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

土壤养分在作物生产中起着多重关键作用。营养物质影响植物的质量和数量，以及它们对减产的不同逆境的抵抗力。因此，要在不不断扩大农业用地面积的情况下，满足全球对优质食品、饲料和纤维日益增长的需求，土壤养分的智能管理至关重要。该项目的研究人员将创造一种基于纳米材料的、在路上的传感器，可以实时和连续地检测多种土壤养分。成功完成后，该项目的研究生和本科生将开发一个手持传感器的演示模块，并将在美国科学与工程节和博览会上向广大公众展出。这一高度跨学科的研究项目也将为化学研究生和本科生提供理想的学习机会，让他们参与从纳米材料合成到传感器开发，再到土壤测量的广泛研究经验。尽管准确、现场检测各种养分对于精准农业和特定地点的土壤管理至关重要，但目前可用于土壤测量的分析技术，包括拉曼光谱，可能存在与不够准确、低可靠性、不够灵敏和费力的样品准备有关的挑战。该研究小组将利用氧化锌纳米棒的优异物理和光学特性来创造用于移动土壤养分传感器的拉曼纳米探测器。具体地说，将利用氧化锌纳米棒的亚波长波导和表面消逝波导属性以及一维纳米材料的高形状各向异性。一旦转化为新型的拉曼纳米探针，垂直排列的氧化锌纳米棒将允许高度增强和空间局域激发，以及有效耦合和传输来自土壤养分的即使是难以检测到的拉曼散射信号。总的来说，基于纳米棒的拉曼土壤传感器将提供多种化学分析，其检测灵敏度足够高，以无背景土壤荧光的方式量化更丰富的宏观营养物质以及痕量水平的微营养物质。将为传感器建立传感器校准、量化和验证步骤，并将确定这种新型拉曼纳米探针传感器的全部性能特性。这项研究工作不仅将通过对拉曼信号进行化学指纹识别来实现土壤养分的多路检测，而且还将利用新开发的纳米探测器传感器确保准确和可靠的土壤养分量化。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.