Non‐covalent Immobilization of Iron‐triazole (Fe(Htrz) 3 ) Molecular Mediator in Mesoporous Silica Films for the Electrochemical Detection of Hydrogen Peroxide

Mesoporous silica thin films encapsulating a molecular iron‐triazole complex, Fe(Htrz) 3 (Htrz=1,2,4,‐1 H ‐triazole), have been generated by electrochemically assisted self‐assembly (EASA) on indium‐tin oxide (ITO) electrode. The obtained modified electrodes are characterized by well‐defined voltammetric signals corresponding to the Fe II/III centers of the Fe(Htrz) 3 species immobilized into the films, indicating fast electron transfer processes and stable operational stability. This is due to the presence of a high density of redox probes in the material (1.6×10 −4  mol g −1 Fe(Htrz) 3 in the mesoporous silica film) enabling efficient charge transport by electron hopping. The mesoporous films are uniformly deposited over the whole electrode surface and they are characterized by a thickness of 110 nm and a wormlike mesostructure directed by the template role played by Fe(Htrz) 3 species in the EASA process. These species are durably immobilized in the material (they are not removed by solvent extraction). The composite mesoporous material (denoted Fe(Htrz) 3 @SiO 2 ) is then used for the electrocatalytic detection of hydrogen peroxide, which can be performed by amperometry at an applied potential of −0.4 V versus Ag/AgCl and by flow injection analysis. The organic‐inorganic hybrid film electrode displays good sensitivity for H 2 O 2 sensing over a dynamic range from 5 to 300 μM, with a detection limit estimated at 2 μM.