Facile and ultrasensitive electrochemical impedance sensing for formaldehyde based on silver ions doped in controllable and homogeneous silica microspheres

Formaldehyde is a highly reactive and toxic compound in air pollutants, exposure to even a low concentration of formaldehyde will do harm to human health. Herein, a novel electrochemical impedance sensor for formaldehyde has been developed based on Ag + -SiO 2 microspheres prepared by the exchange of silver ions with trapped ammonium ions. The probe of silver ion is easily and selectively reduced by formaldehyde, then the silver nanoparticles would be generated. Exposure to more concentration of formaldehyde, more proportionate silver nanoparticles would be loaded on the surface of silica microspheres, and then the decrement of interface charge transfer resistance (R ct ) would be obtained accordingly. The decrement of R ct was linear with the concentration of formaldehyde in the range from 2 to 6000 pmol L −1 with a detection limit of 0.5 pmol L −1 . Enabled by such a unique sensing mechanism, the fabricated sensor has been successfully applied for the detection of formaldehyde in real samples with high performance in selectivity, low power consumption, sensitivity, cost-effectiveness, facility, and portability.