Poly(3,4-ethylenedioxythiophene) doped with engineered carbon quantum dots for enhanced amperometric detection of nitrite.

An electrochemical sensor for nitrite was fabricated by modifying a glassy carbon electrode (GCE) with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) that is doped with carbon quantum dots (CQDs). The negatively charged CQDs were doped into PEDOT via electrodeposition to form a conducting polymer nanocomposite on the GCE. The electrode surface has a flake-like nanostructure and a large specific surface area. The elemental mapping analysis revealed that the CQDs are uniformly distributed across the whole nanocomposite. As a result of the superior catalytic activity of CQDs and the good conductivity of PEDOT, the modified GCE displays excellent electrocatalytic activity towards the oxidation of nitrite, and the oxidation peak current is ten times higher than that of a PEDOT modified GCE without CQDs. Under optimum conditions and at a working voltage of 0.80 V (vs. Ag/AgCl), the sensor has a linear response in the 0.5-1110 μM nitrite concentration range, and an 88 nM limit of detection (at S/N = 3). Three different electrodes prepared under the same experimental conditions were applied for the detection of nitrite, and the RSD was 3.1%. The same sensor was employed to quantify nitrite in three replicate measurements, and the RSD was 2.2%. Graphical abstract Poly(3,4-ethylenedioxythiophene) (PEDOT) was doped with carbon quantum dots and deposited on a glassy carbon electrode to obtain an amperometric sensor for nitrite.