Influence of Electrostatic Interactions Induced via a Nanocomposite Film onto a Glassy Carbon Electrode Used for Highly Selective and Sensitive Ascorbic Acid Detection

A study of the electroanalytical detection of ascorbic acid (AH2) using a glassy carbon electrode (GCE) modified with nanocomposite films constructed with multiwall carbon nanotubes (MWCNT) or functionalized with carboxylic groups (fMWCNT) and gold nanoparticles (AuNP) stabilized with poly(diallyldimethylammonium chloride) (PDDA) or poly(vinylbenzyltrimethylammonium chloride) (pVBA) is presented. A larger loading of AuNP was reached using the fMWCNT instead of the MWCNT, increasing the oxidation current of AH2. However, the modified GCE with the higher electro-analytical response, e.g. GCE/fMWCNT/AuNP@PDDA, also exhibited the adsorption of the analyte onto the electrode, a process that was completely eliminated by attaching a DNA-bioinspired polyanion (P16−) onto the electrode surface. Consequently, the GCE/fMWCNT/AuNP@PDDA/P16− was able to electro-oxidize AH2 thru a diffusion-controlled process, with a sensitivity of (64.6 ± 0.5) nA μM-1 and a detection limit of (75 ± 5) nM at pH 7. The electroanalytical response of the modified GCE was extremely stable over 70 reusing cycles or during several days under certain storage conditions. Additionally, accurate quantification of AH2 was obtained in the presence of interfering compounds or in real complex matrixes. These results indicate the relevance of specific interactions between the electroactive surface and the analyte to obtain better electroanalytical responses.