Screen-printed electrode and manufacturing method thereof

An electrochemical sensor for measuring chemical oxygen demand in a water sample containing organic matter, characterized in that said electrochemical system comprises:

• a screen-printed electrode (1) according to any of the preceding claims;
• means (11) for applying an electric potential between the working electrode (5) and the pseudo-reference electrode (6) of said screen-printed electrode (1);
• and,
• means (12) for measuring and recording a faradaic current at said working electrode (5).

Method of fabrication of a screen-printed electrode (1) according to the preceding claim, wherein the step of preparing a copper nanoparticle-carbon nanocomposite-based ink further comprises:

• preparing an aqueous sample comprising 30-35 wt % resorcinol, 0.2-0.6 wt % sodium carbonate and 64-70 wt % formaldehyde (sample A);
• preparing an aqueous sample comprising copper (II) nitrate hydrate in a concentration between 0.6-0.7 mol/L (sample B);
• mixing samples, A and B in a volume ratio A:B comprised between 3:1 and 3.5:1 for a period between 60-75 minutes (sample C);
• dissolving 450 to 600 mg sodium carbonate in three additions of 150 to 200 mg in sample C and stirring for 1-1.5 hour until the pH is comprised between 8 and 9 (sample D);
• heating sample D at a temperature between 55-65° C. for a period between 20 and 24 hours, resulting a plurality of wet gels:
• placing the wet gels in a fume hood at room temperature for at least 2 days;
• carbonizing the resulting copper nanoparticle-carbon nanocomposite powder under an argon flux comprised between 80-120 cm3/min at a temperature between 1000-1055° C. for a period between 110-130 minutes;
• and,
• mixing the copper nanoparticle-carbon composite powder with 15-20% wt nitrocellulose prepared in 2-butoxyethyl acetate in a weight molar ratio comprised between 3:1 and 3.5:1 until the resulting paste presented a honey-like texture.