Chaper 13 - Chemical and biological sensors based on electroactive inorganic polycrystals

Abstract

This chapter focuses on the use of electroactive polycrystals of transition metals such as hexacyanoferrates in the development of chemical and biological sensors. Metal hexacyanoferrates provide the possibility to develop amperometric sensors for nonelectroactive cations where the sensitivity and selectivity of metal hexacyanoferrates to such ions is provided by their thermodynamic background. Prussian blue is considered as the most advantageous low potential transducer for hydrogen peroxide, not only among hexacyanoferrates, but over all known systems. Prussian blue, or ferric hexacyanoferrate, forms electroactive layers after electrochemical or chemical deposition onto the electrode surface and can be synthesized chemically by mixing the ferric (ferrous) and hexacyanoferrate ions with different oxidation state of iron atoms. The participation of cations in redox reactions of metal hexacyanoferrates provides a unique opportunity for the development of chemical sensors for nonelectroactive ions such as thallium (Tl+), cesium (Cs+), and potassium (K+). A selective electrocatalyst for H2O2 reduction which can operate in the presence of oxygen in a wide potential range can be synthesized by optimizing the deposition procedure for Prussian blue. Various biosensors based on different transition metal hexacyanoferrates have been developed for analysis of glucose, ethanol, D-alanine, oxalate, cholesterol, glutamate, sucrose, and choline. Applications of Prussian blue–based biosensors are also expected in certain areas of clinical diagnostics such as brain research and noninvasive monitoring of blood chemistry, where high sensitivity and selectivity as well as the possibility of miniaturization are required.