Performances of carbon-based screen-printed electrodes modified by diazonium salts with various carboxylic functions for trace metal sensors

• Influence of the grafted carboxy diazonium structure on the electrode analytical response.
• Increase of the mobility and the number of carboxy functions improves the detection signal.
• We have improved substantially carboxy grafted electrode performances.

The electrochemically induced functionalization of carbon-based screen-printed-electrodes (SPEs) by phenyl groups, having one or two carboxylic functions, was achieved by reduction of in situ generated diazonium salts in aqueous media. The corresponding diazonium cations of 4-aminobenzoic acid, 4-aminophthalic acid, 3-(4-aminophenyl) propionic acid, 3-(4-aminophenyl)-2-propenoic acid and 5-aminoisophthalic acid were generated in situ with sodium nitrite in aqueous H2SO4. The electrochemical detection of Pb(II) with the grafted SPEs was investigated using Pb(II) 5 × 10− 8 M solutions. The performances of the grafted SPEs were found to be dependent on the number of carboxylic groups, on their position on the phenyl ring, on the olefinic or the aliphatic character of the chain bearing the carboxylic group. The performances of mono-4-carboxyphenyl and 3,5-dicarboxyphenyl grafted SPEs for Cd(II) and Cu(II) trace detection were tested and compared.