Nitration, polypyrrole

Nitration of the surface of polypyrrole and the subsequent reduction of the nitrate groups has been reported [244] and Bidan et al. [306, 307] have investigated the electrochemistry of a number of polymers based on pyrroles with /V-substituents which are themselves electrochemically active. Polypyrrole has also been successfully deposited onto polymeric films of ruthenium complexes [387], and has been used as an electrode for the deposition and stripping of mercury [388], As with most conducting polymers, several papers have also appeared on the use of polypyrrole in battery systems (e.g. [327, 389] and Ref. therein). 

Hutchins RS, Bachas LG. Nitrate-selective electrode developed by electrochemically mediated imprinting doping of polypyrrole. Anal Chem 1995 67 1654-1660. 

A nitrate-selective potentiometric MIP chemosensor has been devised [197, 198]. For preparation of this chemosensor, a polypyrrole film was deposited by pyrrole electropolymerization on a glassy carbon electrode (GCE) in aqueous solution of the nitrate template. Potentiostatic conditions of electropolymerization used were optimized for enhanced affinity of the resulting MIP film towards this template. In effect, selectivity of the chemosensor towards nitrate was much higher than that to the interfering perchlorate ( o3 cio4 = 5.7 x 10-2) or iodide ( N03, r = x 10 2) anion. Moreover, with the use of this MIP chemosensor the selectivity of the nitrate detection has been improved, as compared to those of commercial ISEs, by four orders of magnitude at the linear concentration range of 50 pM to 0.5 M and LOD for nitrate of (20 10) pM [197]. 

Solid-state ion sensors with conducting polymers as sensing membranes have also proved useful in some applications. Of particular importance are the pH sensors based on polyaniline that can be also applied in non-aqueous solutions. Polypyrrole-based sensors for nitrate also show great promise for water analysis. However, in addition to these two excellent examples, a large number of functionalized conducting polymers have been synthesized already, and these materials may offer unique possibilities for fabrication of durable, miniaturized ion sensors. 

Cadogan et al. [73] deposited polypyrrole onto platinum from a variety of solutions and found the resultant films to be anion sensitive but very unselec-tive. When polypyrrole was deposited from NaN03 solution, however, the resultant electrode gave near-Nernstian responses to nitrate ion in the range 0.5-0.0005 M with selectivities of about 20 over other lipophilic ions such as iodide and perchlorate [74]. Similar electrodes could be fabricated via a screen-... 

Figure 12. (A) The amperometric response of (a) a polypyrrole-viologen-nitrate reductase electrode and (b) an identical electrode constructed without the enzyme, in response to injections (a) increasing the nitrate concentration by 3.5 pM, and (y) of buffer. (B) Calibration curves (inset smaller concentration range) for the response to nitrate of a polypyrrole-viologen-nitrate reductase electrode at —0.7 V vs. SCE. Adapted from Ref. [106a with permission.

This diol was mixed with other diols, then reacted with diisocyanates to form polyurethanes. The electrically conducting polymers, polyaniline and polypyrrole, prevent corrosion of steel.105 One of the best formulations uses polyaniline with zinc nitrate, which is then covered with an epoxy resin topcoat. Polyorganosiloxanes have been grafted to starch using the sol-gel method with alkoxysi-lanes. These materials have been complexed with cerium ions to provide corrosion protection for aircraft that is expected to be 50% cheaper than conventional coatings.106... 

Figure 13.1 Covalent attachment of an enzyme to derivatized polypyrrole (a) polypyrrole polymer (b) nitration of polypyrrole (c) electrochemical reduction of nitro groups to amine groups (d) attachment of enzyme to amine groups with carbodiimide [32],...

Burgmayer P and Murray R W 1984 Ion Gate Electrodes. Polypyrrole as a switchable ion conductor membrane J. Phys. Chem. 88 2515-21 Otero T F and de Larreta E 1988 Conductivity and capacity of polythiophene films impedance study J. Electroanal. Chem. 244 311-18 Sunde S, Hagen G and Odegird R 1993 Impedance analysis of the electrochemical doping of poly(3-methyl-thiophene) from aqueous nitrate solutions J. Electroanal. Chem. 345 59-82 Zaborsky O R 1973 Immobilized Enzymes (Cleveland, OH Chemical Rubber Company) (see especially pp 69,87)... 

Figure 14-18. Covalent binding of enzymes to the conducting polymer polypyrrole. The reaction sequence shows the functionalization of the electrochemically deposited polymer film by nitration and subsequent electrochemical reduction.

S. Aravamudhan and S. Bhansali, Development of micro-fluidic nitrate-selective sensor based on doped-polypyrrole nanowires. Sens. Actuat. B, 132, 623-630 (2008). 

H. Pahlavanzadeh, R. Katal, H. Mohammadi, Synthesize of polypyrrole nanocomposite and its application for nitrate removal from aqueous solution. /Ind Eng Chem 2012, 18 (3), 948-956. 

G.A. Alvarez-Romero, M.E. Palomar-Pardave, M.T. Ramirez-Silva, Development of a novel nitrate-selective composite sensor based on doped polypyrrole. Anal. Bioanal. Chem. 387 (2007) 1533-1541. 

On some occasions the electrolyte plays a decisive role in obtaining polypyrrole in non-inert substrates. This is the case of Fe, for which in aqueous solution only nitrate anions give polypyrrole deposits [97]. This behaviour has been correlated with the tenancy of the nitrate ion to yield radicals at the anode, initiating a radical oxidation of the monomer. In the same way, good-quality PPy films on aluminium in aqueous solutions are only obtained from acid electrolytes [94]. 

Madasamy, T., Pandiaraj, M., Kanugula, A.K., Rajesh, S., Bhargava, K., Sethy, N.K., 2013. Gold nanoparticles with self-assembled cysteine monolayer coupled to nitrate reductase in polypyrrole matrix enhanced nitrate biosensor. Adv. Chem. Lett. 1, 2—9. 

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