Materials selection for gas sensing. An HSAB perspective

This paper introduces the Hard Soft Acid Base (HSAB) concept as a promising tool for the selection of gas sensing layers. Target gas molecule — sensitive layer tandems are discussed and interpreted in the terms of this theory. Sensing layers suitable for carbon dioxide, nitrogen dioxide, sulphur dioxide, and hydrogen sulphide detection are presented and classified according to this concept. For oxygen and mineral acids detection, an indirect HSAB approach is discussed. The paper explains how the HSAB principle can be useful in designing gas sensing layers for different types of sensing structures, such as: surface acoustic waves (SAW), colorimetric, chemoresistive, etc.