This book delves into developing various plasmonic nanosensors to detect toxic heavy metal ions in aqueous media. It includes a significant and burgeoning branch of nanosensor technology based on plasmon resonance and serves as a guide to those researching in this area. Based on this technology, all types of nanosensors for water treatment will also be introduced to the readers to create nanosensors and detect heavy metals. It aims to provide state-of-the-art knowledge to researchers and ecologists, industrialists, and academicians for easy access to create a variety of plasmonic nanosensors. This book also covers paper-based devices based on plasmon for quantifying toxic metals in water. This book also discusses the important applications of different plasmon-based nanomaterials―graphene, core-shell, quantum dots, nanoporous membrane, carbon nanotubes, and nanofibers. It will serve as ready reckoner to all those involved in the field of nanosensors and their applications and can pave the way for a better understanding of nanosensor technology towards toxic metals.