SitS NSF-UKRI: Real-time and Continuous Monitoring of Phosphates in the Soil with Graphene-Based Printed Sensor Arrays

Phosphorus, one of the major three nutrients for plants, is required for plant growth, and it serves as an indicator for global environmental sustainability. It is important to understand the variations of phosphate in soils and soil-water systems in order to address a number of global challenges such as food production and regulating fertilizer applications for crops grown in various soil conditions and climate regimes. The goal of this research project is to use the latest graphene-based technology to develop a low-cost sensor capable of real-time monitoring of the phosphorus content in soil. This collaborative project between researchers at the U.S. institutions of Kansas State University and the University of Alabama at Huntsville, and the U.K. institution of the University of Sheffield, will be conducted by an interdisciplinary team with expertise in soil and water science, geology, electrical engineering, and the fundamental chemistry and physics of soil-graphene interactions. Development of such sensors will enable farmers to choose the right amount of fertilizer to apply to the fields.

This research project aims to develop an additively-manufactured graphene sensor array and a portable wireless system for continuous in-field monitoring of electrochemical signals. Such a system would be applied to the mapping of soil phosphates in diverse agricultural landscapes in the US Midwest (Kansas) and the UK East Midlands (Derbyshire Dales and Peak District). Structurally and chemically tailored graphene materials will be used to print graphene sensors with quasi-three-dimensional and porous graphene morphologies. The materials will be designed to achieve high electrical conductivity as well as reversible and high electron charge-transfer characteristics when exposed to soil phosphates. A fundamental understanding of phosphate ion binding with various graphene morphologies will be gained using state-of-the-art ultrafast laser spectroscopy and high-end computational modeling. A Bluetooth communication module with an Arduino platform will be constructed and interfaced with the sensor arrays for sensor data acquisition. Controlled environmental testing of spatial and temporal variations of phosphate ions over other interfering ions will be carried out at specific sites in Kansas and at Europe's largest controlled environment P3-facility housed at the University of Sheffield. The fundamental sensing characteristics and drift optimization with temperature, humidity, salinity, and soil pH will be identified and optimized for reliable data collection. Soils ranging from coarse calcareous to loamy montmorillonitic and silicate-rich soils in two countries will be utilized as testbeds to measure the sensing capabilities of the printed arrays. Furthermore, the project will explore the detection of phosphates over other interfering ions in soils, such as nitrates, silicates, and heavy metals, by using chemically-functionalized graphene sensors. This research will help to strengthen the national and economic security of both the U.S. and the U.K. and will strengthen the future workforce by bridging the gaps between science, technology, agriculture, and environmental disciplines through the training of graduate students, undergraduate students, and postdoctoral scientists.

Knowledge
The project will generate new knowledge in multiple specialized areas (graphene-based sensor, phosphate sensing, soils monitoring). These outputs will be directly beneficial both for academia and for industry. Since the project involves development of novel graphene sensors and characterisation of graphene materials, the immediate intellectual output of the research will be of great interest to researchers in the field of graphene science and technology. Among the major stakeholders of the project are research communities working on graphene-based sensors, such as the Centre for Graphene Science at the University of Exeter and the National Graphene Institute at the University of Manchester. These groups will be contacted at the start of the project. The goal is to create links between the different centres to keep up-to-date with the latest development in this rapidly growing field as well as to inform them about the project outcomes. Our research results will be disseminated through publications in high-quality journals and presentations in leading conferences. The project also involves development of a functional device capable of acquiring, storing and sending the measurements data. This technology can be directly adopted in other research laboratories involved in small molecules/heavy metal sensing. In this aim, it is planned that informal demonstrations and workshops will be performed in research groups who use similar techniques. To this end, the team will benefit from existing collaborations and will develop further collaborations through interactions with research centres and hubs mentioned above. The team will endeavour to commercialise these technological innovations. Commercial opportunities will be assessed by both the University of Sheffield and Kansas State University and University of Alabama Commercialisation Teams, which work in close collaboration with startup companies specialised in commercialisation of university intellectual property.

Economy, health and society
This project is expected to be an integral part of a transition toward precision farming. In order to enable this transition, the team will work in close collaboration with the P3 institute and Grantham Centre for Sustainable Futures at the University of Sheffield. This collaboration will help translate the knowledge gained from the project into practical guidelines used to inform policy and guidelines for related industries. These policies and guidelines will in turn affect the wider society.
In terms of immediate societal impact, the University of Sheffield, and more specifically, the departments of Chemistry and Animal and Plant Sciences are involved in regular outreach activities such as school visits, open days, STEM activities, participation in charity events. Members of the team have a track record of participation in activities dedicated to popularization of science and, in particular, to schoolchildren. Because the project includes the fabrication of devices that are applied to real-life environments, it is ideally suited for outreach activities that are appealing to the public.

People
The people who will most immediately benefit from this project are postdoctoral research associates (PDRAs), as well as current and future PhD, master and undergraduate students who will work alongside the PDRAs on related projects. The PDRAs and students will be trained to use and develop some of the most sophisticated tools available today within a vibrant and interdisciplinary environment. The PDRAs have access to a wide range of transferable skills training at the University of Sheffield, such as problem solving, giving presentations, writing for publication, training in grant writing skills, industry engagement and policy making. The novelty of the materials, equipment and analytical tools, as well as the interdisciplinary nature of the project will provide the participants with a valuable set of technical and transferable skills.