 Analytes diffuse into the SAMs at proportions defined by their partition coefficient and this characterizes the selectivity and sensitivity of the chemiresistor material.Conductive polymers such as polyaniline and polypyrrole can be used as sensing materials when the target interacts directly with the polymer chain resulting in a change in conductivity of the polymer.These types of systems lack selectivity due to the wide range of target molecules that can interact with the polymer.