The goal of this project is to create a transformative approach for ultrasensitive, cost-efficient and programmable detection of agriculturallyand environmentally important heavy metal ions: (a) Hg2+(b) Ag+and (c) Pb2+using DNA nanotechnology coupled with metallic particles. The major goals are: 1.Colorimetric detection of mercury, silver and lead ions and2.Ultrasensitive fluorometric detection of metal ions.Detection of each heavy metal ion will be demonstrated using real samples; water, soil, plants, and urine, blood and milk samples from farm animals. For the first objective, gold nanoparticles (AuNPs) will be used for the visual and spectroscopic detection of metal ions in natural resources (water and soil), agricultural products (milk, plants and fish) and animal fluids (urine and blood). For the second approach, magnetic particles (MBs) will be used instead of gold nanoparticles in order to achieve the detection of low amounts of each metal ion using fluorescence spectroscopy. The AuNP system depends on color transition in the assay, however the fluorescence-based method using MBs and intercalating fluorescent nanotags is anticipated to be far more sensitive. We propose to develop nanosensors using both colorimetric and fluorometric approaches for Hg2+, Ag+ and Pb2 that can be used for real sample analysis.Milestone for objective 1: The milestones for first objective are to build nanosensors which a) generate visual signals upon detection of the contaminants, b) provide quantitative results with tunable and wide dynamic detection ranges, c) detect free and bound (organic) mercury, silver and lead contaminants in agricultural and environmental samples. We will determine the limit of detection of the nanosensors by monitoring the change in the plasmonic bands of the nanoparticles using UV-Vis spectroscopy. Finally, we will assemble and test simple easy-to-use portable electronic devices that can monitor, record and wirelessly report the contamination.Milestones for objective 2: The milestones for objective 2 are to build fluorometic magnetic sensors using fluorescent nanotags, DNA nanotechnology and magnetic particles. Limit of detection, sensitivity, specificity and dynamic range of the sensors will be determined and compared to the nanosensors developed in objective 1. Fluorometric detection of Hg2+, Ag+ and Pb2+ from different environmental and agricultural resources will be performed. The results will be compared to the data obtained with the mercury analyzer and atomic absorption spectrometer located in our facilities. Finally, we will assemble an easy-to-use portable electronic device that can monitor, record and wirelessly report the contamination.