Amperometric bromate-sensitive sensor via layer-by-layer assembling of metalloporphyrin and polyelectrolytes on carbon nanotubes modified surfaces

A novel amperometric sensor for bromate (BrO₃ ⁻) was developed using the layer-by-layer (LbL) assembly process of iron(III)-porphyrin (Fe(III)P) and polyelectrolytes alongside oxidized multiwall carbon nanotubes (OMWCNTs) on a disposable screen-printed carbon electrode (SPCE). Positively charged Fe(III)P and negatively charged poly(sodium 4-styrenesulfonate) (PSS) were used as structure blocks for LbL assembly on the OMWCNTs modified SPCE. The electrocatalytic response by Fe(III)P from the amperometric LbL sensor for determining BrO₃ ⁻concentration was characterized using cyclic voltammetry. Critical experimental parameters affecting the sensor's performance were optimized, including the number of assembled layers, pH of the buffer solution, and concentration of Fe(III)P immobilized on the electrode surface. A linear response from 100 nM to 2.5 mM of BrO₃ ⁻in 0.2 M SAB solution with a sensitivity of 115.2 μA mM⁻¹and a detection limit of 43 nM were achieved with good selectivity. As a final demonstration, the proposed LbL sensor, [Fe(III)P-PSS]₁-Fe(III)P-OMWCNTs/SPCE, was applied to analyze BrO₃ ⁻concentrations in tap water and mineral water samples.