This volume charts the progress made in the use of quantum dots as the signaling component in optical sensors since their discovery in the early 1980s. It focuses on CdS-, CdSe-, and CdTe-type quantum dots due to their emission in the visible region of the electromagnetic spectrum. The book details the range of methods currently used for the preparation and passivation of core/core-shell quantum dots, discusses their electrochemical properties and potential toxicity, and explains how electron and energy transfer mechanisms can be used to generate a range of quantum dot-based probes.