A metal insulator semiconductor field effect transistor (MISFET)-type sensor for the detection of CO2 dissolved in aqueous solution is presented. This all-solid-state device is based on a Pt-NiO thin film as active sensing material on the top of a gate electrode. The fabrication of the sensor is described and its performance is characterized. In particular the transient characteristics and response curves at different biases V-RS versus the amount of dissolved CO2 are presented. The sensor shows a linear response to the logarithm of the concentration of dissolved CO2 at room temperature. (C) 2010 Elsevier Inc. All rights reserved.