Modification of electrodes with N-and S-doped carbon dots. Evaluation of the electrochemical response

Nitrogen and sulphur-doped Carbons Dots (N-CDs and S-CDs) were synthesized by a hydrothermal method and incorporated as surface electrode modifiers to evaluate their properties for electrochemical sensing. The first task was to characterize the synthesized materials, for which different spectroscopies, scanning microscopes, mass spectrometry and elementary analysis were performed. Next, a glassy carbon electrode (GCE) was surface-modified with the doped CDs and applied to check the electrochemical signal of different organic compounds corresponding to different families. Water solubility of the doped carbon dots forced us to incorporate them in a graphite-polystyrene ink to complete the modification of electrodes. This modification needed a first activation to obtain a properly conductive surface. The organic compounds examined were salicylic acid, cysteine and ascorbic acid. The modified GCEs exhibited an enhanced sensitivity, probably caused by the increase of active surface, but in addition, signals of salicylic acid were shifted ca. 200 mV to lower potentials, what is a proof of the increase of the heterogeneous electron transfer rate, and a demonstration of an enhanced catalytic response.