Analyte Interactions and Acoustic-Wave Chemical Sensors

4 Coating-Analyte Interactions and Acoustic-Wave Chemical Sensors 

Regardless of the detection mechanism(s) involved, the response characteristics of an AW sensor are a function of the nature of the interaction between the analyte and the sensor coating. A fundamental understanding of the types of inter- 

The interactions utilized for chemical sensors can be organized into two broad categories physical and chemical, with a significant gray area between the two. Within each category, there are further distinctions according to the precise nature of the interaction. The classification of these assorted interactions is the topic of Section 5.4.1. 

In the context of this chapter, the sorbent phase is a coating on an AW sensor surface, where sorption can refer to adsorption (onto a surface or sorption site) and/or absorption (dissolution in the bulk). In the discussion following Section 5.4.1, adsorption and absorption are treated separately, and each of these interactions is discussed in terms of its energetics, or thermodynamics, which control the amount of analyte in/on the coating under equilibrium conditions. Kinetic factors, which determine the rate of response and also bear upon the reversibility of the sensor, are then considered. The kinetics of adsorption are described in Section 5.4.3 details of absorption kinetics, which are essentially diffusional in nature, can be found in Chapter 4. With this groundwork in place, a number of instances where these effects have been utilized in AW chemical sensors are described. Section 5.4 concludes with a discussion of biochemical/biological AW sensors. 

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