Chapter 1 - Colorimetric Sensors and Sensor Arrays

Abstract

Colorimetric sensors became more popular and widespread due to high accessibility, ease of use, and low cost together with sensitive and selective response toward various analytes. Colorimetric sensors are a class of optical sensors that change their color when influenced by external stimuli. Any change in a physical or chemical environment can be considered as such stimulus. Therefore a change in a property of the environment that is needed to be detected defines the design of the particular colorimetric sensor. This chapter starts with the description of main principles of colorimetric temperature sensor operation that are required to design thermochromic materials as a representative example of colorimetric sensors responding to a change in physical property. Introducing a concept of assembly/disassembly accompanied by a color change, we come to the design of colorimetric chemical sensors. Describing two main schemes of chemical sensor design (receptor-spacer-reporter and indicator-displacement assay), we come to receptor specificity, a concept of a sensor array and describe most useful strategies of immobilization of sensing molecules on a solid support followed by basics of visual output interpretation and analysis. Finally, we focus on molecular sensors specific to certain heavy metals or demonstrating ability to simultaneously detect different elements and thus having a potential for application in sensing arrays. We pay specific attention to describing the ability to use nanomaterials (carbon dots and metal nanoparticles and nanorods) as reporters. In addition, we demonstrate representative examples of molecular sensors anchored on solid supports.