EAGER SitS: Nanorod-Based, On-the-Go Raman Sensors for Real-Time, Multiplexed Soil Nutrient Monitoring via Direct Ground Probing

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Soil nutrients play multiple crucial roles in crop production. Nutrients affect the quality and quantity of plants and their resistance to different stresses that reduce yield. Hence, smart management of soil nutrients is vital to meeting the increasing global need for quality food, feed, and fiber without continuously expanding the land area for agriculture. The researchers in this project will create a nanomaterial-based, on-the-go sensor which can enable real-time and continuous detection of multiple soil nutrients. When successfully completed, a demonstration module of a hand-held sensor will be developed by the graduate and undergraduate students on the project, and it will be exhibited to the general public at the USA Science and Engineering Festival and Exposition. This highly interdisciplinary research project will also provide ideal learning opportunities for chemistry graduate and undergraduate students by engaging them in a wide breadth of research experiences ranging from nanomaterial synthesis, to sensor development, to soil measurements.Although accurate, on-site detection of various nutrients is critical to precision agriculture and site-specific soil management, analytical techniques currently available for soil measurements including Raman spectroscopy can present challenges associated with inadequate accuracy, low reliability, insufficient sensitivity, and laborious sample preparation. This research group will exploit the superior physical and optical properties of zinc oxide nanorods to create Raman nanoprobes for use as on-the-go soil nutrient sensors. Specifically, the subwavelength waveguiding and surface evanescent waveguiding attributes of zinc oxide nanorods as well as the high shape anisotropy of the one-dimensional nanomaterial will be exploited. Once transformed into a novel Raman nanoprobe, a vertical array of zinc oxide nanorods will permit highly intensified and spatially localized excitation as well as effective coupling and transport of even hard-to-detect Raman scattering signals from soil nutrients. Collectively, the nanorod-based, Raman soil sensor will provide multiplexed chemical analysis with its detection sensitivity high enough to quantify both the more abundant, macro nutrients as well as the trace-level, micro nutrients in a background soil fluorescence-free manner. Sensor calibration, quantification, and validation steps will be established for the sensor, and the full performance characteristics of this novel Raman nanoprobe sensor will be determined. The research efforts will not only permit multiplexed detection of soil nutrients via chemically fingerprinting their Raman signatures but also ensure accurate and reliable soil nutrient quantification by utilizing the newly developed nanoprobe sensor.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.