Recent progress on detection of bivalent, trivalent, and hexavalent toxic heavy metal ions in water using metallic nanoparticles: A review

Abstract

Most of the metal ions are carcinogens and lead to serious health concerns by producing free radicals. Contamination of drinking water sources with heavy metals has a harmful impact on the environment and human health. The most commonly used heavy metals are zinc (Zn), copper (Cu), lead (Pb), tin (Sn), cadmium (Cd), chromium (Cr), iron (Fe), and mercury (Hg), etc. The heavy metal ions are easily absorbed by living things via water and spread throughout the food chain, posing a threat to humans, plants, and animals. Hence, fast and accurate detection of metal ions has become a critical issue. Among various metal ions arsenic, cadmium, lead, mercury and chromium are considered to be highly toxic. To detect these metal ions, colorometric, fluorometric and electrochemical biosensors with interfaces such as nanomaterials like especially metal nanoparticles including gold, silver, copper nanoparticles have been developed. Among these, nanomaterials are considered to be most promising, owing to their strong adsorption, fast electron transfer kinetics, and biocompatibility, which are very apt for biosensing applications. The coupling of various techniques with nanomaterials has enhanced the sensitivity, limit of detection, and robustness of the sensors. In this review, the reduction of toxicity or removal of toxic metal ions from water by various techniques and various metal nanoparticles have been summarized. Also, different types of sensors employed in the detection of metal ions with various interfaces have been highlighted.