Electrical properties of conducting polypyrrole films functionalized with phthalocyanine

Radiolytic synthesis of conducting polypyrrole/carbon nanotube composites

Abstract: Conducting polypyrrole (PPy)/multi-wall carbon nanotube (MWNT) composites have been synthesized by the in situ gamma radiation-induced chemical polymerization method at room temperature. The resulting cable-like morphology of the composite (PPy–MWNT) structures was characterized by elemental analysis, Fourier transform infrared, field-emission scanning electron microscope, thermal gravimetric analysis, X-ray photoelectron spectroscopy, and transmission electron microscope. The standard four-point probe method was utilized for measuring the conductivity of the samples. We observed no significant chemical reaction between the polymer and carbon nanotube, which only showed that polypyrrole chains are tightly coated on to MWNT. The physical properties of the composites (PPy–MWNT) were measured and showed that the MWNT were modified by conducting polypyrrole with various properties enhanced.

Conducting polypyrrole modified with ferrocene for applications in carbon monoxide sensors

Abstract: Polypyrrole (PPy) was modified with ferrocene (Fc) by direct incorporation during polymerization so as to increase its sensitivity for carbon monoxide (CO) gas sensor applications. Synthesis was carried out by chemical oxidative polymerization in the presence of ferrocene using ferric chloride. The presence of these species in PPy was confirmed by different characterization techniques. The CO response measurements were carried out for the sensors fabricated in a surface cell mode with active PPy + Fc films by exposing to CO gas (300 ppm) at room temperature and it was found that the response as well as the recovery characteristics of these materials is very fast and dependent on the film composition. The response factor was found to be maximum for a 1.32 mol% Fc content in the polymer. These various results can be explained on the basis of interaction of CO molecules with Fe atoms of the ferrocene together with charge transfer interaction with the PPy chain.

CO sensor based on polypyrrole functionalized with iron porphyrin

Abstract: Polypyrrole (PPy) was chemically functionalized with 5,10,15,20-tetraphenyl-21H,23H-porphyrin iron(III) chloride (FeTPPCl) with special interest on noxious carbon monoxide (CO) gas in ppm level. Controlled functionalization of PPy was achieved with incorporation of various concentrations of porphyrin. The resulted semiconducting material was well characterized by different techniques such as UV–vis spectroscopy, FTIR, GFAAS, XRD, and EDAX. The functionalized polypyrrole material on interdigitated electrode was experienced an immediate increase in resistance when exposed to carbon monoxide gas at very low concentration. The CO gas interacted very fast with the FeTPPCl functionalized PPy at room temperature (RT) and then slowly saturated. The response of these materials was not unidirectional, but reverses to the original resistance level when CO was removed from the test chamber. The highest response factor (Δ R / R 0 × 100) and lowest response time ( t 50 ) obtained are 12 and 169 s, respectively. An optimum level of doping (1 mol% of FeTPPCl) was established for the highest sensitivity and the detection level is as low as 100 ppm.

Conducting Polymers Functionalized with Phthalocyanine as Nitrogen Dioxide Sensors

Abstract: The conducting polymers such as polyaniline, polypyrrole and polythiophene were functionalized with copper phthalocyanine using chemical oxidation method. The obtained polymers viz. PANI-CuPc, PPy-CuPc and PT-CuPc were studied as chemical sensors by their response characteristics after exposure to various chemical vapors such as methanol, ammonia and nitrogen dioxide. The results obtained showed that these polymers have moderate sensitivity towards the methanol as well as ammonia vapors whereas they show tremendous sensitivity towards nitrogen dioxide vapors. The sensitivity factor of as high as 50,000 was obtained for PT-CuPc polymers in nitrogen dioxide. In comparison to this, the sensitivity factors of about 100 and 40 were obtained, when these polymers were exposed to ammonia and methanol vapors. The very high selectivity towards the nitrogen dioxide was explained on the basis of charge transfer complex formed between, the phthalocyanine donor and nitrogen dioxide acceptor molecules. On the other hand, ammonia becomes a competing electron donor in CuPc containing conducting polymers. The very low response towards the methanol may be explained on the basis very little charge transfer / interaction between CuPc containing polymers and methanol. Thus, CuPc incorporated conducting polymers have much higher selectivity than their original homopolymer

Preparation and electrical conductivity of SiO2/polypyrrole nanocomposite

Abstract: In the present study we have chemically polymerized silica/polypyrrole (SiO2/PPy) nanocomposite in the presence of sodium dodecyl benzene sulfate (SDBS) as dopant and iron chloride (FeCl3) as oxidant. The SiO2/PPy nanocomposite presents an electrical conductivity of 32.41 S cm−1 and percolation threshold of 20 wt%. The resulting SiO2/PPy nanocomposites have been extensively characterized in terms of their molecular structure, particle size, morphology, stability, and electroactivity. These SiO2/PPy particles have a rather polydisperse morphology. The effects of synthesis parameters such as oxidant, PPy, SDBS, reaction temperature and time, on the electrical conductivity of the nanocomposite have been detailedly optimized. And the conducting nanocomposite presented a good environmental stability.

Catalytic electroreduction of molecular oxygen using iron or cobalt 4,4',4",4'"-tetracarboxyphthalocyanine

Abstract: Etudes de l'electroreduction de l'oxygene dans une solution aqueuse contenant des tetracarboxyphtalocyanines de Fe et de Co

The effect of gases on the conductive properties of organic semiconductors

Abstract: Summary The surface conductivity of organic semiconductors can vary strongly in the presence of adsorbed gases. The possibility of using this principle as a method for the detection of air contaminants has been examined. It has been demonstrated that in a high vacuum the surface conductivity of metal-free phthalocyanine and β-carotene depends strongly on the type of gas brought into contact with the sample. This response of semiconductors depends on type of semiconductor, pretreatment, amount of light, pressure of the gas and temperature. Conductivity changes of the substrate (quartz) in the presence of gases have been measured. Although, these changes are in themselves important, they do not interfere with the results obtained with the organic semiconductors.

The cyclic voltammetry of some sulphonated transition metal phthalocyanines in dimethylsulphoxide and in water

Abstract: The aqueous voltammetry of Co, Ni, Cu and Zn sulphonated metallophthalocyanines has been examined and compared to the voltammetry in DMSO. In DMSO, Ni, Cu and Zn phthalocyanines exhibit two quasi-reversible, phthalocyanine ligand based, one-electron transfers. Two reduction waves were also observed for Co phthalocyanine. However, the first reduction wave appeared to involve both a metal based electron transfer and a change in the coordination of the metal. The aqueous voltammetry of the cobalt phthalocyanine was similar to its non-aqueous behaviour. The other three phthalocyanines did not show the quasi-reversible behaviour in aqueous solution. Reversibility was much diminished and the forms of the waves changed greatly, indicating the involvement of protons in the redox processes.