**2.3 Electrochemical measurements**

98 Electropolymerization

anilines (Barbero et al., 1994; Cano-Márquez et al., 2007; Mello et al.,2000; Varela et al.; 2001). In the case of homopolymer of luminol should be studied as influence the chemical nature of film in the proprieties obtain and in the activity electrocatalitic; in fact these proprieties are only reported for the dimmer of luminol (Chen & Lin, 2002). On other hand as the polymer obtained to luminol not is water soluble, in consequence the copolymerization of these two monomers can be result of a deposition a self doping polymer film. The goal of this study is the electrosynthes of three novel conducting polymers: polyANS, polyluminol (only has been reported dimmers of luminol) and copolymer, obtained to ANS, luminol and both respectivally, the evaluation of proprieties of films obtained as well as: activity electrocatalytic to ascorbic acid, electrochemical activity in pH neutral and study the charge compensation using the electrochemical quartz crystal microbalance (EQCM) during the

NH2

SO3H

redox process only for polyANS.

**2. Experimental** 

**2.2 EQCM measurements** 

**2.1 Materials** 

C

O

Fig. 1. Chemical structure of momomers used in the present study.

atmosphere was kept over the solution during each run.

acrylic only aqueous solutions can be used with this cell.

C

NH2 O

NH

**Luminol (3-aminophtalhydrazide) 5-Amino-2-naphtalenesulfonic acid**

The commercial chemicals: luminol (Fluka), ANS (Aldrich), graphite powder (sigma), nujol (Alfa- Aesar), HCl (Fermont), HClO4 (Fermont), HNO3 (Caledón), H2SO4 (Fermont) and camphorsulfonic acid (Aldrich) were of analytical reagents grade and were used without further purification except the aniline (Sigma) which was distilled before use at stored to low temperature in the dark. The aqueous solutions were prepared using deionized water, and the solutions were deoxygenated by purging with nitrogen gas. After this, a nitrogen

EQCM measurements were conducted using a PAR 273A (Princeton Applied Research) potentiostat-galvanostat coupled to an electrochemical quartz crystal microbalance Seiko model QCA922, both controlled by WinEchem V. 1.5 installed in a personal computer. The quartz crystal resonator was mounted in a home-made acrylic cell (Figure 2). This cell is characterized by the commercial holder of quartz and it is united to made in home solution container, so the sample container also hold the quartz crystal. As the sample container is

NH

Electrochemical experiments were carried out in a three–compartment cell in a high purity nitrogen atmosphere at room temperature. The electrode reference consisting of Ag⏐AgCl⏐3 moldm-3 NaCl (BAS) and the counter electrode was a platinum wire. The working electrodes were: carbon paste electrode (0.1452 cm2), glassy carbon, Au and Pt (0.0707 cm2) and a 9 MHz AT-cut quartz crystal coated with gold (0.1963 cm2). Two types of carbon paste electrode were prepared the first by intimately mixing 1.0 g of finely ground graphite powder with 1.0 g of Nujol. The second type of electrode is characterized by included the monomer into the carbon paste bulk, the electrode is prepared mixing graphite powder, nujol and the monomer. In both cases the resulting paste was then packed into a plastic 1 mL syringe in which a piece of coop wire was wound to produce the electrical contact. The surface was smoothed by a weight paper before each experience. The glassy carbon, Au and Pt electrodes were systematically polished successively with 3 and 1 μm polish diamond (BAS) on a Microcloth felt disk (BAS). Following this, the electrodes were thoroughly rinsed with deionised water and sonicated in an ultrasonic bath for 10 minutes. The precoated PANI film for electrodeposition of polyANS was carried out by realizing 10 cycles of potential between -200 and 1200 mV, except for the three first cycles for which the upper limit was 1100 mV. The scan rate was 50 mVs-1, and the electrolyte solution was 0.5 M H2SO4 + 0.5 M aniline.
