Although these sensors are commercially available for the detection of monovalent cations, anions, gases, volatile organic molecules, heavy metal ions, and toxic metal ions, many existing models require significant power and lack advanced technology for more quality selectivity and sensitivity. There is room in these sensors to optimize their selectivity, reversibility, on/off ratio, response time, and their environmental stability in real-world operating conditions. This book explores the methods for the development and design of environmentally-friendly, simple, reliable, and cost effective electrochemical nanosensors using powerful nanostructured materials. More specifically, it highlights the use of various electrochemical-based biosensor sensors involved in the detection of monovalent cations, anions, gases, volatile organic molecules, heavy metal ions, and toxic metal ions, with the ultimate goal of seeing these technologies reach market.