole layer and the buffer. The shape of the cyclic voltammogram is modulated by the negative charge density at this interface, resulting from the immobilized target DNA. The negative charge density increases when the complementary DNA hybridizes with the probe DNA. The hybridization event can be clearly seen in the cyclic voltammogram before and after the addition of the probe DNA. The immobilization is accomplished via the Mg2+ bridging complex between phosphonic acid groups of the poly[2,5-dithienyl-(N-3-phosphorylpropyl)pyrrole] grafted at the polypyrrole surface and the phosphate groups of the target DNA.

DNA Probes↗
PubMed2003

Conducting polymers in electronic chemical sensors.

Conducting organic polymers have found two main kinds of application in electronics so far: as materials for construction of various devices and as selective layers in chemical sensors. In either case, interaction with ambient gases is critical. It may compromise the performance of a device based on conducting polymers, whereas it is beneficial in a sensor. Conductivity has been the primary property of interest. Work function--related to conductivity, but in principle a different property--has received only scant attention. Our aim here is to discuss the usability of conducting polymers in both types of electronic applications in light of these two parameters.

Aniline Compounds↗