Hydrogen polypyrrole

Elemental analysis shows that the polymer generally contains four monomer units per dopant ion [20], and that there is also more hydrogen than would be expected (cf. polypyrrole) [20, 395], although this may vary depending on the starting material [409,410,414], Even in the neutral form, the polymer contains a small quantity of anions (0.5-1%) [19], although Waltman et al. [400] found that the extent to which the counter ion is incorporated into the polymer on polymerisation depends strongly on the nature of the /J-substituent (if present). 

P.A. Fiorito and S.I.C. de Torresi, Hybrid nickel hexacyanoferrate/polypyrrole composite as mediator for hydrogen peroxide detection and its application in oxidase-based biosensors. J. Electroanal. Chem. 581, 31 (2005). 

S. Razola Serradilla, B. Ruiz Lopez, N. Diez Mora, H.B. Mark and J.M. Kauffmann, Hydrogen peroxide sensitive amperometric biosensor based on horseradish peroxidase entrapped in a polypyrrole electrode, Biosens. Bioelectron., 17(11-12) (2002) 921-928. 

Different electron-conducting polymers (polyaniline, polypyrrole, polythiophene) are considered as convenient substrates for the electrodeposition of highly dispersed metal electrocatalysts. The preparation and the characterization of electronconducting polymers modified by noble metal nanoparticles are first discussed. Then, their catalytic activities are presented for many important electrochemical reactions related to fuel cells oxygen reduction, hydrogen oxidation, oxidation of Cl molecules (formic acid, formaldehyde, methanol, carbon monoxide), and electrooxidation of alcohols and polyols. 

On the other hand, Chen et al. developed polypyrrole film electrodes containing nanodispersed platinum particles and investigated their catalytic properties for the electro-oxidation of hydrogen [13]. They confirm the remarkable electrocatalytic activity of these PPy/Pt films compared to bulk platinum electrodes, as the film thickness increases to 5 pm. 

For a polypyrrole film [19], measurements were conducted before and after the film was exposed to hydrazine (H4N2) and hydrogen peroxide (H2O2), as shown in Fig. 15. The measured refractive indices are 1.82 (before exposure to hydrazine) and 1.71 (after exposure to hydrazine). 

Fig. 15 Polypyrrole film response to (a) as deposited, (b) after exposure to hydrazine, (c) after exposure to hydrogen peroxide...

Polypyrrole in the solid state is in an amorphous state [10]. Therefore, some local structures are assumed. The calculations for these structures show that the N NMR chemical shift moves considerably to high frequency when a hydrogen atom bonded to a nitrogen atom (N2 in Fig. 16.7(b) and N4 in Fig. 16.7(d)) is very close to a hydrogen atom bonded to a carbon atom of the other ring. 

The chemical analysis of the oxidized polymer is given in Table I. The analysis indicates there are approximately 0.2 CIO 4 anions/ thiophene ring. lso, there is excess H, ca. 1H/2 thiophene rings thus some hydrogenation may have occurred during the simultaneous oxidation and polymerization. Other researchers have found similar occurrences in polypyrrole and polythiophene. (1,10,11)... 

The interrupted dephasing pulse sequence is also used in order to determine the number of hydrogen atoms bonding to nitrogen atoms in doped and undoped polypyrroles. The same relative intensities of signals in doped and undoped polymers obtained with TD of 20, 100 and 200 ps indicate that the number of bonded hydrogens and the bond lengths in both samples are approximately equal (71). 

More recently, a polypyrrole-modified s-BLM has been found to be sensitive to hydrogen ions [80]. Concerning pH probes, they could be the basis for monitoring blood gases (oxygen, carbon dioxide) and related variables (pH, Na" ", K" ", Ca " ", Cl ) as well as metabolites (glucose, urea, lactate, creatinine) after suitable modification. It is envisioned that all these could be monitored simultaneously and/or sequentially in a small sample of undiluted whole blood or in plasma [78]. 

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