Ascorbic acid sensor based on ion-sensitive field-effect transistor modified with MnO2 nanoparticles

An ascorbic acid (AA) sensor based on an ion-sensitive field-effect transistor (ISFET) was prepared by modifying the sensitive area of the transducer with MnO₂ nanoparticles. An additional Nafion membrane coated on top of the sensor was used to immobilize the MnO₂ nanoparticles and restrict the amount of ascorbic acid entering the membrane. The reaction of the MnO₂ nanoparticles with ascorbic acid produced a local pH change, which was correlated with the ascorbic acid concentration and could be monitored by the ISFET. The linear range of the ascorbic acid sensor was 0.02-1.27 mM, and the detection limit was 0.01 mM. The effects of buffer concentration, pH, and ionic strength on the sensor performance were also examined. In addition, the sensor has good stability and reproducibility, and the construction and renewal of the sensor are simple and inexpensive.