Green Synthesized Nanomaterial-based Colorimetric Sensors for Detection of Environmental Toxicants

Nanotechnology has emerged as a significant tool in various fields of science. Synthesis of metal nanoparticles using physical and chemical methods are based on the use of toxic chemicals which have deleterious effect on the environment. To overcome the limitations of chemical methods, green synthesis provides an eco-friendly and inexpensive alternative path for the synthesis of metal nanoparticles. Since nature provides a variety of products in the form of plants, bacteria, fungi and biopolymers which serve the purpose in a safer way, green resources like plant extracts, certain bacteria, fungus and biopolymers have been used to synthesize metal and metal oxide nanoparticles. Metal nanoparticles as colorimetric sensors gained much attention in recent years due to their sensitive and selective color change which is visible by the naked eye. They are portable and cost effective. This review highlights the green synthesis of metal and metal oxide nanoparticles using plant extracts and biopolymers, and their characterization, mechanism and factors affecting synthesis. Specific application of these green synthesized nanoparticles as colorimetric sensors for the detection of toxic pollutants in water is discussed in detail.