Selective layer interferants binding

The response of a sensor to the primary species (X) is described by the response curve (Fig. 1.2). Besides the analyte (X), many other interfering species (/) also interact with, and competitively bind to, the binding sites in the selective layer. Because such interactions are non-specific, the sites occupied by the interferants are expressed as the sum (XasO- Let us assume that only the occupied sites (ao) in or at the selective layer result in the output signal from the sensor. The total available activity of binding sites ( st) in the layer is... 

One weakness of chemical sensors based on adsorption of analyte at their surface is their poor selectivity, in other words, their vulnerability to interference from other species. Contrast this situation with the sensors having binding sites buried in the bulk of the selective layer. Such sites are accessible only by absorption. 

The shape-selective intercalation of analytes is a bulk (interlayer) process. In order to minimize interferences arising from the adsorption of molecules on particle external surfaces, the ratio of bulk to extmuil binding sites most be increased. Nomudly this might be accomplished by simply increasing the particle size however, thicker layered particles would entail longer solid-state diffusion paths for analyte molecules, and could significantly slow the device response. 

---