P REFACE TO C HEMICAL S ENSORS : F UNDAMENTALS OF S ENSING M ATERIALS Sensing materials play a key role in the successful implementation of chemical and biological sen- sors. The multidimensional nature of the interactions between function and composition, preparation method, and end-use conditions of sensing materials often makes their rational design for real-world applications very challenging. The world of sensing materials is very broad. Practically all well-known materials could be used for the elaboration of chemical sensors. Therefore, in this series we have tried to include the widest pos- sible number of materials for these purposes and to evaluate their real advantages and shortcomings. Our main idea was to create a really useful "encyclopedia" or handbook of chemical sensing materials, which could combine in compact editions the basic principles of chemical sensing, the main properties of sensing materials, the particulars of their synthesis and deposition, and their present or potential ap- plications in chemical sensors. Thus, most of the materials used in chemical sensors are considered in