Chemical Sensors and Biosensors: Fundamentals and Applications

Chapter 9

Thermochemical Sensors

Thermochemical transduction is intrinsically a universal method being based on a property common to a large number of chemical reactions, namely, the generation of heat by exothermal reactions. The thermal effect of a chemical reaction is indicated by the standard enthalpy of reaction (, in kJ mole⁻¹), which represents the change in the energy of the system at normal temperature and pressure when one mole of reactant is transformed by a chemical reaction.

Catalytic reactions are particularly suited for applications in chemical sensors since a large amount of reactant can be converted in a small catalytic reactor to produce a local change in temperature. This effect is quantified by means of a temperature transducer. Under steady-state conditions, the temperature variation with respect to a reference sensor indicates the concentration of the analyte in the sample. The steady state can be achieved by feeding the fluid sample to the reactor at a constant rate.

This chapter introduces first typical temperature transducers employed in thermochemical sensors and then presents two types of thermal sensors, namely enzymatic thermal sensors and thermocatalytic gas sensors.

9.1 Temperature Transducers

In order to convert temperature variations into an electric signal, two main kinds of transducer are used, namely resistive transducers and transducers based ...