These findings collectively confirm that both TEMPO and Fc-COOH act as reducing agents when mixed with dC12 diazonium salts. This redox mediation behavior could explain the effect of TEMPOderivatized diazonium salts dC 12 TEMPO NOBF4 (containing TEMPO in its radical form during electroreduction) on immobilization efficiency. According to this hypothesis, this redox activity could reduce the concentration of diazonium species at the electrode interface, lowering the density of reduced species and, consequently, the density of immobilized ones.